1,3-Diaminopropane, also known as DAP or trimethylenediamine, belongs to the class of organic compounds known as monoalkylamines. These are organic compounds containing a primary aliphatic amine group. 1,3-Diaminopropane is a stable, flammable, and highly hygroscopic fluid. It is a polyamine that is normally quite toxic if swallowed, inhaled, or absorbed through the skin. It is a catabolic byproduct of spermidine. It is also a precursor in the enzymatic synthesis of beta-alanine. 1,3-Diaminopropane is involved in the arginine/proline metabolic pathways and the beta-alanine metabolic pathway. 1,3-Diaminopropane has been detected, but not quantified in, several different foods, such as cassava, shiitakes, oyster mushrooms, muscadine grapes, and cinnamons. This could make 1,3-diaminopropane a potential biomarker for the consumption of these foods.
2-Ketobutyric acid, also known as alpha-ketobutyrate or 2-oxobutyrate, belongs to the class of organic compounds known as short-chain keto acids and derivatives. These are keto acids with an alkyl chain the contains less than 6 carbon atoms. 2-Ketobutyric acid is a substance that is involved in the metabolism of many amino acids (glycine, methionine, valine, leucine, serine, threonine, isoleucine) as well as propanoate metabolism and C-5 branched dibasic acid metabolism. It is also one of the degradation products of threonine. It can be converted into propionyl-CoA (and subsequently methylmalonyl CoA, which can be converted into succinyl CoA, a citric acid cycle intermediate), and thus enter the citric acid cycle. More specifically, 2-ketobutyric acid is a product of the lysis of cystathionine.
2-Methoxyestrone (or 2-ME1) belongs to the class of organic compounds known as estrogens and derivatives. These are steroids with a structure containing a 3-hydroxylated estrane. Thus, 2-methoxyestrone is considered to be a steroid or steroid derivative. It is a by-product of estrone and 2-hydroxyestrone metabolism and has been detected in all mammals. More specifically, 2-methoxyestrone is an endogenous, naturally occurring methoxylated catechol estrogen and a metabolite of estrone that is formed by catechol O-methyltransferase via the intermediate 2-hydroxyestrone. 2-Methoxyestrone is part of the androgen and estrogen metabolic pathway. The acid ionization constant (pKa) of 2-methoxyestrone has been determined to be 10.81 (PMID: 516114). 2-Methoxyestrone can be metabolized to a sulfated derivative (2-methoxyestrone 3-sulfate) via steroid sulfotransferase (EC 2.8.2.15). It can also be glucuronidated to 2-methoxyestrone 3-glucuronide by UDP glucuronosyltransferase (EC 2.4.1.17). Unlike estrone but similarly to 2-hydroxyestrone and 2-methoxyestradiol, 2-methoxyestrone has very low affinity for the estrogen receptor and lacks significant estrogenic activity (PMID: 10865186).
Deoxyuridine, also known as dU, belongs to the class of organic compounds known as pyrimidine 2'-deoxyribonucleosides. Pyrimidine 2'-deoxyribonucleosides are compounds consisting of a pyrimidine linked to a ribose which lacks a hydroxyl group at position 2. It is similar in chemical structure to uridine, but without the 2'-hydroxyl group. Deoxyuridine exists in all living organisms, ranging from bacteria to humans. Within humans, deoxyuridine participates in a number of enzymatic reactions. In particular, deoxyuridine can be biosynthesized from deoxycytidine through its interaction with the enzyme cytidine deaminase. In addition, deoxyuridine can be converted into uracil and deoxyribose 1-phosphate through its interaction with the enzyme thymidine phosphorylase. Deoxyuridine is considered to be an antimetabolite that is converted into deoxyuridine triphosphate during DNA synthesis. Laboratory suppression of deoxyuridine is used to diagnose megaloblastic anemia due to vitamin B12 and folate deficiencies. In humans, deoxyuridine is involved in the metabolic disorder called UMP synthase deficiency (orotic aciduria). Outside of the human body, deoxyuridine has been detected, but not quantified in, several different foods, such as lichee, highbush blueberries, agaves, macadamia nut (M. tetraphylla), and red bell peppers. This could make deoxyuridine a potential biomarker for the consumption of these foods.
Cortexolone, also known as cortodoxone or 11-deoxycortisol, belongs to the class of organic compounds known as 21-hydroxysteroids. These are steroids carrying a hydroxyl group at the 21-position of the steroid backbone. Thus, cortexolone is considered to be a steroid molecule. Cortexolone is an endogenous glucocorticoid steroid hormone, and a metabolic intermediate in the synthesis of cortisol. It was first described by Tadeusz Reichstein in 1938 and named as Substance S. It has also been referred to as Reichstein's Substance S or Compound S. Cortexolone acts as a glucocorticoid, though it is less potent than cortisol. Cortexolone is synthesized from 17Œ±-hydroxyprogesterone by 21-hydroxylase and is converted to cortisol by 11Œ≤-hydroxylase. As a result, the level of cortexolone is often measured in patients to diagnose impaired cortisol synthesis, to identify any enzyme deficiency that may be causing impairment along the pathway to cortisol, and to differentiate adrenal disorders. Cortexolone in mammals has limited biological activity and mainly acts as metabolic intermediate within the glucocorticoid pathway, leading to cortisol. On the other hand, in sea lampreys, cortexolone is the major glucocorticoid, with mineralocorticoid activity. Cortexolone in sea lampreys binds to specific corticosteroid receptors and is involved in intestinal osmoregulation and in sea lamprey at metamorphosis, a process in which they develop seawater tolerance before downstream migration.
11-Deoxycorticosterone (also called desoxycortone, 21-hydroxyprogesterone, DOC, or simply deoxycorticosterone) is a steroid hormone produced by the adrenal gland that possesses mineralocorticoid activity and acts as a precursor to aldosterone. It is classified as a member of the 21-hydroxysteroids. 21-hydroxysteroids are steroids carrying a hydroxyl group at the 21-position of the steroid backbone. Deoxycorticosterone is very hydrophobic, practically insoluble (in water), and relatively neutral. Deoxycorticosterone can be synthesized from progesterone by 21-beta-hydroxylase and is then converted to corticosterone by 11-beta-hydroxylase. Corticosterone is then converted to aldosterone by aldosterone synthase. Deoxycorticosterone stimulates the collecting tubules in the kidney to continue to excrete potassium in much the same way that aldosterone does. Deoxycorticosterone has about 1/20 of the sodium retaining power of aldosterone and about 1/5 the potassium excreting power of aldosterone (Wikipedia). Deoxycorticosterone can be found throughout all human tissues and has been detected in amniotic fluid and blood. When present in sufficiently high levels, deoxycorticosterone can act as a hypertensive agent and a metabotoxin. A hypertensive agent increases blood pressure and causes the production of more urine. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels.  Chronically high levels of deoxycorticosterone are associated with congenital adrenal hyperplasia (CAH) and with adrenal tumors producing deoxycorticosterone (PMID: 20671982). High levels of this mineralocorticoid are associated with resistant hypertension, which can result in polyuria, polydipsia, increased blood volume, edema, and cardiac enlargement. Deoxycorticosterone can be used to treat adrenal insufficiency. In particular, desoxycorticosterone acetate (DOCA) is used as replacement therapy in Addison's disease.
4-Pyridoxic acid is a member of the class of compounds known as methylpyridines. More specifically it is a 2-methylpyridine derivative substituted by a hydroxy group at C-3, a carboxy group at C-4, and a hydroxymethyl group at C-5. 4-Pyridoxic acid is the catabolic product of vitamin B6 (also known as pyridoxine, pyridoxal and pyradoxamine) and is excreted in the urine. Urinary levels of 4-pyridoxic acid are lower in females than in males and will be reduced even further in persons with a riboflavin deficiency. 4-Pyridoxic acid is formed by the action of aldehyde oxidase I (an endogenous enzyme) and by microbial enzymes (pyridoxal 4-dehydrogenase), an NAD-dependent aldehyde dehydrogenase. 4-pyridoxic acid can be further broken down by the gut microflora via the enzyme known as 4-pyridoxic acid dehydrogenase. This enzyme catalyzes the four-electron oxidation of 4-pyridoxic acid to 3-hydroxy-2-methylpyridine-4,5-dicarboxylate, using nicotinamide adenine dinucleotide (NAD) as a cofactor.
p-Hydroxyphenylacetic acid, also known as 4-hydroxybenzeneacetate, is classified as a member of the 1-hydroxy-2-unsubstituted benzenoids. 1-Hydroxy-2-unsubstituted benzenoids are phenols that are unsubstituted at the 2-position. p-Hydroxyphenylacetic acid is considered to be slightly soluble (in water) and acidic.  p-Hydroxyphenylacetic acid can be synthesized from acetic acid. It is also a parent compound for other transformation products, including but not limited to, methyl 2-(4-hydroxyphenyl)acetate, ixerochinolide, and lactucopicrin 15-oxalate.  p-Hydroxyphenylacetic acid can be found in numerous foods such as olives, cocoa beans, oats, and mushrooms. p-Hydroxyphenylacetic acid can be found throughout all human tissues and in all biofluids. Within a cell, p-hydroxyphenylacetic acid is primarily located in the cytoplasm and in the extracellular space. p-Hydroxyphenylacetic acid is also a microbial metabolite produced by Acinetobacter, Clostridium, Klebsiella, Pseudomonas, and Proteus. Higher levels of this metabolite are associated with an overgrowth of small intestinal bacteria from Clostridia species including C. difficile, C. stricklandii, C. lituseburense, C. subterminale, C. putrefaciens, and C. propionicum (PMID: 476929, 12173102). p-Hydroxyphenylacetic acid is detected after the consumption of whole grain.
Iodotyrosine is an iodated derivative of L-tyrosine. This is an early precursor to L-thyroxine, one of the primary thyroid hormones. In the thyroid gland, iodide is trapped, transported, and concentrated in the follicular lumen for thyroid hormone synthesis. Before trapped iodide can react with tyrosine residues, it must be oxidized by thyroid peroxidase. Iodotyrosine is made from tyrosine via thyroid peroxidase and then further iodinated by this enzyme to make the di-iodo and tri-iodo variants. Two molecules of di-iodotyrosine combine to form T4, and one molecule of mono-iodotyrosine combines with one molecule of di-iodotyrosine to form T3.
3-methoxytyramine, also known as 4-(2-amino-Ethyl)-2-methoxy-phenol or 3-O-Methyldopamine, is classified as a member of the Methoxyphenols. Methoxyphenols are compounds containing a methoxy group attached to the benzene ring of a phenol moiety. 3-methoxytyramine is considered to be slightly soluble (in water) and acidic.  3-methoxytyramine can be found primarily in human brain and most tissues tissues; and in blood, cerebrospinal fluid (csf) or urine. Within a cell, 3-methoxytyramine is primarily located in the cytoplasm
(S)-3-Hydroxyisobutyric acid (3-HIBA) (CAS: 2068-83-9) is an organic acid. 3-HIBA is an intermediate in L-valine metabolism. 3-HIBA plays an important role in the diagnosis of the very rare inherited metabolic diseases 3-hydroxyisobutyric aciduria (OMIM: 236795) and methylmalonic semialdehyde dehydrogenase deficiency (OMIM: 603178). Patients with 3-hydroxyisobutyric aciduria excrete a significant amount of 3-HIBA not only during the acute stage but also when stable. 3-Hydroxyisobutyric aciduria is caused by a 3-hydroxyisobutyryl-CoA dehydrogenase deficiency (PMID: 18329219). The severity of this disease varies from case to case. Most patients exhibit dysmorphic features, such as a small triangular face, a long philtrum, low set ears, and micrognathia (PMID: 10686279). Lactic acidemia is also found in the affected patients, indicating that mitochondrial dysfunction is involved. 3-HIBA appears to specifically inhibit the function of the respiratory chain complex I-III and mitochondrial creatine kinase (PMID: 18329219). BioTransformer predicts that 3-HIBA is a product of 2-methylpropanoic acid metabolism via a hydroxylation-of-terminal-methyl reaction catalyzed by CYP2B6 and CYP2E1 enzymes (PMID: 30612223).
3-O-Sulfogalactosylceramide is an acidic, sulfated glycosphingolipid, often known as sulfatide. This lipid occurs in membranes of various cell types, but is found in particularly high concentrations in myelin where it constitutes 3-4% of total membrane lipids. This lipid is synthesized primarily in the oligodendrocytes in the central nervous system. Accumulation of this lipid in the lysosomes is a characteristic of metachromatic leukodystrophy, a lysosomal storage disease caused by the deficiency of arylsulfatase A. Alterations in sulfatide metabolism, trafficking, and homeostasis are present in the earliest clinically recognizable stages of Alzheimer's disease. Cerebrosides are glycosphingolipids. There are four types of glycosphingolipids, the cerebrosides, sulfatides, globosides and gangliosides. Cerebrosides have a single sugar group linked to ceramide. The most common are galactocerebrosides (containing galactose), the least common are glucocerebrosides (containing glucose). Galactocerebrosides are found predominantly in neuronal cell membranes. In contrast glucocerebrosides are not normally found in membranes. Instead, they are typically intermediates in the synthesis or degradation of more complex glycosphingolipids. Galactocerebrosides are synthesized from ceramide and UDP-galactose. Excess lysosomal accumulation of glucocerebrosides is found in Gaucher disease. Sulfatides are glycosphingolipids. There are four types of glycosphingolipids, the cerebrosides, sulfatides, globosides and gangliosides. Sulfatides are the sulfuric acid esters of galactocerebrosides. They are synthesized from galactocerebrosides and activated sulfate, 3'-phosphoadenosine 5'-phosphosulfate (PAPS).
Ureidopropionic acid, also known as 3-ureidopropanoate or N-carbamoyl-beta-alanine, belongs to the class of organic compounds known as ureas. Ureas are compounds containing two amine groups joined by a carbonyl (C=O) functional group. Ureidopropionic acid is an intermediate in the metabolism of uracil. More specifically, it is a breakdown product of dihydrouracil and is produced by the enzyme dihydropyrimidase. It is further decomposed into beta-alanine via the enzyme beta-ureidopropionase. Ureidopropionic acid is essentially a urea derivative of beta-alanine. High levels of ureidopropionic acid are found in individuals with beta-ureidopropionase (UP) deficiency (PMID: 11675655). Enzyme deficiencies in pyrimidine metabolism are associated with a risk for severe toxicity against the antineoplastic agent 5-fluorouracil. Ureidopropionic acid has been detected, but not quantified in, several different foods, such as gram beans, broccoli, climbing beans, oriental wheat, and mandarin orange (clementine, tangerine). This could make ureidopropionic acid a potential biomarker for the consumption of these foods.
Tetrahydrobiopterin (CAS: 17528-72-2), also known as BH4, is an essential cofactor in the synthesis of neurotransmitters and nitric oxide (PMID: 16946131). In fact, it is used by all three human nitric-oxide synthases (NOS) eNOS, nNOS, and iNOS as well as the enzyme glyceryl-ether monooxygenase. It is also essential in the conversion of phenylalanine into tyrosine by the enzyme phenylalanine-4-hydroxylase; the conversion of tyrosine into L-dopa by the enzyme tyrosine hydroxylase; and the conversion of tryptophan into 5-hydroxytryptophan via tryptophan hydroxylase. Specifically, tetrahydrobiopterin is a cofactor for tryptophan 5-hydroxylase 1, tyrosine 3-monooxygenase, and phenylalanine hydroxylase, all of which are essential for the formation of the neurotransmitters dopamine, noradrenaline, and adrenaline. Tetrahydrobiopterin has been proposed to be involved in the promotion of neurotransmitter release in the brain and the regulation of human melanogenesis. A defect in BH4 production and/or a defect in the enzyme dihydropteridine reductase (DHPR) causes phenylketonuria type IV, as well as dopa-responsive dystonias. BH4 is also implicated in Parkinson's disease, Alzheimer's disease, and depression. Tetrahydrobiopterin is present in probably every cell or tissue of higher animals. On the other hand, most bacteria, fungi and plants do not synthesize tetrahydrobiopterin (Wikipedia).
Androsterone is an inactive breakdown metabolite of testosterone, the product of a reaction mediated by the enzyme oxidative 17beta-hydroxysteroid dehydrogenase (EC 1.1.1.51, 17beta-HSD). Androsterone can also be metabolized from other adrenal androgens such as dehydroepiandrosterone, dihydrotestosterone, or androstenedione, and is considered an inactive end product. However, it can be a physiological effector in its own right. Androsterone might be converted back to dihydrotestosterone. Humans (and other primates) are unique among mammals in having high levels of circulating androsterone glucuronide, a process that is the major role of uridine-diphospho-glucuronosyltransferase enzymes (EC 2.4.1.17, UGT) for glucuronidation of steroid metabolism in humans. Conjugation of androsterone is a pathway found in all vertebrates and it is widely recognized that the liver is a major site of glucuronidation. However, it is now clear that extrahepatic tissues are also involved in the conjugation of compounds to which these tissues are exposed. High levels of androsterone glucuronide found in the human prostate, breast cyst fluid, and ovary follicular fluid suggest that glucuronidation of 5alpha-reduced C19 steroids occurs in these tissues as well. In doping control, the ratio of androsterone/etiocholanolone provides valuable information that allows the assignment of a urine specimen to a particular person or the identification of urine samples with identical steroid profiles; this is particularly important to detect attempts of urine manipulation including urine alteration and substitution (PMID: 9188497, 17017935, 14643063, 12943709, 9699884, 17260133).
7-Dehydrocholesterol (7-DHC), also known as provitamin D3 or 5,7-cholestadien-3-b-ol, belongs to the class of organic compounds known as cholesterols and derivatives. Cholesterols and derivatives are compounds containing a 3-hydroxylated cholestane core. Thus, 7-dehydrocholesterol is also classified as a sterol. 7-Dehydrocholesterol is known as a zoosterol, meaning that it is a sterol isolated from animals (to distinguish those sterols isolated from plants which are called phytosterols). 7-DHC functions in the serum as a cholesterol precursor and is photochemically converted to vitamin D3 in the skin. Therefore 7-DHC functions as provitamin-D3. The presence of 7-DHC in human skin enables humans and other mammals to manufacture vitamin D3 (cholecalciferol) from ultraviolet rays in the sun light, via an intermediate isomer pre-vitamin D3. 7-DHC absorbs UV light most effectively at wavelengths between 290 and 320 nm and, thus, the production of vitamin D3 will occur primarily at those wavelengths (PMID: 9625080).  The two most important factors that govern the generation of pre-vitamin D3 are the quantity (intensity) and quality (appropriate wavelength) of the UVB irradiation reaching the 7-dehydrocholesterol deep in the stratum basale and stratum spinosum (PMID: 9625080). 7-DHC is also found in the milk of several mammalian species, including cows (PMID: 10999630; PMID: 225459). It was discovered by Nobel-laureate organic chemist Adolf Windaus. 7-DHC can be produced by animals and plants via different pathways (PMID: 23717318). It is not produced by fungi in significant amounts. 7-DHC is made by some algae and can also be produced by some bacteria.
Adenine is a purine base. Adenine is found in both DNA and RNA. Adenine is a fundamental component of adenine nucleotides. Adenine forms adenosine, a nucleoside, when attached to ribose, and deoxyadenosine when attached to deoxyribose; it forms adenosine triphosphate (ATP), a nucleotide, when three phosphate groups are added to adenosine. Adenosine triphosphate is used in cellular metabolism as one of the basic methods of transferring chemical energy between chemical reactions. Purine inborn errors of metabolism (IEM) are serious hereditary disorders, which should be suspected in any case of neonatal fitting, failure to thrive, recurrent infections, neurological deficit, renal disease, self-mutilation and other manifestations. Investigation usually starts with uric acid (UA) determination in urine and plasma. (OMIM 300322, 229600, 603027, 232400, 232600, 232800, 201450, 220150, 232200, 162000, 164050, 278300). (PMID: 17052198, 17520339).
Taurocholic acid is a bile acid and is the product of the conjugation of cholic acid with taurine. Its sodium salt is the chief ingredient of the bile of carnivorous animals. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine, and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH, and consequently require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135). Taurocholic acid, as with all bile acids, acts as a detergent to solubilize fats for absorption and is itself absorbed. It is used as a cholagogue and choleretic (a bile purging agent). Hydrolysis of taurocholic acid yields taurine, a nonessential amino acid. Taurocholic acid is one of the main components of urinary nonsulfated bile acids in biliary atresia. Raised levels of taurocholate in fetal serum in obstetric cholestasis may result in the development of a fetal dysrhythmia and sudden intra-uterine death (PMID: 3944741, 11256973).
Aldosterone is a steroid hormone produced by the adrenal cortex in the adrenal gland to regulate sodium and potassium balance in the blood. Specifically, it regulates electrolyte and water balance by increasing the renal retention of sodium and the excretion of potassium. It is synthesized from cholesterol by aldosterone synthase, which is absent in other sections of the adrenal gland. It is the sole endogenous member of the class of mineralocorticoids. Aldosterone increases the permeability of the apical (luminal) membrane of the kidney's collecting ducts to potassium and sodium and activates their basolateral Na+/K+ pumps, stimulating ATP hydrolysis, reabsorbing sodium (Na+) ions and water into the blood, and excreting potassium (K+) ions into the urine.
Ascorbic acid is found naturally in citrus fruits and many vegetables and is an essential nutrient in human diets. It is necessary to maintain connective tissue and bone. The biologically active form of ascorbic acid is vitamin C. Vitamin C is a water soluble vitamin. Primates (including humans) and a few other species in all divisions of the animal kingdom, notably the guinea pig, have lost the ability to synthesize ascorbic acid and must obtain it in their food. Vitamin C functions as a reducing agent and coenzyme in several metabolic pathways. Vitamin C is considered an antioxidant (PubChem). Ascorbic acid is an electron donor for enzymes involved in collagen hydroxylation, biosynthesis of carnitine and norepinephrine, tyrosine metabolism, and amidation of peptide hormones. Ascrobic acid (vitamin C) deficiency causes scurvy. The amount of vitamin C necessary to prevent scurvy may not be adequate to maintain optimal health. The ability of vitamin C to donate electrons also makes it a potent water-soluble antioxidant that readily scavenges free radicals such as molecular oxygen, superoxide, hydroxyl radical, and hypochlorous acid. In this setting, several mechanisms could account for a link between vitamin C and heart disease. One is the relation between LDL oxidation and vitamins C and E. Vitamin C in vitro can recycle vitamin E, which can donate electrons to prevent LDL oxidation in vitro. As the lipid-phase vitamin E is oxidized, it can be regenerated by aqueous vitamin C. Other possibilities are that vitamin C could decrease cholesterol by mechanisms not well characterized, or could improve vasodilatation and vascular reactivity, perhaps by decreasing the interactions of nitric oxide with oxidants (PMID: 10799361). Moreover, ascorbic acid is found to be associated with hyperoxalemia, which is an inborn error of metabolism. Ascorbic acid is also a microbial metabolite produced by Ketogulonicigenium (PMID: 15785002).
Adenosine monophosphate, also known as 5'-adenylic acid and abbreviated AMP, is a nucleotide that is found in RNA. It is an ester of phosphoric acid with the nucleoside adenosine. AMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase adenine. AMP can be produced during ATP synthesis by the enzyme adenylate kinase. AMP has recently been approved as a 'Bitter Blocker' additive to foodstuffs. When AMP is added to bitter foods or foods with a bitter aftertaste it makes them seem 'sweeter'. This potentially makes lower calorie food products more palatable.
Melibiose (CAS: 585-99-9) is a disaccharide consisting of one galactose and one glucose moiety in an alpha (1-6) glycosidic linkage. This sugar is produced and metabolized only by enteric and lactic acid bacteria and other microbes, such as Dickeya dadantii, Escherichia, Leuconostoc, and Saccharomyces (PMID: 19734309, 28453942). It is not an endogenous metabolite but may be obtained from the consumption of partially fermented molasses, brown sugar, or honey. Antibodies to melibiose will appear in individuals affected by Chagas' disease (Trypanosoma cruzi infection). Melibiose is not metabolized by humans but can be broken down by gut microflora, such as E. coli. In fact, E. coli is able to utilize melibiose as a sole source of carbon. Melibiose is first imported by the melibiose permease, MelB and then converted into β-D-glucose and β-D-galactose by the α-galactosidase encoded by melA. Because of its poor digestibility, melibiose (along with rhamnose) can be used together for noninvasive intestinal mucosa barrier testing. This test can be used to assess malabsorption or impairment of intestinal permeability. Recent studies with dietary melibiose have shown that it can strongly affect the Th cell responses to an ingested antigen. It has been suggested that melibiose could be used to enhance the induction of oral tolerance (PMID: 17986780).
Adenosine is a nucleoside that is composed of adenine and D-ribose. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. For instance, adenosine plays an important role in energy transfer as adenosine triphosphate (ATP) and adenosine diphosphate (ADP). It also plays a role in signal transduction as cyclic adenosine monophosphate (cAMP). Adenosine itself is both a neurotransmitter and potent vasodilator. When administered intravenously adenosine causes transient heart block in the AV node. Due to the effects of adenosine on AV node-dependent supraventricular tachycardia, adenosine is considered a class V antiarrhythmic agent. Overdoses of adenosine intake (as a drug) can lead to several side effects including chest pain, feeling faint, shortness of breath, and tingling of the senses. Serious side effects include a worsening dysrhythmia and low blood pressure. When present in sufficiently high levels, adenosine can act as an immunotoxin and a metabotoxin. An immunotoxin disrupts, limits the function, or destroys immune cells. A metabotoxin is an endogenous metabolite that causes adverse health effects at chronically high levels. Chronically high levels of adenosine are associated with adenosine deaminase deficiency. Adenosine is a precursor to deoxyadenosine, which is a precursor to dATP. A buildup of dATP in cells inhibits ribonucleotide reductase and prevents DNA synthesis, so cells are unable to divide. Since developing T cells and B cells are some of the most mitotically active cells, they are unable to divide and propagate to respond to immune challenges. High levels of deoxyadenosine also lead to an increase in S-adenosylhomocysteine, which is toxic to immature lymphocytes.
Arginosuccinic acid is a basic amino acid. Some cells synthesize it from citrulline, aspartic acid and use it as a precursor for arginine in the urea cycle or Citrulline-NO cycle. The enzyme that catalyzes the reaction is argininosuccinate synthetase. Argininosuccinic acid is a precursor to fumarate in the citric acid cycle via argininosuccinate lyase. Defects in the argininosuccinate lyase enzyme can lead to argininosuccinate lyase deficiency, which is an inborn error of metabolism. Argininosuccinate (ASA) lyase deficiency results in defective cleavage of ASA. This leads to an accumulation of ASA in cells and an excessive excretion of ASA in urine (argininosuccinic aciduria). In virtually all respects, this disorder shares the characteristics of other urea cycle defects. The most important characteristic of ASA lyase deficiency is its propensity to cause hyperammonemia in affected individuals. ASA in affected individuals is excreted by the kidney at a rate practically equivalent to the glomerular filtration rate (GFR). Whether ASA itself causes a degree of toxicity due to hepatocellular accumulation is unknown; such an effect could help explain hyperammonemia development in affected individuals. Regardless, the name of the disease is derived from the rapid clearance of ASA in urine, although elevated levels of ASA can be found in plasma. ASA lyase deficiency is associated with high mortality and morbidity rates. Symptoms of ASA lyase deficiency include anorexia, irritability rapid breathing, lethargy and vomiting. Extreme symptoms include coma and cerebral edema.
Androstenedione is a delta-4 19-carbon steroid that is produced not only in the testis, but also in the ovary and the adrenal cortex. Depending on the tissue type, androstenedione can serve as a precursor to testosterone as well as estrone and estradiol. It is the common precursor of male and female sex hormones. Some androstenedione is also secreted into the plasma and may be converted in peripheral tissues to testosterone and estrogens. Androstenedione originates either from the conversion of dehydroepiandrosterone or from 17-hydroxyprogesterone. It is further converted to either testosterone or estrone. The production of adrenal androstenedione is governed by ACTH, while the production of gonadal androstenedione is under control by gonadotropins.
Cellobiose, also known as GLCB1-4GLCB or cellose, is a disaccharide. It is also classified as a reducing sugar. In terms of its chemical structure, it is derived from the condensation of a pair beta-glucose molecules creating a beta (1‚Üí4) bond. It belongs to the class of organic compounds known as O-glycosyl compounds. These are glycosides in which a sugar group is bonded through one carbon to another group via a O-glycosidic bond. Cellobiose can be obtained by enzymatic hydrolysis of cellulose and cellulose-rich materials such as cotton, jute, or paper. Cellobiose is a plant metabolite found in flowering plants, conifers and other gymnosperms. Cellobiose can also be found in vertebrates that have consumed plant foods. It has been detected, but not quantified in, several different foods, such as okra, common chokecherries, cherry tomatoes, and welsh onions. Cellobiose can be used as an indicator carbohydrate for Crohn's disease and malabsorption syndrome. Intestinal permeability to detect Crohn's disease and malabsorption syndrome can be measured by the sugar absorption test. This test is based on determining the ratio of the urinary excretion of a large (a disaccharide such as cellobiose) and a small carbohydrate (a monosaccharide such as lactulose or rhamnose) after oral administration. Patients with Crohn's disease or with ulcerative colitis have increased permeability indices in comparison to healthy controls (PMID: 15546811).
Cyclic AMP (cAMP) or cyclic adenosine monophosphate is an adenine nucleotide containing one phosphate group which is esterified to both the 3'- and 5'-positions of the sugar moiety. cAMP is found in all organisms ranging from bacteria to plants to animals. In humans and other mammals it is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon and ACTH. cAMP is synthesized from ATP by adenylate cyclase. Adenylate cyclase is located at the inner side of cell membranes. Adenylate cyclase is activated by the hormones glucagon and adrenaline and by G protein. Liver adenylate cyclase responds more strongly to glucagon, and muscle adenylate cyclase responds more strongly to adrenaline. cAMP decomposition into AMP is catalyzed by the enzyme phosphodiesterase. cAMP is primarily used for intracellular signal transduction, such as transferring into cells the effects of hormones like glucagon and adrenaline, which cannot pass through the plasma membrane. cAMP is also involved in the activation of protein kinases. In addition, cAMP binds to and regulates the function of ion channels such as the HCN channels. Hyperpolarization-activated cyclic nucleotide‚Äìgated (HCN) channels are integral membrane proteins that serve as nonselective voltage-gated cation channels in the plasma membranes of heart and brain cells. HCN channels are sometimes referred to as pacemaker channels because they help to generate rhythmic activity within groups of heart and brain cells.
Acetoacetic acid (AcAc) is a weak organic acid that can be produced in the human liver under certain conditions of poor metabolism leading to excessive fatty acid breakdown (diabetes mellitus leading to diabetic ketoacidosis). It is then partially converted into acetone by decarboxylation and excreted either in urine or through respiration. Persistent mild hyperketonemia is a common finding in newborns. Ketone bodies serve as an indispensable source of energy for extrahepatic tissues, especially the brain and lung of developing rats. Another important function of ketone bodies is to provide acetoacetyl-CoA and acetyl-CoA for synthesis of cholesterol, fatty acids, and complex lipids. During the early postnatal period, acetoacetate and beta-hydroxybutyrate are preferred over glucose as substrates for synthesis of phospholipids and sphingolipids in accord with requirements for brain growth and myelination. Thus, during the first two weeks of postnatal development, when the accumulation of cholesterol and phospholipids accelerates, the proportion of ketone bodies incorporated into these lipids increases. On the other hand, an increased proportion of ketone bodies are utilized for cerebroside synthesis during the period of active myelination. In the lung, AcAc serves better than glucose as a precursor for the synthesis of lung phospholipids. The synthesized lipids, particularly dipalmityl phosphatidylcholine, are incorporated into surfactant, and thus have a potential role in supplying adequate surfactant lipids to maintain lung function during the early days of life (PMID: 3884391). The acid is also present in the metabolism of those undergoing starvation or prolonged physical exertion as part of gluconeogenesis. When ketone bodies are measured by way of urine concentration, acetoacetic acid, along with beta-hydroxybutyric acid or acetone, is what is detected.
Adenosine 3', 5'-diphosphate or PAP is a nucleotide that is closely related to ADP. It has two phosphate groups attached to the 5' and 3' positions of the pentose sugar ribose (instead of pyrophosphoric acid at the 5' position, as found in ADP), and the nucleobase adenine. PAP is converted to PAPS by Sulfotransferase and then back to PAP after the sulfotransferase reaction. Sulfotransferase (STs) catalyze the transfer reaction of the sulfate group from the ubiquitous donor 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to an acceptor group of numerous substrates. This reaction, often referred to as sulfuryl transfer, sulfation, or sulfonation, is widely observed from bacteria to humans and plays a key role in various biological processes such as cell communication, growth and development, and defense. PAP also appears to a role in bipolar depression. Phosphatases converting 3'-phosphoadenosine 5'-phosphate (PAP) into adenosine 5'-phosphate are of fundamental importance in living cells as the accumulation of PAP is toxic to several cellular systems. These enzymes are lithium-sensitive and we have characterized a human PAP phosphatase as a potential target of lithium therapy.
Epinephrine is a catecholamine, a sympathomimetic monoamine derived from the amino acids phenylalanine and tyrosine. It is the active sympathomimetic hormone secreted from the adrenal medulla in most species. It stimulates both the alpha- and beta- adrenergic systems, causes systemic vasoconstriction and gastrointestinal relaxation, stimulates the heart, and dilates bronchi and cerebral vessels. It is used in asthma and cardiac failure and to delay absorption of local anesthetics. Epinephrine also constricts arterioles in the skin and gut while dilating arterioles in leg muscles. It elevates the blood sugar level by increasing hydrolysis of glycogen to glucose in the liver, and at the same time begins the breakdown of lipids in adipocytes. Epinephrine has a suppressive effect on the immune system.
Pipecolic acid is a metabolite of lysine found in human physiological fluids such as urine, plasma and CSF. However, it is uncertain if pipecolic acid originates directly from food intake or from mammalian or intestinal bacterial enzyme metabolism. Recent studies suggest that plasma pipecolic acid, particularly the D-isomer, originates mainly from the catabolism of dietary lysine by intestinal bacteria rather than by direct food intake. In classic Zellweger syndrome (a cerebro-hepato-renal genetic disorder, OMIM 214100) pipecolic acid accumulate in the plasma of the patients. It is known that plasma pipecolic acid levels are also elevated in patients with chronic liver diseases. Pipecolic acid is moderately elevated in patients with pyridoxine-dependent seizures and might therefore be a possible biochemical marker for selecting candidates for pyridoxine therapy (Plecko et al 2000). Pipecolic acid was also elevated in CSF in these vitamin B6-responsive patients (PMID 12705501). Pipecolic acid is found to be associated with adrenoleukodystrophy, infantile Refsum disease, and peroxisomal biogenesis defect, which are also inborn errors of metabolism. Pipecolic acid is a biomarker for the consumption of dried and cooked beans.
Deoxyinosine is a nucleoside that is formed when hypoxanthine is attached to a deoxyribose ring (also known as a ribofuranose) via a beta-N9-glycosidic bond. Deoxyinosine is found in DNA while inosine is found in RNA. Inosine is a nucleic acid important for RNA editing. Adenosine deaminase (ADA) catalyzes the conversion of adenosine and deoxyadenosine to inosine and deoxyinosine, respectively. ADA-deficient individuals suffer from severe combined immunodeficiency (SCID) and are unable to produce significant numbers of mature T or B lymphocytes. This occurs as a consequence of the accumulation of ADA substrates or their metabolites. Inosine is also an intermediate in a chain of purine nucleotides reactions required for muscle movements. Moreover, deoxyinosine is found to be associated with purine nucleoside phosphorylase (PNP) deficiency, which is an inborn error of metabolism.
cis-Aconitic acid is an intermediate in the tricarboxylic acid cycle produced by the dehydration of citric acid. The enzyme aconitase (aconitate hydratase; EC 4.2.1.3) catalyses the stereo-specific isomerization of citrate to isocitrate via cis-aconitate in the tricarboxylic acid cycle.
Dehydroepiandrosterone (DHEA) is a natural steroid hormone produced from cholesterol by the adrenal glands. DHEA is also produced in the gonads, adipose tissue, and the brain. DHEA is structurally similar to and is a precursor of, androstenedione, testosterone, estradiol, estrone, and estrogen. It is the most abundant hormone in the human body. Most of DHEA is sulfated (dehydroepiandrosterone sulfate or DHEA-S) before secretion. DHEA-S is the sulfated version of DHEA; this conversion is reversibly catalyzed by sulfotransferase (SULT2A1) primarily in the adrenals, the liver, and small intestines. In blood, most DHEA is found as DHEA-S with levels that are about 300 times higher than free DHEA. Blood measurements of DHEA-S/DHEA are useful to detect excess adrenal activity as seen in adrenal cancer or hyperplasia, including certain forms of congenital adrenal hyperplasia. Women with polycystic ovary syndrome tend to have normal or mildly elevated levels of DHEA-S.
Cysteinylglycine is a naturally occurring dipeptide composed of cysteine and glycine. It is derived from the breakdown of glutathione (a tripeptide). In plasma, cysteinylglycine is in a reduced, oxidized, and protein-bound form (aminothiol) and interacts via redox and disulphide exchange reactions in a dynamic system referred to as redox thiol status (PMID: 8642471). Spermatozoa of sub-fertile men contain significantly higher thiol concentrations as compared with those of fertile men. The detrimental effect on embryo quality of a high homocysteine (Hcy) concentration in the ejaculate and in the follicular fluid is intriguing and may suggest that Hcy is inversely associated with fertility outcome (PMID: 16556671). Rheumatoid arthritis (RA) is a chronic inflammatory disease which involves the synovial membrane of multiple diarthroidal joints causing damage to cartilage and bones. The damage process seems to be related to an overproduction of oxygen reactive species inducing an oxidative perturbation with an increase in some oxidized forms (disulfides and protein mixed disulfides) and a decrease in free thiols (PMID: 15895891). Imipenem (thienamycin formamidine) is a broad-spectrum beta-lactam antibiotic, always used in combination with cilastatin in order to avoid the premature breakdown of imipenem by renal tubular dipeptidase. As this dipeptidase also hydrolyzes the glutathione metabolite cysteinylglycine, the therapeutic association of imipenem and cilastatin causes plasma levels of cysteinylglycine to increase significantly, while cysteine levels are decreased and homocysteine levels are unaffected. Therefore, antibiotic treatment using imipenem-cilastatin induces important metabolic changes that should not remain unrecognized (PMID: 15843241).
Dihydrothymine (CAS: 696-04-8) is an intermediate breakdown product of thymine. Dihydropyrimidine dehydrogenase catalyzes the reduction of thymine into 5,6-dihydrothymine; then dihydropyrimidinase hydrolyzes 5,6-dihydrothymine into N-carbamyl-beta-alanine. Finally, beta-ureidopropionase catalyzes the conversion of N-carbamyl-beta-alanine into beta-alanine. When present at abnormally high levels, dihydrothymine can be toxic, although the mechanism of toxicity is not clear. In particular, patients with dihydropyrimidinase deficiency exhibit highly increased concentrations of 5,6-dihydrouracil and 5,6-dihydrothymine; and moderately increased concentrations of uracil and thymine can be detected in urine. Dihydropyrimidinase deficiency is a disorder that can cause neurological and gastrointestinal problems in some affected individuals. The most common neurological abnormalities that occur are intellectual disability, seizures, weak muscle tone (hypotonia), abnormally small head size (microcephaly), and autistic behaviours that affect communication and social interaction. Gastrointestinal problems that occur in dihydropyrimidinase deficiency include the backflow of acidic stomach contents into the esophagus (gastroesophageal reflux) and recurrent episodes of vomiting.
Deoxyguanosine, also known as dG, belongs to the class of organic compounds known as purine 2'-deoxyribonucleosides. Purine 2'-deoxyribonucleosides are compounds consisting of a purine linked to a ribose which lacks a hydroxyl group at position 2‚Äô. Deoxyguanosine is a nucleoside consisting of the base guanine and the sugar deoxyribose. Deoxyguanosine is one of the four deoxyribonucleosides that make up DNA. Deoxyguanosine exists in all living species, ranging from bacteria to plants to humans. Deoxyguanosine participates in a number of enzymatic reactions. In particular, deoxyguanosine can be biosynthesized from 2'-deoxyguanosine 5'-monophosphate through the enzyme known as cytosolic purine 5'-nucleotidase. In addition, deoxyguanosine can be converted into 2'-deoxyguanosine 5'-monophosphate (dGMP); which is mediated by the enzyme deoxyguanosine kinase. Deoxyguanosine is involved in the rare, inherited metabolic disorder called the purine nucleoside phosphorylase deficiency (PNP deficiency). In particular PNP deficiency is characterized by elevated levels of dGTP (deoxyguanosine triphosphate). PNP accounts for approximately 4% of patients with severe combined immunodeficiency (PMID: 1931007). PNP-deficient patients suffer from recurrent infections, usually beginning in the first year of life. Two thirds of patients have evidence of neurologic disorders with spasticity, developmental delay and mental retardation. Deoxyguanosine can be converted to 8-hydroxy-deoxyguanosine (8-OHdG) due to hydroxyl radical attack at the C8 of guanine. 8-hydroxy-deoxyguanosine is a sensitive marker of the DNA damage This damage, if left unrepaired, has been proposed to contribute to mutagenicity and cancer promotion.
Glycerophosphorylcholine (GPC) is a choline derivative and one of the two major forms of choline storage (along with phosphocholine) in the cytosol. Glycerophosphorylcholine is also one of the four major organic osmolytes in renal medullary cells, changing their intracellular osmolyte concentration in parallel with extracellular tonicity during cellular osmoadaptation. As an osmolyte, Glycerophosphorylcholine counteracts the effects of urea on enzymes and other macromolecules. Kidneys (especially medullar cells), which are exposed under normal physiological conditions to widely fluctuating extracellular solute concentrations, respond to hypertonic stress by accumulating the organic osmolytes glycerophosphorylcholine (GPC), betaine, myo-inositol, sorbitol and free amino acids. Increased intracellular contents of these osmolytes are achieved by a combination of increased uptake (myo-inositol and betaine) and synthesis (sorbitol, GPC), decreased degradation (GPC) and reduced osmolyte release. GPC is formed in the breakdown of phosphatidylcholine (PtC). This pathway is active in many body tissues, including mammary tissue.
Dimethylamine (DMA) is an organic secondary amine. It is a colorless, liquefied and flammable gas with an ammonia and fish-like odor. Dimethylamine is abundantly present in human urine. Main sources of urinary DMA have been reported to include trimethylamine N-oxide, a common food component, and asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthesis. ADMA is excreted in the urine in part unmetabolized and in part after hydrolysis to DMA by dimethylarginine dimethylaminohydrolase (DDAH). Statistically significant increases in urinary DMA have been found in individuals after the consumption of fish and seafoods. The highest values were obtained for individuals that consumed coley, squid and whiting with cod, haddock, sardine, skate and swordfish (PMID: 18282650). It has also been identified as a uremic toxin according to the European Uremic Toxin Working Group (PMID: 22626821). As a pure chemical substance Dimethylamine is used as dehairing agent in tanning, in dyes, in rubber accelerators, in soaps and cleaning compounds and as an agricultural fungicide. In the body, DMA also undergoes nitrosation under weak acid conditions to give dimethlynitrosamine. Study has shown that DMA is a metabolite of Arthrobacter and Micrococcus (PMID: 11422368 ; PMID: 7191).
Cytidine is a nucleoside that is composed of the base cytosine linked to the five-carbon sugar D-ribose. Cytidine is a pyrimidine that besides being incorporated into nucleic acids, can serve as a substrate for the salvage pathway of pyrimidine nucleotide synthesis. It is a precursor of cytidine triphosphate (CTP) needed in the phosphatidylcholine (PC) and phosphatidylethanolamine (PE) biosynthetic pathways. These variations probably reflect the species differences in cytidine deaminase, the enzyme that converts cytidine to uridine in the body. The transport of cytidine into the brain's extracellular fluid, and then into neurons and glia, are essential prerequisites for cytidine to be utilized in the brain. An efficient mechanism mediating the brain uptake of circulating cytidine has not yet been demonstrated. The biosynthesis of PC, the most abundant phosphatide in the brain, via the Kennedy pathway requires phosphocholine and cytidine triphosphate (CTP), a cytidine nucleotide involved in the rate-limiting step. The enzyme that converts CTP to endogenous CDP-choline (CTP:phosphocholine cytidylyltransferase) is unsaturated at physiological brain CTP levels. APOBEC is a family of enzymes that has been discovered with the ability to deaminate cytidines on RNA or DNA. The human apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G protein (APOBEC3G, or hA3G), provides cells with an intracellular antiretroviral activity that is associated with the hypermutation of viral DNA through cytidine deamination. Indeed, hA3G belongs to a family of vertebrate proteins that contains one or two copies of a signature sequence motif unique to cytidine deaminases (CTDAs) (PMID: 16769123, 15780864, 16720547).
Dimethylglycine (DMG) is an amino acid derivative found in the cells of all plants and animals and can be obtained in the diet in small amounts from grains and meat. The human body produces DMG when metabolizing choline into glycine. Dimethylglycine that is not metabolized in the liver is transported by the circulatory system to body tissue. Dimethylglycine was popular with Russian athletes and cosmonauts owing to its reputed ability to increase endurance and reduce fatigue. DMG is also a byproduct of homocysteine metabolism. Homocysteine and betaine are converted to methionine and N,N-dimethylglycine by betaine-homocysteine methyltransferase. DMG in the urine is a biomarker for the consumption of legumes. It is also a microbial metabolite (PMID: 25901889).
Cytidine monophosphate, also known as 5'-cytidylic acid and abbreviated CMP, is a nucleotide. It is an ester of phosphoric acid with the nucleoside cytidine. CMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase cytosine. Cytidine monophosphate (CMP) is derived from cytidine triphosphate (CTP) with subsequent loss of two phosphates. The synthesis of the pyrimidines CTP and UTP occurs in the cytoplasm and starts with the formation of carbamoyl phosphate from glutamine and CO2. Next, aspartate undergoes a condensation reaction with carbamoyl-phosphate to form orotic acid. In a subsequent cyclization reaction, the enzyme Aspartate carbamoyltransferase forms N-carbamoyl-aspartate which is converted into dihydroorotic acid by Dihydroorotase. The latter is converted to orotate by Dihydroorotate oxidase. Orotate is covalently linked with a phosphorylated ribosyl unit with Orotate phosphoribosyltransferase (aka "PRPP transferase") catalyzing reaction, yielding orotidine monophosphate (OMP). Orotidine-5-phosphate is decarboxylated by Orotidine-5'-phosphate decarboxylase to form uridine monophosphate (UMP). UMP is phosphorylated by two kinases to uridine triphosphate (UTP) via two sequential reactions with ATP. CTP is subsequently formed by amination of UTP by the catalytic activity of CTP synthetase. Cytosine monophosphate (CMP) and uridine monophosphate (UMP) have been prescribed for the treatment of neuromuscular affections in humans. Patients treated with CMP/UMP recover from altered neurological functions. Additionally, the administration of CMP/UMP appears to favour the entry of glucose in the muscle and CMP/UMP may be important in maintaining the level of hepatic glycogen constant during exercise. [PMID:18663991].
Choline is a basic constituent of lecithin that is found in many plants and animal organs. It is important as a precursor of acetylcholine, as a methyl donor in various metabolic processes, and in lipid metabolism. Choline is now considered to be an essential vitamin. While humans can synthesize small amounts (by converting phosphatidylethanolamine to phosphatidylcholine), it must be consumed in the diet to maintain health. Required levels are between 425 mg/day (female) and 550 mg/day (male). Milk, eggs, liver, and peanuts are especially rich in choline. Most choline is found in phospholipids, namely phosphatidylcholine or lecithin. Choline can be oxidized to form betaine, which is a methyl source for many reactions (i.e. conversion of homocysteine into methionine). Lack of sufficient amounts of choline in the diet can lead to a fatty liver condition and general liver damage. This arises from the lack of VLDL, which is necessary to transport fats away from the liver. Choline deficiency also leads to elevated serum levels of alanine amino transferase and is associated with increased incidence of liver cancer.
Xylose or wood sugar is an aldopentose - a monosaccharide containing five carbon atoms and an aldehyde functional group. It has chemical formula C5H10O5 and is 40% as sweet as sucrose. Xylose is found in the embryos of most edible plants. The polysaccharide xylan, which is closely associated with cellulose, consists practically entirely of d-xylose. Corncobs, cottonseed hulls, pecan shells, and straw contain considerable amounts of this sugar. Xylose is also found in mucopolysaccharides of connective tissue and sometimes in the urine. Xylose is the first sugar added to serine or threonine residues during proteoglycan type O-glycosylation. Therefore xylose is involved in the biosythetic pathways of most anionic polysaccharides such as heparan sulphate and chondroitin sulphate. In medicine, xylose is used to test for malabsorption by administering a xylose solution to the patient after fasting. If xylose is detected in the blood and/or urine within the next few hours, it has been absorbed by the intestines. Xylose is said to be one of eight sugars which are essential for human nutrition, the others being galactose, glucose, mannose, N-acetylglucosamine, N-acetylgalactosamine, fucose, and sialic acid. (Wikipedia). Xylose in the urine is a biomarker for the consumption of apples and other fruits.
Cystathionine is a dipeptide formed by serine and homocysteine. Cystathioninuria is a prominent manifestation of vitamin-B6 deficiency. The transsulfuration of methionine yields homocysteine, which combines with serine to form cystathionine, the proximate precursor of cysteine through the enzymatic activity of cystathionase. In conditions in which cystathionine gamma-synthase or cystathionase is deficient, for example, there is cystathioninuria. Although cystathionine has not been detected in normal human serum or plasma by most conventional methods, gas chromatographic/mass spectrometric methodology detected a mean concentration of cystathionine in normal human serum of 140 nM, with a range of 65 to 301 nM. Cystathionine concentrations in CSF have been 10, 1, and 0.5 uM, and "not detected". Only traces (i.e., <1 uM) of cystathionine are present in normal CSF.587. Gamma-cystathionase deficiency (also known as Cystathioninuria), which is an autosomal recessive disorder (NIH: 2428), provided the first instance in which, in a human, the major biochemical abnormality due to a defined enzyme defect was clearly shown to be alleviated by administration of large doses of pyridoxine. The response in gamma-cystathionase-deficient patients is not attributable to correction of a preexisting deficiency of this vitamin (OMMBID, Chap. 88).
Deoxyadenosine is a derivative of the nucleoside adenosine. It is composed of adenine attached to a deoxyribose moiety via a N9-glycosidic bond. Deoxyribose differs from ribose by the absence of oxygen in the 3' position of its ribose ring. Deoxyadenosine is a critical component of DNA. When present in sufficiently high levels, deoxyadensoine can act as an immunotoxin and a metabotoxin. An immunotoxin disrupts, limits the function, or destroys immune cells. A metabotoxin is an endogenous metabolite that causes adverse health effects at chronically high levels. Chronically high levels of deoxyadenosine are associated with adenosine deaminase (ADA) deficiency, an inborn error of metabolism. ADA deficiency damages the immune system and causes severe combined immunodeficiency (SCID). People with SCID lack virtually all immune protection from bacteria, viruses, and fungi. They are prone to repeated and persistent infections that can be very serious or life-threatening. These infections are often caused by "opportunistic" organisms that ordinarily do not cause illness in people with a normal immune system. The main symptoms of ADA deficiency are pneumonia, chronic diarrhea, and widespread skin rashes. The mechanism by which dATP functions as an immunotoxin is as follows: because deoxyadenosine is a precursor to dATP, a buildup of dATP in cells inhibits ribonucleotide reductase and prevents DNA synthesis, so cells are unable to divide. Since developing T cells and B cells are some of the most mitotically active cells, they are unable to divide and propagate to respond to immune challenges. High levels of deoxyadenosine also lead to an increase in S-adenosylhomocysteine, which is toxic to immature lymphocytes.
Galactitol or dulcitol is a sugar alcohol that is a metabolic breakdown product of galactose. Galactose is derived from lactose in food (such as dairy products). When lactose is broken down by the enzyme lactase it produces glucose and galactose. Galactitol has a slightly sweet taste. It is produced from galactose in a reaction catalyzed by aldose reductase. When present in sufficiently high levels, galactitol can act as a metabotoxin, a neurotoxin, and a hepatotoxin. A neurotoxin is a compound that disrupts or attacks neural cells and neural tissue. A hepatotoxin as a compound that disrupts or attacks liver tissue or liver cells. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of galactitol are associated with at least two inborn errors of metabolism, including galactosemia and galactosemia type II. Galactosemia is a rare genetic metabolic disorder that affects an individual's ability to metabolize the sugar galactose properly. Excess lactose consumption in individuals with galactose intolerance or galactosemia activates aldose reductase to produce galactitol, thus depleting NADPH and leading to lowered glutathione reductase activity. As a result, hydrogen peroxide or other free radicals accumulate causing serious oxidative damage to various cells and tissues. In individuals with galactosemia, the enzymes needed for the further metabolism of galactose (galactose-1-phosphate uridyltransferase) are severely diminished or missing entirely, leading to toxic levels of galactose 1-phosphate, galactitol, and galactonate. High levels of galactitol in infants are specifically associated with hepatomegaly (an enlarged liver), cirrhosis, renal failure, cataracts, vomiting, seizure, hypoglycemia, lethargy, brain damage, and ovarian failure.
Glycerylphosphorylethanolamine is a membrane breakdown product resulting from the cleavage of the lipid group from glycerophosphoethanlomine fatty acids (i.e. phosphatidylethanolamine). It acts as a growth stimulant for hepatocytes.
Homovanillic acid (HVA), also known as homovanillate, belongs to the class of organic compounds known as methoxyphenols. Methoxyphenols are compounds containing a methoxy group attached to the benzene ring of a phenol moiety. HVA is also classified as a catechol.  HVA is a major catecholamine metabolite that is produced by a consecutive action of monoamine oxidase and catechol-O-methyltransferase on dopamine. HVA is typically elevated in patients with catecholamine-secreting tumors (such as neuroblastoma, pheochromocytoma, and other neural crest tumors). HVA levels are also used in monitoring patients who have been treated for these kinds tumors. HVA levels may also be altered in disorders of catecholamine metabolism such as monoamine oxidase-A (MOA) deficiency. MOA deficiency can cause decreased urinary HVA values, while a deficiency of dopamine beta-hydrolase (the enzyme that converts dopamine to norepinephrine) can cause elevated urinary HVA values. Within humans, HVA participates in a number of enzymatic reactions. In particular, HVA and pyrocatechol can be biosynthesized from 3,4-dihydroxybenzeneacetic acid and guaiacol. This reaction is catalyzed by the enzyme known as catechol O-methyltransferase. In addition, HVA can be biosynthesized from homovanillin through the action of the enzyme known aldehyde dehydrogenase. HVA has recently been found in a number of beers and appears to arise from the fermentation process (https://doi.org/10.1006/fstl.1999.0593). HVA is also a metabolite of Bifidobacterium (PMID: 24958563) and the bacterial breakdown of dietary flavonoids. Dietary flavonols commonly found in tomatoes, onions, and tea, can lead to significantly elevated levels of urinary HVA (PMID: 20933512). Likewise, the microbial digestion of hydroxytyrosol (found in olive oil) can also lead to elevated levels of HVA in humans (PMID: 11929304).
Glyoxylic acid or oxoacetic acid is an organic compound that is both an aldehyde and a carboxylic acid. Glyoxylic acid is a liquid with a melting point of -93°C and a boiling point of 111°C. It is an intermediate of the glyoxylate cycle, which enables certain organisms to convert fatty acids into carbohydrates. The conjugate base of glyoxylic acid is known as glyoxylate (PMID: 16396466). In humans, glyoxylate is produced via two pathways: (1) through the oxidation of glycolate in peroxisomes and (2) through the catabolism of hydroxyproline in mitochondria. In the peroxisomes, glyoxylate is converted into glycine by glyoxylate aminotransferase (AGT1) or into oxalate by glycolate oxidase. In the mitochondria, glyoxylate is converted into glycine by mitochondrial glyoxylate aminotransferase AGT2 or into glycolate by glycolate reductase. A small amount of glyoxylate is converted into oxalate by cytoplasmic lactate dehydrogenase. Glyoxylic acid is found to be associated with primary hyperoxaluria I, which is an inborn error of metabolism. Under certain circumstances, glyoxylate can be a nephrotoxin and a metabotoxin. A nephrotoxin is a compound that causes damage to the kidney and kidney tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. High levels of glyoxylate are involved in the development of hyperoxaluria, a key cause of nephrolithiasis (commonly known as kidney stones). Glyoxylate is both a substrate and inductor of sulfate anion transporter-1 (SAT-1), a gene responsible for oxalate transportation, allowing it to increase SAT-1 mRNA expression, and as a result oxalate efflux from the cell. The increased oxalate release allows the buildup of calcium oxalate in the urine, and thus the eventual formation of kidney stones. As an aldehyde, glyoxylate is also highly reactive and will modify proteins to form advanced glycation products (AGEs).
Folic acid or folate, is a vitamin that belongs to the class of compounds known as pterins. Chemically, folate consists of three distinct chemical moieties linked together. A pterin (2-amino-4-hydroxy-pteridine) linked by a methylene bridge to a p-aminobenzoyl group that in turn is linked through an amide linkage to glutamic acid. It is a member of the vitamin B family and is primarily known as vitamin B9. Folate is required for the body to make DNA and RNA and metabolize amino acids necessary for cell division for the hematopoietic system. As humans cannot make folate, it is required in the diet, making it an essential nutrient (i.e. a vitamin). Folate occurs naturally in many foods including mushrooms, spinach, yeast, green leaves, and grasses (poaceae). Folic acid, being biochemically inactive, is converted to tetrahydrofolic acid and methyltetrahydrofolate by the enzyme known as dihydrofolate reductase. Tetrahydrofolate and methyltetrahydrofolate are transported across cells by receptor-mediated endocytosis where they are needed to maintain normal erythropoiesis, synthesize purine and thymidylate nucleic acids, interconvert amino acids and generate formic acid. Folic acid is used in the treatment and prevention of folate deficiencies and megaloblastic anemia. Folic acid is also used as a supplement by women during pregnancy to reduce the risk of neural tube defects (NTDs) in babies. Low levels in early pregnancy are believed to be the cause of more than half of babies born with NTDs (PMID: 28097362). Folic acid is also a microbial metabolite produced by Bifidobacterium and Lactobacillus (PMID: 22254078).
Fructose 6-phosphate (F6P) belongs to the class of organic compounds known as hexose phosphates. These are carbohydrate derivatives containing a hexose substituted by one or more phosphate groups. F6P is a derivative of fructose, which has been phosphorylated at the 6-hydroxy group. Fructose 6-phosphate is a fundamental metabolite and exists in all living species, ranging from bacteria to plants to humans. The great majority of glucose is converted to fructose 6-phosphate as part of the glycolytic metabolic pathway (glycolysis). Specifically, F6P is produce is produced by the isomerisation of glucose 6-phosphate via the enzyme phosphoglucose isomerase. F6P is in turn further phosphorylated to fructose-1,6-bisphosphate by the enzyme phosphofructokinase-1. Glycolysis is the metabolic pathway that converts glucose into pyruvic acid. The free energy released in this process is used to form ATP and reduced nicotinamide adenine dinucleotide (NADH). In addition to its key involvement in glycolysis, fructose 6-phosphate can also be biosynthesized from glucosamine 6-phosphate via the enzyme glucosamine-6-phosphate isomerase 1. In addition, fructose 6-phosphate and L-glutamine can be converted into glucosamine 6-phosphate and L-glutamic acid through the action of the enzyme glutamine--fructose-6-phosphate aminotransferase.
Glycerol 3-phosphate is a chemical intermediate in the glycolysis metabolic pathway. It is commonly confused with the similarly named glycerate 3-phosphate or glyceraldehyde 3-phosphate. Glycerol 3-phosphate is produced from glycerol, the triose sugar backbone of triglycerides and glycerophospholipids, by the enzyme glycerol kinase. Glycerol 3-phospate may then be converted by dehydrogenation to dihydroxyacetone phosphate (DHAP) by the enzyme glycerol-3-phosphate dehydrogenase. DHAP can then be rearranged into glyceraldehyde 3-phosphate (GA3P) by triose phosphate isomerase (TIM), and feed into glycolysis. The glycerol 3-phosphate shuttle is used to rapidly regenerate NAD+ in the brain and skeletal muscle cells of mammals (wikipedia).
Glucuronic acid (CAS: 6556-12-3) is a carboxylic acid that has the structure of a glucose molecule that has had its sixth carbon atom (of six total) oxidized. The salts of glucuronic acid are known as glucuronates. Glucuronic acid is highly soluble in water. In humans, glucuronic acid is often linked to toxic or poisonous substances to allow for subsequent elimination, and to hormones to allow for easier transport. These linkages involve O-glycosidic bonds. The process is known as glucuronidation, and the resulting substances are known as glucuronides (or glucuronosides). Glucuronidation uses UDP-glucuronic acid (glucuronic acid linked via a glycosidic bond to uridine diphosphate) as an intermediate. UDP-glucuronic acid is formed in the liver of all animals.
Guanidoacetic acid (GAA), also known as guanidinoacetate or glycocyamine, belongs to the class of organic compounds known as alpha amino acids and derivatives. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon), or a derivative thereof. Guanidinoacetic acid was first prepared in 1861 by Adolph Strecker by reaction of cyanamide with glycine in aqueous solution. Manufactured guanidinoacetic acid is primarily used a feed additive approved by EFSA in poultry farming (for fattening), and pigs for fattening. Guanidoacetic acid exists naturally in all vertebrates. It is formed primarily in the kidneys by transferring the guanidine group of L-arginine to the amino acid glycine via the enzyme known as L-Arg:Gly-amidinotransferase (AGAT). In a further step, guanidinoacetate is methylated to generate creatine using S-adenosyl methionine (as the methyl donor) via the enzyme known as guanidinoacetate N-methyltransferase (GAMT). The resulting creatine is released into the bloodstream. Elevated levels of guanidoacetic acid are a characteristic of an inborn metabolic disorder known as Guanidinoacetate Methyltransferase (GAMT) Deficiency. GAMT converts guanidinoacetate to creatine and deficiency of this enzyme results in creatine depletion and accumulation of guanidinoacetate The disorder is transmitted in an autosomal recessive fashion and is localized to mutations on chromosome 19p13.3. GAMT deficiency is characterized by developmental arrest, medication-resistant epilepsy (myoclonic, generalized tonic-clonic, partial complex, atonic), severe speech impairment, progressive dystonia, dyskinesias, hypotonia, ataxia, and autistic-like behavior.
Glycerol or glycerin is a colourless, odourless, viscous liquid that is sweet-tasting and mostly non-toxic. It is widely used in the food industry as a sweetener and humectant and in pharmaceutical formulations. Glycerol is an important component of triglycerides (i.e. fats and oils) and of phospholipids. Glycerol is a three-carbon substance that forms the backbone of fatty acids in fats. When the body uses stored fat as a source of energy, glycerol and fatty acids are released into the bloodstream. The glycerol component can be converted into glucose by the liver and provides energy for cellular metabolism. Normally, glycerol shows very little acute toxicity and very high oral doses or acute exposures can be tolerated. On the other hand, chronically high levels of glycerol in the blood are associated with glycerol kinase deficiency (GKD). GKD causes the condition known as hyperglycerolemia, an accumulation of glycerol in the blood and urine. There are three clinically distinct forms of GKD: infantile, juvenile, and adult. The infantile form is the most severe and is associated with vomiting, lethargy, severe developmental delay, and adrenal insufficiency. The mechanisms of glycerol toxicity in infants are not known, but it appears to shift metabolism towards chronic acidosis. Acidosis typically occurs when arterial pH falls below 7.35. In infants with acidosis, the initial symptoms include poor feeding, vomiting, loss of appetite, weak muscle tone (hypotonia), and lack of energy (lethargy). These can progress to heart, liver, and kidney abnormalities, seizures, coma, and possibly death. These are also the characteristic symptoms of untreated GKD. Many affected children with organic acidemias experience intellectual disability or delayed development. Patients with the adult form of GKD generally have no symptoms and are often detected fortuitously.
Fumaric acid is a dicarboxylic acid. It is a precursor to L-malate in the Krebs tricarboxylic acid (TCA) cycle. It is formed by the oxidation of succinic acid by succinate dehydrogenase. Fumarate is converted by the enzyme fumarase to malate. Fumaric acid has recently been identified as an oncometabolite or an endogenous, cancer causing metabolite. High levels of this organic acid can be found in tumors or biofluids surrounding tumors. Its oncogenic action appears to due to its ability to inhibit prolyl hydroxylase-containing enzymes. In many tumours, oxygen availability becomes limited (hypoxia) very quickly due to rapid cell proliferation and limited blood vessel growth. The major regulator of the response to hypoxia is the HIF transcription factor (HIF-alpha). Under normal oxygen levels, protein levels of HIF-alpha are very low due to constant degradation, mediated by a series of post-translational modification events catalyzed by the prolyl hydroxylase domain-containing enzymes PHD1, 2 and 3, (also known as EglN2, 1 and 3) that hydroxylate HIF-alpha and lead to its degradation. All three of the PHD enzymes are inhibited by fumarate. Fumaric acid is found to be associated with fumarase deficiency, which is an inborn error of metabolism. It is also a metabolite of Aspergillus.
Glyceric acid is a colourless syrupy acid, obtained from oxidation of glycerol. It is a compound that is secreted excessively in the urine by patients suffering from D-glyceric aciduria, an inborn error of metabolism, and D-glycerate anemia. Deficiency of human glycerate kinase leads to D-glycerate acidemia/D-glyceric aciduria. Symptoms of the disease include progressive neurological impairment, hypotonia, seizures, failure to thrive, and metabolic acidosis. At sufficiently high levels, glyceric acid can act as an acidogen and a metabotoxin. An acidogen is an acidic compound that induces acidosis, which has multiple adverse effects on many organ systems. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Glyceric acid is an organic acid. Abnormally high levels of organic acids in the blood (organic acidemia), urine (organic aciduria), the brain, and other tissues lead to general metabolic acidosis. Acidosis typically occurs when arterial pH falls below 7.35. In infants with acidosis, the initial symptoms include poor feeding, vomiting, loss of appetite, weak muscle tone (hypotonia), and lack of energy (lethargy). These can progress to heart abnormalities, seizures, coma, and possibly death. These are also the characteristic symptoms of untreated glyceric aciduria. Many affected children with organic acidemias experience intellectual disability or delayed development. In adults, acidosis or acidemia is characterized by headaches, confusion, feeling tired, tremors, sleepiness, and seizures. Elevated values may also be due to microbial sources such as yeast (Aspergillus, Penicillium, probably Candida) or due to dietary sources containing glycerol (glycerine). Glyceric acid is isolated from various plants (e.g. brassicas, pulses, and Vicia faba).
Formic acid is the simplest carboxylic acid. Formate is an intermediate in normal metabolism. It takes part in the metabolism of one-carbon compounds and its carbon may appear in methyl groups undergoing transmethylation. It is eventually oxidized to carbon dioxide. Formate is typically produced as a byproduct in the production of acetate. It is responsible for both metabolic acidosis and disrupting mitochondrial electron transport and energy production by inhibiting cytochrome oxidase activity, the terminal electron acceptor of the electron transport chain. Cell death from cytochrome oxidase inhibition by formate is believed to result partly from depletion of ATP, reducing energy concentrations so that essential cell functions cannot be maintained. Furthermore, inhibition of cytochrome oxidase by formate may also cause cell death by increased production of cytotoxic reactive oxygen species (ROS) secondary to the blockade of the electron transport chain. In nature, formic acid is found in the stings and bites of many insects of the order Hymenoptera, including bees and ants. The principal use of formic acid is as a preservative and antibacterial agent in livestock feed. When sprayed on fresh hay or other silage, it arrests certain decay processes and causes the feed to retain its nutritive value longer. Urinary formate is produced by Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Enterobacter, Acinetobacter, Proteus mirabilis, Citrobacter frundii, Enterococcus faecalis, Streptococcus group B, Staphylococcus saprophyticus (PMID: 22292465).
D-Galactose (CAS: 59-23-4) is an aldohexose that occurs naturally in the D-form in lactose, cerebrosides, gangliosides, and mucoproteins. D-Galactose is an energy-providing nutrient and also a necessary basic substrate for the biosynthesis of many macromolecules in the body. Metabolic pathways for D-galactose are important not only for the provision of these pathways but also for the prevention of D-galactose metabolite accumulation. The main source of D-galactose is lactose in the milk of mammals, but it can also be found in some fruits and vegetables. Utilization of D-galactose in all living cells is initiated by the phosphorylation of the hexose by the enzyme galactokinase (E.C. 2.7.1.6) (GALK) to form D-galactose-1-phosphate. In the presence of D-galactose-1-phosphate uridyltransferase (E.C. 2.7.7.12) (GALT) D-galactose-1-phosphate is exchanged with glucose-1-phosphate in UDP-glucose to form UDP-galactose. Glucose-1-phosphate will then enter the glycolytic pathway for energy production. Deficiency of the enzyme GALT in galactosemic patients leads to the accumulation of D-galactose-1-phosphate. Classic galactosemia, a term that denotes the presence of D-galactose in the blood, is the rare inborn error of D-galactose metabolism, diagnosed by the deficiency of the second enzyme of the D-galactose assimilation pathway, GALT, which, in turn, is caused by mutations at the GALT gene (PMID: 15256214, 11020650, 10408771). Galactose in the urine is a biomarker for the consumption of milk.
Estrone is a major mammalian estrogen. The conversion of the natural C19 steroids, testosterone and androstenedione into estrone is dependent on a complex key reaction catalyzed by the cytochrome P450 aromatase (EC 1.14.14.1, unspecific monooxygenase), which is expressed in many tissues of the adult human (e.g. ovary, fat tissue), but not in the liver. The ovaries after menopause continue to produce androstenedione and testosterone in significant amounts and these androgens are converted in fat, muscle, and skin into estrone. When women between the ages of 45 and 64 years have prophylactic oophorectomy (when hysterectomy is performed for benign disease to prevent the development of ovarian cancer), evidence suggests that oophorectomy increases the subsequent risk of coronary heart disease (CHD) and osteoporosis. Whereas 14,000 women die of ovarian cancer every year nearly 490,000 women die of heart disease and 48,000 women die within 1 year after hip fracture. Therefore, the decision to perform prophylactic oophorectomy should be approached with great caution for the majority of women who are at low risk of developing ovarian cancer. Steroid sulfatase (EC 3.1.6.2, STS) hydrolyzes steroid sulfates, such as estrone sulfate to estrone which can be converted to steroids with potent estrogenic properties, that is, estradiol; STS activity is much higher in breast tumors and high levels of STS mRNA expression in tumors are associated with a poor prognosis. The biological roles of estrogens in tumorigenesis are certainly different between the endometrium and breast, although both are considered "estrogen-dependent tissues". 17beta-hydroxysteroid dehydrogenases (EC 1.1.1.62, 17-HSDs) are enzymes involved in the formation of active sex steroids. estrone is interconverted by two enzymes 17-HSD types. Type 1 converts estrone to estradiol and Type 2 catalyzes the reverse reaction. (PMID: 17653961, 17513923, 17470679, 17464097).
Ethanolamine (MEA), also known as monoethanolamine, aminoethanol or glycinol, belongs to the class of organic compounds known as 1,2-aminoalcohols (or simply aminoalcohols). These are organic compounds containing an alkyl chain with an amine group bound to the C1 atom and an alcohol group bound to the C2 atom. Ethanolamine is a colorless, viscous liquid with an odor reminiscent of ammonia. In pharmaceutical formulations, ethanolamine is used primarily for buffering or preparation of emulsions. Ethanolamine can also be used as pH regulator in cosmetics. Biologically, ethanolamine is an initial precursor for the biosynthesis of two primary phospholipid classes, phosphatidylcholine (PC) and phosphatidylethanolamine (PE). In this regard, ethanolamine is the second-most-abundant head group for phospholipids. Ethanolamine serves as a precursor for a variety of N-acylethanolamines (NAEs). These are molecules that modulate several animal and plant physiological processes such as seed germination, plant‚Äìpathogen interactions, chloroplast development and flowering (PMID: 30190434). Ethanolamine, when combined with arachidonic acid (C20H32O2; 20:4, œâ-6), can also form the endocannabinoid anandamide. Ethanolamine can be converted to phosphoethanolamine via the enzyme known as ethanolamine kinase. the two substrates of this enzyme are ATP and ethanolamine, whereas its two products are ADP and O-phosphoethanolamine. In most plants ethanolamine is biosynthesized by decarboxylation of serine via a pyridoxal 5'-phosphate-dependent l-serine decarboxylase (SDC). Ethanolamine exists in all living species, ranging from bacteria to plants to humans. Ethanolamine has been detected, but not quantified in, several different foods, such as narrowleaf cattails, mung beans, blackcurrants, white cabbages, and bilberries.
Gluconolactone, also known as glucono-delta-lactone or GDL (gluconate), belongs to the class of organic compounds known as gluconolactones. These are polyhydroxy acids (PHAs) containing a gluconolactone molecule, which is characterized by a tetrahydropyran substituted by three hydroxyl groups, one ketone group, and one hydroxymethyl group. Gluconolactone is a lactone of D-gluconic acid. Gluconolactone can be produced by enzymatic oxidation of D-glucose via the enzyme glucose oxidase. It is a fundamental metabolite found in all organisms ranging from bacteria to plants to animals. Gluconolactone has metal chelating, moisturizing and antioxidant activities. Its ability in free radicals scavenging accounts for its antioxidant properties. Gluconolactone, is also used as a food additive with the E-number E575. In foods it is used as a sequestrant, an acidifier or a curing, pickling, or leavening agent. Gluconolactone is also used as a coagulant in tofu processing. Gluconolactone is widely used as a skin exfoliant in cosmetic products, where it is noted for its mild exfoliating and hydrating properties. Pure gluconolactone is a white odorless crystalline powder. It is pH-neutral, but hydrolyses in water to gluconic acid which is acidic, adding a tangy taste to foods. Gluconic acid has roughly a third of the sourness of citric acid. One gram of gluconolactone yields roughly the same amount of metabolic energy as one gram of sugar.
Gentisic acid, also known as gentisate or 2,5-dioxybenzoate, belongs to the class of organic compounds known as hydroxybenzoic acid derivatives. Hydroxybenzoic acid derivatives are compounds containing a hydroxybenzoic acid (or a derivative), which is a benzene ring bearing a carboxyl and a hydroxyl groups. Gentisic acid is also classified as a dihydroxybenzoic acid.  It is a derivative of benzoic acid and a minor (1%) product of the metabolic break down of aspirin, which is excreted by the kidneys. Gentisic acid is found in essentially all organisms ranging from bacteria to fungi to plants to animals. Gentisic acid has been associated with a number of useful effects on human health and exhibits anti-inflammatory, antigenotoxic, hepatoprotective, neuroprotective, antimicrobial, and especially antioxidant activities (PMID: 31825145). It is widely distributed in plants as a secondary plant product such as Gentiana spp., Citrus spp., Vitis vinifera, Pterocarpus santalinus, Helianthus tuberosus, Hibiscus rosa-sinensis, Olea europaea, and Sesamum indicum and in fruits such as avocados, batoko plum, kiwi fruits, apple, bitter melon, black berries, pears, and some mushrooms (PMID: 31825145). Gentisic acid is found in higher concentrations in a number of foods such as tarragons, common thymes, and common sages and in a lower concentration in grape wines, rosemaries, and sweet marjorams. Gentisic acid has also been shown to act as a pathogen-inducible signal for the activation of plant defenses in tomato plants and cucumbers (PMID: 16321412; https://doi.org/10.1094/MPMI.1999.12.3.227).
Estriol is a metabolite of estrone metabolized via 16alpha-hydroxyestrone through the enzyme 16alpha-hydroxysteroid dehydrogenase (EC 1.1.1.147) or to 2- or 4-hydroxyestrone (catechol estrogens) by the action of catecho-O-methyltransferase (EC 2.1.1.6). The latter metabolites can be formed in the brain and may compete with receptors for catecholamines. Metabolites are conjugated with sulfate or glucuronide before excretion by the kidney. During pregnancy, estriol constitutes 60-70% of the total estrogens, increasing to 300-500-fold in relation to non-pregnant women. The late term human fetus produces relatively large amounts of 16 alphahydroxy DHEA, which serves the mother as a precursor of estriol. It has been shown that 90% of the precursors for the formation of estriol are of fetal origin. If abnormal maternal serum screening results, specifically low levels of unconjugated estriol in the second trimester are detected, a diagnosis of Smith-Lemli-Opitz syndrome (SLOS),or RSH is suspected. SLOS is an autosomal recessive disorder caused by mutations of the gene encoding 7-dehydrocholesterol reductase (EC 1.3.1.21, DHCR7). (PMID: 16202579, 16112271, 16097001).
Malic acid (CAS: 6915-15-7) is a tart-tasting organic dicarboxylic acid that plays a role in many sour or tart foods. Apples contain malic acid, which contributes to the sourness of a green apple. Malic acid can make a wine taste tart, although the amount decreases with increasing fruit ripeness (Wikipedia). In its ionized form, malic acid is called malate. Malate is an intermediate of the TCA cycle along with fumarate. It can also be formed from pyruvate as one of the anaplerotic reactions. In humans, malic acid is both derived from food sources and synthesized in the body through the citric acid cycle or Krebs cycle which takes place in the mitochondria. Malate's importance to the production of energy in the body during both aerobic and anaerobic conditions is well established. Under aerobic conditions, the oxidation of malate to oxaloacetate provides reducing equivalents to the mitochondria through the malate-aspartate redox shuttle. During anaerobic conditions, where a buildup of excess reducing equivalents inhibits glycolysis, malic acid's simultaneous reduction to succinate and oxidation to oxaloacetate is capable of removing the accumulating reducing equivalents. This allows malic acid to reverse hypoxia's inhibition of glycolysis and energy production. In studies on rats, it has been found that only tissue malate is depleted following exhaustive physical activity. Other key metabolites from the citric acid cycle needed for energy production were found to be unchanged. Because of this, a deficiency of malic acid has been hypothesized to be a major cause of physical exhaustion. Notably, the administration of malic acid to rats has been shown to elevate mitochondrial malate and increase mitochondrial respiration and energy production. Malic acid has been found to be a metabolite in Aspergillus (Hugo Vanden Bossche, D.W.R. Mackenzie and G. Cauwenbergh. Aspergillus and Aspergillosis, 1987).
D-Maltose, also known as maltose, maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an alpha (1‚Üí4) bond. Its name comes from malt, combined with the suffix '-ose' which is used in names of sugars. Maltose is a key structural motif of starch. When alpha-amylase breaks down starch, it removes two glucose units at a time, producing maltose. Maltose can be further broken down to glucose by the maltase enzyme, which catalyses the hydrolysis of the glycosidic bond. D-maltose exists in all living species, ranging from bacteria to plants to humans. Within humans, D-maltose participates in a number of enzymatic reactions. In particular, maltose can be converted into glucose; which is mediated by the enzyme maltase-glucoamylase. In addition, maltose can be converted into glucose through its interaction with the enzyme glycogen debranching enzyme. Maltose is found in high concentrations in oriental wheats and in a lower concentrations in sweet potato, grape wines, yellow pond-lilies, sunflowers, and spinach. Maltose is a component of malt, a substance which is obtained in the process of allowing grain to soften in water and germinate. It is also present in highly variable quantities in partially hydrolysed starch products like maltodextrin, corn syrup and acid-thinned starch. Maltose has a sweet taste but is only about 30‚Äì60% as sweet as sucrose, depending on the concentration.
Methylamine occurs endogenously from amine catabolism and its tissue levels increase in some pathological conditions, including diabetes. Interestingly, methylamine and ammonia levels are reciprocally controlled by a semicarbazide-sensitive amine oxidase activity that deaminates methylamine to formaldehyde with the production of ammonia and hydrogen peroxide. Methylamine also targets the voltage-operated neuronal potassium channels, probably inducing release of neurotransmitter(s). Semicarbazide-sensitive amine oxidase (SSAO) catalyzes the deamination of primary amines. Such deamination has been shown capable of regulating glucose transport in adipose cells. It has been independently discovered that the primary structure of vascular adhesion protein-1 (VAP-1) is identical to SSAO. Increased serum SSAO activities have been found in patients with diabetic mellitus, vascular disorders, and Alzheimer's disease. The SSAO-catalyzed deamination of endogenous substrates like methylamine led to production of toxic formaldehyde. Chronic elevated methylamine increases the excretion of malondialdehyde and microalbuminuria. Amine oxidase substrates such as methylamine have been shown to stimulate glucose uptake by increasing the recruitment of the glucose transporter GLUT4 from vesicles within the cell to the cell surface. Inhibition of this effect by the presence of semicarbazide and catalase led to the suggestion that the process is mediated by the hydrogen peroxide produced in the oxidation of these amines (PMID: 16049393 , 12686132 , 17406961). Methylamine has been identified as a uremic toxin according to the European Uremic Toxin Working Group (PMID: 22626821).
Fucose (CAS: 2438-80-4) is a hexose deoxy sugar with the chemical formula C6H12O5. L-Fucose (6-deoxy-L-galactose) is a monosaccharide that is a common component of many N- and O-linked glycans and glycolipids produced by mammalian cells. It is the fundamental subunit of the fucoidan polysaccharide. As a free sugar, L-fucose is normally found at very low levels in mammals. It is unique in that it is the only levorotatory sugar synthesized and utilized by mammals. Fucose polymers are synthesized by fucosyltransferases. All fucosyltransferases utilize a nucleotide-activated form of fucose, GDP-fucose, as a fucose donor in the construction of fucosylated oligosaccharides. The ABO blood group antigens are among the most well known fucosylated glycans. The alpha-1->3 linked core fucose is a suspected carbohydrate antigen for IgE-mediated allergy. Two structural features distinguish fucose from other six-carbon sugars present in mammals: the lack of a hydroxyl group on the carbon at the 6-position (C-6) and the L-configuration. In fucose-containing glycan structures, fucosylated glycans, fucose can exist as a terminal modification or serve as an attachment point for adding other sugars. Fucose is metabolized by an enzyme called alpha-fucosidase. Fucose is secreted in urine when the liver is damaged. Free L-fucose in serum and urine can be used as a marker for cancer, cirrhosis, alcoholic liver disease and gastric ulcers (PMID: 2311216, 8488966). Elevated levels of serum fucose have been reported in breast cancer, ovarian cancer, lung cancer, liver cancer, diabetes, and cardiovascular disease. It has been shown that feeding rats a diet high in L-fucose induces neuropathy similar to that seen in diabetics.
Inosinic acid, also known as inosine monophosphate, IMP, 5'-inosinate or 5'-IMP, belongs to the class of organic compounds known as purine ribonucleoside monophosphates. These are nucleotides consisting of a purine base linked to a ribose to which one monophosphate group is attached. IMP is also classified as a nucleotide (a nucleoside monophosphate). Inosinic acid exists in all living species, ranging from bacteria to plants to humans. IMP is widely used as a flavor enhancer. In the food industry it is known as E number reference E630.  Inosinic acid can be converted into various salts including disodium inosinate (E631), dipotassium inosinate (E632), and calcium inosinate (E633). These three inosinate compounds are used as flavor enhancers for the basic taste umami. These inosinate salts are mostly used in soups, sauces, and seasonings for the intensification and balance of the flavor of meat. Inosinic acid is typically obtained from chicken byproducts or other meat industry waste. Inosinic acid or IMP is important in metabolism. It is the ribonucleotide of hypoxanthine and the first nucleotide formed during the synthesis of purine nucleotides. It can also be formed by the deamination of adenosine monophosphate by AMP deaminase.  GMP is formed by the inosinate oxidation to xanthylate (XMP). Within humans, inosinic acid participates in a number of enzymatic reactions. In particular, inosinic acid can be converted into phosphoribosyl formamidocarboxamide; which is catalyzed by the bifunctional purine biosynthesis protein. In addition, inosinic acid can be converted into xanthylic acid; which is catalyzed by the enzyme inosine-5'-monophosphate dehydrogenase 1.
Maleic acid is a dicarboxylic acid, a molecule with two carboxyl groups. It consists of an ethylene group flanked by two carboxylic acid groups. Maleic acid is the cis isomer of butenedioic acid, whereas fumaric acid is the trans isomer. The cis isomer is the less stable one of the two; the difference in heat of combustion is 22.7 kJ/mol. The physical properties of maleic acid are very different from that of fumaric acid. Maleic acid is soluble in water whereas fumaric acid is not and the melting point of maleic acid (130 - 131 oC) is also much lower than that of fumaric acid (287 oC). Maleic acid is converted into maleic anhydride by dehydration, to malic acid by hydration, and to succinic acid by hydrogenation. Maleic acid is used in making polyesters for fibre-reinforced laminated moldings and paint vehicles. More specifically it is used in the manufacture of phthalic-type alkyd and polyester resins, surface coatings, copolymers, plasticizers, lubricant additives and agricultural chemicals. It is also found in adhesives and sealants and as a preservative for oils and fats. In the natural world, maleic acid has been identified in ginseng, pineapple, cacao plants, sour cherries and corn. A large number of microbes are able to convert maleic acid to D-malate using the enzyme maleate hydratase (PMID: 1444397).
Inosine triphosphate (ITP) is an intermediate in the purine metabolism pathway. Relatively high levels of ITP in red cells are found in individuals as result of deficiency of inosine triphosphatase (EC 3.1.3.56, ITPase) ITPase is a cytosolic nucleoside triphosphate pyrophosphohydrolase specific for ITP catalysis to inosine monophosphate (IMP) and deoxy-inosine triphosphate (dITP) to deoxy-inosine monophosphate. ITPase deficiency is not associated with any defined pathology other than the characteristic and abnormal accumulation of ITP in red blood cells. Nevertheless, ITPase deficiency may have pharmacogenomic implications, and the abnormal metabolism of 6-mercaptopurine in ITPase-deficient patients may lead to thiopurine drug toxicity. ITPase's function is not clearly understood but possible roles for ITPase could be to prevent the accumulation of rogue nucleotides which would be otherwise incorporated into DNA and RNA, or compete with nucleotides such as GTP in signalling processes. (PMID: 170291, 1204209, 17113761, 17924837).
Cystine is an oxidized dimeric form of cysteine. It is formed by linking two cysteine residues via a disulfide bond (Cys-S-S-Cys) between the -SH groups. Cystine is found in high concentrations in digestive enzymes and in the cells of the immune system, skeletal and connective tissues, skin, and hair. Hair and skin are 10-14% cystine. Cystine is the preferred form of cysteine for the synthesis of glutathione in cells involved in the immune system (e.g. macrophages and astrocytes). Lymphocytes and neurons prefer cysteine for glutathione production. Optimizing glutathione levels in macrophages and astrocytes with cystine allows these cells to provide cysteine to lymphocytes and neurons directly upon demand (Wikipedia).
Isocitric acid, also known as isocitrate belongs to the class of organic compounds known as tricarboxylic acids and derivatives. These are carboxylic acids containing exactly three carboxyl groups. Isocitric acid is a TCA (tricarboxylic acid) cycle intermediate. It is a structural isomer of citric acid and is formed from citrate with the help of the enzyme aconitase. More specifically, Isocitric acid is synthesized from citric acid via the intermediate cis-aconitic acid by the enzyme aconitase (aconitate hydratase). Isocitrate is acted upon by isocitrate dehydrogenase (IDH) to form alpha-ketoglutarate. This is a two-step process, which involves oxidation of isocitrate to oxalosuccinate (a ketone), followed by the decarboxylation of the carboxyl group beta to the ketone, forming alpha-ketoglutarate. In humans, IDH exists in three isoforms: IDH3 catalyzes the third step of the citric acid cycle while converting NAD+ to NADH in the mitochondria. The isoforms IDH1 and IDH2 catalyze the same reaction outside the context of the citric acid cycle and use NADP+ as a cofactor instead of NAD+. They localize to the cytosol as well as the mitochondrion and peroxisome. Isocitric acid exists in all living species, ranging from bacteria to plants to humans. Isocitric acid is a minor organic acid found in most fruit juices, especially in blackberries, youngberries, and boyberries, and in vegetables, especially in carrots. The determination of D-isocitric acid has become of importance in the analysis of fruit juices for the detection of illegal additives (adulteration). Since the quantities of citric and isocitric acids are correlated in fruit juices, a high ratio of citric to isocitric acid can indicate the addition of citric acid as an alduterant. In authentic orange juice, for example, the ratio of citric acid to D-isocitric acid is usually less than 130. Isocitric acid is mostly used in the food industry (food additive) as a food acidulant.
Indoleacetic acid (IAA) is a breakdown product of tryptophan metabolism and is often produced by the action of bacteria in the mammalian gut. Higher levels of IAA are associated with bacteria from Clostridium species including C. stricklandii, C. lituseburense, C. subterminale, and C. putrefaciens (PMID: 12173102). IAA can be found in Agrobacterium, Azospirillum, Bacillus, Bradyrhizobium, Clostridium, Enterobacter, Pantoea, Pseudomonas, Rhizobium (PMID: 12173102, PMID: 17555270, PMID: 12147474, PMID: 19400643, PMID: 9450337, PMID: 21397014) (https://link.springer.com/chapter/10.1007/978-1-4612-3084-7_7) (https://escholarship.org/uc/item/1bf1b5m3). Some endogenous production of IAA in mammalian tissues also occurs. It may be produced by the decarboxylation of tryptamine or the oxidative deamination of tryptophan. IAA frequently occurs at low levels in urine and has been found in elevated levels in the urine of patients with phenylketonuria (PMID: 13610897). IAA has also been identified as a uremic toxin according to the European Uremic Toxin Working Group (PMID: 22626821). Using material extracted from human urine, it was discovered by Kogl in 1933 that indoleacetic acid is also an important plant hormone (PMID: 13610897). Specifically, IAA is a member of the group of phytohormones called auxins. IAA is generally considered to be the most important native auxin. Plant cells synthesize IAA from tryptophan (Wikipedia). IAA and some derivatives can be oxidized by horseradish peroxidase (HRP) into cytotoxic species. IAA is only toxic after oxidative decarboxylation; the effect of IAA/HRP is thought to be due in part to the formation of methylene-oxindole, which may conjugate with DNA bases and protein thiols. IAA/HRP could be used as the basis for targeted cancer, a potential new role for plant auxins in cancer therapy (PMID: 11163327).
Oleic acid (or 9Z)-Octadecenoic acid) is an unsaturated C-18 or an omega-9 fatty acid that is the most widely distributed and abundant fatty acid in nature. It occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. The name derives from the Latin word oleum, which means oil. Oleic acid is the most abundant fatty acid in human adipose tissue, and the second most abundant in human tissues overall, following palmitic acid. Oleic acid is a component of the normal human diet, being a part of animal fats and vegetable oils. Triglycerides of oleic acid represent the majority of olive oil (about 70%). Oleic acid triglycerides also make up 59‚Äì75% of pecan oil, 61% of canola oil, 36‚Äì67% of peanut oil, 60% of macadamia oil, 20‚Äì80% of sunflower oil, 15‚Äì20% of grape seed oil, sea buckthorn oil, 40% of sesame oil, and 14% of poppyseed oil. High oleic variants of plant sources such as sunflower (~80%) and canola oil (70%) also have been developed. consumption has been associated with decreased low-density lipoprotein (LDL) cholesterol, and possibly with increased high-density lipoprotein (HDL) cholesterol, however, the ability of oleic acid to raise HDL is still debated. Oleic acid may be responsible for the hypotensive (blood pressure reducing) effects of olive oil that is considered a health benefit. Oleic acid is used in manufacturing of surfactants, soaps, plasticizers. It is also used as an emulsifying agent in foods and pharmaceuticals. Oleic acid is used commercially in the preparation of oleates and lotions, and as a pharmaceutical solvent.
Phenyl acetate (or phenylacetate) is a carboxylic acid ester that has been found in the biofluids of patients with nephritis and/or hepatitis as well as patients with phenylketonuria (PKU), an inborn error of metabolism. Phenyl acetate has been identified as a uremic toxin according to the European Uremic Toxin Working Group (PMID: 22626821). Excess phenylalanine in the body can be disposed of through a transamination process leading to the production of phenylpyruvate. The phenylpyruvate can be further metabolized into a number of products. Decarboxylation of phenylpyruvate gives phenylacetate, while a reduction reaction gives phenyllactate. The phenylacetate can be further conjugated with glutamine to give phenylacetyl glutamine. All of these metabolites can be detected in serum and urine of PKU patients. Phenyl acetate is also produced endogenously as the metabolite of 2-Phenylethylamine, which is mainly metabolized by monoamine oxidase to form phenyl acetate. 2-phenylethylamine is an "endogenous amphetamine" which may modulate central adrenergic functions, and the urinary phenyl acetate levels have been postulated as a marker for depression. (PMID: 17978765 , 476920 , 6857245). Phenylacetate is also found in essential oils, e.g. neroli, rose oil, free and as esters' and in many fruits. As a result it is used as a perfumery and flavoring ingredient. Phenyl acetate is a microbial metabolite.
Pantothenic acid, also called vitamin B5, is a water-soluble vitamin required to sustain life. Pantothenic acid is needed to form coenzyme-A (CoA), and is thus critical in the metabolism and synthesis of carbohydrates, proteins, and fats. Its name is derived from the Greek pantothen meaning "from everywhere" and small quantities of pantothenic acid are found in nearly every food, with high amounts in whole grain cereals, legumes, eggs, meat, and royal jelly. Pantothenic acid is classified as a member of the secondary alcohols. Secondary alcohols are compounds containing a secondary alcohol functional group, with the general structure HOC(R)(R') (R,R'=alkyl, aryl). Pantothenic acid is considered to be soluble (in water) and acidic.
myo-Inositol 1-phosphate, also known as I1P or ins(1)p, belongs to the class of organic compounds known as inositol phosphates. Inositol phosphates are compounds containing a phosphate group attached to an inositol (or cyclohexanehexol) moiety. myo-Inositol 1-phosphate is a metabolite of inositol phosphate metabolism and the phosphatidylinositol signalling system. Inositol phosphatases (EC:3.1.3.25) play a crucial role in the phosphatidylinositol signalling pathway. Expression is substantially higher in the subcortical regions of the brain, most prominently in the caudate. The phosphatidylinositol pathway is thought to be modified by lithium, a commonly prescribed medication in treating bipolar disorder (OMIM: 605922).
N-Acetyl-D-Glucosamine (N-acetlyglucosamine) is a monosaccharide derivative of glucose. Chemically it is an amide between glucosamine and acetic acid. A single N-acetlyglucosamine moiety linked to serine or threonine residues on nuclear and cytoplasmic proteins -O-GlcNAc, is an ubiquitous post-translational protein modification. O-GlcNAc modified proteins are involved in sensing the nutrient status of the surrounding cellular environment and adjusting the activity of cellular proteins accordingly. O-GlcNAc regulates cellular responses to hormones such as insulin, initiates a protective response to stress, modulates a cell's capacity to grow and divide, and regulates gene transcription. In humans, it exists in skin, cartilage and blood vessel as a component of hyaluronic acid, and bone tissue, cornea and aorta as a component of keratan sulfate. (PMID 16237703).
Norepinephrine is the precursor of epinephrine that is secreted by the adrenal medulla and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers and of the diffuse projection system in the brain arising from the locus ceruleus. It is also found in plants and is used pharmacologically as a sympathomimetic. Norepinephrine is elevated in the urine of people who consume bananas. Norepinephrine is also a microbial metabolite; urinary noradrenaline is produced by Escherichia, Bacillus, and Saccharomyces (PMID: 24621061). Norepinephrine is found in alcoholic beverages, banana peels and pulp (Musa paradisiaca), red plum fruit (Prunus domestica), orange pulp (Citrus sinensis), potato tubers (Solanum tuberosum), and whole purslane (Portulaca oleracea). P. oleracea is the richest of these sources. Norepinephrine has also been identified as a uremic toxin according to the European Uremic Toxin Working Group (PMID: 22626821).
Nicotinamide adenine dinucleotide phosphate (NADP) is a coenzyme composed of ribosylnicotinamide 5'-phosphate (NMN) coupled with a pyrophosphate linkage to 5'-phosphate adenosine 2',5'-bisphosphate. NADP serves as an electron carrier in a number of reactions, being alternately oxidized (NADP+) and reduced (NADPH). NADP is formed through the addition of a phosphate group to the 2' position of the adenosyl nucleotide through an ester linkage (Dorland, 27th ed). This extra phosphate is added by the enzyme NAD+ kinase and removed via NADP+ phosphatase. NADP is also known as TPN (triphosphopyridine nucleotide) and it is an important cofactor used in anabolic reactions in all forms of cellular life. Examples include the Calvin cycle, cholesterol synthesis, fatty acid elongation, and nucleic acid synthesis (Wikipedia).
Orotidylic acid (OMP), is a pyrimidine nucleotide which is the last intermediate in the biosynthesis of uridine monophosphate. Decarboxylation by Orotidylate decarboxylase affords Uridine 5'-phosphate which is the route to Uridine and its derivatives de novo and consequently one of the most important processes in nucleic acid synthesis (Dictionary of Organic Compounds). In humans, the enzyme UMP synthase converts OMP into uridine 5'- monophosphate. If UMP synthase is defective, orotic aciduria can result. (Wikipedia).
Palmitic acid, or hexadecanoic acid, is one of the most common saturated fatty acids found in animals, plants, and microorganisms. As its name indicates, it is a major component of the oil from the fruit of oil palms (palm oil). Excess carbohydrates in the body are converted to palmitic acid. Palmitic acid is the first fatty acid produced during fatty acid synthesis and is the precursor to longer fatty acids. As a consequence, palmitic acid is a major body component of animals. In humans, one analysis found it to make up 21–30% (molar) of human depot fat (PMID: 13756126), and it is a major, but highly variable, lipid component of human breast milk (PMID: 352132). Palmitic acid is used to produce soaps, cosmetics, and industrial mould release agents. These applications use sodium palmitate, which is commonly obtained by saponification of palm oil. To this end, palm oil, rendered from palm tree (species Elaeis guineensis), is treated with sodium hydroxide (in the form of caustic soda or lye), which causes hydrolysis of the ester groups, yielding glycerol and sodium palmitate. Aluminium salts of palmitic acid and naphthenic acid were combined during World War II to produce napalm. The word "napalm" is derived from the words naphthenic acid and palmitic acid (Wikipedia). Palmitic acid is also used in the determination of water hardness and is a surfactant of Levovist, an intravenous ultrasonic contrast agent.
NADPH is the reduced form of NADP+, and NADP+ is the oxidized form of NADPH. Nicotinamide adenine dinucleotide phosphate (NADP) is a coenzyme composed of ribosylnicotinamide 5'-phosphate (NMN) coupled with a pyrophosphate linkage to 5'-phosphate adenosine 2',5'-bisphosphate. NADP serves as an electron carrier in a number of reactions, being alternately oxidized (NADP+) and reduced (NADPH). NADP is formed through the addition of a phosphate group to the 2' position of the adenosyl nucleotide through an ester linkage (Dorland, 27th ed). This extra phosphate is added by the enzyme NAD+ kinase and removed via NADP+ phosphatase. NADP is also known as TPN (triphosphopyridine nucleotide) and it is an important cofactor used in anabolic reactions in all forms of cellular life. Examples include the Calvin cycle, cholesterol synthesis, fatty acid elongation, and nucleic acid synthesis (Wikipedia).
Oxalacetic acid, also known as oxaloacetic acid, keto-oxaloacetate or 2-oxobutanedioate, belongs to the class of organic compounds known as short-chain keto acids and derivatives. These are keto acids with an alkyl chain the contains less than 6 carbon atoms. Oxalacetic acid is a metabolic intermediate in many processes that occur in animals and plants. It takes part in gluconeogenesis, the urea cycle, the glyoxylate cycle, amino acid synthesis, fatty acid synthesis and the citric acid cycle. Oxalacetic acid exists in all living species, ranging from bacteria to plants to humans. Within humans, oxalacetic acid participates in a number of enzymatic reactions. In particular, oxalacetic acid is an intermediate of the citric acid cycle, where it reacts with acetyl-CoA to form citrate, catalyzed by citrate synthase. It is also involved in gluconeogenesis and the urea cycle. In gluconeogenesis oxaloacetate is decarboxylated and phosphorylated by phosphoenolpyruvate carboxykinase and becomes 2-phosphoenolpyruvate using guanosine triphosphate (GTP) as phosphate source. In the urea cycle, malate is acted on by malate dehydrogenase to become oxaloacetate, producing a molecule of NADH. After that, oxaloacetate can be recycled to aspartate, as this recycling maintains the flow of nitrogen into the cell. In mice, injections of oxalacetic acid have been shown to promote brain mitochondrial biogenesis, activate the insulin signaling pathway, reduce neuroinflammation and activate hippocampal neurogenesis (PMID: 25027327). Oxalacetic acid has also been reported to reduce hyperglycemia in type II diabetes and to extend longevity in C. elegans (PMID: 25027327). Outside of the human body, oxalacetic acid has been detected, but not quantified in, several different foods, such as Persian limes, lemon balms, wild rice, canola, and peanuts. This could make oxalacetic acid a potential biomarker for the consumption of these foods.
O-Phosphoethanolamine, also known as PEA, phosphorylethanolamine, colamine phosphoric acid or ethanolamine O-phosphate, belongs to the class of organic compounds known as phosphoethanolamines. Phosphoethanolamines are compounds containing a phosphate linked to the second carbon of an ethanolamine. O-Phosphoethanolamine is used in the biosynthesis of two different types of phospholipids: glycerophospholipids and sphingolipids. O-Phosphoethanolamine exists in all living species, ranging from bacteria to plants to humans. Within humans, O-phosphoethanolamine participates in a number of enzymatic reactions. In particular, cytidine triphosphate and O-phosphoethanolamine can be converted into CDP-ethanolamine; which is mediated by the enzyme ethanolamine-phosphate cytidylyltransferase. In addition, O-phosphoethanolamine can be biosynthesized from ethanolamine; which is catalyzed by the enzyme choline/ethanolamine kinase. In humans, O-phosphoethanolamine is involved in phosphatidylcholine biosynthesis. O-phosphoethanolamine is also a product of the metabolism of sphingolipids. In particular, sphinglipids are metabolized in vivo to phosphorylethanolamine and a fatty aldehyde, generally palmitaldehyde. Both metabolites are ultimately converted to glycerophospholipids. The lipids are first phosphorylated by a kinase and then cleaved by the pyridoxal-dependent sphinganine-1-phosphate aldolase. Elevated urine levels of O-Phosphoethanolamine or PEA can be used to help in the diagnosis of Hypophosphatasia (HPP). Reference ranges for urinary PEA vary according to age and somewhat by diet, and follow a circadian rhythm. Outside of the human body, O-phosphoethanolamine has been detected, but not quantified in, several different foods, such as oxheart cabbages, anises, shiitakes, abalones, and teffs.
2-Oxoadipic acid is produced from lysine in the cytosol of cells via the saccharopine and the pipecolic acid pathways. Catabolites of hydroxylysine and tryptophan enter these pathways as 2-aminoadipic- -semialdehyde and 2-oxoadipate, respectively. In the matrix of mitochondria, 2-oxoadipate is decarboxylated to glutaryl-CoA by the 2-oxoadipate dehydrogenase complex and then converted to acetyl-CoA. 2-Oxoadipic aciduria is an in-born error of metabolism of lysine, tryptophan, and hydroxylysine, in which abnormal quantities of 2-aminoadipic acid are found in body fluids along with 2-oxoadipic acid. Patients with 2-Oxoadipic acidemias are mentally retarded with hypotonia or seizures. 2-Oxoadipic aciduria can occur in patients with Kearns-Sayre Syndrome, a progressive disorder with onset prior to 20 years of age in which multiple organ systems are affected, including progressive external ophthalmoplegia, retinopathy, and the age of onset, and these are associated classically with abnormalities in cardiac conduction, cerebellar signs, and elevated cerebrospinal fluid protein (PMID: 10655159, 16183823, 11083877). Oxoadipic acid is found to be associated with alpha-aminoadipic aciduria, which is an inborn error of metabolism.
Phenol, is a toxic, colourless crystalline solid with a sweet tarry odor that resembles a hospital smell. It is commonly used as an antiseptic and disinfectant. It is active against a wide range of micro-organisms including some fungi and viruses, but is only slowly effective against spores. It has been used to disinfect skin and to relieve itching. Phenol is also used in the preparation of cosmetics including sunscreens, hair dyes, and skin lightening preparations. It is also used in the production of drugs (it is the starting material in the industrial production of aspirin), weedkillers, and synthetic resins. Phenol can be found in areas with high levels of motor traffic, therefore, people living in crowded urban areas are frequently exposed to traffic-derived phenol vapor. The average (mean +/- SD) phenol concentration in urine among normal individuals living in urban areas is 7.4 +/- 2.2 mg/g of creatinine. Exposure of the skin to concentrated phenol solutions causes chemical burns which may be severe; in laboratories where it is used, it is usually recommended that polyethylene glycol solution is kept available for washing off splashes. Notwithstanding the effects of concentrated solutions, it is also used in cosmetic surgery as an exfoliant, to remove layers of dead skin (Wikipedia). In some bacteria phenol can be directly synthesized from tyrosine via the enzyme tyrosine phenol-lyase [EC:4.1.99.2]. It can be produced by Escherichia and Pseudomonas. Phenol has been identified as a uremic toxin according to the European Uremic Toxin Working Group (PMID: 22626821).
Nicotinamide ribotide (NMN) (CAS: 1094-61-7) is an important intermediate metabolite in the nicotinate and nicotinamide metabolism pathway. Mammals predominantly use nicotinamide rather than nicotinic acid as a precursor for NAD biosynthesis. Instead of the deamidation into nicotinic acid, nicotinamide is directly converted into NMN by nicotinamide phosphoribosyltransferase (NAMPT, EC 2.4.2.12). The enzyme nicotinamide mononucleotide adenylyltransferase (NMNAT, EC 2.7.7.1), which is a member of the nucleotidyltransferase alpha/beta-phosphodiesterase superfamily, catalyzes the reaction NMN + ATP <=> nicotinamide adenine dinucleotide (NAD) + PPi, representing the final step in the biosynthesis of NAD. NAD is a molecule that plays a fundamental role as a cofactor in cellular redox reactions. Thus NMN is an important metabolite for the maintenance of normal NAD biosynthesis. Circulating NMN levels may play an important role in regulating cell function in physiological and pathophysiological conditions (PMID: 15078171, 17983582).
Pyridoxine, also known vitamin B6, is commonly found in food and is used as a dietary supplement. Pyridoxine is an essential nutrient, meaning the body cannot synthesize it, and it must be obtained from the diet. Sources in the diet include fruit, vegetables, and grain. Although pyridoxine and vitamin B6 are still frequently used as synonyms, especially by medical researchers, this practice is sometimes misleading (PMID: 2192605). Technically, pyridoxine is one of the compounds that can be called vitamin B6 or it is a member of the family of B6 vitamins. Healthy human blood levels of pyridoxine are 2.1 - 21.7 ng/mL. Pyridoxine is readily converted to pyridoxal phosphate which is a coenzyme for synthesis of amino acids, neurotransmitters (serotonin, norepinephrine), sphingolipids and aminolevulinic acid. Pyridoxine assists in the balancing of sodium and potassium as well as promoting red blood cell production. Therefore pyridoxine is required by the body to make amino acids, carbohydrates, and lipids. It is linked to cancer immunity and helps fight the formation of homocysteine. It has been suggested that pyridoxine might help children with learning difficulties, and may also prevent dandruff, eczema, and psoriasis. In addition, pyridoxine can help balance hormonal changes in women and aid in immune system. Lack of pyridoxine may cause anemia, nerve damage, seizures, skin problems, and sores in the mouth (Wikipedia). Deficiency of pyridoxine, though rare because of widespread distribution in foods, leads to the development of peripheral neuritis in adults and affects the central nervous system in children (DOSE - 3rd edition). As a supplement pyridoxine is used to treat and prevent pyridoxine deficiency, sideroblastic anaemia, pyridoxine-dependent epilepsy, certain metabolic disorders, problems from isoniazid, and certain types of mushroom poisoning. Pyridoxine in combination with doxylamine is used as a treatment for morning sickness in pregnant women.
Pyruvic acid or pyruvate is a simple alpha-keto acid. It is a three-carbon molecule containing a carboxylic acid group and a ketone functional group. Pyruvate is the simplest alpha-keto acid and according to official nomenclature by IUPAC, it is called alpha-keto propanoic acid. Like other keto acids, pyruvic acid can tautomerize from its ketone form to its enol form, containing a double bond and an alcohol. Pyruvate is found in all living organisms ranging from bacteria to plants to humans. It is intermediate compound in the metabolism of carbohydrates, proteins, and fats. Pyruvate is a key intermediate in several metabolic pathways throughout the cell. In particular, pyruvic acid can be made from glucose through glycolysis, converted back to carbohydrates (such as glucose) via gluconeogenesis, or to fatty acids through a reaction with acetyl-CoA. Pyruvic acid supplies energy to cells through the citric acid cycle (TCA or Krebs cycle) when oxygen is present (aerobic respiration), and alternatively ferments to produce lactate when oxygen is lacking (lactic acid). In glycolysis, phosphoenolpyruvate (PEP) is converted to pyruvate by pyruvate kinase. This reaction is strongly exergonic and irreversible. In gluconeogenesis, it takes two enzymes, pyruvate carboxylase and PEP carboxykinase, to catalyze the reverse transformation of pyruvate to PEP. Pyruvic acid is also a metabolite of Corynebacterium (PMID: 27872963).
Riboflavin or vitamin B2 is an easily absorbed, water-soluble micronutrient with a key role in maintaining human health. Like the other B vitamins, it supports energy production by aiding in the metabolizing of fats, carbohydrates, and proteins. Vitamin B2 is also required for red blood cell formation and respiration, antibody production, and for regulating human growth and reproduction. It is essential for healthy skin, nails, hair growth and general good health, including regulating thyroid activity. Riboflavin is found in milk, eggs, malted barley, liver, kidney, heart, and leafy vegetables. Riboflavin is yellow or orange-yellow in color and in addition to being used as a food coloring it is also used to fortify some foods. It can be found in baby foods, breakfast cereals, sauces, processed cheese, fruit drinks and vitamin-enriched milk products. The richest natural source is yeast. It occurs in the free form only in the retina of the eye, in whey, and in urine; its principal forms in tissues and cells are as flavin mononucleotide and flavin adenine dinucleotide.
Porphobilinogen (PBG) is a pyrrole-containing intermediate in the biosynthesis of porphyrins. It is generated from aminolevulinate (ALA) by the enzyme ALA dehydratase. Porphobilinogen is then converted into hydroxymethylbilane by the enzyme porphobilinogen deaminase (also known as hydroxymethylbilane synthase). Under certain conditions, porphobilinogen can act as a phototoxin, a neurotoxin, and a metabotoxin. A phototoxin leads to cell damage upon exposure to light. A neurotoxin causes damage to nerve cells and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of porphyrins are associated with porphyrias such as porphyria variegate, acute intermittent porphyria, and hereditary coproporphyria (HCP). There are several types of porphyrias (most are inherited). Hepatic porphyrias are characterized by acute neurological attacks (seizures, psychosis, extreme back and abdominal pain, and an acute polyneuropathy), while the erythropoietic forms present with skin problems (usually a light-sensitive blistering rash and increased hair growth). The neurotoxicity of porphyrins may be due to their selective interactions with tubulin, which disrupt microtubule formation and cause neural malformations (PMID: 3441503).
Tetrahydrofuran (THF) is a cyclic ether. It is a colorless, water-miscible organic liquid with low viscosity and a smell similar to diethyl ether. At low concentrations it has a faint, fruity aroma. It is one of the most polar ethers. THF is naturally present in coffee aroma, floured chickpeas, and cooked chicken. It is used in the manufacture of polymers as well as agricultural, pharmaceutical, and commodity chemicals. Because of its widespread use (industrially) and its presence in many foods, THF is a contaminant of exposure and can appear in human biofluids. THF oxidizes readily, which can lead to instability and result in cytotoxicity. In chemical synthesis applications, THF is often used for hydroborations used to synthesize primary alcohols. THF is frequently used as a solvent for Grignard reagents because of the oxygen atom's ability to coordinate to the magnesium ion component of the Grignard reagent (an organometallic chemical reaction involving alkyl- or aryl-magnesium halides). THF is often used in polymer science. For example, it can be used to dissolve rubber prior to determining its molecular mass using gel permeation chromatography. THF tends to form peroxides on storage in air. (PMID: 16999122, 12742700, 14619948). THF can be degraded by certain strains of Rhodococcus bacteria (PMID: 19230656).
Sorbitol is a polyhydric alcohol with about half the sweetness of sucrose. Sorbitol occurs naturally and is also produced synthetically from glucose. It was formerly used as a diuretic and may still be used as a laxative and in irrigating solutions for some surgical procedures. It is also used in many manufacturing processes, as a pharmaceutical aid, and in several research applications. Ascorbic acid fermentation; in solution form for moisture-conditioning of cosmetic creams and lotions, toothpaste, tobacco, gelatin; bodying agent for paper, textiles, and liquid pharmaceuticals; softener for candy; sugar crystallization inhibitor; surfactants; urethane resins and rigid foams; plasticizer, stabilizer for vinyl resins; food additive (sweetener, humectant, emulsifier, thickener, anticaking agent); dietary supplement. (Hawley's Condensed Chemical Dictionary) Biological Source: Occurs widely in plants ranging from algae to the higher orders. Fruits of the plant family Rosaceae, which include apples, pears, cherries, apricots, contain appreciable amounts. Rich sources are the fruits of the Sorbus and Crataegus species Use/Importance: Used for manufacturing of sorbose, propylene glycol, ascorbic acid, resins, plasticizers and as antifreeze mixtures with glycerol or glycol. Tablet diluent, sweetening agent and humectant, other food uses. Sorbitol is used in photometric determination of Ru(VI) and Ru(VIII); in acid-base titration of borate (Dictionary of Organic Compounds).
The anion, the salts, and the esters of pyrophosphoric acid are called pyrophosphates. The pyrophosphate anion is abbreviated PPi and is formed by the hydrolysis of ATP into AMP in cells. This hydrolysis is called pyrophosphorolysis. The pyrophosphate anion has the structure P2O74-, and is an acid anhydride of phosphate. It is unstable in aqueous solution and rapidly hydrolyzes into inorganic phosphate. Pyrophosphate is an osteotoxin (arrests bone development) and an arthritogen (promotes arthritis). It is also a metabotoxin (an endogenously produced metabolite that causes adverse health affects at chronically high levels). Chronically high levels of pyrophosphate are associated with hypophosphatasia. Hypophosphatasia (also called deficiency of alkaline phosphatase or phosphoethanolaminuria) is a rare, and sometimes fatal, metabolic bone disease. Hypophosphatasia is associated with a molecular defect in the gene encoding tissue non-specific alkaline phosphatase (TNSALP). TNSALP is an enzyme that is tethered to the outer surface of osteoblasts and chondrocytes. TNSALP hydrolyzes several substances, including inorganic pyrophosphate (PPi) and pyridoxal 5'-phosphate (PLP), a major form of vitamin B6. When TSNALP is low, inorganic pyrophosphate (PPi) accumulates outside of cells and inhibits the formation of hydroxyapatite, one of the main components of bone, causing rickets in infants and children and osteomalacia (soft bones) in adults. Vitamin B6 must be dephosphorylated by TNSALP before it can cross the cell membrane. Vitamin B6 deficiency in the brain impairs synthesis of neurotransmitters which can cause seizures. In some cases, a build-up of calcium pyrophosphate dihydrate crystals in the joints can cause pseudogout.
Sphingosine, also known as (4E)-sphingenine or sphing-4-enine, belongs to the class of organic compounds known as 1,2-aminoalcohols. These are organic compounds containing an alkyl chain with an amine group bound to the C1 atom and an alcohol group bound to the C2 atom. Sphingosine is an 18-carbon amino alcohol with an unsaturated hydrocarbon chain, which forms a primary part of sphingolipids. Sphingolipids are a class of cell membrane lipids that include sphingomyelin. Thus, sphingosine is considered to be a sphingoid base lipid. Sphingosine is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Sphingosine is found in all living organisms ranging from bacteria to plants to humans.  Sphingosine is synthesized from palmitoyl CoA and serine in a condensation required to yield dehydrosphingosine. Dehydrosphingosine is then reduced by NADPH to dihydrosphingosine (sphinganine), and finally oxidized by FAD to sphingosine. Within humans and other mammals, sphingosine participates in a number of enzymatic reactions. In particular, sphingosine can be converted into sphingosine 1-phosphate through its interaction with the enzyme sphingosine kinase 2. sphingosine 1-phosphate is an important signaling molecule. In addition, sphingosine can be biosynthesized from sphingosine 1-phosphate; which is mediated by the enzyme sphingosine-1-phosphate phosphatase 2. Sphingosine and its derivative sphinganine are the major bases of the sphingolipids in mammals. In humans, sphingosine is involved in globoid cell leukodystrophy.
Pregnenolone is a derivative of cholesterol, the product of cytochrome P450 side-chain cleavage (EC 1.14.15.6, CYP11A1. This reaction consists of three consecutive monooxygenations, a 22-hydroxylation, a 20-hydroxylation, and the cleavage of the C20-C22 bond, yielding pregnenolone. Pregnenolone is the precursor to gonadal steroid hormones and the adrenal corticosteroids. This reaction occurs in steroid hormone-producing tissues such as the adrenal cortex, corpus luteum, and placenta. The most notable difference between the placenta and other steroidogenic tissues is that electron supply to CYP11A1 limits the rate at which cholesterol is converted into pregnenolone in the placenta. The limiting component for electron delivery to CYP11A1 is the concentration of adrenodoxin reductase in the mitochondrial matrix which is insufficient to maintain the adrenodoxin pool in a fully reduced state. Pregnenolone is also a neurosteroid, and is produced in the spinal cord; CYP11A1 is the key enzyme catalyzing the conversion of cholesterol into pregnenolone, the rate-limiting step in the biosynthesis of all classes of steroids, and has been localized in sensory networks of the spinal cord dorsal horn. In the adrenal glomerulosa cell, angiotensin II, one of the major physiological regulators of mineralocorticoid synthesis, appears to affect most of the cholesterol transfer to the mitochondrial outer membrane and many steps in the transport to the inner membrane. Thus, it exerts a powerful control over the use of cholesterol for aldosterone production (PMID: 17222962, 15823613, 16632873, 15134809).
Squalene is an unsaturated aliphatic hydrocarbon (carotenoid) with six unconjugated double bonds found in human sebum (5%), fish liver oils, yeast lipids, and many vegetable oils (e.g. palm oil, cottonseed oil, rapeseed oil). Squalene is a volatile component of the scent material from Saguinus oedipus (cotton-top tamarin monkey) and Saguinus fuscicollis (saddle-back tamarin monkey) (Hawley's Condensed Chemical Reference). Squalene is a component of adult human sebum that is principally responsible for fixing fingerprints (ChemNetBase). It is a natural organic compound originally obtained for commercial purposes primarily from shark liver oil, though there are botanical sources as well, including rice bran, wheat germ, and olives. All higher organisms produce squalene, including humans. It is a hydrocarbon and a triterpene. Squalene is a biochemical precursor to the whole family of steroids. Oxidation of one of the terminal double bonds of squalene yields 2,3-squalene oxide which undergoes enzyme-catalyzed cyclization to afford lanosterol, which is then elaborated into cholesterol and other steroids. Squalene is a low-density compound often stored in the bodies of cartilaginous fishes such as sharks, which lack a swim bladder and must therefore reduce their body density with fats and oils. Squalene, which is stored mainly in the shark's liver, is lighter than water with a specific gravity of 0.855 (Wikipedia) Squalene is used as a bactericide. It is also an intermediate in the manufacture of pharmaceuticals, rubber chemicals, and colouring materials (Physical Constants of Chemical Substances).
Sucrose is a nonreducing disaccharide composed of glucose and fructose linked via their anomeric carbons. It is obtained commercially from sugarcane (Saccharum officinarum), sugar beet (Beta vulgaris), and other plants and used extensively as a food and a sweetener. Sucrose is derived by crushing and extracting sugarcane with water or by extracting sugar beet with water, evaporating, and purifying with lime, carbon, and various liquids. Sucrose is also obtainable from sorghum. Sucrose occurs in low percentages in honey and maple syrup. Sucrose is used as a sweetener in foods and soft drinks, in the manufacture of syrups, in invert sugar, confectionery, preserves and jams, demulcent, pharmaceutical products, and caramel. Sucrose is also a chemical intermediate for detergents, emulsifying agents, and other sucrose derivatives. Sucrose is widespread in the seeds, leaves, fruits, flowers, and roots of plants, where it functions as an energy store for metabolism and as a carbon source for biosynthesis. The annual world production of sucrose is in excess of 90 million tons mainly from the juice of sugar cane (20%) and sugar beet (17%). In addition to its use as a sweetener, sucrose is used in food products as a preservative, antioxidant, moisture control agent, stabilizer, and thickening agent. BioTransformer predicts that sucrose is a product of 6-O-sinapoyl sucrose metabolism via a hydrolysis-of-carboxylic-acid-ester-pattern1 reaction occurring in human gut microbiota and catalyzed by the liver carboxylesterase 1 (P23141) enzyme (PMID: 30612223).
Thymine, also known as 5-methyluracil, belongs to the class of organic compounds known as hydroxypyrimidines. These are organic compounds containing a hydroxyl group attached to a pyrimidine ring. Pyrimidine is a 6-membered ring consisting of four carbon atoms and two nitrogen centers at the 1- and 3- ring positions. Thymine was first isolated in 1893 by Albrecht Kossel and Albert Neumann from calves' thymus glands, hence its name. Thymine is one of the 4 nuelcoebases found in DNA and is essential to all life. Thymine exists in all living species, ranging from bacteria to plants to humans. Thymine combined with deoxyribose creates the nucleoside deoxythymidine (also called thymidine) which when phosphorylated to dTDP can be incorporated into DNA via DNA polymerases. Thymidine can be phosphorylated with up to three phosphoric acid groups, producing dTMP (deoxythymidine monophosphate) dTDP and/or dTTP. In RNA thymine is replaced with uracil in most cases. In DNA, thymine binds to adenine via two hydrogen bonds to assist in stabilizing the nucleic acid structures. Within humans, thymine participates in a number of enzymatic reactions. In particular, thymine and deoxyribose 1-phosphate can be biosynthesized from thymidine through its interaction with the enzyme thymidine phosphorylase. In addition, thymine can be converted into dihydrothymine; which is mediated by the enzyme dihydropyrimidine dehydrogenase [NADP(+)].
Phosphoenolpyruvate (PEP) is an important chemical compound in biochemistry. It has a high energy phosphate bond, and is involved in glycolysis and gluconeogenesis. In glycolysis, PEP is formed by the action of the enzyme enolase on 2-phosphoglycerate. Metabolism of PEP to pyruvate by pyruvate kinase (PK) generates 1 molecule of adenosine triphosphate (ATP) via substrate-level phosphorylation. ATP is one of the major currencies of chemical energy within cells. In gluconeogenesis, PEP is formed from the decarboxylation of oxaloacetate and hydrolysis of 1 guanosine triphosphate molecule. This reaction is catalyzed by the enzyme phosphoenolpyruvate carboxykinase (PEPCK). This reaction is a rate-limiting step in gluconeogenesis. (wikipedia).
Liothyronine is a T3 thyroid hormone normally synthesized and secreted by the thyroid gland in much smaller quantities than thyroxine (T4). Most T3 is derived from peripheral monodeiodination of T4 at the 5' position of the outer ring of the iodothyronine nucleus. The hormone that is finally delivered and used by the tissues is mainly T3. Liothyronine is mildly toxic by ingestion and is an experimental teratogen. When heated to decomposition it emits toxic fumes of NOx, I(-), and Cl(-) (Sax's Dangerous Properties of Industrial Materials).
Tetrahydrocorticosterone belongs to the class of organic compounds known as 21-hydroxysteroids. These are steroids carrying a hydroxyl group at the 21-position of the steroid backbone. Thus, tetrahydrocorticosterone is considered to be a steroid lipid molecule. Tetrahydrocorticosterone is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Tetrahydrocorticosterone is one of the major urinary metabolites from corticosterone. Premenopausal patients with early breast cancer excrete subnormal amounts of tetrahydrocorticosterone as compared with the normal subjects of corresponding ages (PMID: 1133844).
Sphinganine belongs to the class of organic compounds known as 1,2-aminoalcohols. These are organic compounds containing an alkyl chain with an amine group bound to the C1 atom and an alcohol group bound to the C2 atom. Thus, sphinganine is considered to be a sphingoid base lipid molecule. Sphinganine is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Sphinganine exists in all living species, ranging from bacteria to humans. Within humans, sphinganine participates in a number of enzymatic reactions. In particular, sphinganine can be converted into 3-dehydrosphinganine through its interaction with the enzyme 3-ketodihydrosphingosine reductase. In addition, sphinganine can be converted into sphinganine 1-phosphate; which is catalyzed by the enzyme sphingosine kinase 2. Outside of the human body, sphinganine has been detected, but not quantified in, several different foods, such as Mexican oregano, jostaberries, winter squash, angelica, and epazotes. This could make sphinganine a potential biomarker for the consumption of these foods. Sphinganine blocks postlysosomal cholesterol transport by inhibiting low-density lipoprotein-induced esterification of cholesterol and causing unesterified cholesterol to accumulate in perinuclear vesicles. It has been suggested that endogenous sphinganine may inhibit cholesterol transport in Niemann-Pick Type C (NPC) disease (PMID: 1817037).
Sarcosine is the N-methyl derivative of glycine. Sarcosine is metabolized to glycine by the enzyme sarcosine dehydrogenase, while glycine-N-methyl transferase generates sarcosine from glycine. Sarcosine is a natural amino acid found in muscles and other body tissues. In the laboratory it may be synthesized from chloroacetic acid and methylamine. Sarcosine is naturally found in the metabolism of choline to glycine. Sarcosine is sweet to the taste and dissolves in water. It is used in manufacturing biodegradable surfactants and toothpastes as well as in other applications. Sarcosine is ubiquitous in biological materials and is present in such foods as egg yolks, turkey, ham, vegetables, legumes, etc. Sarcosine is formed from dietary intake of choline and from the metabolism of methionine, and is rapidly degraded to glycine. Sarcosine has no known toxicity, as evidenced by the lack of phenotypic manifestations of sarcosinemia, an inborn error of sarcosine metabolism. Sarcosinemia can result from severe folate deficiency because of the folate requirement for the conversion of sarcosine to glycine (Wikipedia). Sarcosine has recently been identified as a biomarker for invasive prostate cancer. It was found to be greatly increased during prostate cancer progression to metastasis and could be detected in urine. Sarcosine levels were also increased in invasive prostate cancer cell lines relative to benign prostate epithelial cells (PMID: 19212411).
Phosphoserine is the phosphoric acid ester of the amino acid serine. It is found in essentially all living organisms ranging from microbes to plants to mammals. Phosphoserine is a component of many proteins as the result of posttranslational modifications to the native protein‚Äôs serine residue(s). The phosphorylation of the hydroxyl functional group in serine to produce phosphoserine is catalyzed by various types of kinases. Serine is one of three amino acid residues that are commonly phosphorylated by kinases during cell signalling in eukaryotes. Free phosphoserine is found in many biofluids and likely arises from the proteolysis of proteins containing phosphoserine residues (PMID: 7693088).
Thymidine, also known as deoxythymidine or deoxyribosylthymine or thymine deoxyriboside, is a pyrimidine deoxynucleoside. It consists of the nucleobase thymine attached to deoxyribose through a beta N- glycosidic bond. Thymidine also belongs to the class of organic compounds known as pyrimidine 2'-deoxyribonucleosides. Pyrimidine 2'-deoxyribonucleosides are compounds consisting of a pyrimidine linked to a ribose which lacks a hydroxyl group at position 2. Deoxythymidine (or thymidine) is the DNA nucleoside T, which pairs with deoxyadenosine (A) in double-stranded DNA. Therefore, thymidine is essential to all life. Indeed, thymidine exists in all living species, ranging from bacteria to plants to humans. Within humans, thymidine participates in a number of enzymatic reactions. In particular, thymidine can be biosynthesized from 5-thymidylic acid through its interaction with the enzyme cytosolic purine 5'-nucleotidase. In addition, thymidine can be converted into 5-thymidylic acid; which is catalyzed by the enzyme thymidine kinase. Deoxythymidine can be phosphorylated with one, two or three phosphoric acid groups, creating dTMP (deoxythymidine monophosphate), dTDP, or dTTP (for the di- and tri- phosphates, respectively). dTMP can be incorporated into DNA via DNA polymerases. In cell biology, thymidine can be used to synchronize the cells in S phase. Derivatives of thymidine are used in a number of drugs, including Azidothymidine (AZT), which is used in the treatment of HIV infection. AZT inhibits the process of reverse transcription in the human immunodeficiency virus.
Sphingosine 1-phosphate (S1P), also known as sphing-4-enine-1-phosphate, is classified as a member of the phosphosphingolipids. Phosphosphingolipids are sphingolipids with a structure based on a sphingoid base that is attached to a phosphate head group. They differ from phosphonospingolipids which have a phosphonate head group. S1P is a compound with potent bioactive actions in sphingolipid metabolism, the calcium signalling pathway, and neuroactive ligand-receptor interaction. Generated by sphingosine kinases and ceramide kinase, S1P control numerous aspects of cell physiology, including cell survival and mammalian inflammatory responses. S1P is involved in cyclooxygenase-2 induction (COX-2) and regulates the production of eicosanoids (important inflammatory mediators). S1P functions mainly via G-protein-coupled receptors and probably also has intracellular targets (PMID: 16219683). S1P is considered to be practically insoluble (in water) and acidic.
Phosphoribosyl pyrophosphate, also known as PRPP or PRib-PP, belongs to the class of organic compounds known as pentose phosphates. These are carbohydrate derivatives containing a pentose substituted by one or more phosphate groups. Phosphoribosyl pyrophosphate is an extremely weak basic (essentially neutral) compound (based on its pKa). Phosphoribosyl pyrophosphate exists in all living species, ranging from bacteria to humans. Within humans, phosphoribosyl pyrophosphate participates in a number of enzymatic reactions. In particular, guanine and phosphoribosyl pyrophosphate can be biosynthesized from guanosine monophosphate through its interaction with the enzyme adenine phosphoribosyltransferase. In addition, guanine and phosphoribosyl pyrophosphate can be biosynthesized from guanosine monophosphate; which is catalyzed by the enzyme hypoxanthine-guanine phosphoribosyltransferase. In humans, phosphoribosyl pyrophosphate is involved in adenosine deaminase deficiency. Phosphoribosyl pyrophosphate is a pentosephosphate and it is the key substance in the biosynthesis of histidine, tryptophan, and purine and pyrimidine nucleotides. It is formed from ribose 5-phosphate by the enzyme ribose-phosphate diphosphokinase. It plays a role in transferring phosphate groups in several reactions.
D-Ribose, commonly referred to as simply ribose, is a five-carbon sugar found in all living cells. Ribose is not an essential nutrient because it can be synthesized by almost every tissue in the body from other substances, such as glucose. It is vital for life as a component of DNA, RNA, ATP, ADP, and AMP. In nature, small amounts of ribose can be found in ripe fruits and vegetables. Brewer's yeast, which has a high concentration of RNA, is another rich source of ribose. D-ribose is also a component of many so-called energy drinks and anti-ageing products available on the market today. Ribose is a structural component of ATP, which is the primary energy source for exercising muscle. The adenosine component is an adenine base attached to the five-carbon sugar ribose. ATP provides energy to working muscles by releasing a phosphate group, hence becoming ADP, which in turn may release a phosphate group, then becoming AMP. During intense muscular activity, the total amount of ATP available is quickly depleted. In an effort to correct this imbalance, AMP is broken down in the muscle and secreted from the cell. Once the breakdown products of AMP are released from the cell, the energy potential (TAN pool) of the muscle is reduced and ATP must then be reformed using ribose. Ribose helps restore the level of adenine nucleotides by bypassing the rate-limiting step in the de novo (oxidative pentose phosphate) pathway, which regenerates phosphoribosyl pyrophosphate (PRPP), the essential precursor for ATP. If ribose is not readily available to a cell, glucose may be converted to ribose. Ribose supplementation has been shown to increase the rate of ATP resynthesis following intense exercise. The use of ribose in men with severe coronary artery disease resulted in improved exercise tolerance. Hence, there is interest in the potential of ribose supplements to boost muscular performance in athletic activities (PMID: 17618002, Curr Sports Med Rep. 2007 Jul;6(4):254-7.).
Uridine triphosphate, also known as 5'-UTP or UTP, belongs to the class of organic compounds known as pyrimidine ribonucleoside triphosphates. These are pyrimidine ribobucleotides with triphosphate group linked to the ribose moiety. More specifically, UTP is a pyrimidine nucleoside triphosphate, consisting of the organic base uracil linked to the 1‚Ä≤ carbon of the ribose sugar, and esterified with tri-phosphoric acid at the 5‚Ä≤ position. Uridine triphosphate exists in all living species, ranging from bacteria to plants to humans. The main role of UTP is as substrate for the synthesis of RNA during transcription. UTP is the precursor for the production of CTP via the enzyme known as CTP Synthetase. UTP can be biosynthesized from UDP by the enzyme known as nucleoside diphosphate kinase by using phosphate group from ATP. UTP also has the role of a source of energy or an activator of substrates in a variety of metabolic reactions. For instance UTP can be used to activate Glucose-1-phosphate, leading to the formation of UDP-glucose and inorganic phosphate. The resulting UDP-glucose can be used in the synthesis of glycogen. UTP is also used in the metabolism of galactose, where the activated form of galactose, called UDP-galactose can be converted to UDP-glucose. UDP-glucuronate, another product of UTP reacting with glucuronic acid, is a sugar used in the creation of polysaccharides and is an intermediate in the biosynthesis of ascorbic acid (except in primates and guinea pigs).
Uridine diphosphate glucose, also known as UDP-glucose or UDP-alpha-D-glucose, belongs to the class of organic compounds known as pyrimidine nucleotide sugars. These are pyrimidine nucleotides bound to a saccharide derivative through the terminal phosphate group. Uridine diphosphate glucose exists in all living species, ranging from bacteria to plants to humans. Uridine diphosphate glucose is a key intermediate in carbohydrate metabolism. For instance, UDP-glucose is a precursor of glycogen and can be converted into UDP-galactose and UDP-glucuronic acid, which can then be used as substrates by the enzymes that make polysaccharides containing galactose and glucuronic acid. UDP-glucose can also be used as a precursor for the biosynthesis of sucrose, lipopolysaccharides and glycosphingolipids. Within humans, uridine diphosphate glucose participates in a number of enzymatic reactions. In particular, ceramide (D18:1/18:0) and uridine diphosphate glucose can be converted into glucosylceramide (D18:1/18:0) and uridine 5'-diphosphate through the action of the enzyme ceramide glucosyltransferase. In addition, glucosylceramide (D18:1/18:0) and uridine diphosphate glucose can be biosynthesized from lactosylceramide (D18:1/18:0) and uridine 5'-diphosphate through its interaction with the enzyme Beta-1,4-galactosyltransferase 6.
Uridine 5'-monophosphate (UMP), also known as uridylic acid or uridylate, belongs to the class of organic compounds known as pyrimidine ribonucleoside monophosphates. These are pyrimidine ribobucleotides with monophosphate group linked to the ribose moiety. UMP consists of a phosphate group, a pentose sugar ribose, and the nucleobase uracil; hence, it is a ribonucleotide monophosphate. Uridine 5'-monophosphate exists in all living species, ranging from bacteria to plants to humans. UMP is a nucleotide that is primarily used as a monomer in RNA biosynthesis. Uridine monophosphate is formed from Orotidine 5'-monophosphate (orotidylic acid) in a decarboxylation reaction catalyzed by the enzyme orotidylate decarboxylase. Within humans, uridine 5'-monophosphate participates in a number of enzymatic reactions. In particular, uridine 5'-monophosphate can be converted into uridine 5'-diphosphate through the action of the enzyme UMP-CMP kinase. In addition, uridine 5'-monophosphate can be biosynthesized from uridine 5'-diphosphate through its interaction with the enzyme soluble calcium-activated nucleotidase 1. In brain research studies, uridine monophosphate has been used as a convenient delivery compound for uridine.  Uridine is present in many foods, mainly in the form of RNA. Non-phosphorylated uridine is not bioavailable beyond first-pass metabolism. In a study, gerbils fed a combination of uridine monophosphate, choline, and docosahexaenoic acid (DHA) were found to have significantly improved performance in running mazes over those not fed the supplements, implying an increase in cognitive function (PMID: 18606862).
Uridine diphosphate-N-acetylglucosamine (uridine 5'-diphosphate-GlcNAc, or UDP-Glc-NAc) is an acetylated aminosugar nucleotide. UDP-GlcNAc is the donor substrate for modification of nucleocytoplasmic proteins at serine and threonine residues with N-acetylglucosamine (O-GlcNAc). Nutrient sensing in mammals is done through the hexosamine biosynthetic pathway (HSP), which produces uridine 5'-diphospho-N-acetylglucosamine (UDP-Glc-NAc) as its end product. Mammals respond to nutrient excess by activating O-GlcNAcylation (addition of O-linked N-acetylglucosamine). O-GlcNAc addition (and removal) is key to histone remodeling, transcription, proliferation, apoptosis, and proteasomal degradation. This nutrient-responsive signaling pathway also modulates important cellular pathways, including the insulin signaling cascade in. Alterations in O-GlcNAc metabolism are associated with various human diseases including diabetes mellitus and neurodegeneration. (PMID: 16317114) Due to the chemical makeup of UDP-GlcNAc, it is well positioned to serve as a glucose sensor in that it is a high-energy compound that requires and/or responds to glucose, amino acid, fatty acid and nucleotide metabolism for synthesis. Elevated levels of O-GlcNAc have an effect on insulin-stimulated glucose uptake. (PMID: 12678487).
Vanillylmandelic acid, also known as vanillylmandelate or VMA, belongs to the class of organic compounds known as methoxyphenols. Methoxyphenols are compounds containing a methoxy group attached to the benzene ring of a phenol moiety. Vanillylmandelic acid is a sweet and vanilla tasting compound. Vanillylmandelic acid (VMA) is a chemical intermediate in the synthesis of artificial vanilla flavorings and is an end-stage metabolite of the catecholamines (dopamine, epinephrine, and norepinephrine). Vanillylmandelic acid exists in all living organisms, ranging from bacteria to plants to humans. Within humans, vanillylmandelic acid participates in a number of enzymatic reactions. In particular, vanillylmandelic acid can be biosynthesized from 3-methoxy-4-hydroxyphenylglycolaldehyde through its interaction with the enzyme aldehyde dehydrogenase. In addition, vanillylmandelic acid and pyrocatechol can be biosynthesized from 3,4-dihydroxymandelic acid and guaiacol through the action of the enzyme catechol O-methyltransferase. Urinary VMA is elevated in patients with tumors that secrete catecholamines. Urinary VMA tests may also be used to diagnose neuroblastomas, and to monitor treatment of these conditions. VMA urinalysis tests can be used to diagnose an adrenal gland tumor called pheochromocytoma, a tumor of catecholamine-secreting chromaffin cells. Vanillylmandelic acid (VMA) is produced in the liver and is a major product of norepinephrine and epinephrine metabolism excreted in the urine.
Xanthine, also known as 2,6-dioxopurine, belongs to the class of organic compounds known as xanthines. These are purine derivatives with a ketone group conjugated at carbons 2 and 6 of the purine moiety. Xanthine is also classified as an oxopurine. An oxopurine in which the purine ring is substituted by oxo groups at positions 2 and 6 and N-9 is protonated. Xanthine exists in all living species, ranging from bacteria to plants to humans. In plants, several stimulants can be derived from xanthine, including caffeine, theophylline, and theobromine. Derivatives of xanthine (known collectively as xanthines) are a group of alkaloids commonly used for their effects as mild stimulants and as bronchodilators, notably in the treatment of asthma or influenza symptoms. Within humans, xanthine participates in a number of enzymatic reactions. In particular, xanthine can be biosynthesized from guanine; which is mediated by the enzyme guanine deaminase. In addition, xanthine and ribose 1-phosphate can be biosynthesized from xanthosine through the action of the enzyme purine nucleoside phosphorylase. In humans and other primates, xanthine can be converted to uric acid by the action of the xanthine oxidase enzyme. People with rare genetic disorders, specifically xanthinuria and Lesch‚ÄìNyhan syndrome, lack sufficient xanthine oxidase and cannot convert xanthine to uric acid. Individuals with xanthinuria have unusually high concentrations of xanthine in their blood and urine, which can lead to health problems such as renal failure and xanthine kidney stones. Individuals with Lesch-Nyhan syndrome have a deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT). The HGPRT deficiency causes a build-up of uric acid in all body fluids. This results in both high levels of uric acid in the blood and urine, associated with severe gout and kidney problems. Neurological signs include poor muscle control and moderate intellectual disability.
Xanthosine 5-triphosphate (XTP) is a Guanosine triphosphate (GTP) analogue. The base of XTP, xanthine, bears a keto group instead of an amino group at C2 of the purine rings. XTP can substitute for GTP in supporting receptor-mediated adenylyl cyclase activation. XTP competitively inhibits the binding of GTP to the guanine nucleotide-binding site of retinal G-protein, transducin (TD). These suggests that GTP, ITP, and XTP are differential signal sorters and signal amplifiers at the G-protein level. G-proteins mediate signal transfer from receptors to effector systems. (PMID: 9337071). Xanthosine 5-triphosphate is an intermediate of the Purine metabolism pathway, a substrate of the enzymes dinucleoside tetraphosphatase (EC 3.6.1.17) and nucleoside-triphosphate pyrophosphatase (EC 3.6.1.19). (KEGG).
Urea is a highly soluble organic compound formed in the liver from ammonia produced by the deamination of amino acids. It is the principal end product of protein catabolism and constitutes about one half of the total urinary solids. Urea is formed in a cyclic pathway known simply as the urea cycle. In this cycle, amino groups donated by ammonia and L-aspartate are converted to urea. Urea is essentially a waste product; it has no physiological function. It is dissolved in blood (in humans in a concentration of 2.5 - 7.5 mmol/liter) and excreted by the kidney in the urine. In addition, a small amount of urea is excreted (along with sodium chloride and water) in human sweat. Urea is found to be associated with primary hypomagnesemia, which is an inborn error of metabolism.
Xanthosine, also known as xanthine riboside, belongs to the class of organic compounds known as purine nucleosides. Purine nucleosides are compounds comprising a purine base attached to a ribosyl or deoxyribosyl moiety. Xanthosine is a nucleoside derived from xanthine and ribose. Xanthosine exists in all living species, ranging from bacteria to plants to humans. In plants xanthosine is the biosynthetic precursor to 7-methylxanthosine which is produced by the action of the enzyme known as 7-methylxanthosine synthase. 7-Methylxanthosine in turn is the precursor to theobromine (the active alkaloid in chocolate), which in turn is the precursor to caffeine, the active alkaloid in coffee and tea. Within humans, xanthosine participates in a number of enzymatic reactions. In particular, xanthosine can be biosynthesized from xanthylic acid; which is catalyzed by the enzyme cytosolic purine 5'-nucleotidase. In addition, xanthosine can be converted into xanthine and ribose 1-phosphate; which is mediated by the enzyme purine nucleoside phosphorylase. Xanthosine monophosphate (XMP) is an intermediate in purine metabolism, formed from IMP (inosine monophosphate).
Urocanic acid (CAS: 104-98-3) is a breakdown (deamination) product of histidine. In the liver, urocanic acid is an intermediate in the conversion of histidine to glutamic acid, whereas, in the epidermis, it accumulates and may be both a UV protectant and an immunoregulator. Urocanic acid (UA) exists as a trans isomer (t-UA, approximately 30 mg/cm2) in the uppermost layer of the skin (stratum corneum). t-UA is formed as the cells of the second layer of the skin become metabolically inactive. During this process, proteins and membranes degrade, histidine is released, and histidase (histidine ammonia lyase) catalyzes the deamination of histidine to form t-UA. t-UA accumulates in the epidermis until removal by either the monthly skin renewal cycle or sweat. Upon absorption of UV light, the naturally occurring t-UA isomerizes to its cis form, c-UA. Because DNA lesions (e.g., pyrimidine dimers) in the lower epidermis can result from UV-B absorption, initial research proposed that t-UA acted as a natural sunscreen absorbing UV-B in the stratum corneum before the damaging rays could penetrate into lower epidermal zones. Researchers have found that c-UA also suppresses contact hypersensitivity and delayed hypersensitivity, reduces the Langerhans cell count in the epidermis, prolongs skin-graft survival time, and affects natural killer cell activity. (E)-Urocanic acid is found in mushrooms. It has been isolated from Coprinus atramentarius (common ink cap) and Phallus impudicus (common stinkhorn).
Uridine diphosphategalactose (UDPgal) is a nucleoside diphosphate sugar which can be epimerized into UDPglucose for entry into the mainstream of carbohydrate metabolism. UDPgal is a pivotal compound in the metabolism of galactose. UDPgal is a product of the galactose-l-phosphate uridyl transferase (EC 2.7.7.10) reaction but may also be made from Glucose-l-P, involving uridine diphosphate galactose-4-epimerase (EC 5.1.3.2). UDPgal is the necessary galactosyl donor of galactose in the metabolism to incorporate it into complex oligosaccharides, glycoproteins and glycolipids (galactosides). Defective galactosylation of complex glycoconjugates exists in tissues from galactosemic patients. There is a tendency for galactosemic red cell UDPgal to be in the low normal range with a high uridine diphosphate glucose to UDP-gal ratio. This may reflect an inability of red cell UDPgal-4'-epimerase to maintain a normal ratio and consequently higher levels of UDPgal. In the more complex white blood cells and cultured fibroblasts, the UDPgal content and the uridine diphosphate glucose to UDPgal ratio of galactosemics are normal. Therefore, defective galactosylation observed in galactosemic fibroblasts must result from a defect in the transfer of galactose from UDPgal to these moieties. (PMID: 2122114, 7671968).
Tryptamine, also known as TrpN, is a catabolite of tryptophan converted by the gut microbiota. After absorption through the intestinal epithelium, tryptophan catabolites enter the bloodstream and are later excreted in the urine. Both Clostridium sp. and Ruminococcus sp. have been found to convert tryptophan into tryptamine (PMID: 30120222). Tryptamine is a monoamine compound that is a common precursor molecule to many hormones and neurotransmitters. Biosynthesis generally proceeds from the amino acid tryptophan, with tryptamine acting as a precursor for other compounds. Substitutions to the tryptamine molecule give rise to a group of compounds collectively known as tryptamines. The most well-known tryptamines are serotonin, an important neurotransmitter, and melatonin, a hormone involved in regulating the sleep-wake cycle. Tryptamine has been detected, but not quantified in, several different foods, such as onion-family vegetables, acerola, Japanese walnuts, custard apples, and green zucchinis. This could make tryptamine a potential biomarker for the consumption of these foods.
Uridine diphosphate-N-acetylgalactosamine (UDP-GalNAc) is a sugar donor metabolite, transferring N-acetylgalactosamine (GalNAc, an O-glycan) from UDP-GalNAc to serine and threonine residues, forming an alpha-anomeric linkage in a reaction catalyzed by enzymes known as UDP-N-acetylgalactosamine: polypeptide N-acetylgalactosaminyltransferases. The addition of GalNAc to serine or threonine represents the first committed step in mucin biosynthesis. O-Glycans impart unique structural features to mucin glycoproteins and numerous membrane receptors, and resistance to thermal change and proteolytic attack in a number of diverse proteins. O-Linked carbohydrate side chains function as ligands for receptors, lymphocyte and leukocyte homing, and as signals for protein sorting (PMID: 12634319). Animal studies suggest that overactivity of the hexosamine pathway, resulting in increased UDP-hexosamines (i.e. UDP-GalNAc) is an important mechanism by which hyperglycemia causes insulin resistance. However, to date, human studies concerning the role of the hexosamine pathway in hyperglycemia-induced insulin resistance are scarce and restricted to measurements of glutamine fructose-6-phosphate amidotransferase (GFAT) enzyme activity. Both positive and negative correlations between GFAT activity in human muscle tissue from patients with type 2 DM and glucose disposal rate have been reported (PMID: 12414889).
Vitamin A (retinol) is a yellow fat-soluble, antioxidant vitamin important in vision and bone growth. It belongs to the family of chemical compounds known as retinoids. Retinol is ingested in a precursor form; animal sources (milk and eggs) contain retinyl esters, whereas plants (carrots, spinach) contain pro-vitamin A carotenoids. Hydrolysis of retinyl esters results in retinol while pro-vitamin A carotenoids can be cleaved to produce retinal. Retinal, also known as retinaldehyde, can be reversibly reduced to produce retinol or it can be irreversibly oxidized to produce retinoic acid. Retinol and derivatives of retinol that play an essential role in metabolic functioning of the retina, the growth of and differentiation of epithelial tissue, the growth of bone, reproduction, and the immune response. Dietary vitamin A is derived from a variety of carotenoids found in plants. It is enriched in the liver, egg yolks, and the fat component of dairy products.
Tyramine is a monoamine compound derived from the amino acid tyrosine. Tyramine is metabolized by the enzyme monoamine oxidase. In foods, it is often produced by the decarboxylation of tyrosine during fermentation or decay. Foods containing considerable amounts of tyramine include fish, chocolate, alcoholic beverages, cheese, soy sauce, sauerkraut, and processed meat. A large dietary intake of tyramine can cause an increase in systolic blood pressure of 30 mmHg or more. Tyramine acts as a neurotransmitter via a G protein-coupled receptor with high affinity for tyramine called TA1. The TA1 receptor is found in the brain as well as peripheral tissues including the kidney. An indirect sympathomimetic, Tyramine can also serve as a substrate for adrenergic uptake systems and monoamine oxidase so it prolongs the actions of adrenergic transmitters. It also provokes transmitter release from adrenergic terminals. Tyramine is a biomarker for the consumption of cheese
1beta-Hydroxycholic acid is a C24 bile acid in the serum of healthy human fetuses and a urinary bile acid in the neonatal and pediatric periods. It is also excreted in the urine of pregnant women (PMID: 9483300, 10203155, 1400756). Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
3alpha,16beta-Dihydroxyandrostenone belongs to the class of organic compounds known as androgens and derivatives. These are 3-hydroxylated C19 steroid hormones. They are known to favour the development of masculine characteristics. They also show profound effects on scalp and body hair in humans. Thus, 3alpha,16beta-dihydroxyandrostenone is considered to be a steroid lipid molecule. 3alpha,16beta-Dihydroxyandrostenone is an unusual steroid found in the urinary excretion of a subject having a virilizing malignant adrenocortical tumor; apparent 21-steroid hydroxylase deficiency is discussed in the light of these results as well as the hormonogenesis enzymatic induction of the tumour biopsy (PMID: 198067).
Methylacetoacetic acid, also known as 3-oxo-butanoate or methyl acetylacetate, belongs to the class of organic compounds known as beta-keto acids and derivatives. These are organic compounds containing an aldehyde substituted with a keto group on the C3 carbon atom. Methylacetoacetic acid is an extremely weak basic (essentially neutral) compound (based on its pKa). Methylacetoacetic acid is a citrus, fresh, and fruity tasting compound. Methylacetoacetic acid has been identified in the urine of patients with an inherited deficiency of propionyl-CoA carboxylase (PMID 630060), and after isoleucine loading in the diagnosis of 2-methylacetoacetyl-CoA thiolase deficiency.
3b,4b,7a,12a-Tetrahydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g., membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues.
3alpha,7alpha,12beta-Trihydroxy-5beta-cholanoic acid, also known as lagocholic acid, is a bile acid. Bile acids with beta-hydroxyl and carbonyl groups at the C-3,7, and/or 12 positions are bile acids usually found in the urine of healthy humans (PMID: 8743575). Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
16b-Hydroxyestrone is an aromatized C18 steroid with a 3-hydroxyl group and a 17-ketone, a major mammalian estrogen. It is converted from androstenedione directly, or from testosterone via estradiol. In humans, it is produced primarily by the cyclic ovaries, placenta, and the adipose tissue of men and postmenopausal women.
3b-Allotetrahydrocortisol is one of the tetrahydrometabolites of cortisol. The 11-beta-hydroxysteroid dehydrogenase (11beta-HSD) is responsible for the interconversion of both the hormonally inactive cortisone and the active cortisol, which has implications in the pathogenesis of numerous diseases, as reflected in the ratio of tetrahydrometabolites of cortisol. (PMID: 16310418). The daily excretion of allotetrahydrocortisol is above normal in hyperthyroid patients; In contrast, in hyperthyroidism the excretion is diminished below normal levels to approximately half that of normal subjects. (PMID 13906284). A decreased activity of the enzyme 11beta-HSD produces a pattern of urinary steroid metabolites with an abnormal elevation of tetrahydrocortisol and allo-tetrahydrocortisol compared to tetrahydrocortisone; this pattern of steroid excretion is essential for the diagnosis of the syndrome of apparent mineralocorticoid excess type 1. (PMID: 8834992).
16-alpha-hydroxypregnenolone, also known as 16A OH-Preg or (3beta,16alpha)-3,16-dihydroxypregn-5-en-20-one, is classified as a gluco/mineralocorticoid, a progestogin or aprogestogin derivative. Gluco/mineralocorticoids are steroids with a structure based on a hydroxylated prostane moiety. Thus, 16-alpha-hydroxypregnenolone is a steroid or more correctly a 16alpha-hydroxy steroid. 16-alpha-hydroxypregnenolone is also classified as a hydroxypregnenolone. A hydroxypregnenolone is a pregnenolone substituted by an alpha-hydroxy group at position 16. It is a steroid molecule that is produced by all vertebrates. In humans, 16-alpha-hydroxypregnenolone can be found primarily in blood, urine and in human umbilical cord tissue. 16-alpha-Hydroxypregnenolone is a normal urinary metabolite with increased total excretion in newborn infants with congenital adrenal hyperplasia due to 21-hydroxylase deficiency (PMID 6980322). It is therefore an important urinary marker for the occurrence of an adrenal 21-hydroxylase-deficiency. Its levels are an indication for the effectiveness of medication (cortisol supplement) against this disease. (PMID: 10399855).
2b,3a,7a,12a-Tetrahydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
2-Hydroxy-3-methylpentanoic acid or 2-hydroxy-3-methylvaleric acid (HMVA) is an organic acid generated by L-isoleucine metabolism. It is derived from the reduction of 2-Keto-3-methylvaleric acid (KMVA), possibly through the action of a lactate dehydrogenase (PMID: 1429566). There are 4 stereoisomers of HMVA (2S,3S-HMVA, 2R,3R-HMVA, 2S,3R-HMVA and 2R,3S-HMVA), of which the 2S,3S and 2S,3R derivatives are generally separable. HMVA is found in the urine and blood of normal individuals but in very elevated levels in patients with maple syrup urine disease (MSUD) (PMID: 1429566). Maple syrup urine disease (MSUD) is an inherited metabolic disease predominantly characterized by neurological dysfunction including psychomotor/delay/mental retardation.
18-Hydroxycorticosterone is a corticosteroid and a derivative of corticosterone. If it is present in sufficiently high concentrations, it can lead to serious electrolyte imbalances (an electrolyte toxin). 18-Hydroxycorticosterone serves as an intermediate in the synthesis of aldosterone by the enzyme aldosterone synthase in the zona glomerulosa. Chronically high levels of 18-hydroxycorticosterone are associated with at least three inborn errors of metabolism including adrenal hyperplasia type V, corticosterone methyl oxidase I deficiency, and corticosterone methyl oxidase II deficiency. Each of these conditions is characterized by excessive amounts of sodium being released in the urine (salt wasting), along with insufficient release of potassium in the urine, usually beginning in the first few weeks of life. This imbalance leads to low levels of sodium and high levels of potassium in the blood (hyponatremia and hyperkalemia, respectively). Individuals with corticosterone methyloxidase deficiency can also have high levels of acid in the blood (metabolic acidosis). Acidosis typically occurs when arterial pH falls below 7.35. In infants with acidosis the initial symptoms include poor feeding, vomiting, loss of appetite, weak muscle tone (hypotonia), and lack of energy (lethargy). The hyponatremia, hyperkalemia, and metabolic acidosis associated with corticosterone methyloxidase deficiency can cause nausea, vomiting, dehydration, low blood pressure, extreme tiredness (fatigue), and muscle weakness.
3a,4b,7a-Trihydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12. 3a,4b,7a-Trihydroxy-5b-cholanoic acid accounts for 5-15% of the total biliary bile acids in early gestation, has been identified in the feces from healthy newborn infants many days after birth, indicating a hepatic origin for C-4 hydroxylation of bile acids. PMID 2794778).
2-Hydroxyadipic acid is a hydroxy-dicarboxylic acid formed by the reduction of 2-ketoadipic acid. A deficiency of 2-ketoadipic dehydrogenase causes 2-ketoadipic acidemia or 2-oxoadipic acidemia (OMIM: 245130), a genetic disorder characterized by accumulation and excretion of 2-hydroxyadipic acid (with 2-ketoadipic and 2-aminoadipic) (OMMBID - The Online Metabolic and Molecular Bases of Inherited Disease, CH.95). When present in sufficiently high levels, 2-hydroxyadipic acid can act as an acidogen and a metabotoxin. An acidogen is an acidic compound that induces acidosis, which has multiple adverse effects on many organ systems. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of 2-hydroxyadipic acid are associated with at least three inborn errors of metabolism including  2-oxoadipic acidemia, 2-aminoadipic aciduria, and 2-oxoadipic aciduria. 2-Hydroxyadipic acid is an organic acid. Abnormally high levels of organic acids in the blood (organic acidemia), urine (organic aciduria), the brain, and other tissues lead to general metabolic acidosis. Acidosis typically occurs when arterial pH falls below 7.35. In infants with acidosis, the initial symptoms include poor feeding, vomiting, loss of appetite, weak muscle tone (hypotonia), and lack of energy (lethargy). These can progress to heart abnormalities, kidney abnormalities, liver damage, seizures, coma, and possibly death. These are also the characteristic symptoms of the untreated IEMs mentioned above. Many affected children with organic acidemias experience intellectual disability or delayed development. In adults, acidosis or acidemia is characterized by headaches, confusion, feeling tired, tremors, sleepiness, and seizures.
16-Oxoandrostenediol is a naturally occurring androgenic steroid hormone generated by the adrenal glands. It has been found in the urine of newborn infants. Secretion of this steroid is suppressed by dexamethasone. Levels of this hormone are almost absent by 5 months of age. ((Steroids (1964), 3(1), 77-83.) ). 16-Oxoandrostenediol is a natural hormone with androgenic activity and that two potent antiandrogens: hydroxyflutamide (Eulexin) and bicalutamide (Casodex).
3-Amino-2-piperidone is a delta-lactam of ornithine. It is found in the urine of patients with hyperornithinemia (PMID 679477), due to Ornithine keto acid aminotransferase (EC 2.6.1.13) deficiency (OMIM 258870).
3alpha,16alpha-Dihydroxyandrostenone belongs to the class of organic compounds known as androgens and derivatives. These are 3-hydroxylated C19 steroid hormones. They are known to favour the development of masculine characteristics. They also show profound effects on scalp and body hair in humans. Thus, 3alpha,16alpha-dihydroxyandrostenone is considered to be a steroid lipid molecule. 3alpha,16alpha-Dihydroxyandrostenone is the most abundant single urinary metabolite of 16alpha-hydroxydehydroisoandrosterone present in normal, non-pregnant humans (PMID: 6049445). 3alpha,16alpha-Dihydroxyandrostenone was found in the urine sample from a patient who had an inoperable asymptomatic adrenal carcinoma and who excreted about 5 mg/day (PMID: 4733093). 3alpha,16-Dihydroxyandrostenone is a urinary C19 steroid usually present at a very low level in normal pregnancy; however, it is increased in women with androgenic alopecia (PMID: 10751586).
3-Hydroxysuberic acid is a metabolite derived from the w-oxidation of 3-hydroxy fatty acids and the subsequent beta-oxidation of longer-chain 3-hydroxy dicarboxylic acids (PMID 2001377). It has been found increased in ketoaciduria (PMID 1591279).
1b,3a,12a-Trihydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g., membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues.
12-Ketodeoxycholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
2-Phenylbutyric acid, also known as alpha-phenylbutyrate or alpha-ethyl-alpha-toluate, belongs to the class of organic compounds known as phenylpropanes. Phenylpropanes are organic compounds containing a phenylpropane moiety. 2-Phenylbutyric acid is slightly soluble (in water) and a weakly acidic compound (based on its pKa). 2-Phenylbutyric acid can be biosynthesized from butyric acid. 2-Phenylbutyric acid is used as an anticholesteremic.
3a,4b,12a-Trihydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12.
3a,7b,12a-Trihydroxyoxocholanyl-Glycine is an acyl glycine and a bile acid-glycine conjugate. It is a secondary bile acid produced by the action of enzymes existing in the microbial flora of the colonic environment. In hepatocytes, both primary and secondary bile acids undergo amino acid conjugation at the C-24 carboxylic acid on the side chain, and almost all bile acids in the bile duct therefore exist in a glycine conjugated form (PMID: 16949895). 3a,7b,12a-Trihydroxyoxocholanyl-Glycine is a specific ketonic bile acid found in the urine of infants during the neonatal period. Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12.
18-Oxocortisol shares structural characteristics with cortisol and aldosterone and is secreted from the adrenal cortex. The plasma levels of 18-Oxocortisol are significantly higher in patients with adrenocortical disorders than in control subjects. (PMID 8013138).
Isohomovanillic acid is a deaminated metabolite of catecholamines formed by the enzyme catechol-O-methyltransferase (COMT; EC 2.1.1.6) which catalyzes the transfer of a methyl group from S-adenosylmethionine to catecholamines, including the neurotransmitters dopamine, epinephrine, and norepinephrine. This O-methylation results in one of the major degradative pathways of the catecholamine transmitters. (OMIM 116790).
16a-Hydroxyestrone or 16alpha-hydroxyestrone (16Œ±-OH-E1 or 16a OHE1), or hydroxyestrone, is an endogenous steroidal estrogen and a major metabolite of estrone and estradiol.  16a-hydroxyestrone belongs to the class of organic compounds known as estrogens and derivatives. These are steroids with a structure containing a 3-hydroxylated estrane. Thus, 16a-hydroxyestrone is considered to be a steroid molecule. 16a-hydroxyestrone is found in all vertebrates. Vertebrates, especially mammals, metabolizes estrogen into two major pathways and one minor. The two major pathways lead to 2-hydroxyestrone and 16a-hydroxyestrone (2-OHE1 and 16a OHE1 respectively). The minor pathway leads to 4-hydroxyestrone (4-OHE1). 2a-hydroxyestrone is considered to be the good metabolite (PMID: 8943806) as 2-hydroxyestrone does not stimulate cell growth and it blocks the action of stronger estrogens that may be carcinogenic. 16a-Hydroxyestrone, on the other hand, has a significantly stronger estrogenic activity, and studies show that it may increase the risk of breast cancer. The binding of 16a-hydroxyestrone to the estrogen receptor is reported to be covalent and irreversible (PMID: 3186693). A low urinary ratio of 2-hydroxyestrone to 16-alpha-hydroxyestrone is a strong predictor of breast cancer risk among women (PMID: 19502596).
(R)-3-Hydroxyisobutyric acid (3-HIBA) is an organic acid. The chiral metabolites 3-hydroxyisobutyric acid (HIBA) and 3-aminoisobutyric acid (AIBA) are intermediates in the pathways of L-valine and thymine and play an important role in the diagnosis of the very rare inherited metabolic diseases 3-hydroxyisobutyric aciduria (OMIM: 236795) and methylmalonic semialdehyde dehydrogenase deficiency (OMIM: 603178) (PMID: 10686279). (R)-3-Hydroxyisobutyric acid has been identified in the human placenta (PMID: 32033212).
3,4-Dihydroxybutyric acid (also known as 3,4-Dihydroxybutanoic acid or 3,4-DB, or 2-deoxytetronic acid, or 2-DTA) is a normal human urinary metabolite that is excreted in increased concentration in patients with succinic semialdehyde dehydrogenase (SSADH) deficiency (PMID 12127325), which is a genetic disorder. SSADH deficiency is caused by an enzyme deficiency in GABA degradation. The most constant features with this disease are developmental delay, hypotonia and intellectual disability. Nearly half of SSADH patients exhibit ataxia, behavioral problems, seizures, and hyporeflexia. Normal adults excrete 0.37 +/- 0.15 (SD) mmoles of 3,4-dihydroxybutyrate per 24 hr. 3,4-dihydroxybutyrate is also detectable in blood. The renal clearance of 3,4-dihydroxybutyrate is roughly equal that of creatinine. 3,4-dihydroxybutyric acid has also been found in foods and is believed to be formed via the degradation (cooking) of di- and poly-saccharides (PMID: 1167165).  3,4-Dihydroxybutyric acid is believed to play a role in satiety or the feeling of fullness and suppresses food intake (PMID: 3191387; PMID: 6720928). 3,4-dihydroxybutyric acid is also elevated in the serum of individuals with dementia and may even serve as a predictive biomarker for dementia (PMID: 25177334). 3,4-Dihydroxybutyric acid is also a metabolite produced in Escherichia (PMID: 28342964).
2-Hydroxyestradiol (2-OHE2), also known as estra-1,3,5(10)-triene-2,3,17beta-triol, is an endogenous steroid, catechol estrogen. 2-Hydroxyestradiol belongs to the class of organic compounds known as estrogens and derivatives. These are steroids with a structure containing a 3-hydroxylated estrane. Thus, 2-hydroxyestradiol is considered to be a steroid molecule. It is a metabolite of estradiol, as well as a positional isomer of estriol. Transformation of estradiol to 2-hydroxyestradiol is a major metabolic pathway of estradiol in the liver. 2-Hydroxyestradiol is generated from estradiol via several cytochrome P450 enzymes. Specifically, CYP1A2 and CYP3A4 are the major enzymes catalyzing the 2-hydroxylation of estradiol. Conversion of estradiol into 2-hydroxyestradiol has been detected in the liver, uterus, breast, kidney, brain, and pituitary gland, as well as the placenta. 2-Hydroxyestradiol binds, with a low affinity, to estrogen receptors. 2-Hydroxyestradiol has approximately 7% and 11% of the affinity of estradiol at the estrogen receptors (ERs) ERalpha and ERbeta, respectively (PMID: 9048584). 2-Hydroxyestradiol is a catechol estrogen and in this regard bears some structural resemblance to the catecholamines dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline) (PMID: 447670).  In accordance, 2-hydroxyestradiol has been found to interact with catecholamine systems. The steroid is known to compete with catecholamines for binding to catechol O-methyltransferase and tyrosine hydroxylase and to competitively inhibit these enzymes (PMID: 447670). Inactivity of COMT blocks inactivation of catechol hormones and catecholamine neurotransmitters. 2-Hydroxyestradiol is also reported to inhibit angiongensis and tumor cell growth (PMID: 9472688).
3a,7a,12a,19-Tetrahydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g., membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues.
2-Octenedioic acid is an unsaturated dicarboxylic acid found in the urine of persons with abnormal fatty acid metabolism, such as patients with Dicarboxylic aciduria (PMID 2094705, 2614263).
2-Hydroxyestrone (2-OHE1), also known as estra-1,3,5(10)-trien-2,3-diol-17-one, is an endogenous, naturally occurring catechol estrogen and a major metabolite of estrone and estradiol. 2-Hydroxyestrone belongs to the class of organic compounds known as estrogens and derivatives. These are steroids with a structure containing a 3-hydroxylated estrane. Thus, 2-Hydroxyestrone is considered to be a steroid molecule. It is formed irreversibly from estrone in the liver and to a lesser extent in other tissues via 2-hydroxylation mediated by cytochrome P450 enzymes, mainly the CYP3A and CYP1A subfamilies. 2-OHE1 is the most abundant catechol estrogen in the body. 2-Hydroxyestrone is found in all vertebrates. Vertebrates, especially mammals, metabolizes estrogen into two major pathways and one minor. The two major pathways lead to 2-hydroxyestrone and 16a-hydroxyestrone (2-OHE1 and 16a OHE1, respectively). The minor pathway leads to 4-hydroxyestrone (4-OHE1). 2a-hydroxyestrone is considered to be the good steroid metabolite (PMID: 8943806) as 2-hydroxyestrone does not stimulate cell growth and it blocks the action of stronger estrogens that may be carcinogenic. 2-hydroxyestrone is not significantly uterotrophic, whereas other hydroxylated estrogen metabolites including 2-hydroxyestradiol, 16a-hydroxyestrone, estriol, 4-hydroxyestradiol, and 4-hydroxyestrone all are. A low urinary ratio of 2-hydroxyestrone to 16-alpha-hydroxyestrone is a strong predictor of breast cancer risk among women (PMID: 19502596).
Generally refers to the 17-beta-isomer of estradiol, an aromatized C18 steroid with hydroxyl group at 3-beta- and 17-beta-position. estradiol-17-beta is the most potent form of mammalian estrogenic steroids. In humans, it is produced primarily by the cyclic ovaries and the placenta. It is also produced by the adipose tissue of men and postmenopausal women. The 17-alpha-isomer of estradiol binds weakly to estrogen receptors (receptors, estrogen) and exhibits little estrogenic activity in estrogen-responsive tissues. Various isomers can be synthesized.
3-Hydroxyadipic acid is a normal urinary dicarboxylic acid derived from the omega-oxidation of 3-hydroxy fatty acids and the subsequent beta-oxidation of longer chain 3-hydroxy dicarboxylic acids (PMID 2001377). It is found to be elevated in patients with 3-hydroxydicarboxylic aciduria (PMID 1444166) and non-ketotic hypoglycemia (PMID 3168281).
3-Deoxyarabinohexonic acid, also known as arabino-3-deoxyhexonate or D-2-keto-3-deoxygluconate, belongs to the class of organic compounds known as medium-chain hydroxy acids and derivatives. These are hydroxy acids with a 6 to 12 carbon atoms. 3-deoxyarabinohexonic acid is a thermal decomposition product of plant-derived sugars such as nigerose (3-O-Œ±-D-glucopyranosyl-D-glucose), turanose and 3-O-methyl glucose. 3-deoxyarabinohexonic acid is found in plants and plant products that have been heated. As a consequence, it can be detected in the biofluids of animals that have consumed plant foods (including humans).
16b-Hydroxyestradiol, which is better known as epiestriol (or 16beta-epiestriol or 16beta-hydroxy-17beta-estriol), belongs to the class of organic compounds known as estrogens and derivatives. These are steroids with a structure containing a 3-hydroxylated estrane. Thus, epiestriol is considered to be a steroid molecule. Formally 16b-hydroxyestradiol is a 3-hydroxy steroid that is 17beta-estradiol substituted by a beta-hydroxy group at position 16.  In other words, it has hydroxyl groups at the C3, 16-beta, and 17-beta positions. It is an oxidative metabolite of 17beta-estradiol (PMID: 12865317). Epiestriol is found in all vertebrates. Epiestriol is a minor and weak endogenous estrogen. It is the 16beta-epimer of estriol (which is 16alpha-hydroxy-17beta-estradiol).  Epiestriol has been used clinically in the treatment of acne. In addition to its estrogenic actions, epiestriol has been found to possess significant anti-inflammatory properties without glycogenic activity or immunosuppressive effects (PMID: 9120824).
3b,12a-Dihydroxy-5a-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g., membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues.
Erythrono-1,4-lactone has been identified as a lactone of tetronic acid in the urine from normal adults and neonates. The formation of this compound may be a consequence of lactonization of erythronic acid during the extraction/isolation process. Lactonization is a potential problem when measuring acids that contain a hydroxyl group at the number 4 carbon, as lactones are formed under acidic conditions. Evidence indicates that most 4-hydroxy acids do not normally exist to any appreciable extent as lactones in urine. (PMID 1192581).
3-Hydroxydecanedioic is a dicarboxylic acid that belongs to the class of compounds known hydroxy fatty acids. Hydroxy fatty acids are fatty acids that have hydroxyl functional groups attached to the principal chain. 3-Hydroxydecanedioic acid is found in most vertebrates. Urine from patients with ketoacidosis typically contains a number of aliphatic 3-hydroxy dicarboxylic acids, with the major compound being 3-hydroxydecanedioic acid (PMID: 7353273). The excretion of 3-hydroxydecanedioic acid is correlated with the excretion of hexanedioic acid, another metabolite frequently found in ketoacidosis (PMID: 5031780). It is thought that the 3-hydroxy dicarboxylic acids such as 3-hydroxydecanedioic acid are formed from fatty acids by a combination of omega-oxidation and incomplete beta-oxidation (PMID: 7353273). Marked elevation of urinary 3-hydroxydecanedioic acid has also been reported in a malnourished infant with glycogen storage disease (PMID: 8295400). Subsequent studies have shown that increased amounts of dicarboxylic acids, such as 3-hydroxydecanedioic acid, are typically excreted in human urine under conditions of medium-chain triglyceride (MCT) feeding, abnormal fatty acid oxidation (FAO) and fasting (PMID: 8596483).
3-Hydroxy-2-methylbutanoic acid (HMBA) is a normal urinary metabolite involved in isoleucine catabolism, beta-oxidation of fatty acids, and ketogenesis. HMDB is excreted in abnormally high amounts in beta-ketothiolase deficiency. Differences in the enantiomeric ratio of HMBA may originate from the enantioselectivity of different enzyme systems (PMID: 10755375).
16a-Hydroxydehydroisoandrosterone is a metabolite present during pregnancy with increased concentrations as it progresses (PMID 6461703). A reduced level of 16a-Hydroxydehydroisoandrosterone is observed in cases of Placental sulfatase deficiency (PSD), a rare disorder with low estrogen production due to placental enzymatic deficiency. (PMID 2150812).
3b,15b,17a-Trihydroxy-pregnenone is a major 15 beta-hydroxylated metabolite unique to the human perinatal period. (PMID 8750436). The chemical synthesis of 15&#946;-hydroxylated steroids is for use in the (a) development of new immunoassay techniques for application to newborn screening programs and fetal well-being; (b) development of new anti-androgenic drugs; and (c) study of androgen/estrogen interaction in late pregnancy.
3-Hydroxy-2-methyl-butanoic acid (HMBA) is a normal urinary metabolite involved in the isoleucine catabolism, as well as presumably beta-oxidation of fatty acids and ketogenesis, excreted in abnormally high amounts in beta-ketothiolase deficiency, which is a genetic disorder. Differences in the enantiomeric ratio of HMBA may originate from the enantioselectivity of different enzyme systems (PMID 10755375).
17-Epiestriol, also known as 17alpha-estriol, belongs to the class of organic compounds known as estrogens and derivatives. These are steroids with a structure containing a 3-hydroxylated estrane. Thus, 17-epiestriol is considered to be a steroid lipid molecule. 17-Epiestriol is a hydroxylated metabolite of estradiol or estrone that has a hydroxyl group at the C3-beta, 16-alpha, and 17-beta positions. Estriol is a major urinary estrogen. During pregnancy, a large amount of estriol is produced by the placenta. Isomers with inversion of the hydroxyl group or groups are called epiestriol.
3α,7α-Dihydroxycoprostanic acid is a bile acid excreted in small amounts in the urine of healthy subjects (PMID: 864325). 3α,7α-Dihydroxycoprostanic acid is the precursor to chenodeoxycholic acid, a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine, and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH, and consequently require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues.
2,4-Dihydroxybutanoic acid or 3-Deoxytetronic acid is usually absent in normal human urine extracts or in only trace constituents in neonates. (PMID 1192581) However, various cases of succinic semialdehyde dehydrogenase deficiency have shown consistently increased amounts of this metabolite. (PMID 3126356).
3b,7a-Dihydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
2-Phosphoglyceric acid (2PGA) is a glyceric acid which serves as the substrate in the ninth step of glycolysis. It is catalyzed by enolase into phosphoenolpyruvate (PEP), the penultimate step in the conversion of glucose to pyruvate. Enolase catalyzes the beta-elimination reaction in a stepwise manner wherein OH- is eliminated from C3 of a discrete carbanion (enolate) intermediate. This intermediate is created by removal of the proton from C2 of 2PGA by a base in the active site (PMID: 8994873, Wikipedia).
17a-Hydroxypregnenolone is a 21-carbon steroid that is converted from pregnenolone by cytochrome P450 17alpha hydroxylase/C17,20 lyase (CYP17, EC 1.14.99.9). 17a-Hydroxypregnenolone is an intermediate in the delta-5 pathway of biosynthesis of gonadal steroid hormones and the adrenal corticosteroids. The first, rate-limiting and hormonally regulated step in the biosynthesis of all steroid hormones is the conversion of cholesterol to pregnenolone. The conversion of cholesterol to pregnenolone is accomplished by the cleavage of the cholesterol side chain, catalyzed by a mitochondrial cytochrome P450 enzyme termed P450scc where scc designates Side Chain Cleavage. All steroid hormones are made from the pregnenolone produced by P450scc; thus, the presence or absence of each of the activities of CYP17 directs this pregnenolone towards its final metabolic pathway. While all cytochrome P450 enzymes can catalyze multiple reactions on a single active site, CYP17 is the only one described to date in which these multiple activities are differentially regulated by a physiologic process. 17a-Hydroxypregnenolone is converted to dehydroepiandrosterone by the 17,20 lyase activity of CYP17. The ratio of the 17,20 lyase to 17 alpha-hydroxylase activity of CYP17 determines the ratio of C21 to C19 steroids produced. This ratio is regulated post-translationally by at least three factors: the abundance of the electron-donating protein P450 oxidoreductase, the presence of cytochrome b5, and the serine phosphorylation of CYP17. (PMID: 12573809).
3a,6a,7b-Trihydroxy-5b-cholanoic acid is an unusual trihydroxy bile acid found in the urine of healthy humans, mainly in newborns (PMID 3769218). Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 6, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Epiandrosterone is a naturally occurring steroid synthesized in the adrenal cortex, gonads, brain, and gastrointestinal tract. It is less active than androsterone and excreted in small amounts in normal human urine. Epiandrosterone is a metabolite of the most abundant adrenal androgenic steroid dehydroepiandrosterone (DHEA) in young adult humans, but is not completely inactive and is considered an effector as well. Epiandrosterone is a precursor or substrate for cytochrome P450 species and enzymes (EC 1.14.13.100, 25-hydroxycholesterol 7alpha-hydroxylase) that produce 7alpha- and 7beta-hydroxylated metabolites in the human brain and other organs. These 7-hydroxylated derivatives exert anti-glucocorticoid and neuroprotective effects (PMID: 17017935, 12475725, 15650074, 15784286).
2-Deoxyribonic acid is the acid form of deoxyribonate (interconvertible with 2-Deoxyribonolactone), produced as part of bistranded lesions by DNA damaging agents, including the antitumor agents bleomycin and the neocarzinostatin chromophore (PMID 2523732). This lesion is also produced by ionizing radiation, organometallic oxidants, and is a metastable intermediate in DNA damage mediated by copper phenanthroline nucleases, and is also formed under anaerobic conditions in the presence of the radiosensitizing agent tirapazamine. (PMID 12600212), and it has been found in normal human biofluids (PMID 2925825, 3829393, 6725493, 7228943).
3a.6b,7b,12a-tetrahydroxy-5b-cholan-24-oic is an unusual bile acid that has been identified in amniotic fluid and urine samples from adult patients with cholestatic liver disease. (PMID 2075618). Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12.
2(R)-Hydroxyadipic acid is an unusual metabolic isomer of 2-hydroxyadipic acid (a metabolite that accumulates in 2-ketoadipic acidemia) normally present in bacteria and described in normal human biofluids (PMID: 6788787).
The unspecified form of the steroid, normally a major metabolite of testosterone with androgenic activity. It has been implicated as a regulator of gonadotropin secretion.
2-Amino-3-phosphonopropionic acid (AP-3 or 2-AP3), also known as 3-phosphonoalanine, is a non-proteinogenc alpha-amino acid that is alanine in which one of the hydrogens of the terminal methyl group has been replaced by a dihydroxy(oxido)-lambda(5)-phosphanyl group. It is found in many organisms ranging from microbes to invertebrates to animals. In humans AP-3 is found in diverse tissues, such as liver, intestine and spleen. (PMID: 2627760). 2-Amino-3-phosphonopropionic acid is a ubiquitous naturally occurring phosphonate used as a source of phosphorus by many prokaryotic organisms (PMID: 30119975). The natural occurrence of 2-amino-3-phosphonopropionic acid. the phosphonate analogue of aspartic acid, was first reported by Kittredge & Hughes (PMID: 14214094) in the sea anemone Zoanthus sociatus and the protozoon Tetrahymena pyriformis. It has since been established to be one of the most widely distributed of the biogenic C‚ÄìP compounds, particularly among the lower marine invertebrates (PMID: 19191873). AP-3 has been determined to be a metabotropic glutamate receptor agonist (PMID: 8836635). It has been shown to block the amyloid precursor protein (APP) release evoked by glutamate receptor stimulation in neurons of the cortex and hippocampus. APP accumulation is believed to produce the damage in Alzheimer‚Äôs disease (PMID: 7644542).
1,3,12-Trihydroxycholan-24-oic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Estrone (also oestrone) is an estrogenic hormone secreted by the ovary. Its molecular formula is C18H22O2. estrone has a melting point of 254.5 degrees Celsius. estrone is one of the three estrogens, which also include estriol and estradiol. estrone is the least prevalent of the three hormones, estradiol being prevalent almost always in a female body, estriol being prevalent primarily during pregnancy. estrone sulfate is relevant to health and disease due to its conversion to estrone sulfate, a long-lived derivative of estrone. estrone sulfate acts as a pool of estrone which can be converted as needed to the more active estradiol.
17-Hydroxyprogesterone also known as 17-OH progesterone (17-OHP), or hydroxyprogesterone (OHP), is an endogenous progestogen steroid hormone related to progesterone. Formally it is a 17alpha-hydroxy steroid that is the 17alpha-hydroxy derivative of progesterone. 17-Hydroxyprogesterone is found in all vertebrates. It is a chemical intermediate in the biosynthesis of many endogenous steroids, including androgens, estrogens, glucocorticoids, mineralocorticoids and neurosteroids. In particular, 17-Hydroxyprogesterone serves as an intermediate in the biosynthesis of hydrocortisone and gonadal steroid hormones. It is derived from progesterone via the enzyme known as 17-hydroxylase, a cytochrome P450 enzyme also known as CYP17A1. It can also be biosynthesized from 17-hydroxypregnenolone via the enzyme 3beta-hydroxysteroid dehydrogenase/delta5-4 isomerase (PMID: 1955079). 17-OHP is an agonist of the progesterone receptor (PR). It is also an antagonist of the mineralocorticoid receptor (MR) as well as a partial agonist of the glucocorticoid receptor (GR). 17-Hydroxyprogesterone is a natural progestin and in pregnancy it increases in the third trimester primarily due to fetal adrenal production. 17-Hydroxyprogesterone is primarily produced in the adrenal glands and to some degree in the gonads, specifically the corpus luteum of the ovary. Normal levels are 3-90 ng/dl in children, and in women, 15-70 ng/dl prior to ovulation, and 35-290 ng/dl during the luteal phase. Measurements of levels of 17-hydroxyprogesterone are useful in the evaluation of patients with suspected congenital adrenal hyperplasia as the typical enzymes that are defective, namely 21-hydroxylase, lead to a build-up of 17-OHP. 17-OHP levels can also be used to measure contribution of progestational activity of the corpus luteum during pregnancy as progesterone but not 17-OHP is also contributed by the placenta.
3-(3-Hydroxyphenyl)propanoic (hMPP) acid is one of the major metabolites of ingested caffeic acid (PMID: 15479001) and of the phenolic degradation products of proanthocyanidins (the most abundant polyphenol present in chocolate) by the microflora in the colon (PMID: 12663291). mHPP is suspected to have antioxidants properties and is actively absorbed by the monocarboxylic acid transporter (MCT) in intestinal Caco-2 cell monolayers (PMID: 15479001, 12663291). hMPP has been found to be a metabolite of Clostridium, Escherichia, and Eubacterium (PMID: 28393285, 19520845). 3-(3-Hydroxyphenyl)propanoic acid is a flavonoid metabolite. 3-(3-Hydroxyphenyl)propanoic acid is a phenolic acid metabolite formed by the gut microflora detected after the consumption of whole grain.
3b,7a,12a-Trihydroxy-5a-Cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12. 3b,7a,12a-Trihydroxy-5a-Cholanoic acid has been identified in the bile, plasma and urine of patients with delta 4-3-oxosteroid 5 beta-reductase deficiency with neonatal hepatitis, an inborn error in bile acid synthesis. (PMID 3198770).
3a,6b,7b,12b-Tetrahydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12. 3a,6b,7b,12b-Tetrahydroxy-5b-cholanoic acid is an uncommon bile acid with OH groups at C-3, 6, 7, and 12 positions. (High-performance liquid chromatography of bile acids. Effect of hydroxyl groups at C-3, 6, 7 and 12 on bile acid mobility. Batta, Ashok K. Aggarwal, Suresht K. Salen, Gerald. New Jersey Med. Sch., Univ. Med. Dent., Newark, NJ, USA. Journal of Liquid Chromatography (1992), 15(3), 467-78.).
Methylcitric acid (MCA) is elevated in body fluids of patients with propionic acidaemia (PA; OMIM 232000, 232050), methylmalonic aciduria (MMA; OMIM 251000, 251120) and multiple carboxylase deficiency (OMIM 253260, 253270), which are inherited disorders. MCA is formed by condensation of accumulated propionyl- CoA and oxalacetate by the enzyme si-citrate synthase (EC 4.1.3.7). MCA molecule has two stereogenic centers so that it can occur in the form of four stereoisomers. Only two stereoisomers of MCA, (2S, 3S) and (2R, 3S), were found in human urine (PMID: 17295121).
2-Hydroxyestradiol-3-methylether is a methoxylated derivative of 2-hydroxyestradiol. 2-hydroxy estrogen metabolites can be converted to anticarcinogenic methoxylated metabolites (2-methoxyestrone and 2-methoxyestradiol, 2-hydroxyestrone and 2-hydroxyestradiol 3-methyl ether) by catechol O-methyltransferase (PMID: 11172156). 2-hydroxyestradiol 3-methyl ether has been found in the urine of pregnant women (along with other 2-hydroxyestrogen ethers) although the amounts are generally small (less than 5 ug/24 hours). (PMID: 966757).
Allolithocholic acid is a bile acid present in normal serum and feces, with a tendency to be at higher concentrations in patients with colon cancer, particularly in men (PMID 16548228). A bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
The unspecified form of the steroid, normally a major metabolite of testosterone with androgenic activity. It has been implicated as a regulator of gonadotropin secretion.3a,17a-Dihydroxy-5b-androstane is a metabolite of natural androgens (testosterone, epitestosterone, dihydrotestosterone, and dehydroepiandrosterone) present in small amount in the urine of normal individuals (PMID 9381514).
3a,7a-Dihydroxycholanoic acid is a chenodeoxycholic or bile acid present in human blood serum. (PMID 13324110) and in the biliary excretion of patients with choledochostomy drainage (PMID 16695472). Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12.
12a-Hydroxy-3-oxocholadienic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
3-Hydroxydodecanoic acid (CAS: 1883-13-2) is a medium-chain fatty acid associated with fatty acid metabolic disorders (PMID: 11948802). Deficiency of medium-chain acyl-CoA dehydrogenase is characterized by an intolerance to prolonged fasting, recurrent episodes of hypoglycemic coma with medium-chain dicarboxylic aciduria, impaired ketogenesis, and low plasma and tissue carnitine levels (OMIM: 201450). 3-Hydroxydodecanoic acid is also a microbial metabolite found in Acinetobacter, Moraxella, and Pseudomonas (PMID: 21687748). 3-Hydroxydodecanoic acid has been identified in the human placenta (PMID: 32033212).
2'-Deoxysepiapterin is a metabolite of the catabolism of tetrahydrobiopterin, present in variable amounts in various human biofluids (blood, urine, feces) and tissues (kidney, liver, adrenal, brain, and blood). (PMID 6638488, 7356152, 7374483) 2'-Deoxysepiapterin can also be degraded or catabolized by microorganisms located within the cecal contents (PMID 7469409).
3a,7b,12b-Trihydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
7-Ketodeoxycholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
2-Octenoic acid, also known as 2-octenoate, belongs to the class of organic compounds known as medium-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 4 and 12 carbon atoms. 2-Octenoic acid has 8 carbon atoms.  2-Octenoic acid is also known as an olefinic fatty acid carrying a double bond at position 2. It can exist in two isomeric forms, the cis and the trans form, with the trans or 2-E form being more abundant. 2-Octenoic acid is a relatively hydrophobic molecule with a water solubility of approximately 1 g/L. The 2E-isomer has a musty, sour, cheesy aroma and a fatty or waxy taste. 2-Octenoic acid is found in the human body and is naturally produced by hepatic microsomal oxidation of aliphatic aldehydes. 2-Octenoic acid has been detected in human urine and plasma (PMID 1883862, 8087979, 4086594, 1417834, 6480773). 2-Octenoic acid has also been identified as a potential pheromone excreted by the male abdominal glands of the cockroach Leucophaea maderae (PMID: 17200891). Outside the human body 2-Octenoic acid has been detected in coffee, cranberries, mushrooms, black tea and strawberries. It is also used as a food flavourant for baked goods and candies.
3-Hexenedioic acid is a normal human unsaturated dicarboxylic acid metabolite with increased excretion in patients with Dicarboxylic aciduria caused by fatty acid metabolism disorders. (PMID 2614263, 7096501) The urinary excretion of 3-Hexenedioic acid is increased in conditions of augmented mobilization of fatty acids or inhibited fatty acid oxidation. (PMID 2001377).
3-Hydroxytetradecanedioic acid is an unusual 3-hydroxydicarboxylic acid human metabolite found occasionally in urine. (PMID 2925825) High levels of 3-Hydroxytetradecanedioic acid (and other 3-hydroxydicarboxylic acids) were detected in the urine of a patient with 3-hydroxydicarboxylic aciduria (PMID 1507493), due to acute intoxication associated with hopantenate occurs owing to pantothenic acid deficiency or the inhibition of CoA-requiring reactions during stress, i.e., infection, prolonged fasting, or malnutrition (PMID 2026687), and in a patient with thanatophoric dysplasia due to enhanced but incomplete oxidation of fatty acid, a consequence of a heterozygous point mutation, S249C in the fibroblast growth factor receptor 3 gene. (PMID 11879084).
3b,7b,12a-Trihydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Isolated excretion of 2-ethylhydracrylic acid (2-methylbutyrylglycine; 2-MBG) is the hallmark of short/branched-chain acyl-CoA dehydrogenase deficiency (SBCADD), a defect in the proximal pathway of L-isoleucine oxidation (PMID: 15615815). Normal human urine contains small amounts (less than 4 mg/g of creatinine) of 2-ethylhydracrylic acid. Urinary excretion of 2-ethylhydracrylic acid is variably increased in defects of isoleucine oxidation at distal steps in the catabolic pathway (3-oxoacyl-CoA thiolase deficiency and methylmalonyl-CoA mutase deficiency) and is diminished when proximal steps of the oxidative pathway are blocked as in branched-chain oxo acid decarboxylase deficiency (maple syrup urine disease) (PMID: 1016232). 2-Ethylhydracrylic acid has been identified in the human placenta (PMID: 32033212).
2-Pyrocatechuic acid is a normal human benzoic acid metabolite found in plasma (PMID 16351159), and is normally found with increased levels after consumption of many nutrients and drugs, i.e.: cranberry juice (PMID 14733499), aspirin ingestion. (PMID 3342084) It has been found associated with idiopathic oro-facial pain due to stress (oxidative stress might enhance the production of free radicals); it has been suggested that OH radicals are responsible for the production of many systemic and local tissue injury diseases which may initially manifest as pain syndrome, and 2-Pyrocatechuic acid is a biological marker for the detection and quantification of OH radicals, and patients had significantly increased circulating levels of 2-Pyrocatechuic acid after aspirin ingestion than control subjects. (PMID 7748148).
3-Oxoadipic acid is a regularly occurring Adipic dicarboxylic acid human metabolite found occasionally in biofluids of healthy individuals. (PMIDs 8340451, 1769109, 2338430) Increased amounts of 3-Oxoadipic acid are excreted after ingestion of Sebacic acid, supporting the hypothesis that dicarboxylic acids are degraded by ordinary beta-oxidation. (PMID 3220884).
3a,6b,7a,12a-Tetrahydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12. 3 alpha,6 alpha,7 alpha,12 alpha-Tetrahydroxy-5 beta-cholan-24-oic acid has been identified from human meconium and healthy neonatal urine. (PMID 2743505).
3,7-Dihydroxy-12-oxocholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
2,8-Dihydroxyadenine is a Purine metabolite usually not detectable in biofluids of normal individuals; this insoluble metabolite (at physiological urinary pH) cause urinary tract calculi and arthritis, and is identified in Adenine phosphoribosyltransferase deficiency (APRT, OMIM 102600). (PMID 16613999) In APRT, 2,8-dihydroxyadenine (DHA) accumulates in crystals within the tubular lumens (a feature of many kidney stone diseases) creating crystal-induced injury in human kidney epithelial cells. (PMID 16374038) Urinary DHA crystals are easily recognized under a microscope, and effective treatment can be offered and therefore the prognosis depends upon the renal function at diagnosis; treatment consists of adequate fluid intake, a low-purine diet and administration of allopurinol. (PMID 15764278).
2-Isopropylmalic acid (CAS: 3237-44-3), also known as 3-carboxy-3-hydroxyisocaproic acid, belongs to the class of organic compounds known as hydroxy fatty acids. These are fatty acids in which the chain bears a hydroxyl group. 2-Isopropylmalic acid is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. 2-Isopropylmalic acid is an alpha-hydroxy organic acid regularly occurring in the urine of healthy individuals (PMID: 2338430, 544608), and in hemofiltrates (PMID: 7251751). 2-Isopropylmalic acid is elevated during fasting and diabetic ketoacidosis (PMID: 1591279). It is also a metabolite found in Acetobacter (PMID: 6035258).
2-Hydroxyadenine (2-OH-Ade) is formed by hydroxyl radical attack on DNA bases and shows a genotoxicity in human, being the source of the mutations induced by reactive oxygen species. 2-OH-Ade in DNA is miscoding and elicits various mutations, and is a mutagenic in bacterial and mammalian cells. (Recent Research Developments in Biochemistry (2000)2:41-50).
2b,3a,7a-Trihydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
2-Methoxyestradiol (2ME2) is a drug that prevents the formation of new blood vessels that tumours need in order to grow (angiogenesis). It is derived from estrogen, although it binds poorly to known estrogen receptors, and belongs to the family of drugs called angiogenesis inhibitors. It has undergone phase 1 clinical trials against breast cancers. Preclinical models also suggest that 2ME2 could also be effective against inflammatory diseases such as rheumatoid arthritis. 2ME2 also acts as a vasodilator.
16-Ketoestradiol is found in the estrogen patch. The estrogen patch is a delivery system for estradiol used as hormone replacement therapy to treat the symptoms of menopause, such as hot flashes and vaginal dryness, and to prevent osteoporosis. Originally marketed as Vivelle (Novartis), it was discontinued in 2003 and reintroduced in a smaller form as Vivelle-Dot. Although the estrogen is given transdermally rather than in the standard oral tablets, the estrogen patch carries similar risks and benefits as more conventional forms of estrogen-only hormone replacement therapy.
2-Hydroxy-3-methylbutyric acid (also known as 2-hydroxyisovaleric acid) is a metabolite found in the urine of patients with phenylketonuria (PMID: 7978272), methylmalonic acidemia, propionic acidemia, 3-ketothiolase deficiency, isovaleric acidemia, 3-methylcrotonylglycemia, 3-hydroxy-3-methylglutaric acidemia, multiple carboxylase deficiency, glutaric aciduria, ornithine transcarbamylase deficiency, glyceroluria, tyrosinemia type I, galactosemia, and maple syrup urine disease (PMID: 11048741). 2-Hydroxyisovaleric acid has also been identified in the urine of patients with lactic acidosis and ketoacidosis (PMID: 884872), and in the urine of severely asphyxiated babies (PMID: 1610944). 2-Hydroxyisovaleric acid originates mainly from ketogenesis and from the metabolism of valine, leucine, and isoleucine (PMID: 6434570). 2-Hydroxy-3-methylbutyric acid has been identified in the human placenta (PMID: 32033212).
2-Methyl-3-ketovaleric acid is a metabolite of beta-leucine in the beta-keto pathway of leucine metabolism. 2-Methyl-3-ketovaleric acid is a known pathological metabolite and associated with propionic acidemia, especially during periods of ketoacidosis; a severe deficiency of propionyl-CoA carboxylase in cultured fibroblasts has been detected in some neonatal cases. (PMID 7389125, 6820422, 7119896, 7430116, 3356699). 2-Methyl-3-ketovaleric acid induces a strong activity of inosine-5'-monophosphate dehydrogenase (IMPDH; the rate-limiting enzyme in GTP synthesis), mimicking glucose. (PMID: 11145582).
5-hydroxyhexanoic acid is produced during omega-oxidation of fatty acids in people unable to beta-oxidize fatty acids properly. Excessive excretion of 5-hydroxyhexanoic acid appears to be a part of Reye's syndrome.
3-Hydroxy-2-methyl-butanoic acid (HMBA) is a normal urinary metabolite involved in the isoleucine catabolism, as well as presumably b-oxidation of fatty acids and ketogenesis, excreted in abnormally high amounts in beta-ketothiolase deficiency. Differences in the enantiomeric ratio of HMBA may originate from the enantioselectivity of different enzyme systems (PMID 10755375).
3a,12b-Dihydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
3beta,17alpha-Dihydroxy-5alpha-androstane is a steroid found in the monosulfate fraction of normal human feces. Several steroids identified in the disulfate fraction of human bile are found in the monosulfate fraction of human feces, indicating partial hydrolysis of diconjugates in the intestine. The androstanediols and pregnanediols found in the feces are primarily of a 3beta-hydroxy-5alpha- or 3beta-hydroxy-5beta-structure, whereas those in the bile are of a 3alpha-hydroxy-5alpha- or 3alpha-hydroxy-5beta-structure. This suggests the conversion of a 3alpha-hydroxyl to a 3beta-hydroxyl in the intestine in vivo. 3beta,17alpha-Dihydroxy-5alpha-androstane is also found unconjugated in normal human plasma (PMID: 4245755, 4223807, 4321841, 1769135).
3-Hydroxydecanedioic acid appears in the urine of children affected with peroxisomal disorders. Peroxisomal biogenesis disorders (PBDs) are characterized by generalized peroxisomal dysfunction due to defective assembly of the organelle and include the Zellweger, neonatal adrenoleukodystrophy and infantile Refsum phenotypes (PMID 10896310).
1b,3a,7a-Trihydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12.
17-Hydroxypregnenolone sulfate is a precursor steroid. 17-Hydroxypregnenolone is a C21 steroid that is obtained by hydroxylation of pregnenolone at the C17 alpha position.17-Hydroxypregnenolone is considered a prohormone in the formation of dehydroepiandrosterone (DHEA), itself a prohormone of the sex steroids (Wikipedia).
3D,7D,11D-Phytanic acid is an isomer of Phytanic acid, an unusual 20-carbon branched-chain fatty acid; Phytanic acid accumulates in blood and tissues of patients with Refsum disease (RD, an inborn error of lipid metabolism inherited as an autosomal recessive trait (OMIM 266500)), and is a reliable identifier of RD from a large number of other neurological disorders. Phytanic acid also accumulates in a number of other disorders with a very different clinical course: disorders of peroxisome biogenesis (Zellweger syndrome (OMIM 214100), neonatal adrenoleukodystrophy (OMIM 202370), infantile Refsum disease (OMIM 266510)) and rhizomelic chondrodysplasia punctata, type 1 (OMIM 215100). Phytanic acid is a 3-methyl fatty acid that cannot be beta-oxidized directly, and first undergoes an alpha-oxidation a reaction catalyzed by the enzyme phytanoyl-CoA hydroxylase, which is deficient in RD, the only true disorder of phytanic acid alpha-oxidation. (The Metabolic and Molecular Bases of Inherited Disease).
18-Hydroxycortisol is a derivative of cortIsolated It may be synthesized by zona fasciculata 11-beta hydroxylase in normal human adrenal cortex. (PMID 15356073; 1751390) Overproduction of 18-hydroxycortisol is an aid in the detection of Glucocorticoid-remediable aldosteronism which is an inherited form of mineralocorticoid excess associated with moderate overproduction of aldosterone, in which biochemical and clinical remission is dramatically induced by small amounts of glucocorticoids.(PMID: 1879399).
3b,7a,12a-Trihydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
2,3-Dihydroxyvaleric acid (DHVA) belongs to the class of organic compounds known as hydroxy fatty acids. These are fatty acids in which the chain bears a hydroxyl group. This compound has been detected in extracts from the purple carrot (https://doi.org/10.3390/app10238493). It is likely a hydroxylation derivative of the more common 2-hydroxyvaleric acid (an algal metabolite derived from a valeric acid) or 3-hydroxyvaleric acid (a 5-carbon ketone body made from odd carbon fatty acids in the liver). Very little is known about the origin of this particular hydroxy fatty acid.
2-Methylglutaric acid, also known as alpha-methylglutarate or 2-methylpentanedioate, belongs to the class of organic compounds known as methyl-branched fatty acids. These are fatty acids with an acyl chain that has a methyl branch. Usually, they are saturated and contain only one or more methyl group. However, branches other than methyl may be present. 2-Methylglutaric acid is also classified as an alpha,omega-dicarboxylic acid. It is glutaric acid substituted at position 2 by a methyl group. 2-Methylglutaric acid arises from the microbial metabolism of the isoprenoid alkaloid pristane (PMID: 4327007; PMID: 20143352).
3,4-Dihydroxyhydrocinnamic acid, also known as dihydrocaffeic acid (DHCA), is a metabolite product of the hydrogenation of caffeoylquinic acids, occurring in normal human biofluids, with potent antioxidant properties. DHCA has been detected in human plasma following coffee ingestion (PMID: 15607645) and is increased with some dietary sources, such as after ingestion of phenolic constituents of artichoke leaf extract (PMID: 15693705). Polyphenol-rich foods such as vegetables and fruits have been shown to significantly improve platelet function in ex vivo studies in humans (PMID: 16038718). Its antioxidant activity has been tested to reduce ferric iron in the ferric reducing antioxidant power (FRAP) assay, and it has been suggested that its catechol structure conveys the antioxidant effect in plasma and in erythrocytes (PMID: 11768243). 3,4-Dihydroxyhydrocinnamic acid is a microbial metabolite found in Bifidobacterium, Escherichia, Lactobacillus, and Clostridium (PMID: 28393285).
2-Hydroxydecanedioic acid appears in the urine of children affected with peroxisomal disorders such as urines of children with neonatal adrenoleukodystrophy and Zellweger syndrome and is a useful marker for these diseases. (PMID 2943344).
3-Deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN) is a sialic acid (Sia) that is ubiquitously expressed in vertebrates during normal development and tumorigenesis. Its expression is thought to be regulated by multiple biosynthetic steps catalyzed by several enzymes, including CMP-Sia synthetase. (PMID 11479279) Sialic acids are frequently the terminal sugars on secreted and cell surface glycoproteins and glycolipids, and their presence can have considerable influence on the biological properties of a cell. For example, the temporal appearance and disappearance of polysialic polymers has been intimately linked with the proper development of neural tissues during embryogenesis. In pathogenic diseases, including meningitis and gastric inflammation, particular microbes recognize cell surface sialic acids when invading host cells. Sialic acid residues can also mask recognition sites such as galactose residues on glycoproteins to prevent their in vivo removal by asialoglycoprotein receptors. In certain cancers, changes in sialic acid amounts, types, and linkages have been associated with tumorogenesis and cancer metastasis. (PMID 10749855).
Citramalic acid, also known as 2-Methylmalic acid, is an analog of malic acid. The structure of citramalic acid is similar to the structure of malic acid except it has an extra CH3 group on position 2. It is also classified as a 2-hydroxydicarboxylic acid. Citramalic acid exists in two isomers, L-citramalic acid and D-citramalic acid.  The L-isomer is more biologically relevant isomer. Citramalic acid is found in almost all living organisms from microbes to plants to humans although citramalate is primarily produced from bacteria. L-citramalic acid was first isolated from the peel of apples in 1954 (PMID: 13160011). It has also been isolated in wine and other ripening fruit (PMID: 13807713). Citramalic acid can inhibit the production of malic acid. Citramalic acid is also an important microbial metabolite and has been found to be a byproduct of Saccharomyces yeast species, as well as Propionibacterium acnes and Aspergillus niger (PMID: 31827810) (http://drweyrich.weyrich.com/labs/oat.html) (PMID: 7628083). Citramalic acid is a component of the C5-branched dibasic acid metabolism pathway. It can be broken down by the enzyme citramalate lyase, which converts citramalate to acetate and pyruvate. Citramalate synthase is an enzyme found in bacteria that synthesizes citramalic acid from acetyl-CoA, pyruvate and water. Citramalic acid may have a useful role in medical diagnoses. It has been found in the urine of two brothers with autistic features (PMID: 7628083). Citramalic acid can also be used as a urinary marker for gut dysbiosis (PMID: 31669633). Dysbiosis is a disorder of the bacterial flora of the human digestive tract. It is usually diagnosed clinically by direct detection of an abnormal pattern of the intestinal microbiota.
3b,7b,12a-Trihydroxy-5a-Cholanoic acid is a bile acid present in the urine of healthy humans, predominantly found in the glycine conjugate fraction (PMID 864325). Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12.
3-Hydroxyglutaric acid is a member of the class of compounds known as dicarboxylic acids and derivatives. These are organic compounds containing exactly two carboxylic acid groups. 3-Hydroxyglutaric acid is soluble (in water) and a weakly acidic compound (based on its pKa). When present in sufficiently high levels, 3-hydroxyglutaric acid can act as an acidogen and a metabotoxin. An acidogen is an acidic compound that induces acidosis, which has multiple adverse effects on many organ systems. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of 3-hydroxyglutaric acid are associated with glutaric aciduria type I (glutaric acidemia type I, glutaryl-CoA dehydrogenase deficiency, GA1, or GAT1). GA1 is an inherited disorder in which the body is unable to completely break down the amino acids lysine, hydroxylysine, and tryptophan due to a deficiency of mitochondrial glutaryl-CoA dehydrogenase (EC 1.3.99.7, GCDH). Excessive levels of their intermediate breakdown products (e.g. glutaric acid, glutaryl-CoA, 3-hydroxyglutaric acid, glutaconic acid) can accumulate and cause damage to the brain (and also other organs), but particularly the basal ganglia. GA1 is associated with a risk for intracranial and retinal hemorrhage, and non-specific white matter changes. Babies with glutaric acidemia type I are often born with unusually large heads (macrocephaly). Other symptoms include spasticity (increased muscle tone/stiffness) and dystonia (involuntary muscle contractions resulting in abnormal movement or posture), but many affected individuals are asymptomatic. Seizures and coma (encephalopathy) are rare. GA1 also causes secondary carnitine deficiency because 3-hydroxyglutaric acid, like other organic acids, is detoxified by carnitine.
17alpha-Estradiol (also known as 17alpha-E2, 17-epiestradiol) belongs to the class of organic compounds known as estrogens and derivatives. These are steroids with a structure containing a 3-hydroxylated estrane. Thus, epiestriol is considered to be a steroid molecule. 17alpha-Estradiol is also classified as an estradiol. Specifically, estradiols are characterized by an estra-1,3,5(10)-triene substituted by hydroxy groups at positions 3 and 17. 17alpha-Estradiol is considered as a 17alpha-hydroxy steroid and a 3-hydroxy steroid. 17alpha-Estradiol is a weak endogenous steroidal estrogen that is related to 17beta-estradiol.  17beta-estradiol is better known simply as estradiol or E2 (PMID: 16728493). Therefore, 17alpha-Estradiol is the C17 alpha epimer of 17beta-estradiol (PMID: 16728493).  17alpha-Estradiol is found in all vertebrates. It has approximately 100-fold lower estrogenic potency than 17beta-estradiol. 17alpha-estradiol is a non-feminizing estrogen with significantly reduced binding affinity for the classic estrogen receptors ERalpha and ERbeta. Although 17alpha-estradiol is far weaker than 17beta-estradiol as an agonist of the nuclear estrogen receptors, it has been found to bind to and activate the brain-expressed ER-X with a greater potency than that of 17beta-estradiol.  17alpha-Estradiol is a potent 5-alpha reductase inhibitor that has been shown to improve metabolic function, enhance insulin sensitivity, and reduce fat and inflammation in older lab animals without causing feminization (PMID: 26809497). It has also been shown that 17alpha-Estradiol also increases AMPK levels and reduced mTOR activity in visceral adipose tissue (PMID: 26809497).
24,25-Dihydroxyvitamin D (24R,25(OH)2D3) circulates in blood at concentrations about 1000 times higher than 1alpha,25(OH)2D3. 24-Hydroxylase is present in the proximal convoluted tubule cells of the kidney and in virtual all target cells of 1alpha,25(OH)2D3. Interestingly, 1alpha,25(OH)2D3 is a very strong inducer of 24-hydroxylase activity and 24R,25(OH)2D3 formation. Also parathyroid hormone (PTH) regulates 24-hydroxylase activity but in a tissue specific manner, i.e. inhibitory in the kidney while a synergistic effect together with 1alpha,25(OH)2D3 is observed in osteoblasts. Generally, 24-hydroxylation has been considered the first step in the degradation pathway of 1alpha,25(OH)2D3 and 25-(OH)D3. However, through the past decades data have accumulated that 24R,25(OH)2D3 is not merely a degradation product but has effects on its own. Classic studies have demonstrated the significance of 24R,25(OH)2D3 for normal chicken egg hatchability and calcium and phosphorus homeostasis. More recently it became apparent that 24R,25(OH)2D3 also has distinct effects on cartilage in particular the resting zone cells. 24R,25(OH)2D3 stimulates osteocalcin synthesis in human osteoblasts. 24R,25(OH)2D3 plays a role in bone metabolism but that it acts in concert with 1alpha,25(OH)2D3 to obtain an optimal effect. (PMID: 11179746).
16,17-Epiestriol is a hydroxylated metabolite of estradiol or estrone that has a hydroxyl group at C3-beta, 16-, and 17- position. Estriol is a major urinary estrogen. During pregnancy, large amount of estriol is produced by the placenta. Isomers with inversion of the hydroxyl group or groups are called epiestriol (16-beta, 17-alpha).
3a,7b,12a-Trihydroxy-5a-Cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
1,3,7,12-Tetrahydroxycholan-24-oic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Homoveratric acid is the main metabolite of 3,4-dimethoxyphenylethylamine (DMPEA) in urine. It has been suggested that DMPEA and other amines are in higher concentrations in drug-free schizophrenics than in normal subjects. DMPEA is a the di-methylated metabolite of L-DOPA, the major treatment for Parkinson's disease (PD). (PMID 7059639, 14311254, 588645, 10834300).
3a,4b,7a,12a-Tetrahydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
3b,12a-Dihydroxy-5b-cholanoic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
2-Furoylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction:. acyl-CoA + glycine < -- > CoA + N-acylglycine. Dietary studies show that 2-Furoylglycine precursors are of exogenous origin. Most probably from furan derivatives found in food prepared by strong heating. This may explain the absence of 2-furoylglycine in urine of breastfed children (PMID 4630229). 2-Furoylglycine is also a microbial metabolite.
3-Hydroxyphenylacetic acid is a rutin metabolite and an antioxidant. It has a protective biological activity in human. It is a substrate of enzyme 4-hydroxyphenylacetate 3-monooxygenase [EC 1.14.13.3] in the pathway tyrosine metabolism (KEGG, PMID 155437). 3-Hydroxyphenylacetic acid is found to be associated with phenylketonuria, which is an inborn error of metabolism. It is also a marker of gut Clostridium species. Higher levels are associated with higher levels of Clostridia (PMID: 27123458). 3-Hydroxyphenylacetic acid can also be found in Klebsiella (PMID: 1851804).
(S)-3-Hydroxybutyric acid is a normal human metabolite that has been found elevated in geriatric patients remitting from depression (PMID: 17048218). 3-Hydroxybutyric acid is a ketone body. Like the other ketone bodies (acetoacetate and acetone), levels of 3-hydroxybutyric acid are raised in ketosis. In humans, 3-hydroxybutyric acid is synthesized in the liver from acetyl-CoA, and can be used as an energy source by the brain when blood glucose is low.
3-Furoic acid is an organic acid regularly occurring in urine of healthy individuals. (PMID 2338430). 3-Furoic acid is also a compound found in honey and honeydew samples (PMID 11403496), and is a structural analog of nicotinic acid (niacin, a vitamin of the B complex). (PMID 12563315).
Alpha-Tetrasaccharide is a metabolite that accumulates in the urine of glucosidase I deficient patients, a defect due to missense mutations in the glucosidase I gene. (PMID 10788335). A tetrasaccharide is a carbohydrate which gives upon hydrolysis four molecules of the same or different monosaccharides. For example, stachyose upon hydrolysis gives one molecule each of glucose and fructose and two molecules of galactose. The general formula of a tetrasaccharide is typically C24H42O21. (Wikipedia).
7a,12a-Dihydroxy-3-oxo-4-cholenoic acid is an unusual bile acids that have been detected in urine early in life, especially during the period up to 1 mo of age. This indicate that bile acid synthesis and metabolism in the liver of developing infants is significantly different from that occurring in the liver of adults. (PMID 10203155).
Adipic acid is an important inudstrial dicarboxylic acid with about 2.5 billion kilograms produced per year. It is used mainly in the production of nylon. It occurs relatively rarely in nature. It has a tart taste and is also used as an additive and gelling agent in jello or gelatins. It is also used in some calcium carbonate antacids to make them tart. Adipic acid has also been incorporated into controlled-release formulation matrix tablets to obtain pH-independent release for both weakly basic and weakly acidic drugs. Adipic acid in the urine and in the blood is typically exogenous in origin and is a good biomarker of jello consumption. In fact, a condition known as adipic aciduria is actually an artifact of jello consumption (PMID: 1779643). However, certain disorders (such as diabetes and glutaric aciduria type I.) can lead to elevated levels of adipic acid snd other dicarboxcylic acids (such as suberic acid) in urine (PMID: 17520433; PMID: 6778884). Moreover, adipic acid is also found to be associated with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency, carnitine-acylcarnitine translocase deficiency, malonyl-Coa decarboxylase deficiency, and medium Chain acyl-CoA dehydrogenase deficiency, which are inborn errors of metabolism. Adipic acid is also microbial metabolite found in Escherichia.
5a-tetrahydrocorticosterone is highly sensitive to adrenocorticotropic hormone (ACTH) secretion. High levels of 5a-Tetrahydrocorticosterone are a warning sign of hypertension. (PMID: 16597193,7473516).
5-Hydroxylysine (Hyl), also known as hydroxylysine or 5-Hydroxy-L-lysine, belongs to the class of organic compounds known as L-alpha-amino acids. These are alpha amino acids which have the L-configuration of the alpha-carbon atom. Amino acids are organic compounds that contain amino (‚ÄìNH2) and carboxyl (‚ÄìCOOH) functional groups, along with a side chain (R group) specific to each amino acid. 5-Hydroxylysine is a hydroxylated derivative of the amino acid lysine that is present in certain collagens, the chief structural protein of mammalian skin and connective tissue. 5-Hydroxylysine arises from a post-translational hydroxy modification of lysine and is biosynthesized from lysine via oxidation by lysyl hydroxylase enzymes. 5-Hydroxylysine can then undergo further modification by glycosylation, giving rise to galactosyl hydroxylysine (GH) and glucosylgalactosyl hydroxylysine (GGH). These glycosylated forms of hydroxylysine contribute to collagen‚Äôs unusual toughness and resiliency. The monoglycosylated, galactosyl-hydroxylysine is enriched in bone compared with the disaccharide form, glucosyl-galactosyl-hydroxylysine, which is the major form in skin. 5-Hydroxylysine exists in all eukaryotes, ranging from yeast to humans. It was first discovered in 1921 by Donald Van Slyke. Free forms of hydroxylysine arise through proteolytic degradation of collagen.  Urinary excretion of 5-Hydroxylysine and its glycosides can be used as an index of collagen degradation, with high levels being indicative of more rapid or extensive collagen degradation (often seen in patients with thermal burns, Paget's disease of bone or hyperphosphatasia) (PMID: 404321).
cis-4-Hydroxycyclohexylacetic acid is a tyrosine metabolite that has been found in the urine of a patient with a defect of 4-hydroxyphenylpyruvate dioxygenase (or HPPD) (EC 1.13.11.27), an inborn error of metabolism (PMIDs 701419, 719903) also called hawkinsinuria. 4-Hydroxyphenylpyruvate dioxygenase participates in the tyrosine catabolic pathway by catalyzing the conversion of 4-hydroxyphenylpyruvate to homogentisate (Hager et al., 1957). The mechanism of action of 4-hydroxyphenylpyruvate dioxygenase involves a decarboxylation step and an oxidation step, followed by a rearrangement step to form homogentisic acid (Tomoeda et al., 2000). Awata et al. (1994) determined that the HPD gene contains 14 exons. Analysis of the 5-prime flanking sequence of the gene suggested that expression of the gene is regulated by hepatocyte-specific and liver-enriched transcription factors, as well as by hormones (OMIM: 609695). cis-4-Hydroxycyclohexylacetic acid has also been found to be a microbial metabolite (PMID: 20615997).
L-alpha-Aminobutyric acid, also known as (S)-2-aminobutanoic acid, homoalanine, 2-AABA, or alpha-Aminobutyric acid, is a member of the class of compounds known as L-alpha-amino acids. L-alpha-Amino acids are alpha amino acids which have the L-configuration of the alpha-carbon atom. Amino acids are organic compounds that contain amino (‚ÄìNH2) and carboxyl (‚ÄìCOOH) functional groups, along with a side chain (R group) specific to each amino acid. L-alpha-Aminobutyric acid is a non-proteogenic amino acid that can be found in the human kidney, in liver tissues, and in most biofluids or excreta (e.g. feces, breast milk, urine, and blood). Within the cell, L-alpha-aminobutyric acid is primarily located in the cytoplasm. alpha-Aminobutyric acid is biosynthesized by transamination of oxobutyrate, a metabolite in isoleucine biosynthesis. As a non-proteogenic amino acid, alpha-aminobutyric acid can be used by nonribosomal peptide synthases. One example of a nonribosomal peptide containing alpha-aminobutyric acid is ophthalmic acid, which was first isolated from calf lens. alpha-Aminobutyric acid is a non-essential amino acid that is primarily derived from the catabolism of methionine, threonine, and serine. High protein diets can result in significantly higher alpha-aminobutyrate levels in plasma (PMID: 26227325). alpha-Aminobutyric acid is elevated in the plasma of children with Reye's syndrome, tyrosinemia, homocystinuria, nonketotic hyperglycinemia, and ornithine transcarbamylase deficiency (PMID: 420125). alpha-Aminobutyric acid is one of the three isomers of aminobutyric acid. The two others are the neurotransmitter gamma-aminobutyric acid (GABA) and beta-aminobutyric acid (BABA) which is known for inducing plant disease resistance.
delta-Hexanolactone is the lactone of 5-hydroxyhexanoic acid. Lactones are internal esters that exist in equilibrium between their closed (lactone) and open (hydroxy acid) forms in an aqueous environment. The lactone/hydroxy acid ratio at equilibrium is pH-dependent, with the closed form being favored at lower pH values, and can be greatly influenced by structural features of the lactone such as the ring size, substituents on the ring and the presence of double bonds within the ring. Many drugs and endogenous compounds are lactones or hydroxy acids and an enzyme capable of catalyzing the interchange between the open and closed forms in vivo could have pronounced effects upon their biological activity and/or distribution. delta-Hexanolactone is the substrate of paraoxonases (PON) in humans. Human PON1 hydrolyzes over 30 different lactones (cyclic esters) and catalyzes the reverse reaction (lactonization) of a broad range of hydroxy acids. Hydroxy acid lactonization or lactone hydrolysis is catalyzed until equilibrium between the open and closed forms is reached (PMID: 15772423, 12963475, 12963475).
Allocystathionine belongs to the class of organic compounds known as cysteines and cysteine derivatives. Cysteine and cysteine derivatives are compounds containing cysteine or a derivative thereof resulting from the reaction of cysteine at the amino group or the carboxy group, or from the replacement of any hydrogen of glycine by a heteroatom. Allocystathionine is a stereo-isomer of cystathionine. Both cystathionine and allocystathionine are modified amino acids generated by enzymic means from homocysteine and serine. Allocystathionine is a product of enzyme cystathionine synthetase (EC 2.5.1.48) which converts homocysteine into allocystathionine in the sulfur metabolism pathway. It is also the substrate of enzyme cystathionine beta-lyase (EC 4.4.1.8) in the same pathway (KEGG). Cystathionine and allocystathionine can be used by the enzymes cystathionine gamma-lyase (CTH), cysteine dioxygenase (CDO), and sulfinoalanine decarboxylase to produce hypotaurine and then taurine.
5alpha-Androstane-3alpha,17a-diol belongs to the class of organic compounds known as androgens and derivatives. These are 3-hydroxylated C19 steroid hormones. They are known to favour the development of masculine characteristics. They also show profound effects on scalp and body hair in humans. 5alpha-Androstane-3alpha,17a-diol is a steroid found in feces from pregnant women (PMID: 5440628), the monosulfate and disulfate fractions from normal human feces (PMID: 4245755), and the glucuronide and mono- and disulphate conjugates of neutral steroids in human bile (PMID: 5493463).
3-Methylcrotonylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction: acyl-CoA + glycine < -- > CoA + N-acylglycine. 3-Methylcrotonylglycine is a normal amino acid metabolite found in urine. Increased levels of this metabolite are found in patients suffering from leucine catabolic disorders, such as 3-methylcrotonyl-CoA carboxylase deficiency. 3-Methylcrotonylglycine is often considered to be a diagnostic marker of organic acidemias (PMID 11170888). Moreover, 3-methylcrotonylglycine is found to be associated with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency and propionic acidemia, which are also inborn errors of metabolism.
7-Hydroxy-3-oxocholanoic acid is a bile acid found in human serum (PMID 2338448). Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12.
Allantoin is a diureide of glyoxylic acid with the chemical formula C4H6N4O3. It is also called 5-ureidohydantoin or glyoxyldiureide. It is a product of the oxidation of uric acid. It is also a product of purine metabolism in most mammals except for higher apes, and it is present in their urine. In humans, uric acid is excreted instead of allantoin. The presence of allantoin in the urine can be an indication of microbial overgrowth or it can be created via non-enzymatic means through high levels of reactive oxygen species. In this regard, allantoin is sometimes used as a marker of oxidative stress. Allantoin can be isolated from cow urine or as a botanical extract of the comfrey plant. It has long been used for its healing, soothing, and anti-irritating properties. Allantoin helps to heal wounds and skin irritations and stimulates the growth of healthy tissue. Allantoin can be found in anti-acne products, sun care products, and clarifying lotions because of its ability to help heal minor wounds and promote healthy skin. Allantoin is frequently present in toothpaste, mouthwash, and other oral hygiene products as well as in shampoos, lipsticks, various cosmetic lotions and creams, and other cosmetic and pharmaceutical products. It is also a metabolite of Bacillus (PMID: 18302748) and Streptomyces (PMID: 24292080).
Calcium is essential for the normal growth and maintenance of bones and teeth, and calcium requirements must be met throughout life. Requirements are greatest during periods of growth, such as childhood, during pregnancy and when breast-feeding. Long-term calcium deficiency can lead to osteoporosis, in which the bone deteriorates and there is an increased risk of fractures. Adults need between 1,000 and 1,300 mg of calcium in their daily diet. Calcium is essential for living organisms, particularly in cell physiology, and is the most common metal in many animals. Physiologically, it exists as an ion in the body. Calcium combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Calcium is an important component of a healthy diet. A deficit can affect bone and tooth formation, while overretention can cause kidney stones. Vitamin D is needed to absorb calcium. Dairy products, such as milk and cheese, are a well-known source of calcium. However, some individuals are allergic to dairy products and even more people, particularly those of non-European descent, are lactose-intolerant, leaving them unable to consume dairy products. Fortunately, many other good sources of calcium exist. These include: seaweeds such as kelp, wakame and hijiki; nuts and seeds (like almonds and sesame); beans; amaranth; collard greens; okra; rutabaga; broccoli; kale; and fortified products such as orange juice and soy milk. Calcium has also been found to assist in the production of lymphatic fluids. Furthermore, calcium is found to be associated with primary hypomagnesemia, which is an inborn error of metabolism.
Nutriacholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Biopterin, also known as tetrahydrobiopterin or BH4, belongs to the class of organic compounds known as biopterins and derivatives. These are coenzymes containing a 2-amino-pteridine-4-one derivative. Biopterin or tetrahydrobiopterin is also classified as a pterin derivative that consists of pterin group bearing an amino, an oxo and a 1,2-dihydroxypropyl substituent at positions 2, 4 and 6, respectively. Biopterin compounds found within the animals include BH4 (tetrahydrobiopterin), the free radical BH3, and BH2 (also a free radical, called Dihydrobiopterin). BH2 is produced in the synthesis of L-DOPA, dopamine, norepinephrine and epinephrine. It is restored to the required cofactor tetrahydrobiopterin by the enzyme dihydrobiopterin reductase. Tetrahydrobiopterin (BH4) is a cofactor of the three aromatic amino acid hydroxylase enzymes, used in the degradation of amino acid phenylalanine and in the biosynthesis of the neurotransmitters serotonin (5-hydroxytryptamine, 5-HT), melatonin, dopamine, norepinephrine (noradrenaline), epinephrine (adrenaline). It is also a cofactor for the production of nitric oxide (NO) by the nitric oxide syntheses.    Tetrahydrobiopterin is biosynthesized from guanosine triphosphate (GTP) by three chemical reactions mediated by the enzymes GTP cyclohydrolase I (GTPCH), 6-pyruvoyltetrahydropterin synthase (PTPS), and sepiapterin reductase (SR). Biopterin synthesis disorders are a cause of hyperphenylalaninemia. There are 3 distinct forms of phenylketonuria or hyperphenylalaninemia, each caused by lack of aromatic amino acid hydroxylase enzymes. The variant forms of hyperphenylalaninemia that are caused by the lack of dihydropteridine reductase or tetrahydrobiopterin are characterized by severe neurological deterioration, impaired functioning of tyrosine and tryptophan hydroxylases, and the resultant deficiency of tyrosine- and tryptophan-derived monoamine neurotransmitters in brain. (PMID 3930837).
5-Hydroxymethyluracil (5hmU), also known as alpha-hydroxythymine, belongs to the class of organic compounds known as pyrimidones. Pyrimidones are compounds that contain a pyrimidine ring, which bears a ketone. Pyrimidine is a 6-membered ring consisting of four carbon atoms and two nitrogen centers at the 1- and 3- ring positions. 5hmU has been identified as a thymine base modification found in the genomes of a diverse range of organisms (PMID: 28137275). 5-hydroxymethyluracil has been detected in bacteriophages, dinoflagellates, leishmania, and in eukaryotic genomes where its level appears to be cell type-specific. 5-Hydroxymethyluracil  arises from the oxidation of thymine.  5-Hydroxymethyluracil is produced by the enzyme thymine dioxygenase (EC 1.14.11.6) which catalyzes the chemical reaction thymine + 2-oxoglutarate + O2 <->  5-hydroxymethyluracil + succinate + CO2. The 3 substrates of this enzyme are thymine, 2-oxoglutarate, and O2, whereas its 3 products are 5-hydroxymethyluracil, succinate, and CO2. The 5hmU base can also be generated by oxidation/hydroxylation of thymine by the Ten-Eleven-Translocation (TET) proteins or result from deamination of 5hmC (PMID: 29184924). DNA containing 5hmU has been reported to be more flexible and hydrophilic (PMID: 29184924).
6-Dimethylaminopurine, also known as 6,6-dimethyladenine or 6-DMAP, belongs to the class of organic compounds known as 6-alkylaminopurines. 6-alkylaminopurines are compounds that contain an alkylamine group attached at the 6-position of a purine. Purine is a bicyclic aromatic compound made up of a pyrimidine ring fused to an imidazole ring. 6-Dimethylaminopurine is a puromycin analog that was first identified in the spores of Streptomyces alboniger (PMID: 5019066). It has subsequently been identified in several algae species (PMID: 4206669). 6-DMAP is widely used in the lab as a cell cycle inhibitor and a cyclin dependent kinase inhibitor. It also induces cell apoptosis. 6-DMAP is widely used for oocyte activation in eukaryotic cloning experiments (PMID: 29467049).
Butanone occurs as a natural product. It is made by some trees and found in some fruits and vegetables in small amounts. It is also released to the air from car and truck exhausts. The known health effects to people from exposure to butanone are irritation of the nose, throat, skin, and eyes. (wikipedia).
3-Oxo-4,6-choladienoic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
7Z,10Z-Hexadecadienoic acid is a conjugated dienoic fatty acid metabolite of conjugated linoleic acid (CLA). CLAs are a naturally occurring group of positional and geometric isomers of linoleic acid, with potential beneficial effects on atherosclerosis, carcinogenesis or obesity in human. Although the molecular mechanisms are largely unknown, it has been proposed that the anti-atherogenic actions comprise reduction of membrane-bound arachidonic acid and peroxisome proliferator-activated receptor (PPAR)-&#947;-dependent inhibition of Nuclear Factor kappa B (NF-&#954;B) activation and subsequently reduced prostanoid release. (PMID 16275160).
Allodeoxycholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Allopurinol is an analog of the natural purines in the body, and is quickly metabolized to oxypurines which is also a xanthine oxidase inhibitor. Allopurinol is a white, powdery drug used to treat gout. Its use in the United States was started in 1964. It is an isomer of hypoxanthine and inhibits the production of uric acid, the metabolite responsible for gout, by inhibiting the enzyme xanthine oxidase. The side effects of high levels of precursors are usually minor. A small percentage of people develop a rash and must discontinue this drug. The most serious adverse event is a hypersensitivity syndrome consisting of fever, skin rash, eosinophilia, hepatitis, and worsening renal function. In some cases, allopurinol hypersensitivity syndrome.
Caprylic acid is the common name for the eight-carbon straight-chain fatty acid known by the systematic name octanoic acid. It is found naturally in coconuts and breast milk. It is an oily liquid with a slightly unpleasant rancid taste that is minimally soluble in water. Caprylic acid is used commercially in the production of esters used in perfumery and also in the manufacture of dyes (Wikipedia). Caprylic acid can be found in numerous foods such as Prunus (Cherry, Plum), pineapple sages, black raspberries, and shallots. Caprylic acid is found to be associated with medium-chain acyl-CoA dehydrogenase deficiency, which is an inborn error of metabolism.
5b-Cholestane-3a,7a,12a,23S,25-pentol is a bile alcohol found in the urine of patients with cerebrotendinous xanthomatosis. (PMID 3700361).
Vanillic acid is a phenolic acid found in some forms of vanilla and many other plant extracts. It is a flavouring and scent agent that produces a pleasant, creamy odour. It is the intermediate product in the two-step bioconversion of ferulic acid to vanillin (J Biotechnol 1996;50(2-3):107-13). Vanillic acid, which is a chlorogenic acid, is an oxidized form of vanillin. It is also an intermediate in the production of vanillin from ferulic acid. Vanillic acid is a metabolic byproduct of caffeic acid and is often found in the urine of humans who have consumed coffee, chocolate, tea, and vanilla-flavoured confectionary. Vanillic acid selectively and specifically inhibits 5'nucleotidase activity (PMID: 16899266). Vanillic acid is a microbial metabolite found in Amycolatopsis, Delftia, and Pseudomonas (PMID: 11152072, 10543794, 11728709, 9579070).
7-Hydroxyoctanoic acid is a normal metabolite of medium-chain fatty acid oxidation, and is excreted in the urine as 7-hydroxyoctanoyl-beta-D-glucuronide (PMID 8799296), and have been found slightly elevated in the urine of persons with abnormal fatty acid metabolism (PMID 2094705).
(4E,15Z)-Bilirubin IXa belongs to the class of organic compounds known as bilirubins. These are organic compounds containing a dicarboxylic acyclic tetrapyrrole derivative. Bilirubin (BR) is a yellow compound that occurs in the normal catabolic pathway that breaks down heme in vertebrates. (4E,15Z)-Bilirubin IXa is a linear tetrapyrrole, and a product of heme degradation. It is a member of the class of compounds known as biladienes. Biladienes consist of two linear tetrapyrroles in which the carbon bridges contain two more double bonds than bilane.  (4E,15Z)-Bilirubin IXa is an isomer of bilirubin, which appears to have antioxidant effects. Bilirubin's antioxidant activity may be particularly important in the brain, where it prevents excitotoxicity and neuronal death by scavenging superoxide during N-methyl-D-aspartic acid neurotransmission. (4E,15Z)-Bilirubin IXa is formed by oxidative cleavage of a porphyrin in heme, which first produces biliverdin. Biliverdin is then reduced to bilirubin by biliverdin reductase. Some of the double-bonds in bilirubin isomerize when exposed to light. The E,Z-isomers of bilirubin, such s (4E,15Z)-Bilirubin IXa formed upon light exposure are more soluble than the unilluminated Z,Z-isomer. Altered levels of (4E,15Z)-Bilirubin IXa in human serum have been used as a biomarker of acrylamide exposure (PMID: 28163100).
Aspartylglycosamine, also known as n4-(beta-N-acetyl-D-glucosaminyl)-L-asparagine or 1-beta-aspartyl-N-acetyl-D-glucosaminylamine, is a member of the class of compounds known as glycosylamines. Glycosylamines are compounds consisting of an amine with a beta-N-glycosidic bond to a carbohydrate, thus forming a cyclic hemiaminal ether bond (alpha-amino ether). Aspartylglycosamine is soluble (in water) and a moderately acidic compound (based on its pKa). Aspartylglycosamine can be found primarily in urine, as well as in human spleen tissue. Within the cell, aspartylglycosamine is primarily located in the cytoplasm. Moreover, aspartylglycosamine is found to be associated with aspartylglucosaminuria, which is an inborn error of metabolism. Large amount of aspartylglycosamine appears in patients with aspartylglycosaminuria corresponding to decreased activity of aspartylglycosamine amido hydrolase.
Etiocholanolone is the 5-beta-reduced isomer of androsterone. Etiocholanolone is a major metabolite of testosterone and androstenedione in many mammalian species including humans. It is excreted in the urine and is androgenically inactive. Classified a ketosteroid, it causes fever (it is a pyrogen), immunostimulation and leukocytosis. The pyrogenic effect of Etiocholanolone has been shown to be due to the release of interleukin-1 (IL-1) from the leukocytes that are mobilized in response to its production or injection. Etiocholanolone has anticonvulsant activity and may be an endogenous modulator of seizure susceptibility. Significantly increased values of etiocholanolone (along with testoterone and androsterone) an be detected in the urine of men with androgenic alopecia (male pattern baldness).
Under standard conditions, chlorine exists as a diatomic molecule. Chlorine is a highly toxic, pale yellow-green gas that has a specific strong smell. In nature, chlorine is most abundant as a chloride ion. Physiologically, it exists as an ion in the body. The chloride ion is an essential anion that the body needs for many critical functions. It also helps keep the body's acid-base balance. The amount of chloride in the blood is carefully controlled by the kidneys. Chloride ions have important physiological roles. For instance, in the central nervous system, the inhibitory action of glycine and some of the action of GABA relies on the entry of Cl- into specific neurons. Also, the chloride-bicarbonate exchanger biological transport protein relies on the chloride ion to increase the blood's capacity of carbon dioxide, in the form of the bicarbonate ion. Chloride-transporting proteins (CLC) play fundamental roles in many tissues in the plasma membrane as well as in intracellular membranes. CLC proteins form a gene family that comprises nine members in mammals, at least four of which are involved in human genetic diseases. GABA(A) receptors are pentameric complexes that function as ligand-gated chloride ion channels. WNK kinases are a family of serine-threonine kinases that have been shown to play an essential role in the regulation of electrolyte homeostasis, and they are found in diverse epithelia throughout the body that are involved in chloride ion flux. Cystic fibrosis (CF) is caused by alterations in the CF transmembrane conductance regulator (CFTCR) gene that result in deranged sodium and chloride ion transport channels. (PMID: 17539703, 17729441, 17562499, 15300163) (For a complete review see Evans, Richard B. Chlorine: state of the art. Lung (2005), 183(3), 151-167. PMID: 16078037).
Androstane-3,17-diol is a metabolite of dihydrotestosterone. It doesn't bind androgen receptors, but efficiently binds the estrogen receptor beta and inhibits prostate cancer cell migration through the activation of estrogen receptor beta (PMID: 15958594).
Stigmastanol, also known as sitostanol or (3b)-stigmastan-3-ol, belongs to stigmastanes and derivatives class of compounds. Those are sterol lipids with a structure based on the stigmastane skeleton, which consists of a cholestane moiety bearing an ethyl group at the carbon atom C24. Stigmastanol is practically insoluble (in water) and an extremely weak acidic compound (based on its pKa). Stigmastanol can be found primarily in blood and feces, as well as in human skeletal muscle tissue. Stigmastanol can be found anywhere throughout the human cell, such as in in the peroxisome, in the cytoplasm, in the Golgi apparatus, and in the membrane (predicted from logP). It can also be found in the extracellular space. Moreover, stigmastanol is found to be associated with sitosterolemia, an inborn error of metabolism. Stigmastanol (sitostanol) is a phytosterol found in a variety of plant sources. Similar to sterol esters and stanol esters, stigmastanol inhibits the absorption of cholesterol from the diet. Animal studies suggest that it also inhibits biosynthesis of cholesterol in the liver (Wikipedia). Stigmastanol is plant stanol. It can decrease the circulating LDL-cholesterol level by reducing intestinal cholesterol absorption (PMID 16910223).
Androstanediol is a metabolite of dihydrotestosterone, itself a metabolite of testosterone. Androstanediol is implicated in the regulation of gonadotropin secretion. As a metabolite of dihydroxytestosterone formed in the peripheral tissues, androstanediol and androstnediol-glucuronide can be used to estimate peripheral androgen activity. Androstanediol is a potential GABA (A) receptor-modulating neurosteroid with anticonvulsant properties and hence could act as a key neuromodulator in the central nervous system. It is considered that androstanediol has hedonic effects; therefore it is anticipated that androgens that are readily metabolized to androstanediol may have higher abuse potential than androgens that are not as easily metabolized to androstanediol. These results add to the growing literature indicating that athletes and non-athletes may be at considerable risk when they abuse androgens. (PMID: 11500254, 16040068, 11744084).
3-Methoxy-4-hydroxyphenylglycol (HMPG) glucuronide is the main form of HMPG in human urine. HMPG is a major metabolite of norepinephrine that is found in urine and cerebrospinal fluid (CSF). It has been determined that 25-50% of it is derived from brain norepinephrine. The conjugated form is reported to be derived mainly from the metabolism of systemic norepinephrine. (PMID 528605).
Dihydrouridine is a pyrimidine which is the result of adding two hydrogen atoms to a uridine. Dihydrouridine is found only in tRNA molecules. An inhibitor of nucleotide metabolism.
4-Deoxyerythronic acid is a normal organic acid present in human biofluids (PMIDs 2338430, 3829393, 3525594, 14708889, 1560100, 6725493), derived presumably from L-threonine. (PMID 2947647) It has been associated with uremia (PMID 1149237) and diabetes mellitus type 1. (PMID 2947647).
5-Tetradecenoic acid (CAS: 544-66-1), also known as physeterate or physeteric acid, is a member of the class of compounds known as long-chain fatty acids. Long-chain fatty acids are fatty acids with an aliphatic tail that contains between 13 and 21 carbon atoms. Thus, 5-tetradecenoic acid is considered to be a fatty acid lipid molecule. 5-Tetradecenoic acid is practically insoluble (in water) and a weakly acidic compound (based on its pKa). 5-Tetradecenoic acid can be found primarily in blood. Within the cell, 5-tetradecenoic acid is primarily located in the cytoplasm and in the membrane. It can also be found in the extracellular space. 5-Tetradecenoic acid is an intermediate of unsaturated fatty acid metabolism found in the plasma of patients with very long chain acyl-CoA dehydrogenase (VLCAD) deficiency, a genetic disorder (PMID: 7586519).
3-Oxocholic acid, also known as 7alpha,12alpha-dihydroxy-3-oxo-5beta-cholan-24-oic acid, is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. 3-Oxocholic acid is considered to be practically insoluble (in water) and acidic.
7alpha-Hydroxy-3-oxo-5beta-cholan-24-oic acid, also known as 3-dehydrochenodeoxycholic acid or (5beta,7alpha)-7-hydroxy-3-oxocholan-24-oate, is classified as a monohydroxy bile acids, alcohol or a monohydroxy bile acids, alcohol derivative. Monohydroxy bile acids, alcohols are bile acids, alcohols or any of their derivatives bearing a hydroxyl group. 7alpha-Hydroxy-3-oxo-5beta-cholan-24-oic acid is considered to be practically insoluble (in water) and acidic. 7alpha-Hydroxy-3-oxo-5beta-cholan-24-oic acid is a bile acid lipid molecule. Glycine- and taurine-conjugated 7alpha-hydroxy-3-oxo-5beta-cholan-24-oic acid has been identified in normal human serum (PMID: 1939467) and as a cholesterol metabolite in bile acids produced in HepG2 cells, a well-differentiated human hepatoblastoma cell line (PMID: 1655725).
Allocholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
alpha-Muricholic acid is a hydroxylated bile acid present in normal human urine (PMID: 1629271), and in free glycine-conjugated, taurine-conjugated, and sulfated forms in human feces (PMID: 3667743). Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Ribitol is a pentose alcohol formed by the reduction of ribose. It occurs naturally in plants as well as in the cell walls of some Gram-positive bacteria. Ribitol forms part of the chemical structure of riboflavin and flavin mononucleotide (FMN). It is also a metabolic end product formed by the reduction of ribose in human fibroblasts and erythrocytes. In this regard ribitol is found in all organisms from bacteria to plants to humans. Ribitol is a normal constituent of human urine (PMID: 2736321). Elevated levels of ribitol in the serum or urine can be found in patients with transaldolase deficiency (PMID: 11283793). Transaldolase is an important enzyme in the pentose phosphate pathway (PPP).  Elevated levels of ribitol in the serum or urine can be found in patients with Ribose-5-phosphate isomerase deficiency (PMID: 14988808).  Ribose-5-phosphate isomerase is an important enzyme in the pentose phosphate pathway (PPP). Export of ribitol across the cell membrane indicates that can be cleared from the body without metabolic conversion (PMID 15234337). Ribitol is normally absent in Breast milk (PMID 16456418).
Senecioic acid, also known as 3-methylcrotonate, 3-methylcrotonic acid or 3,3-dimethylacrylic acid, belongs to the class of organic compounds known as methyl-branched fatty acids. These are fatty acids with an acyl chain that has a methyl branch. Usually, they are saturated (however senecioic acid is unsaturated) and contain only one or more methyl group. However, branches other than methyl may be present. Senecioic acid is a methyl-branched fatty acid that has a but-2-enoic acid skeleton bearing a methyl substituent at position 3. Senecioic acid is an unsaturated fatty acid found in the pheromones of mealybug species, the Madeira cockroach and the Southern long-nosed bat. It also appears in the urine of patients with 3-Methylcrotonic aciduria caused by 3-hydroxy-3-methylglutaryl-CoA lyase deficiency (PMID: 6157502) and those with 3-Hydroxy-3-methylglutaric aciduria (PMID: 947633). The appearance of 3-methylcrotonic acid in urine indicates a blockage in the sixth step of leucine catabolism, which is the cleavage of 3-hydroxy-3-methylglutaryl-CoA to acetoacetic acid and acetyl-CoA.
Capric acid, also known as decanoic acid is a C10 saturated fatty acid. It is a member of the series of fatty acids found in oils and animal fats. The names of caproic, caprylic, and capric acids are all derived from the word caper (Latin for goat). These fatty acids are light yellowish transparent oily liquids with a sweaty, unpleasant aroma that is reminiscent of goats. Capric acid is used in the manufacture of esters for artificial fruit flavors and perfumes. It is also used as an intermediate in chemical syntheses. Capric acid is used in organic synthesis and industrially in the manufacture of perfumes, lubricants, greases, rubber, dyes, plastics, food additives and pharmaceuticals. Capric acid occurs naturally in coconut oil (about 10%) and palm kernel oil (about 4%), otherwise it is uncommon in typical seed oils. It is found in the milk of various mammals and to a lesser extent in other animal fats. Capric acid, caproic acid (a C6:0 fatty acid) and caprylic acid (a C8:0 fatty acid) account for about 15% of the fatty acids in goat milk fat (PMID 16747831). Capric acid may be responsible for the mitochondrial proliferation associated with the ketogenic diet, which may occur via PPARgamma receptor agonism and the targeting of genes involved in mitochondrial biogenesis (PMIDL 24383952).
5b-Cholestane-3a,7a,12a,23R,25-pentol is a bile alcohol present in the urine of patients with cerebrotendinous xanthomatosis, but not in feces. A possible explanation for the urinary cholestanepentols is that the major serum bile alcohol, 5b-cholestane-3a,7a,12a,25-tetrol, might be hydroxylated at C-23 to form (23)-5b-cholestane-3a,7a,12a,23,25-pentols in the kidneys, an hypothesis supported by the fact that in our patient (23R)-5b-cholestane-3a,7a,12a,23,25-pentol was detected only in urine but were virtually absent in bile. (PMID 3700361).
Allochenodeoxycholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Chenodeoxycholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135). Usually conjugated with either glycine or taurine. It acts as a detergent to solubilize fats for intestinal absorption and is reabsorbed by the small intestine. It is used as cholagogue, a choleretic laxative, and to prevent or dissolve gallstones.
5a-Cholestane-3a,7a,12a,25-tetrol is a bile alcohols which is excreted mainly as glucurono-conjugates in bile and urine, and as unconjugated form in feces of patients with cerebrotendinous xanthomatosis (PMID 3700361).
5Z-Tetradecenoic acid is an intermediate of unsaturated fatty acid oxidation that is incorporated in triglycerides, but not in phospholipids. 5Z-Tetradecenoic acid is found in the tissues of patients with mitochondrial beta-oxidation defects, particularly in very long-chain acyl-CoA dehydrogenase deficiency (VLCADD1/VLCADD2), a genetic disorder (PMID: 2051892). 5Z-Tetradecenoic acid is also found to be associated with long-chain 3-hydroxyacyl-CoA dehydrogenase and multiple acyl-CoA dehydrogenase deficiency (MADD), which are also inborn errors of metabolism.
3-Methylglutaconic acid is an intermediate (as the CoA thioester) in the leucine degradative pathway as well as the mevalonate shunt, a pathway that links isoprenoid metabolism with mitochondrial acetyl-CoA metabolism (PMID: 7603789). 3-methylglutaconyl-CoA hydratase is involved in the metabolism process of 3-methylglutaconic acid. When present in sufficiently high levels, 3-methylglutaconic acid can act as an acidogen and a metabotoxin. An acidogen is an acidic compound that induces acidosis, which has multiple adverse effects on many organ systems. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of 3-methylglutaconic acid are associated with at least five inborn errors of metabolism including 3-hydroxy-3-methylglutaryl-CoA lyase deficiency, 3-methylglutaconic aciduria type I, 3-methylglutaconic aciduria type III, 3-methylglutaconic aciduria type IV, and guanidinoacetate methyltransferase deficiency (GAMT deficiency). 3-Methylglutaconic acid is an organic acid. Abnormally high levels of organic acids in the blood (organic acidemia), urine (organic aciduria), the brain, and other tissues lead to general metabolic acidosis. Acidosis typically occurs when arterial pH falls below 7.35. In infants with acidosis, the initial symptoms include poor feeding, vomiting, loss of appetite, weak muscle tone (hypotonia), and lack of energy (lethargy). These can progress to heart, liver, and kidney abnormalities, seizures, coma, and possibly death. These are also the characteristic symptoms of the untreated IEMs mentioned above. Many affected children with organic acidemias experience intellectual disability or delayed development. In adults, acidosis or acidemia is characterized by headaches, confusion, feeling tired, tremors, sleepiness, and seizures.
5-Androstene-3b,16b,17a-triol is an steroid found in the urine of human pregnancy (PMID 4452739), in the urine of newborns and infants (PMID 5126818), and in the mono- and disulfate fractions of human bile. (PMID 5410667).
5β-Cholestane-3α,7α,12α,25-tetrol is an intermediate in the bile acid synthetic pathway, and is secreted into the bile and urine following glucuronidation. It does not undergo enterohepatic circulation. In cerebrotendinous xanthomatosis (CTX), a bile acid synthesis disorder caused by sterol 27-hydroxylase (CYP27) deficiency, early intermediates and cholestanol accumulate in a variety of tissues, and glucuronides of 25-hydroxylated bile alcohols are released in bile, blood, and urine (PMID: 11181760). Bile acid synthesis from cholesterol is tightly regulated via a feedback mechanism mediated by the farnesoid X receptor (FXR), a nuclear receptor activated by bile acids. Synthesis via the classic pathway is initiated by a series of cholesterol ring modifications and followed by the side chain cleavage. The enhanced cholesterol 7 alpha-hydroxylase (CYP7A1) expression in CYP27 deficiency may be the result of a decreased flux of bile acids and bile alcohols into the liver, while production of FXR-activating 5β-cholestane-3α,7α,12α,25-tetrol is increased (PMID: 15145977).
5-Hydroxyhexanoic acid is a normal dicarboxylic acid degradation product of fatty acids; however, it has been found in patients with non-ketotic dicarboxylic aciduria and one patient on a diet containing excessive amounts of medium-chain triglycerides. Increased amounts of dicarboxylic acids are excreted in human urine under conditions of medium-chain triglyceride (MCT) feeding, abnormal fatty acid oxidation (FAO) and fasting. Criteria to distinguish dicarboxylic aciduria originating from MCT feeding and other conditions are needed in urinary organic acid profiling for detecting inborn errors of metabolism. Medium-chain triglycerides (MCTs) are absorbed and metabolized differently from long-chain triglycerides (LCTs). MCTs may be useful as a dietary substitute in a variety of clinical disorders. Urinary excretion of 5-hydroxyhexanoic acid, the (omega-1) hydroxylation product, was increased during MCT feeding as compared with LCT feeding in patients with non-insulin-dependent diabetes mellitus (PMID: 6897376, 2239769, 8596483). Moreover, 5-hydroxyhexanoic acid is also found to be associated with Medium chain acyl-CoA dehydrogenase deficiency (MCADD), which is also an inborn error of metabolism. 5-Hydroxyhexanoic acid has be found to be a microbial metabolite (PMID: 20615997).
5alpha-Tetrahydrocortisol is a normal human metabolite. However its increased ratio (5alpha-tetrahydrocortisol + tetrahydrocortisol) over tetrahydrocortisone in urine is the biochemical marker for the syndrome of apparent mineralocorticoid excess (AME). AME is a heritable form of hypertension due to an inborn error of cortisol metabolism and is characterized by hypokalemia and low renin levels despite subnormal or normal levels of aldosterone and other known mineralocorticoids. The syndrome is attributable to congenital deficiency of the enzyme 11 beta-hydroxydehydrogenase (11-beta-HSD), which converts cortisol to biologically inactive cortisone. This results in a prolonged half-life of cortisol, which acts at the kidney level as a potent mineralocorticoid (PMID: 8732999).
6a,12a-Dihydroxylithocholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135). 6a,12a-Dihydroxylithocholic acid has been identified in the urine of patients with cholestasis (PMID 7444367).
4,5-Dihydroorotic acid, also known as dihydroorotate or hydroorotate is a pyrimidinemonocarboxylic acid that results from the base-catalysed cyclisation of N-alpha-carbethoxyasparagine. It is classified as a secondary amide, a monocarboxylic acid, a pyrimidinemonocarboxylic acid and a N-acylurea. 4,5-Dihydroorotic acid is a derivative of orotic acid which serves as an intermediate in pyrimidine biosynthesis. 4,5-Dihydroorotic acid exists in all living species, ranging from bacteria to plants to humans. 4,5-Dihydroorotic acid is synthesized by the enzyme known as Dihydroorotase (EC 3.5.2.3) which converts carbamoyl aspartic acid into 4,5-dihydroorotic acid as part of the de novo pyrimidine biosynthesis pathway (PMID: 13163076). 4,5-Dihydroorotic acid is also a substrate for the enzyme known as dihydroorotate dehydrogenase (DHODH).  In mammalian species, DHODH catalyzes the fourth step in the de novo pyrimidine biosynthesis pathway, which involves the ubiquinone-mediated oxidation of dihydroorotate to orotate and the reduction of flavin mononucleotide (FMN) to dihydroflavin mononucleotide (FMNH2). Inhibition of DHODH activity with teriflunomide (an immunomodulatory drug) or expression with RNA interference results in reduced ROS generation and consequent apoptosis of transformed skin and prostate epithelial cells. Mutations in the DHOD gene have been shown to cause Miller syndrome, also known as Genee-Wiedemann syndrome, Wildervanck-Smith syndrome or post-axial acrofacial dystosis (PMID: 19915526).
5Z-Dodecenoic acid, also known as 5-dodecenoic acid or 5-dodecenoate, is a monounsaturated fatty acid that has a C12 chain as a backbone and a cis double bond at the C5 position. 5-Dodecenoic acid is a member of the class of compounds known as medium-chain fatty acids. Medium-chain fatty acids are fatty acids with an aliphatic tail that contains between 4 and 12 carbon atoms. Thus, 5-dodecenoic acid is considered to be a fatty acid lipid molecule. 5-Dodecenoic acid is practically insoluble (in water) and a weakly acidic compound (based on its pKa). Within the cell, 5-dodecenoic acid is primarily located in the cytoplasm and in the membrane (predicted from logP). It can also be found in the extracellular space. An increase of 5-dodecenoic acid in plasma is associated with acyl-CoA dehydrogenase deficiency disorders (PMID: 7586519). 5-Dodecenoic acid is an intermediate of unsaturated fatty acid oxidation.
6-Ketoestriol is a normal human metabolite that is in elevated concentration in the urine of patients with prolactinoma. (PMID 9812172).
3-Hydroxyvaleric acid may be products of the condensation of propionyl-CoA with acetyl-CoA catalyzed by 3-oxoacyl-CoA thiolases. An increase amount of 3-hydroxyvaleric acid can be found in methylmalonic acidemia and propionic acidemia. (PMID: 630060).
Campestanol is plant stanol. It can decrease the circulating LDL-cholesterol level by reducing intestinal cholesterol absorption. (PMID 8143759).
Caproic acid, also known as hexanoic acid or C6:0, is a medium-chain fatty acid. Medium-chain fatty acids (MCFA) are fatty acids with aliphatic tails of 6 to 12 carbons, which can form medium-chain triglycerides. Caproic acid is a colourless oily liquid that smells like cheese with an overlying waxy or barnyard odor like that of goats or other barnyard animals. Its name comes from the Latin word capra, meaning "goat". Two other fatty acids are named after goats: caprylic acid (C8) and capric acid (C10). Along with caproic acid, they account for 15% of the fat in goat's milk. Caproic acid is a fatty acid found naturally in various animal fats and oils. While generally more abundant in animals, caproic acid is found in all organisms ranging from bacteria to plants to animals. Caproic acid is one of the chemicals that gives the decomposing fleshy seed coat of the ginkgo fruit its characteristic unpleasant odor. It is also one of the components of vanilla and cheese. Industrially, the primary use of caproic acid is in the manufacture of its esters for use as artificial flavors and in the manufacture of hexyl derivatives, such as hexylphenols. Caproic acid has been associated with medium chain acyl-CoA dehydrogenase deficiency, which is an inborn error of metabolism. As a relatively volatile organic compound, caproic acid has been identified as a fecal biomarker of Clostridium difficile infection (PMID: 30986230).
Adenylsuccinic acid, also known as adenylosuccinate, succinyladenosine or aspartyl adenylate, belongs to the class of organic compounds known as purine ribonucleoside monophosphates. These are nucleotides consisting of a purine base linked to a ribose to which one monophosphate group is attached. Adenylsuccinic acid is found in all living organisms, ranging from bacteria to plants to animals. Adenylsuccinic acid is an important intermediate in the de novo purine biosynthesis pathway.  Specifically, adenylsuccinic acid is an intermediate in the interconversion of purine nucleotides inosine monophosphate (IMP) and adenosine monophosphate (AMP). The enzyme adenylosuccinate synthase carries out the reaction by the addition of aspartate to IMP. This reaction requires the input of energy from a phosphoanhydride bond in the form of guanosine triphosphate (GTP). Adenylsuccinic acid is a substrate least one other important metabolic reaction in purine biosynthesis. In particular, adenylsuccinic acid can be converted into fumaric acid through its interaction with the enzyme known as adenylosuccinate lyase (or adenylosuccinase). Adenylosuccinate lyase deficiency, is a rare autosomal recessive metabolic disorder characterized by the appearance of succinylaminoimidazolecarboxamide riboside (SAICA riboside) and adenylsuccinic acid in cerebrospinal fluid and urine (PMID: 8412002). Adenylosuccinate lyase deficiency presents with varying degrees of psychomotor retardation, autism, muscle wasting, and epilepsy. The exact cause of the symptoms is unknown, but possibilities include not enough purine nucleotide synthesis for cell replication, malfunctioning of the purine nucleotide cycle, and a buildup of substrates to toxic levels.
Adenosine triphosphate (ATP) is a nucleotide consisting of a purine base (adenine) attached to the first carbon atom of ribose (a pentose sugar). Three phosphate groups are esterified at the fifth carbon atom of the ribose. ATP is incorporated into nucleic acids by polymerases in the processes of DNA replication and transcription. ATP contributes to cellular energy charge and participates in overall energy balance, maintaining cellular homeostasis. ATP can act as an extracellular signaling molecule via interactions with specific purinergic receptors to mediate a wide variety of processes as diverse as neurotransmission, inflammation, apoptosis, and bone remodelling. Extracellular ATP and its metabolite adenosine have also been shown to exert a variety of effects on nearly every cell type in human skin, and ATP seems to play a direct role in triggering skin inflammatory, regenerative, and fibrotic responses to mechanical injury, an indirect role in melanocyte proliferation and apoptosis, and a complex role in Langerhans cell-directed adaptive immunity. During exercise, intracellular homeostasis depends on the matching of adenosine triphosphate (ATP) supply and ATP demand. Metabolites play a useful role in communicating the extent of ATP demand to the metabolic supply pathways. Effects as different as proliferation or differentiation, chemotaxis, release of cytokines or lysosomal constituents, and generation of reactive oxygen or nitrogen species are elicited upon stimulation of blood cells with extracellular ATP. The increased concentration of adenosine triphosphate (ATP) in erythrocytes from patients with chronic renal failure (CRF) has been observed in many studies but the mechanism leading to these abnormalities still is controversial. (PMID: 15490415, 15129319, 14707763, 14696970, 11157473).
Arabinonic acid (CAS: 13752-83-5) is a substrate of L-arabinonate dehydratase [EC 4.2.1.25] in the pathway ascorbate and aldarate metabolism (KEGG).
5-Androstene-3b,16a,17a-triol is a normal urinary steroid in newborn infants (PMID 14709852), in the mono- and disulfate fractions of human bile (PMID 5410667), and was found in the blood of a patient with paraquat poisoning (PMID 7094338).
7b-Hydroxy-3-oxo-5b-cholanoic acid was one of the bile acids present in significant proportions during early gestation, identified in amniotic fluid. (PMID 2373959). A bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Benzenebutanoic acid (also known as 4-phenylbutyrate, or 4-PBA) is the oral form of butyrate, which is known to be a transcriptional regulator. Sodium-4-PBA has been shown to induce fetal hemoglobin, and it has been used in clinical trials for sickle cell anemia and &#946;-thalassemia. Because gene expression profiles became more differentiated, it is in phase I trials in several different malignant disorders. The potential for therapeutic benefit in cystic fibrosis (CF) resides in an additional mechanism, involving protein folding and the ER (endoplasmic reticulum) environment (PMID 12458151). 4-PBA is a drug that was developed to treat elevated blood ammonia in urea cycle disorders, a histone deacetylase inhibitor that promotes mutation &#916;F508 cystic fibrosis transmembrane conductance regulator (CFTR) trafficking (PMID 16798551).
5-Hydroxymethyl-6-methyl- 2,4-(1H,3H)-pyrimidinedione. Uracil derivative used in combination with toxic antibiotics to lessen their toxicity; also to stimulate leukopoiesis and immunity.
Chenodeoxycholic acid disulfate is a bile acid derviative. A bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Epietiocholanolone is an anabolic steroid similar in structure to androstenedione. Used by body-builders to add muscle mass, but with unknown side effects.
Magnesium salts are essential in nutrition, being required for the activity of many enzymes, especially those concerned with oxidative phosphorylation. Physiologically, it exists as an ion in the body. It is a component of both intra- and extracellular fluids and is excreted in the urine and feces. Deficiency causes irritability of the nervous system with tetany, vasodilatation, convulsions, tremors, depression, and psychotic behavior. Magnesium ion in large amounts is an ionic laxative, and magnesium sulfate (Epsom salts) is sometimes used for this purpose. So-called "milk of magnesia" is a water suspension of one of the few insoluble magnesium compounds, magnesium hydroxide; the undissolved particles give rise to its appearance and name. Milk of magnesia is a mild base, and is commonly used as an antacid. Moreover, magnesium is found to be associated with primary hypomagnesemia, which is an inborn error of metabolism.
Gamma-butyrolactone (GBL), also known as 1,4-butanolide or 1,4-lactone, belongs to the class of organic compounds known as gamma butyrolactones. Gamma butyrolactones are compounds containing a gamma butyrolactone moiety, which consists of an aliphatic five-member ring with four carbon atoms, one oxygen atom, and bears a ketone group on the carbon adjacent to the oxygen atom. GBL can also be classified as a tetrahydrofuran substituted by an oxo group at position 2. Gamma-butyrolactone is soluble in ethanol and moderately miscible in water. Gamma-butyrolactone is a sweet, caramel, and creamy tasting compound. Gamma-butyrolactone exists in all living species, ranging from bacteria to plants to humans. It can be endogenously produced from gamma-aminobutyrate and is the precursor of gamma-hydroxybutyrate. Outside of the human body, gamma-butyrolactone has been detected, but not quantified in, several different foods, such as pepper (c. annuum), yellow bell peppers, orange bell peppers, soy beans, evergreen blackberries and a variety of wines (at a concentration of 5 ug/mL) (PMID: 15939164). This could make gamma-butyrolactone a potential biomarker for the consumption of these foods.  Gamma-butyrolactone is rapidly converted into gamma-hydroxybutyrate by paraoxonase (lactonase) enzymes, found in the blood.  Because it can serve as a prodrug for gamma-hydroxybutyrate (GHB), Gamma-butyrolactone is commonly used as a recreational CNS depressant with effects similar to those of barbiturates.  Industrially gamma-butyrolactone is used as a common solvent for polymers and alcohols, a chemical intermediate, a raw material for pharmaceuticals, and as a paint stripper, superglue remover, and a stain remover.
5-Androstenetriol is a metabolite of dehydroepiandrosterone (DHEA) found in normal urine in healthy subjects during growth (PMID 15671100), and is one of the markers that reflects the changes of the adrenarche process in boys and girls (Adrenarche is the adrenal glands maturaty).
Etiocholanediol is one of the compounds tested to allow for the unequivocal identification of the presence of urinary anabolic steroids and metabolites banned for use in sport by athletes. In urine samples collected for anti-doping purposes with moderately elevated testosterone and epitestosterone ratio, or when a suspicion of manipulation of the sample occurs, Etiocholanediol is tested for further clarification. It is worth mentioning that the concentration parameters vary enormously according to the gender of the subjects, ethnic origin, the urine collection period (before or after effort, period of the day) and the hydration state of the athlete. Urinary steroid data using several methodologies are not appropriate for identification purposes and to an extent not unique to individuals. (PMID: 16337352, 16338181, 16337352, 17260133).
3L,7D,11D-Phytanic acid is an isomer of Phytanic acid, an unusual 20-carbon branched-chain fatty acid; Phytanic acid accumulates in blood and tissues of patients with Refsum disease (RD, an inborn error of lipid metabolism inherited as an autosomal recessive trait (OMIM 266500)), and is a reliably identifier of RD from a large number of other neurological disorders. Phytanic acid also accumulates in a number of other disorders with a very different clinical course: disorders of peroxisome biogenesis (Zellweger syndrome (OMIM 214100), neonatal adrenoleukodystrophy (OMIM 202370), infantile Refsum disease (OMIM 266510)) and rhizomelic chondrodysplasia punctata, type 1 (OMIM 215100). Phytanic acid is a 3-methyl fatty acid that cannot be beta-oxidized directly, and first undergoes an alpha-oxidation a reaction catalyzed by the enzyme phytanoyl-CoA hydroxylase, which is deficient in RD, the only true disorder of phytanic acid alpha-oxidation. (The Metabolic and Molecular Bases of Inherited Disease).
Dihydroandrosterone is a major metabolite of testosterone. Dihydroandrosterone is the main steroid produced by the immature ovary; at puberty the synthesis of steroids shifts toward 4-ene-3-oxo steroids. testosterone 5a-reduced metabolites, including dihydrotestosterone are produced in the anterior pituitary and the central nervous system. Anabolic androgen steroid (AAS) are one of primary performance-enhancing substances abused by athletes. To defeat doping controls, athletes changed to take endogenous androgens from the application of synthetic AAS. testosterone was one candidate of endogenous androgens abused in sports. testosterone and its relevant steroids in urine is detected and monitored with GC/MS. The abuse of anabolic-androgenic steroids (AS) is a growing problem; however, the effects and mechanisms underlying their addictive effects are not well understood. (PMID: 17112575, 6243214, 491593, 491592).
3-Methyladipic acid is a metabolite of the catabolism of phytanic acid. Patients with adult Refsums disease (ARD) are unable to detoxify phytanic acid by alpha-oxidation, and so the w-oxidation pathway is the only metabolic pathway available for phytanic acid degradation. This pathway produces 3-methyladipic acid as the final metabolite, which is excreted in the urine (Wanders et al. 2001). Activity of the w-oxidation pathway is approximately doubled in ARD patients compared with normal individuals (PMID: 11948235).
5b-Cholestane-3a,7a,12a,24,25-pentol has been found excreted in the urine from a patient with sitosterolemia as glycine- and taurine-conjugated bile acids (PMID 7896564).
L-alloisoleucine is a branched chain amino acid and is a stereo-isomer of L-isoleucine. It is a common constituent of human plasma (albeit at low levels). L-alloisoleucine is produced as a byproduct of isoleucine transamination. L-Isoleucine is one of the four common amino acids (the 3 others being threonine, hydroxyproline, and hydroxylysine) that have two asymmetric carbon atoms which produce four structural possibilities for the same chemical composition. L-alloisoleucine differs from L-isoleucine by having having different stereochemistry around its beta carbon. Plasma L-alloisoleucine, which is derived from L-isoleucine in vivo, can be used for the diagnosis of maple syrup urine disease (MSUD), a genetic disorder. Indeed, plasma L-alloisoleucine levels above 5 umol/L is the most specific and most sensitive diagnostic marker for all forms of MSUD (PMID: 10508118). In MSUD the degradation of the essential branched-chain L-amino acids leucine, valine, and isoleucine and their derived 2-oxoacids is impaired because of an inherited deficiency in branched-chain 2-oxoacid dehydrogenase complex (EC 1.2.4.4) activity. The accumulation of branched-chain compounds in blood and other body fluids can exert neurotoxic effects.
5a-Cholestane-3a,7a,12a,23,25-pentol is a bile acid found in the urine of patients with cerebrotendinous xanthomatosis. (PMID 1805458).
3-Methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4) is the major metabolite of noradrenaline in serum. Chronic schizophrenics have lower serum levels than healthy individuals. Treatment of both groups with 7 daily 3-mg doses of haloperidol caused similar decreases in MHPG-SO4 concentration (PMID: 7343757). In human urine, MHPG-SO4 constitutes 44% of the total 3-methoxy-4-hydroxyphenylethylene glycol (PMID: 7379456).
Goshuyic acid, also known as (Z,Z)-5,8-tetradecadienoic acid, is a member of the class of compounds known as long-chain fatty acids. Long-chain fatty acids are fatty acids with an aliphatic tail that contains between 13 and 21 carbon atoms. Goshuyic acid is practically insoluble (in water) and a weakly acidic compound (based on its pKa). Within the cell, goshuyic acid is primarily located in the membrane (predicted from logP). It can also be found in the extracellular space. Goshuyic acid is an intermediate of unsaturated fatty acid oxidation. An increase of goshuyic acid in plasma is associated with acyl-CoA dehydrogenase deficiency disorders (PMID: 7586519). Goshuyic acid is found in fats and oils and is a minor constituent of rape oil.
Beta-Carotene belongs to the class of organic compounds known as carotenes. These are a type of polyunsaturated hydrocarbon molecules containing eight consecutive isoprene units. Carotenes are characterized by the presence of two end-groups (mostly cyclohexene rings, but also cyclopentene rings or acyclic groups) linked by a long branched alkyl chain. Beta-carotene is therefore considered to be an isoprenoid lipid molecule. Beta-carotene is a strongly coloured red-orange pigment abundant in fungi, plants, and fruits. It is synthesized biochemically from eight isoprene units and therefore has 40 carbons. Among the carotenes, beta-carotene is distinguished by having beta-rings at both ends of the molecule. Beta-Carotene is biosynthesized from geranylgeranyl pyrophosphate. It is the most common form of carotene in plants. In nature, Beta-carotene is a precursor (inactive form) to vitamin A. Vitamin A is produed via the action of beta-carotene 15,15'-monooxygenase on carotenes. In mammals, carotenoid absorption is restricted to the duodenum of the small intestine and dependent on a class B scavenger receptor (SR-B1) membrane protein, which is also responsible for the absorption of vitamin E. One molecule of beta-carotene can be cleaved by the intestinal enzyme Beta-Beta-carotene 15,15'-monooxygenase into two molecules of vitamin A. Beta-Carotene contributes to the orange color of many different fruits and vegetables. Vietnamese gac and crude palm oil are particularly rich sources, as are yellow and orange fruits, such as cantaloupe, mangoes, pumpkin, and papayas, and orange root vegetables such as carrots and sweet potatoes. Excess beta-carotene is predominantly stored in the fat tissues of the body. The most common side effect of excessive beta-carotene consumption is carotenodermia, a physically harmless condition that presents as a conspicuous orange skin tint arising from deposition of the carotenoid in the outermost layer of the epidermis.
Creatinine, or creatine anhydride, is a breakdown product of creatine phosphate in muscle. The loss of a water molecule from creatine results in the formation of creatinine. Creatinine is transferred to the kidneys by blood plasma, whereupon it is eliminated from the body by glomerular filtration and partial tubular excretion. Creatinine is usually produced at a fairly constant rate by the body. Measuring serum creatinine is a simple test and it is the most commonly used indicator of renal function. A rise in blood creatinine levels is observed only with marked damage to functioning nephrons. Therefore, this test is not suitable for detecting early kidney disease. The typical reference range for women is considered about 45-90 µmol/L; for men 60-110 µmol/L. Creatine and creatinine are metabolized in the kidneys, muscle, liver, and pancreas.
Phenyllactic acid is a product of phenylalanine catabolism. An elevated level of phenyllactic acid is found in body fluids of patients with or phenylketonuria.
PC(16:0/16:0) is a phosphatidylcholine (PC or GPCho). It is a glycerophospholipid in which a phosphorylcholine moiety occupies a glycerol substitution site. As is the case with diacylglycerols, glycerophosphocholines can have many different combinations of fatty acids of varying lengths and saturation attached at the C-1 and C-2 positions. Fatty acids containing 16, 18 and 20 carbons are the most common. PC(16:0/16:0), in particular, consists of two chains of palmitic acid at the C-1 and C-2 positions. The palmitic acid moieties are derived from fish oils, milk fats, vegetable oils and animal fats. Phospholipids, are ubiquitous in nature and are key components of the lipid bilayer of cells, as well as being involved in metabolism and signaling. Dipalmitoylphosphatidylcholine (DPPC) is the major constituent of pulmonary surfactant. It is also used for research purposes in studying liposomes, lipid bilayers, and model biological membranes. While most phospholipids have a saturated fatty acid on C-1 and an unsaturated fatty acid on C-2 of the glycerol backbone, the fatty acid distribution at the C-1 and C-2 positions of glycerol within phospholipids is continually in flux, owing to phospholipid degradation and the continuous phospholipid remodeling that occurs while these molecules are in membranes. PCs can be synthesized via three different routes. In one route, choline is activated first by phosphorylation and then by coupling to CDP prior to attachment to phosphatidic acid. PCs can also synthesized by the addition of choline to CDP-activated 1,2-diacylglycerol. A third route to PC synthesis involves the conversion of either PS or PE to PC.
Galactonic acid is a sugar acid that is a metabolic breakdown product of galactose. Galactose dehydrogenase is responsible for converting galactose to galactonolactone, which then spontaneously or enzymatically converts to galactonic acid. Once formed, galactonic acid may enter the pentose phosphate pathway. Galactonic acid is increased in red blood cells of galactosemic patients, due to a galactose-1-phosphate uridyltransferase (GALT) deficiency (PMID: 14680973, OMMBID: The Online Metabolic and Molecular Bases of Inherited Disease, Ch.72). When present in sufficiently high levels, galactonic acid can act as an acidogen and a metabotoxin. An acidogen is an acidic compound that induces acidosis, which has multiple adverse effects on many organ systems. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of galactonic acid are associated with at least two inborn errors of metabolism, including galactosemia and galactosemia type II. Galactonic acid is an organic acid. Abnormally high levels of organic acids in the blood (organic acidemia), urine (organic aciduria), the brain, and other tissues lead to general metabolic acidosis. Acidosis typically occurs when arterial pH falls below 7.35. In infants with acidosis, the initial symptoms include poor feeding, vomiting, loss of appetite, weak muscle tone (hypotonia), and lack of energy (lethargy). These can progress to heart abnormalities, liver abnormalities (jaundice), kidney abnormalities, seizures, coma, and possibly death. These are also the characteristic symptoms of untreated galactosemia. Many affected children with organic acidemias experience intellectual disability or delayed development. High levels of galactonic acid in infants are specifically associated with hepatomegaly (an enlarged liver), cirrhosis, renal failure, cataracts, vomiting, seizure, hypoglycemia, lethargy, brain damage, and ovarian failure.
Cinnamic acid, also known as (Z)-cinnamate or 3-phenyl-acrylate, belongs to the class of organic compounds known as cinnamic acids. These are organic aromatic compounds containing a benzene and a carboxylic acid group forming 3-phenylprop-2-enoic acid. Cinnamic acid can be obtained from oil of cinnamon, or from balsams such as storax. Cinnamic acid is a weakly acidic compound (based on its pKa). It is a white crystalline compound that is slightly soluble in water, and freely soluble in many organic solvents. Cinnamic acid exists in all living organisms, ranging from bacteria to plants to humans. Outside of the human body, cinnamic acid has been detected, but not quantified in, chinese cinnamons. In plants, cinnamic acid is a central intermediate in the biosynthesis of myriad natural products include lignols (precursors to lignin and lignocellulose), flavonoids, isoflavonoids, coumarins, aurones, stilbenes, catechin, and phenylpropanoids.
D-Arabitol is a polyol. Polyols are sugar alcohols linked to the pentose phosphate pathway (PPP). They are classified on the basis of the number of carbon atoms. Polyols occur in body fluids. A patient with leukoencephalopathy and peripheral neuropathy has been identified as suffering from ribose-5-phosphate isomerase (RPI) deficiency, a defect in the PPP. In this disorder, highly elevated concentrations of the C5 polyols such as D-arabitol are found in body fluids. In addition, transaldolase deficiency, another defect in the PPP, has been diagnosed in a patient with mainly liver problems among others. This patient had increased concentrations of polyols, mainly D-arabitol. So far, the pathophysiological role of polyols is relatively unknown. It is thought that D-arabitol is a metabolic end-product in humans. The strong brain-CSF-plasma gradient of polyols in the patient with RPI deficiency suggested a primary metabolic disorder. The mechanisms of brain and neuronal damage in RPI deficiency remain to be elucidated. A neurotoxic effect due to the accumulation of the polyols may play a role. D-Arabitol is a product of the enzyme D-arabinitol 4-dehydrogenase (EC 1.1.1.11) in the pentose and glucuronate interconversion pathway (PMID: 16435225, J Inherit Metab Dis. 2005;28(6):1181-3). D-Arabitol has also been found to be a fungal metabolite, urinary D-Arabinitol is a marker for invasive candidiasis or infection by Candida fungal species (PMID: 15183861; PMID: 10647119). It can also a metabolite in Debaryomyces, Pichia and Zygosaccharomyces (PMID: 25809659).
Deoxypyridinoline (DPD) is a breakdown product of type I fibrillar collagen, it occurs mainly in Type I collagen of bone. DPD shows a high specificity for bone, and the measurement of urinary DPD is not influenced by newly collagens and dietary intake. DPD cross-links of type 1 collagen are excreted in urine either as free or peptide-bound moieties. It is the peptide-bound cross-links that decrease by the greatest amount in response to bisphosphonate therapy. DPD is one of the most extensively characterized biochemical bone markers, but the interpretation of results is hampered by biologic and other preanalytical variability. Biochemical bone markers can provide a valuable tool in the management of metabolic bone diseases. Their most recognized application in clinical practice is for monitoring treatment for osteoporosis as an adjunct to bone mineral density measurements. Other applications that have been investigated include their use as a diagnostic tool for bone diseases other than osteoporosis and as predictive markers for bone loss and the risk of bone fracture. DPD measured in urine follow a circadian or diurnal cycle with a peak in the early morning and nadir in the late afternoon to early evening. The magnitude of the diurnal change, i.e., nadir concentration divided by peak concentration, expressed as a percentage is around 70% (range, 53-75%). (PMID: 11805003, 17229003, 16751696).
Coproporphyrin III is a porphyrin metabolite arising from heme synthesis. Porphyrins are pigments found in both animal and plant life. Coproporphyrin III is a tetrapyrrole dead-end product from the spontaneous oxidation of the methylene bridges of coproporphynogen, arising from heme synthesis and secreted in feces and urine. Increased levels of coproporphyrins can indicate congenital erythropoietic porphyria or sideroblastic anaemia, which are inherited disorders. Porphyria is a pathological state characterised by abnormalities of porphyrin metabolism and results in the excretion of large quantities of porphyrins in the urine and in extreme sensitivity to light. A large number of factors are capable of increasing porphyrin excretion, owing to different and multiple causes and etiologies: 1) the main site of the chronic hepatic porphyria disease process concentrates on the liver, 2) a functional and morphologic liver injury is almost regularly associated with this chronic porphyria, 3) the toxic form due to occupational and environmental exposure takes mainly a subclinical course. Hepatic factors includes disturbance in coproporphyrinogen metabolism, which results from inhibition of coproporphyrinogen oxidase as well as from the rapid loss from, and diminished utilization of coproporphyrinogen in the hepatocytes, which may also explain why coproporphyrin, its autoxidation product, predominates physiologically in the urine; decreased biliary excretion of coproporphyrin leading to a compensatory urinary excretion, so that the coproporphyrin ring isomer ratio (1:III) becomes a sensitive index for impaired liver function and intrahepatic cholestasis; and disturbed activity of hepatic uroporphyrinogen decarboxylase. In itself, secondary coproporphyrinuria is not associated with porphyria symptoms of a hepatologic-gastroenterologic, neurologic, or dermatologic order, even though coproporphyrinuria can occur with such symptoms. (PMID: 3327428).
Desmosine is formed by condensation of four molecules of lysine into a pyridinium ring. Elastin molecules aggregate in the extracellular space where they are crosslinked by stable desmosine bridges. The resulting polymer is structurally organized as branched fibers and lamellae, which, in skin, are wider (a few microns) in the deep dermis and become progressively thinner (fraction of a micron) towards the papillary dermis. Several general and local factors seem to regulate elastin gene expression, deposition and degradation. (PMID: 9297692). Desmosines are crosslinking amino acids unique to mature elastin in humans. Owing to this unicity, they have been discussed as potentially indicators of connective tissue disorders whose clinical manifestations are mostly the result of elastin degradation. (PMID: 17390614). Emphysema (Pulmonary emphysema is a devastating disease for which there is no effective treatment) is associated with degradation of elastic fibers (PMID: 14704646). It has been shown that the urinary concentration of elastin specific crosslinks, desmosine correlates well with liver fibrosis score in biopsy specimens from patients with liver disease secondary to hepatitis C virus and alcohol. (PMID: 10996125).
Elaidic acid, also known as (9E)-octadecenoic acid, belongs to the class of organic compounds known as long-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 13 and 21 carbon atoms. Elaidic acid is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Elaidic acid is the major trans fat found in hydrogenated vegetable oils and occurs in small amounts in caprine and bovine milk (very roughly 0.1 % of the fatty acids) and some meats. It is the trans isomer of oleic acid. The name of the elaidinization reaction comes from elaidic acid. Elaidic acid increases CETP activity, which in turn raises VLDL and lowers HDL cholesterol (Wikipedia).
Homocystine is the oxidized form of homocysteine.  Homocystine is a dipeptide consisting of two homocysteine molecules joined by a disulfide bond. Homocysteine is a sulfur-containing amino acid that arises during methionine metabolism. Homocystine occurs only transiently before being reduced to homocysteine and converted to the harmless cystathionine via a vitamin B6-dependent enzyme. Homocystine and homocysteine-cysteine mixed disulfides account for >98% of total homocysteine in plasma from healthy individuals (PMID 11592966).  Homocystine has been shown to stereospecifically induce endothelial nitric oxide synthase-dependent lipid peroxidation in endothelial cells, thereby inducing a vascular cell type-specific oxidative stress. This vascular stress is associated with atherothrombotic cardiovascular disease (PMID: 14980706).  High levels of homocysteine (and homocysteine) can be found in individuals suffering from homocystinura due to cystathionine synthase deficiency (PMID: 4685596)
Monoethyl malonic acid is an organic acid identified in the urine in a healthy pediatric population. (PMID 14708889).
Coprosterol or coprostanol is a cholesterol derivative found in human feces, gallstones, eggs, and other biological matter. Coprosterol is the odorous principle of feces. It is formed from the biohydrogenation of cholesterol (cholest-5en-3&#946;-ol) in the gut of most higher animals and birds. This compound has frequently been used as a biomarker for the presence of human faecal matter in the environment. American physician Austin Flint named it stercorin (Wikipedia). The transformation of cholesterol into coprosterol in its passage through the body involves a reduction of the C5:C6 double bond, and a transition from the allocholanic- to the cholanic-ring system. Although it is established that the bacterial flora of the intestine is concerned in the reduction process, the mechanism by which the stereochemical change is brought about is unknown. Current data suggests that cholestenone and coprostanone, and not cholesterol itself, are the immediate precursors of coprosterol which is formed from them in the intestine by bacterial reduction. Coprosterol is also a microbial metabolite, it can be produced by Lactobacillus (PMID: 20338415).
Deuteroporphyrin IX is a non-natural dicarboxylic porphyrin. Deuteroporphyrins are porphyrins with four methyl and two propionic acid side chains attached to the pyrrole rings. Deuteroporphyrin IX is described as a fecal porphyrin in patients with endemic chronic arsenic poisoning. (Environmental Sciences (Tokyo, Japan) (2001), 8(6), 561-570.). Excess accumulation of the biosynthetic intermediate protoporphyrin can lead to extensive tissue damage upon exposure to light since protoporpyhyrin is a potent photosensitizing agent, giving rise to membrane-destroying oxygen radicals or singlet oxygen. For instance, in the human porphyria disease porphyria variegata, a genetic deficiency in a heme biosynthetic enzyme, protoporphyrinogen oxidase, leads to protoporphyrin accumulation and lightdependent skin photosensitivity. Horseradish peroxidase (HRP) in the presence of glutathione (GSH) could oxidize the non-natural porphyrin deuteroporphyrin IX, which is closely related to protoporphyrin IX. The product is a unique green chlorin. One of the pyrrole rings had been modified by addition of an hydroxy and an oxo group, thus giving the characteristic reduced pyrrole ring of the chlorine. Of most importance for human medicine, peroxidative enzymes present in mammalian cells can also carry out these GSH-dependent oxidative conversions of protoporphyrin and deuteroporphyrin. (PMID: 10334939).
3,5-Diiodothyronine, also known as 3,5-T2, belongs to the class of organic compounds known as phenylalanines and derivatives. Phenylalanine and derivatives are compounds containing phenylalanine or a derivative thereof resulting from reaction of phenylalanine at the amino group or the carboxy group, or from the replacement of any hydrogen of glycine by a heteroatom. It is also a member of the class of compounds known as iodothyronines. Iodothyronines are phenolic amino acids with iodine substituents. 3,5-Diiodothyronine is a metabolite of the two main thyroid hormones T3 and T4 (thyroxine and triiodo-L-thyronine). It is a biologically active iodothyronine with mitochondria and bioenergetic mechanisms being the major targets of 3,5-T2. Nanomolar concentrations of 3,5-T2 significantly increases cytochrome oxidase (COX) activity (PMID: 30090086). It increases COX activity by preventing the interaction of adenosine triphosphate (ATP) as an allosteric inhibitor. At 1 pM concentration, 3,5-T2 stimulates oxygen consumption more rapidly than thyroxine (T3). A case report involving two human participants revealed that administration of 3,5-T2 to humans (1‚Äì5 ug/kg BW) rapidly (after 4‚Äì6 h) increased resting metabolic rate. Chronic 3,5-T2 administration (28 days, approximately 5 ug/kg BW) increased resting metabolic rate by approximately 15% and decreased body weight by approximately 4 kg in both participants (PMID: 22217997). 3,5-T2 stimulates the thyroid receptor (TR)-beta receptor for thyroid hormones and thus increases energy expenditure. It has agonistic (thyromimetic) effects on myocardial tissue and on the pituitary, which results in 3,5-T2 suppressing thyroid stimulating hormone release.
Docosanamide is a primary fatty acid amide. Primary fatty acid amides (R-CO-NH2) is a class of compounds that have only recently been isolated and characterized from biological sources. Key questions remain regarding how these lipid amides are produced and degraded in biological systems. (PMID 15282088).
Glucosylgalactosyl hydroxylysine is a Glycoside of hydroxylysine. Hydroxylation of lysine is an important post-translational modification of collagen, (PMID 10928217) a reaction catalyzed by the enzyme Lysyl hydroxylase (EC 1.14.11.4) forming hydroxylysine in collagens and other proteins with collagen-like amino acid sequences, by the hydroxylation of lysine residues in X-lys-gly sequences. The hydroxylysine residues formed in the lysyl hydroxylase reaction have 2 important functions: first, their hydroxy groups serve as sites of attachment for carbohydrate units, either the monosaccharide galactose or the disaccharide glucosylgalactose; and second, they are essential for the stability of the intermolecular collagen crosslinks. (OMIM 153454). Hydroxylysine-deficient skin collagen is manifested in Ehlers-Danlos syndrome, type VIA, A heritable disorder of connective tissue (PMID 5016372).
Sodium ions are necessary for regulation of blood and body fluids, transmission of nerve impulses, heart activity, and certain metabolic functions. Physiologically, it exists as an ion in the body. Sodium is needed by animals, which maintain high concentrations in their blood and extracellular fluids, but the ion is not needed by plants. The human requirement for sodium in the diet is less than 500 mg per day, which is typically less than a tenth as much as many diets "seasoned to taste." Most people consume far more sodium than is physiologically needed. For certain people with salt-sensitive blood pressure, this extra intake may cause a negative effect on health.
Glutarylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction:. acyl-CoA + glycine < -- > CoA + N-acylglycine. Glutarylglycine is involved in lysine metabolism. An elevated level of glutarylglycine occurs in patients with glutaric acidemia type II, which is an autosomal recessive inborn error of metabolism due to a mitochondrial respiratory electron chain transport defect. (http://www.pediatricneuro.com/alfonso/pg75.htm).
Glucosamine 6-sulfate is a naturally occurring compound present in many of the body's tissues, and belongs to a class of compounds known as glycosaminoglycans (GAGs). Glucosamine 6-sulfate is being used in the treatment of arthritis. Glucosamine for arthritis products is usually formulated as the hydrochloride salt or glucosamine sulfate and often combined with chondroitin sulphate. It is notable that while both the hydrochloride salt and glucosamine sulfate are used in pharmaceutical preparations, glucosamine sulfate is thought to have a higher biological activity due to the presence of the sulfate. It should also be noted that there is a large cost difference between the two salts, with the hydrochloride salt being significantly less expensive. (PMID: 15925239).
PC(18:1(9Z)/18:1(9Z)) is a phosphatidylcholine (PC or GPCho). It is a glycerophospholipid in which a phosphorylcholine moiety occupies a glycerol substitution site. As is the case with diacylglycerols, glycerophosphocholines can have many different combinations of fatty acids of varying lengths and saturation attached at the C-1 and C-2 positions. Fatty acids containing 16, 18 and 20 carbons are the most common. PC(18:1(9Z)/18:1(9Z)), in particular, consists of two chains of oleic acid at the C-1 and C-2 positions. The oleic acid moieties are derived from vegetable oils, especially olive and canola oil. Phospholipids, are ubiquitous in nature and are key components of the lipid bilayer of cells, as well as being involved in metabolism and signaling. Dioleoylphosphatidylcholine is found in human platelets and red blood cells, in mitochondria from skeletal muscle, lung, umbilical artery and vein endothelial cells (PMID: 15351277, 7138900, 2351875, 4046747, 2755318).While most phospholipids have a saturated fatty acid on C-1 and an unsaturated fatty acid on C-2 of the glycerol backbone, the fatty acid distribution at the C-1 and C-2 positions of glycerol within phospholipids is continually in flux, owing to phospholipid degradation and the continuous phospholipid remodeling that occurs while these molecules are in membranes. PCs can be synthesized via three different routes. In one route, choline is activated first by phosphorylation and then by coupling to CDP prior to attachment to phosphatidic acid. PCs can also synthesized by the addition of choline to CDP-activated 1,2-diacylglycerol. A third route to PC synthesis involves the conversion of either PS or PE to PC.
gamma-Glutamylphenylalanine is a dipeptide composed of gamma-glutamate and phenylalanine, and is a proteolytic breakdown product of larger proteins. It is probably formed by transpeptidation between glutathione and the corresponding amino acid, catalyzed by gamma-glutamyl transpeptidase (PMID: 237763). gamma-Glutamylphenylalanine belongs to the family of N-acyl-alpha amino acids and derivatives. These are compounds containing an alpha amino acid which bears an acyl group at its terminal nitrogen atom. gamma-Glutamylphenylalanine is an incomplete breakdown product of protein digestion or protein catabolism. Some dipeptides are known to have physiological or cell-signaling effects although most are simply short-lived intermediates on their way to specific amino acid degradation pathways following further proteolysis. It can be detected in the urine of patients with phenylketonuria, which is a human genetic disorder due to the lack of phenylalanine hydroxylase to metabolize phenylalanine to tyrosine (Wikipedia). gamma-Glutamylphenylalanine is found in adzuki bean, onion (Allium cepa), garlic (Allium sativum), and soybean.
Glucosylsphingosine is a cytotoxic compound. Accumulation of glucosylsphingosine in brain and other tisues occurs in patients with Gaucher disease, which is an inherited deficiency of lysosomal glucocerebrosidase. Glucocerebrosidase converts glucosylsphingosine to glucose and sphingosine.
Galactosylhydroxylysine is released during bone resorption and elevated in subjects with metabolic bone loss. Galactosylhydroxylysine is a sensitive and specific marker of bone resorption. (PMID 10222355).
Coprocholic acid, also called 3α,7α,12α-Trihydroxy-5β-cholestan-26-oic acid, is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine, and the portal vein to form an enterohepatic circuit. They exist as anions at physiological pH, and consequently require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
cis-4-Decenedioic acid is a member of the class of compounds known as medium-chain fatty acids. Medium-chain fatty acids are fatty acids with an aliphatic tail that contains between 4 and 12 carbon atoms. Thus, cis-4-decenedioic acid is considered to be a fatty acid lipid molecule. Cis-4-decenedioic acid is slightly soluble (in water) and a weakly acidic compound (based on its pKa). Cis-4-decenedioic acid can be found primarily in urine. Within the cell, cis-4-decenedioic acid is primarily located in the membrane. It can also be found in the extracellular space. Moreover, cis-4-decenedioic acid is an unsaturated dicarboxylic acid. Its level increases in patients with medium chain acyl-CoA dehydrogenase deficiency (MCADD), which is a genetic disorder of fatty acid oxidation.
Cyanocobalamin (commonly known as Vitamin B12) is the most chemically complex of all the vitamins. Cyanocobalamin's structure is based on a corrin ring, which, although similar to the porphyrin ring found in heme, chlorophyll, and cytochrome, has two of the pyrrole rings directly bonded. The central metal ion is Co (cobalt). Cyanocobalamin cannot be made by plants or by animals, as the only type of organisms that have the enzymes required for the synthesis of cyanocobalamin are bacteria and archaea. Higher plants do not concentrate cyanocobalamin from the soil and so are a poor source of the substance as compared with animal tissues. Cyanocobalamin is naturally found in foods including meat (especially liver and shellfish), eggs, and milk products.
DL-DOPA, also known as (+-)-DOPA or (R,S)-DOPA or DL-3,4-dihydroxyphenylalanine is an alpha amino acid. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). DL-DOPA also belongs to the class of organic compounds known as tyrosines and derivatives. Tyrosines and derivatives are compounds containing tyrosine or a derivative thereof resulting from reaction of tyrosine at the amino group or the carboxy group, or from the replacement of any hydrogen of glycine by a heteroatom. DL-DOPA is a racemic mixture of both D-DOPA and L-DOPA. D-DOPA is similar to L-DOPA (levodopa), but with opposite chirality. Levo- and dextro- rotation refer to a molecule's ability to rotate planes of polarized light in one or the other direction. Whereas L-DOPA is moderately effective in the treatment of Parkinson's disease (PD) by stimulating the production of dopamine in the brain, D-DOPA was at one time thought to be biologically inactive. However, it has recently been found that D-DOPA can be converted to L-DOPA and then to dopamine via the human enzyme known as D-amino acid oxidase and that racemic mixtures of DL-DOPA can be effective in treating Parkinsonism (PMID: 17924443; PMID: 3129126; PMID: 17042912).  The biological production or biosynthesis of D-DOPA is thought to occur through bacterial conversion of tyrosine.  L-DOPA is found naturally in both animals and plants. It is made via biosynthesis from the amino acid L-tyrosine by the enzyme tyrosine hydroxylase. L-DOPA is the precursor to the neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline), which are collectively known as catecholamines.
Cholesteryl linoleic acid is a cholesteryl ester. A cholesteryl ester is an ester of cholesterol. Fatty acid esters of cholesterol constitute about two-thirds of the cholesterol in the plasma. Cholesterol is a sterol (a combination steroid and alcohol) and a lipid found in the cell membranes of all body tissues, and transported in the blood plasma of all animals. The accumulation of cholesterol esters in the arterial intima (the innermost layer of an artery, in direct contact with the flowing blood) is a characteristic feature of atherosclerosis. Atherosclerosis is a disease affecting arterial blood vessels. It is a chronic inflammatory response in the walls of arteries, in large part to the deposition of lipoproteins (plasma proteins that carry cholesterol and triglycerides). Cholesteryl linoleate is contained in low density lipoprotein and atherosclerotic lesions. The oxidation products of cholesteryl linoleate may cause chronic inflammatory processes. (PMID 9684755, 11950694).
Erythronic acid is a sugar component of aqueous humour (eye). It may be derived from glycated proteins or from degradation of ascorbic acid. Erythronic acid is a normal organic acid present in a healthy adult and pediatric population. It has been found in urine, plasma, CSF, and synovial fluid (PMID: 14708889, 8087979, 8376520, 10420182). Erythronic acid is formed when N-acetyl-D-glucosamine (GlcNAc) is oxidized. GlcNAc is a constituent of hyaluronic acid (HA), a polysaccharide consisting of alternating units of glucuronic acid and GlcNAc, present as an aqueous solution in synovial fluid. In the synovial fluid of patients suffering from rheumatoid arthritis, HA is thought to be degraded either by radicals generated by Fenton chemistry (Fe2+/H2O2) or by NaOCl generated by myeloperoxidase (PMID: 10614067).
Furoic acid is a metabolite that appears in the urine of workers occupationally exposed to furfural and is a marker of exposure to this compound. Furfural is a heterocyclic aldehyde that is commonly used as a solvent in industry. It is readily absorbed into the body via the lungs and has significant skin absorption. Furfural is an irritant of the eyes, mucous membranes, and skin and is a central nervous system depressant. Furfural as a confirmed animal carcinogen with unknown relevance to humans (It has been suggested that is a substance that produces hepatic cirrhosis). Once in the body, furfural is metabolized rapidly via oxidation to the metabolite furoic acid, which is then conjugated with glycine and excreted in the urine in both free and conjugated forms. (PMID: 3751566, 4630229, 12587683). 2-Furoic acid is a biomarker for the consumption of beer
D-Ribulose 5-phosphate is a metabolite in the following pathways: pentose phosphate pathway, pentose and glucuronate interconversions, and riboflavin metabolism (KEGG).
D-Ribulose (CAS: 488-84-6) is a ketopentose - a monosaccharide containing five carbon atoms, including a ketone functional group. D-Ribulose is an intermediate in the fungal pathway for D-arabitol production. As the 1,5-bisphosphate, it combines with CO2 at the start of the photosynthetic process in green plants (carbon dioxide trap). D-Ribulose is the epimer of D-xylulose (Wikipedia). Ribulose is also a microbial metabolite found in Acetobacter and Gluconobacter (PMID: 16232643, 11272814).
Dodecanedioic acid is an aliphatic dicarboxylic acid containing 12 carbon atoms. More formally it is an alpha,omega-dicarboxylic acid with both the first and last carbons of the aliphatic chain having carboxylic acids. Dodecanedioic acid is water soluble. It can be produced in yeast and fungi through the oxidation of dodecane via fungal peroxygenases (PMID: 27573441). High levels of dodecanedioic acid is an indicator of hepatic carnitine palmitoyltransferase I (CPT IA) deficiency (PMID: 16146704). CPT IA deficiency is characterized by hypoketotic dicarboxylic aciduria with high urinary levels of dodecanedioic acid. It is thought that carnitine palmitoyltransferase I may play a role in the uptake of long-chain dicarboxylic acids by mitochondria after their initial shortening by beta-oxidation in peroxisomes (PMID: 16146704). CPT IA deficiency is characterized by acute encephalopathy with hypoglycemia and hepatomegaly.
D-Leucic acid is an alpha-hydroxycarboxylic acid present in patients affected with Short-bowel syndrome (an Inborn errors of metabolism, OMIM 175200) (PMID 9766851), and in Maple Syrup Urine Disease (MSUD, an autosomal recessive inherited metabolic disorder of branched-chain amino acid) (PMID 9766851).
Epitestosterone, or isotestosterone, also known as 17alpha-testosterone or as androst-4-en-17alpha-ol-3-one belongs to the class of organic compounds known as androgens and derivatives. These are 3-hydroxylated C19 steroid hormones. Epitestosterone is an endogenous steroid and a C-17 epimer of the androgen sex hormone testosterone. It is a weak competitive antagonist of the androgen receptor (AR) and a potent 5alpha-reductase inhibitor. Structurally, epitestosterone differs from testosterone only in the configuration at the hydroxy-bearing carbon, C17. Epitestosterone is believed to form in a similar way to testosterone with 50% of epitestosterone production in human males taking place in the testis. Epitestosterone levels are typically highest in young males; however, by adulthood, most healthy males exhibit a testosterone to epitestosterone ratio (T/E ratio) of about 1:1 (PMID: 11901061). A study of Australian athletes found that the mean T/E ratio in the study was 1.15:1. Another study found that the max T/E ratio for the 95th percentile of athletes was 3.71:1, and the max T/E ratio for the 99th percentile was 5.25:1. Epitestosterone has not been shown to enhance athletic performance, although administration of epistestosterone can be used to mask a high level of testosterone if the standard T/E ratio test is used. As such, epitestosterone is banned by many sporting authorities as a masking agent for testosterone. Interestingly, small amounts of ethanol can elevate T/E values, with women being more susceptible (PMID: 28671321).
Cytosine, also known as C, belongs to the class of organic compounds known as pyrimidones. Pyrimidones are compounds that contain a pyrimidine ring, which bears a ketone. Pyrimidine is a 6-membered ring consisting of four carbon atoms and two nitrogen centers at the 1- and 3- ring positions. Cytosine is also classified as a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at position 2). Cytosine is one of the four main bases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA). The nucleoside of cytosine is cytidine. In Watson-Crick base pairing, cytosine forms three hydrogen bonds with guanine. Cytosine was discovered and named by Albrecht Kossel and Albert Neumann in 1894 when it was hydrolyzed from calf thymus tissues. Cytosine exists in all living species, ranging from bacteria to plants to humans. Within cells, cytosine can undergo several enzymatic reactions. It can be methylated into 5-methylcytosine by an enzyme called DNA methyltransferase (DNMT) or be methylated and hydroxylated to make 5-hydroxymethylcytosine. The DNA methyltransferase (DNMT) family of enzymes transfer a methyl group from S-adenosyl-l-methionine (SAM) to the 5‚Äô carbon of cytosine in a molecule of DNA. High levels of cytosine can be found in the urine of individuals with severe combined immunodeficiency syndrome (SCID). Cytosine concentrations as high as (23-160 mmol/mol creatinine) were detected in SCID patients compared to normal levels of <2 mmol/mol creatinine (PMID: 262183).
D-Biopterin is a pterin which is a chemical compound composed of a pyrazine ring and a pyrimidine ring. The level of biopterin decreases in the urine of patients with guanosine triphosphate cyclohydrolase I. (PMID 10770663).
Citraconic acid, also known as 2-methylmaleate or methylmaleic acid, belongs to the class of organic compounds known as methyl-branched fatty acids. These are fatty acids with an acyl chain that has a methyl branch. Usually, they are saturated and contain only one or more methyl group. However, branches other than methyl may be present. Citraconic acid is a dicarboxylic acid consisting of maleic acid having a methyl substituent at the 2-position. Citraconic acid exists as a white solid. It is the cis-isomer of mesaconic acid and is one of the pyrocitric acids formed upon the heating of citric acid.  Citraconic acid has been detected in the urine of both normal and fasting individuals (PMID: 6778884). Citraconic acid is also elevated in the urine of individuals with methylmalonic acidaemia who have suffered ketotic attacks (PMID: 116077).  Altered serum levels of citraconic acid have been detected in patients with primary biliary cholangitis (PMID: 28400566).
Chenodeoxycholic acid glycine conjugate is an acyl glycine and a bile acid-glycine conugate. It is a secondary bile acid produced by the action of enzymes existing in the microbial flora of the colonic environment. In hepatocytes, both primary and secondary bile acids undergo amino acid conjugation at the C-24 carboxylic acid on the side chain, and almost all bile acids in the bile duct therefore exist in a glycine conjugated form (PMID: 16949895). This compound usually exists as the sodium salt and acts as a detergent to solubilize fats for absorption and is itself absorbed. It is a cholagogue and choleretic.
Dodecanoic acid, also known as dodecanoate or lauric acid, belongs to the class of organic compounds known as medium-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 4 and 12 carbon atoms. Dodecanoic acid is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Dodecanoic acid is the main fatty acid in coconut oil and in palm kernel oil, and is believed to have antimicrobial properties. It is a white, powdery solid with a faint odour of bay oil. Dodecanoic acid, although slightly irritating to mucous membranes, has a very low toxicity and so is used in many soaps and shampoos.
Galactaric acid, also known as mucic acid or galactarate, belongs to the class of organic compounds known as glucuronic acid derivatives. Glucuronic acid derivatives are compounds containing a glucuronic acid moiety (or a derivative), which consists of a glucose moiety with the C6 carbon oxidized to a carboxylic acid. Technically, galactaric acid is an aldaric acid obtained by oxidation of galactose. Galactaric acid exists as a white crystalline powder, which melts at 210 - 230 oC. It is insoluble in alcohol, and nearly insoluble in cold water (1 g/300 mL) but more soluble in hot water (1 g/60 mL).. Galactaric acid exists in all living organisms, ranging from bacteria to plants to humans. In plants, galactaric acid is commonly produced or utilized as an osmorgulator (PMID: 31505987). Galactaric acid has been detected, but not quantified in, several different foods, such as fruits, vegetables and bovine milk. A recent large-scale dietary study found that galactaric acid can serve as a biomarker for long-term dairy intake and for the consumption of carotenoid-rich vegetables (PMID: 33566801). In food production, galactaric acid can be used to replace tartaric acid in self-rising flour or fizzies.
Levoglucosan is an anhydrohexose that is the 1,6-anhydro-derivative of beta-D-glucopyranose. It is formed from the pyrolysis of carbohydrates, such as starch and cellulose. As a result, levoglucosan is often used as a chemical tracer for biomass burning in atmospheric chemistry studies, particularly with respect to airborne particulate matter. Levoglucosan in urine has been shown to be highly correlated with regional fires and as a biomarker for wood smoke exposure (PMID: 19165390). This is because the gas emitted by the pyrolysis of wood (biomass) contains significant amounts of levoglucosan. The hydrolysis of levoglucosan generates the fermentable sugar glucose, and therefore lignocellulosic material exhibits great potential as a renewable feedstock for the production of bioethanol. Levoglucosan can also be utilized in the synthesis of chiral polymers such as unhydrolysable glucose polymers. Levoglucosan is also produced via caramelization of sugar. Consumption of caramel or caramel-containing sweets can lead to a short-term 5X increase in urinary levels of levoglucosan (from 20 uM/mM creatinine to 100 uM/mM creatinine) (PMID: 19707249). Urinary levoglucosan levels increase within 2 h of caramel consumption and return to pre-exposure levels within 24 h. These data suggest that diet is a major factor in determining urinary levoglucosan levels and that recent dietary history needs to be taken into account to use levoglucosan as a marker for wood smoke exposure. Excretory levels of levoglucosan vary widely from zero up to 5.3 mmol/L (PMID: 3757263, 16448658, 16317539).
Erythronilic acid, also known as (2R,3S)-3-hydroxy-2-methylbutanoic acid (HMBA), is a normal urinary metabolite involved in isoleucine catabolism, beta-oxidation of fatty acids, and ketogenesis. HMDB is excreted in abnormally high amounts in beta-ketothiolase deficiency. Differences in the enantiomeric ratio of HMBA may originate from the enantioselectivity of different enzyme systems (PMID: 10755375).
Coproporphyrin I is a porphyrin metabolite arising from heme synthesis. Porphyrins are pigments found in both animal and plant life. Coproporphyrin I is a tetrapyrrole dead-end product from the spontaneous oxidation of the methylene bridges of coproporphynogen, arising from heme synthesis and secreted in feces and urine. Increased levels of coproporphyrins can indicate congenital erythropoietic porphyria or sideroblastic anaemia. Porphyria is a pathological state characterised by abnormalities of porphyrin metabolism and results in the excretion of large quantities of porphyrins in the urine and in extreme sensitivity to light. A large number of factors are capable of increasing porphyrin excretion, owing to different and multiple causes and etiologies: 1) the main site of the chronic hepatic porphyria disease process concentrates on the liver, 2) a functional and morphologic liver injury is almost regularly associated with this chronic porphyria, 3) the toxic form due to occupational and environmental exposure takes mainly a subclinical course. Hepatic factors includes disturbance in coproporphyrinogen metabolism, which results from inhibition of coproporphyrinogen oxidase as well as from the rapid loss from, and diminished utilization of coproporphyrinogen in the hepatocytes, which may also explain why coproporphyrin, its autoxidation product, predominates physiologically in the urine; decreased biliary excretion of coproporphyrin leading to a compensatory urinary excretion, so that the coproporphyrin ring isomer ratio (1:III) becomes a sensitive index for impaired liver function and intrahepatic cholestasis; and disturbed activity of hepatic uroporphyrinogen decarboxylase. In itself, secondary coproporphyrinuria is not associated with porphyria symptoms of a hepatologic-gastroenterologic, neurologic, or dermatologic order, even though coproporphyrinuria can occur with such symptoms. (PMID: 3327428).
Galactose 1-phosphate, also known as D-Galactose-1-phosphate or alpha-D-gal-1-P, belongs to the class of organic compounds known as monosaccharide phosphates. These are monosaccharides comprising a phosphate group linked to the carbohydrate unit. Galactose-1-phosphate is an intermediate in the interconversion of glucose and uridine diphosphate galactose. Galactose 1-phosphate exists in all living species, ranging from bacteria to plants to humans. Within humans, galactose 1-phosphate participates in a number of enzymatic reactions. In particular, uridine diphosphate glucose and galactose 1-phosphate can be biosynthesized from uridine diphosphategalactose and glucose 1-phosphate; which is mediated by the enzyme galactose-1-phosphate uridylyltransferase (GALT). In addition, galactose 1-phosphate can be biosynthesized from D-galactose through the action of the enzyme galactokinase. The improper metabolism of galactose-1-phosphate is a characteristic of a condition known as galactosemia (PMID: 7671964). Type I galactosemia is a genetic disorder that is caused by the impairment of galactose-1-phosphate uridylyltransferase (EC 2.7.7.12). Evidence suggests that misfolding of the galactose 1-phosphate uridylyltransferase enzyme is the underlying cause of type I galactosemia (PMID: 23583749). Outside of the human body, galactose 1-phosphate has been detected, but not quantified in, several different foods, such as gooseberries, anises, turmerics, caraway, and cumins.
Galactosylsphingosine (also known as psychosine), is an intermediate in the biosynthesis of cerebrosides. It is formed from the reaction of sphingosine with UDP-galactose and then reacts with fatty acid-coenzyme A to form the cerebroside. It is a galactoside metabolite of sphingosine and can function as a neurotoxin and a metabotoxin. A neurotoxin is a compound that disrupts or attacks neural cells and neural tissue. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of galactosylsphingosine are associated with globoid cell leukodystrophy (Krabbe disease), which is characterized by the dysfunction of galactosylceramidase. Galactosylsphingosine is a highly cytotoxic lipid capable of inducing cell death in a wide variety of cell types including oligodendrocytes. It is known to accumulate in the nervous system in the absence of galactosylceramidase. Galactosylsphingosine localizes to lipid rafts and perturbs membrane integrity. It also inhibits protein kinase C translocation to the plasma membrane (PMID: 24006512). Symptoms of Krabbe disease begin between the ages of 3 and 6 months with irritability, fevers, limb stiffness, seizures, feeding difficulties, vomiting, and slowing of mental and motor development. In the first stages of the disease, the symptoms are often mistaken with those of cerebral palsy. Other symptoms include muscle weakness, spasticity, deafness, optic atrophy, optic nerve enlargement, blindness, paralysis, and difficulty when swallowing.
Clionasterol is a triterpenoid isolated from the Indian marine red alga Gracilaria edulis, the sponge Veronica aerophoba and the Kenyan Marine Green. Macroalga Halimeda macroloba. It is a potent inhibitor of complement component C1. (PMID 12624828).
D-alpha-Aminobutyric acid (AABA), also known as alpha-aminobutyrate, (R)-2-aminobutanoic acid or D-homoalanine, belongs to the class of organic compounds known as D-alpha-amino acids. These are alpha amino acids which have the D-configuration of the alpha-carbon atom. D-alpha-aminobutyric acid is an optically active form of alpha-aminobutyric acid having D-configuration. It is an enantiomer of a L-alpha-aminobutyric acid and a non-proteinogenic amino acid. Alpha-aminobutyric acid is one of the three isomers of aminobutyric acid. The two others are the neurotransmitter Gamma-Aminobutyric acid (GABA) and Beta-Aminobutyric acid (BABA) which is known for inducing plant disease resistance. Optically active organic compounds found in meteorites typically exist in racemic form, yet life on Earth has almost exclusively selected for L- over D-enantiomers of amino acids. D-enantiomers of non-proteinogenic amino acids are known to inhibit aerobic microorganisms. D-alpha-aminobutyric acid has been shown to inhibit microbial iron reduction by a number of Geobacter strains including Geobacter bemidjiensis, Geobacter metallireducens and Geopsychrobacter electrodiphilus (PMID: 25695622). D-alpha-Aminobutyric acid is a known substrate of D-amino acid oxidase (PMID: 6127341).
Cholesterol sulfate, or cholest-5-en-3beta-ol sulfate, is an endogenous steroid and the C3beta sulfate ester of cholesterol. It is formed from cholesterol by steroid sulfotransferases (SSTs) such as SULT2B1b (also known as cholesterol sulfotransferase) and is converted back into cholesterol by steroid sulfatase (STS). Accumulation of cholesterol sulfate in the skin is implicated in the pathophysiology of X-linked ichthyosis, a congenital disorder in which STS is non-functional and the body cannot convert cholesterol sulfate back into cholesterol. Cholesterol sulfate is quantitatively the most important known sterol sulfate in human plasma, where it is present in a concentration that overlaps that of the other abundant circulating steroid sulfate, dehydroepiandrosterone (DHEA) sulfate (PMID 12730293). Cholesterol sulfate has a stabilizing function on the membrane, supports platelet adhesion and is involved in signal transduction (PMID 12730293). It plays a role in protecting erythrocytes from osmotic lysis and regulating sperm capacitation. Cholesterol sulfate can regulate the activity of serine proteases, e.g., those involved in blood clotting, fibrinolysis, and epidermal cell adhesion (PMID 12730293). As a result of its ability to regulate the activity of selective protein kinase C isoforms and modulate the specificity of phosphatidylinositol 3-kinase, cholesterol sulfate is involved in signal transduction (PMID 12730293). Cholesterol sulfate functions in keratinocyte differentiation, inducing genes that encode for key components involved in development of the barrier (PMID 12730293).
Cysteineglutathione disulfide is a molecule that is formed upon oxidative stress of glutathione, that will form mixed disulfides with protein thiol groups, causing reversible S-glutathionylation. S-glutathionylation is an important post-translational modification responsible for transducing oxidant signals. S-glutathionylation of thiols confers protection against their irreversible oxidation, like for instance the formation of sulphonic acid moieties. If the targeted cysteine is a functionally critical amino acid, S-glutathionylation will however also modify protein function. (PMID 16515838). S-sulfonation and S-thiolation of transthyretin Phe33Cys has been detected in a patient with familial transthyretin amyloidosis. (PMID 12876326). In Cystinotic human skin fibroblasts in tissue culture there is an accumulation of cystine. Stored cystine in cystinotic tissues may derive in part from glutathione-cysteine mixed disulfide via transpeptidation. (PMID 6130452). Cystinosis is an autosomal recessive disorder caused by an impaired transport of cystine out of lysosomes. (PMID 15042893).
CE(16:1(9Z)), also known as (Z)-cholesterol 9-hexadecenoate or 1-palmitoleoyl-cholesterol, is an important plasma cholesteryl ester. A cholesteryl ester is an ester of cholesterol. Fatty acid esters of cholesterol constitute about two-thirds of the cholesterol in the plasma. Cholesterol is a sterol (a combination steroid and alcohol) and a lipid found in the cell membranes of all body tissues and transported in the blood plasma of all animals. The accumulation of cholesterol esters in the arterial intima (the innermost layer of an artery, in direct contact with the flowing blood) is a characteristic feature of atherosclerosis. Atherosclerosis is a disease affecting arterial blood vessels. It is a chronic inflammatory response in the walls of arteries, in large part to the deposition of lipoproteins (plasma proteins that carry cholesterol and triglycerides). Cholesteryl palmitoleate is one of the two more prevalent esters that are a component of dehydroepiandrosterone fatty acid esters (DHEA-FA). DHEA-FA is formed from DHEA by lecithin-cholesterol acyltransferase, localized on high-density lipoprotein (HDL). Once DHEA-FA is formed, it is subsequently transferred to very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL), like cholesteryl esters. Cholesteryl palmitoleate constitutes 20% of the total lipoidal pregnenolone (an important precursor steroid) in follicular fluid. The fatty acid components of the resulting lipoidal pregnenolone derivatives resemble those of cholesteryl esters formed in plasma by the enzymatic activity of lecithin–cholesterol acyltransferase (LCAT) (PMID: 2770299, 8943795). CE(16:1(9Z)) is considered to be practically insoluble (in water) and basic.
Deoxycholic acid disulfate is a substrate for Proteinase activated receptor 2, Heterogeneous nuclear ribonucleoprotein H, Small inducible cytokine A24 and Hemoglobin alpha chain.
Glucaric acid, also known as glucarate or D-saccharic acid, belongs to the class of organic compounds known as glucuronic acid derivatives. Glucuronic acid derivatives are compounds containing a glucuronic acid moiety (or a derivative), which consists of a glucose moiety with the C6 carbon oxidized to a carboxylic acid. Glucaric acid is a sugar acid derived from D-glucose in which both the aldehydic carbon atom and the carbon atom bearing the primary hydroxyl group are oxidized to carboxylic acid groups. D-glucaric acid is found in fruits, vegetables, and mammals. The highest concentrations of glucaric acid are found in grapefruits, apples, oranges, and cruciferous vegetables (PMID: 18772850). Glucaric acid is produced through the oxidation of glucose. Cytochrome P450 is thought to be responsible for the production of D-glucaric acid in vivo (PMID: 3779687). In mammals, D-glucaric acid and D-glucaro-l,4-lactone are also known end-products of the D-glucuronic acid pathway (PMID: 18772850). Glucaric is available as a dietary supplement in the form of calcium D-glucarate and has been studied for therapeutic purposes including cholesterol reduction and cancer chemotherapy (PMID: 9101079). D-Glucaric acid has a potential use as a building block for a number of polymers, including new nylons and hyperbranched polyesters. D-glucaric acid produced from D-glucose has been successfully utilized to produce a hydroxylated nylon.
Isohyodeoxycholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Leucinic acid, also known as leucic acid, 2-hydroxyisocaproic acid or 2-hydroxy-4-methylvaleric acid, belongs to the class of organic compounds known as hydroxy fatty acids. These are fatty acids in which the chain bears a hydroxyl group. Leucinic acid is a valeric acid derivative having a hydroxy substituent at the 2-position and a methyl substituent at the 4-position. It is an alpha-hydroxy analogue of leucine and a metabolite of the branched-chain amino acid leucine. Leucinic acid is found in all organisms ranging from bacteria to plants to animals. Leucinic acid has been found in a patient with dihydrolipoyl dehydrogenase (DLD) deficiency (PMID: 6688766). DLD deficiency is caused by mutations in the DLD gene and is inherited in an autosomal recessive manner. A common feature of dihydrolipoamide dehydrogenase deficiency is a potentially life-threatening buildup of lactic acid in tissues (lactic acidosis), which can cause nausea, vomiting, severe breathing problems, and an abnormal heartbeat. Neurological problems are also common in this condition; the first symptoms in affected infants are often decreased muscle tone (hypotonia) and extreme tiredness (lethargy). As the problems worsen, affected infants can have difficulty feeding, decreased alertness, and seizures. Liver problems can also occur in dihydrolipoamide dehydrogenase deficiency, ranging from an enlarged liver (hepatomegaly) to life-threatening liver failure. In some affected people, liver disease, which can begin anytime from infancy to adulthood, is the primary symptom. Leucinic acid is also present in the urine of patients with short bowel syndrome (PMID: 4018104)
Heptanoic acid, or C7:0 also known as enanthic acid or heptylic acid, belongs to the class of organic compounds known as medium-chain fatty acids. Medium-chain fatty acids (MCFA) are fatty acids with aliphatic tails of 6 to 12 carbons, which can form medium-chain triglycerides Heptanoic acid is an oily liquid with an unpleasant, rancid odor. It contributes to the odor of some rancid oils. It is slightly soluble in water, but very soluble in ethanol and ether. Its name derives from the Latin oenanthe which is in turn derived from the Ancient Greek oinos "wine" and anthos "blossom." Heptanoic acid is used in the preparation of esters, such as ethyl enanthate, which are used in fragrances and as artificial flavors.  The triglyceride ester of heptanoic acid is the triheptanoin, which is used in certain medical conditions as a nutritional supplement.
Thyronine (T0) is a de-iodinated form of thyroxine. Thyronine are a group of metabolites derived from thyroxine and triiodothyronine via the peripheral enzymatic removal of iodines from the thyroxine nucleus. Thyronine is the thyroxine nucleus devoid of its four iodine atoms. Thyronine (T0) has been identified in human urine. In 22 normal individuals urinary thyronine concentrations were found to range between 8-25 nmol‚ÅÑ24h (PMID: 479355). Thyronine is thought to be a byproduct of thyroxine metabolism and arises through the action of thyroxine deiodinases.
Iron-free derivatives of heme with 4 methyl groups, 2 hydroxyethyl groups and 2 propionic acid groups attached to the pyrrole rings. Some of these phosphosensitizing agents are used in the phototherapy of malignant neoplasms. -- Pubchem.
ortho-Hydroxyphenylacetic acid, also known as (o-hydroxyphenyl)acetate or 2-hydroxybenzeneacetic acid, is a member of the class of compounds known as 2(hydroxyphenyl)acetic acids. 2(Hydroxyphenyl)acetic acids are phenylacetic acids that carry a hydroxyl group at the 2-position. ortho-Hydroxyphenylacetic acid is slightly soluble (in water) and a weakly acidic compound (based on its pKa). ortho-Hydroxyphenylacetic acid can be found in a number of food items such as natal plum, lemon verbena, half-highbush blueberry, and parsley, which makes ortho-hydroxyphenylacetic acid a potential biomarker for the consumption of these food products. ortho-Hydroxyphenylacetic acid can be found primarily in blood, feces, and urine. Moreover, ortho-hydroxyphenylacetic acid is found to be associated with phenylketonuria, which is an inborn error of metabolism. ortho-Hydroxyphenylacetic acid is a substrate of the enzyme oxidoreductases (EC 1.14.13.-) in the pathway styrene degradation (KEGG). ortho-Hydroxyphenylacetic acid is also a microbial metabolite.
L-homoarginine, also known as N6-(aminoiminomethyl)-L-lysine or N6-amidino-L-lysine, is a member of the class of compounds known as L-alpha-amino acids. L-alpha-amino acids are alpha amino acids which have the L-configuration of the alpha-carbon atom. More specifically, L-homoarginine is a naturally occurring, non-proteinogenic, cationic amino acid. It is formed in the liver in a reaction catalyzed by L-arginine:glycine amidinotransferase (AGAT) when transferring the amidino group from arginine to lysine. It is an alternative substrate for nitric oxide (NO) synthase. L-homoarginine increases the availability of NO and thereby affects endothelial function. High homoarginine levels may exert positive actions that are relevant to cardiovascular health, including enhanced endothelial function, inhibition of platelet aggregation and stimulation of insulin secretion (PMID: 30866658). Recent studies have demonstrated that low serum homoarginine levels are a strong predictor of cardiovascular mortality (PMID: 24583919). L-homoarginine is a substrate of the human cationic amino acid CAT1 [solute carrier family 7 (SLC7A1)], CAT2A (SLC7A2A) or CAT2B (SLC7A2B) (PMID: 28684763). According to published human metabolomic data, L-homoarginine can be found primarily in blood, cerebrospinal fluid (CSF), and urine, as well as in human intestinal and testes tissues. Moreover, L-homoarginine has been found to be associated with liver cirrhosis and the genetic disorder, hyperargininemia. Homoarginine is an organ-specific uncompetitive inhibitor of human liver and bone alkaline phosphohydrolase (PMID: 5063678).
Indolelactic acid (CAS: 1821-52-9) is a tryptophan metabolite found in human plasma, serum, and urine. Tryptophan is metabolized by two major pathways in humans, either through kynurenine or via a series of indoles, and some of its metabolites are known to be biologically active. Indolelactic acid is present in various amounts, significantly higher in umbilical fetal plasma than in maternal plasma in the protein-bound form (PMID 2361979, 1400722, 3597614, 11060358, 1400722). Indolelactic acid is also a microbial metabolite; urinary indole-3-lactate is produced by Clostridium sporogenes (PMID: 29168502).
Hexadecanedioic acid, also known as thapsic acid, belongs to the class of organic compounds known as long-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 13 and 21 carbon atoms. Hexadecanedioic acid is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Hexadecanedioic acid is activated by mitochondrial and microsomal fractions in the liver (PMID: 4372285). It has antitumor activity (PMID: 14987827).
Linoleic acid is a doubly unsaturated fatty acid, also known as an omega-6 fatty acid, occurring widely in plant glycosides. In this particular polyunsaturated fatty acid (PUFA), the first double bond is located between the sixth and seventh carbon atom from the methyl end of the fatty acid (n-6). Linoleic acid is an essential fatty acid in human nutrition because it cannot be synthesized by humans. It is used in the biosynthesis of prostaglandins (via arachidonic acid) and cell membranes (From Stedman, 26th ed). Linoleic acid is found to be associated with isovaleric acidemia, which is an inborn error of metabolism.
Isovalerylglycine (IVG) is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction: acyl-CoA + glycine < -- > CoA + N-acylglycine. Isovalerylglycine is a byproduct of the catabolism of the aminoacid leucine. Accumulation of isovalerylglycine occurs in Isovaleric Acidemia (IVA). IVA (OMIM/ McKusick 243500) is an autosomal recessive disorder caused by mutations in the isovaleryl-CoA dehydrogenase (EC 1.3.99.10) gene. The deficiency of this enzyme in the metabolism of leucine leads to the accumulation of a series of isovaleryl-CoA metabolites, such as isovalerylglycine. It is very important to caution for false positive results when screening for isovaleric acidemia by tandem mass spectrometry based on dried blood-spot levels of C5-acylcarnitines, including isovalerylcarnitine and its isomer, pivaloylcarnitine; pivaloylcarnitine is derived from pivalate-generating antibiotics, and has caused many false-positive results (PMID: 17850781). Isovalerylglycine is a biomarker for the consumption of cheese.
Homocitrulline is a metabolite that can be detected in larger amounts in the urine of individuals with urea cycle disorders (OMIM 238970). The accumulation of carbamylphosphate due to depleted supply of ornithine for the urea cycle may be responsible for the enhanced synthesis of homocitrulline and homoarginine in some cases (PMID 2474087). Homocitrulline has been identified in the human placenta (PMID: 32033212).
Indoxyl sulfate is a dietary protein metabolite and also a metabolite of the common amino acid tryptophan. It has been identified as a uremic toxin according to the European Uremic Toxin Working Group (PMID: 22626821). It is a circulating uremic toxin stimulating glomerular sclerosis and interstitial fibrosis. Indoxyl sulfate is one of the well-known substances of a group of protein-bound uremic retention solutes. Indoxyl sulfate increases the rate of progression of renal failure. In plasma, indoxyl sulfate is a protein-bound uremic solute that induces endothelial dysfunction by inhibiting endothelial proliferation and migration in vitro. Some studies suggest that indoxyl sulfate is also involved in oxidative stress. In hemodialyzed patients, serum levels of indoxyl sulfate are associated with levels of pentosidine, a marker of carbonyl and oxidative stress. In vitro, indoxyl sulfate increases reactive oxygen species (ROS) production in tubular cells and increases NAD(P)H oxidase activity in endothelial cells. Indoxyl sulfate impairs osteoblast function and induces abnormalities of bone turnover. Indoxyl sulfate strongly decreases the levels of glutathione, one of the most active antioxidant systems of the cell (PMID: 10681668 , 14681860 , 17471003 , 17403109). Indoxyl sulfate is a microbial metabolite found in Escherichia (PMID: 19946322).
Harderoporphyrin is an intermediate in heme biosynthesis. It is formed in the conversion of coproporphyrinogen to protoporphyrinogen and excreted excessively in the feces in harderoporphyria.
Kynurenine is a metabolite of the amino acid tryptophan used in the production of niacin. L-Kynurenine is a central compound of the tryptophan metabolism pathway since it can change into the neuroprotective agent kynurenic acid or to the neurotoxic agent quinolinic acid. The break-up of these endogenous compounds' balance can be observable in many disorders such as stroke, epilepsy, multiple sclerosis, and amyotrophic lateral sclerosis. It can also occur in neurodegenerative disorders such as Parkinson's disease, Huntington's, and Alzheimer's disease; and in mental disorders such as schizophrenia and depression.
Isoursodeoxycholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Isovalerylcarnitine is the phenotypic abnormality in isovaleric acidemia (OMIM 243500) resulting from an accumulation of isovaleric acid, which is toxic to the central nervous system. Isovaleric acidemia is an autosomal recessive inborn error of leucine metabolism caused by a deficiency of the mitochondrial enzyme isovaleryl-CoA dehydrogenase (EC 1.3.99.10) resulting in the accumulation of derivatives of isovaleryl-CoA. It was the first organic acidemia recognized in humans and can cause significant morbidity and mortality. Early diagnosis and treatment with a protein restricted diet and supplementation with carnitine and glycine are effective in promoting normal development in severely affected individuals. An alternative pathway through glycine-N-acylase (EC 2.3.1.13) allows detoxification by producing isovalerylglycine, which is excreted. Thus, isovalerylcarnitine and isovalerylglycine are the hallmarks of this disorder in plasma and urine, respectively, and are elevated regardless of a patient's metabolic condition (PMID: 16602101). Moreover, isovalerylcarnitine is found to be associated with celiac disease and very long-chain acyl-CoA dehydrogenase deficiency (VLCAD), which are also inborn errors of metabolism.
Isocaproic acid, a metabolite of 20 alpha-hydroxycholesterol (PMID 14446007) and is an important metabolite in early placentas enabling the convertion from cholesterol to pregnenolone to Dehydroepiandrosterone (DHEA) (PMID 11972299).
Malonic acid (IUPAC systematic name: propanedioic acid) is a dicarboxylic acid with structure CH2(COOH)2. The ionised form of malonic acid, as well as its esters and salts, are known as malonates. For example, diethyl malonate is malonic acid's ethyl ester. The name originates from Latin malum, meaning apple. Malonic acid is the archetypal example of a competitive inhibitor: it acts against succinate dehydrogenase (complex II) in the respiratory electron transport chain. Malonic acid is found to be associated with malonyl-CoA decarboxylase deficiency, which is an inborn error of metabolism.
Heparan sulfate (HS) is a linear polysaccharide that belongs to the class of compounds known as glycosaminoglycans (PMID: 24146040). It is found in all animal tissues and consists of repeating subunits of N-acetylglucosamine and glucuronic acid, and closely related in structure to heparin. It occurs as a proteoglycan (HSPG) in which two or three HS chains are attached to either cell surface components or the extracellular matrix (ECM), where they serve to reinforce cell adhesion (PMID: 27241222). HS synthesis starts with the transfer of xylose from UDP-xylose by the enzyme known as xylosyltransferase (XT) to specific serine residues within the protein core. Attachment of two galactose (Gal) residues by galactosyltransferases I and II (GalTI and GalTII) and glucuronic acid (GlcA) by the enzyme glucuronosyltransferase I (GlcATI) completes the formation of a tetrasaccharide linker. After attachment of the first N-acetylglucosamine (GlcNAc) residue by the enzyme known as GalNAc Transferase I (GalNAcT-I), elongation of the tetrasaccharide linker is continued by the stepwise addition of GlcA and GlcNAc residues. These are transferred from their respective UDP-sugar nucleotides. HS functions through binding to a variety of protein ligands including interferon gamma, Wnt, antithrombin III, interleukin 8, fibroblast growth factor, endostatin and others. HS thereby regulates a wide range of developmental signaling pathways such as the Wnt, Hedgehog, transforming growth factor-β, and fibroblast growth factor pathways (PMID: 15563523). Heparan sulfate plays a role in a number of biological activities, including developmental processes, angiogenesis, blood coagulation, abolishing detachment activity by GrB (Granzyme B) and tumour metastasis.
Ketoleucine is an abnormal metabolite that arises from the incomplete breakdown of branched-chain amino acids. Ketoleucine is both a neurotoxin and a metabotoxin. A neurotoxin causes damage to nerve cells and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of ketoleucine are associated with maple syrup urine disease (MSUD). MSUD is a metabolic disorder caused by a deficiency of the branched-chain alpha-keto acid dehydrogenase complex (BCKDC), leading to a buildup of the branched-chain amino acids (leucine, isoleucine, and valine) and their toxic by-products (ketoacids) in the blood and urine. The symptoms of MSUD often show in infancy and lead to severe brain damage if untreated. MSUD may also present later depending on the severity of the disease. If left untreated in older individuals, during times of metabolic crisis, symptoms of the condition include uncharacteristically inappropriate, extreme, or erratic behaviour and moods, hallucinations, anorexia, weight loss, anemia, diarrhea, vomiting, dehydration, lethargy, oscillating hypertonia and hypotonia, ataxia, seizures, hypoglycemia, ketoacidosis, opisthotonus, pancreatitis, rapid neurological decline, and coma.  In maple syrup urine disease, the brain concentration of branched-chain ketoacids can increase 10- to 20-fold. This leads to a depletion of glutamate and a consequent reduction in the concentration of brain glutamine, aspartate, alanine, and other amino acids. The result is a compromise of energy metabolism because of a failure of the malate-aspartate shuttle and a diminished rate of protein synthesis (PMID: 15930465).
Isocoproporphyrin is a porphyrin derivative found in the feces and in urine for patients suffering from PCT (porphyria cutanea tarda). PCT is probably the most common of the porphyrias. It manifests as vesicle formation in sun-exposed areas, particularly the dorsum of the hands, A finding that is virtually diagnostic of PCT is the presence of isocoproporphyrin in stool.
Lithocholic acid glycine conjugate is an acyl glycine and a bile acid-glycine conjugate. is an acyl glycine and a bile acid-glycine conjugate. It is a secondary bile acid produced by the action of enzymes existing in the microbial flora of the colonic environment. In hepatocytes, both primary and secondary bile acids undergo amino acid conjugation at the C-24 carboxylic acid on the side chain, and almost all bile acids in the bile duct therefore exist in a glycine conjugated form (PMID: 16949895). Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
1-Methylnicotinamide is a metabolite of nicotinamide and is produced primarily in the liver. It has anti-inflammatory properties (PMID 16197374). It is a product of nicotinamide N-methyltransferase [EC 2.1.1.1] in the pathway of nicotinate and nicotinamide metabolism (KEGG). 1-Methylnicotinamide may be an endogenous activator of prostacyclin production and thus may regulate thrombotic as well as inflammatory processes in the cardiovascular system (PMID: 17641676).
Hexanoylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction: acyl-CoA + glycine < -- > CoA + N-acylglycineHexanoylglycine is a fatty acid metabolite, it appears in the urine of patients with hereditary medium-chain acyl-CoA dehydrogenase (MCAD) deficiency (PMID 2775902), which is a genetic disorder.
It is an isomer of cresotinic acid (2-hydroxy-3-methylbenzoic acid) and oxymethylbenzoic acid (2-methoxybenzoic acid). Derivatives of mandelic acid are formed as a result of metabolism of adrenaline and noradrenaline by monoamine oxidase and catechol-o-methyl transferase. It is also present in certain skin care products, is an intermediate molecule in the production of other biochemicals, may be used as an analytical reagent and is a precursor in the manufacture of dyes. Mandelic acid is an aromatic alpha hydroxy acid with the molecular formula C8H8O3. It is a white crystalline solid that is soluble in water and most common organic solvents. Mandelic acid is found to be associated with phenylketonuria, which is an inborn error of metabolism.
Isoxanthopterin is a pteridine normally present in plasma, urine, and other bodily fluids also vary from normal concentrations in some disease states and also have diagnostic value. Pteridines' urinary concentrations seem to vary independently from each other and from normal values to yield a pattern of excreted pteridines that is diagnostic for different species, tissues, and tumor types. Intravenous or intramuscular administration of isoxanthopterin inhibits the growth rates of animal tumor models. Pteridin derivatives are a family of organic compound with very similar chemical structures which play an important biochemistry role. Pteridines metabolism and its regulation in normal and pathological conditions have not been extensively investigated due to the difficulty of their quantification. A significant decrease of isoxanthopterin has been determined in cancer patients. (PMID 15837549, 9800651). Xanthine dehydrogenase (XDH) is the enzymes responsible for the conversion of xanthine to uric acid. It requires the presence of the molybdenum cofactor for its proper functioning. XDH is reported to have additional functions, i.e., the conversion of pterin to isoxanthopterin, one of the steps the degradation pathway of 5,6,7,8-tetrahydrobiopterin (BH4). Isoxanthopterin is very low in some cases of hereditary xanthinuria (OMIM 278300) and molybdenum cofactor deficiency (OMIM 252150). (PMID: 8812740).
Aspartylphenylalanine is a dipeptide composed of aspartate and phenylalanine, and is a metabolic byproduct of its methyl ester, aspartame (Nutrasweet). After hydrolysis of the ester bond in the intestinal lumen, the dipeptide is apparently absorbed and digested in the same manner as dipeptides derived from protein digestion. There are several Asp-Phe dipeptidases that degrade this peptide. It has been suggested that individuals with aspartame allergies may be deficient in this peptidase (PMID: 3743970). It has been observed that N-beta-aspartylphenylalanine (a breakdown product of Asp-Phe) is a naturally occurring peptide found in both blood and urine (PMID: 2723819).
4-Hydroxyphenylpyruvic acid (4-HPPA) is a keto acid that is involved in the tyrosine catabolism pathway. It is a product of the enzyme (R)-4-hydroxyphenyllactate dehydrogenase (EC 1.1.1.222) and is formed during tyrosine metabolism. The conversion from tyrosine to 4-HPPA is catalyzed by tyrosine aminotransferase. Additionally, 4-HPPA can be converted to homogentisic acid which is one of the precursors to ochronotic pigment. The enzyme 4-hydroxyphenylpyruvic acid dioxygenase (HPD) catalyzes the reaction that converts 4-hydroxyphenylpyruvic acid to homogentisic acid. A deficiency in the catalytic activity of HPD is known to lead to tyrosinemia type III, an autosomal recessive disorder characterized by elevated levels of blood tyrosine and massive excretion of tyrosine derivatives into urine. It has been shown that hawkinsinuria, an autosomal dominant disorder characterized by the excretion of 'hawkinsin,' may also be a result of HPD deficiency (PMID: 11073718). Moreover, 4-hydroxyphenylpyruvic acid is also found to be associated in phenylketonuria, which is also an inborn error of metabolism. There are two isomers of HPPA, specifically 4HPPA and 3HPPA, of which 4HPPA is the most common. 4-HPPA has been found to be a microbial metabolite in Escherichia (ECMDB).
Glycoursodeoxycholic acid is an acyl glycine and a bile acid-glycine conjugate. It is a secondary bile acid produced by the action of enzymes existing in the microbial flora of the colonic environment. In hepatocytes, both primary and secondary bile acids undergo amino acid conjugation at the C-24 carboxylic acid on the side chain, and almost all bile acids in the bile duct therefore exist in a glycine conjugated form (PMID: 16949895). Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
L-Cysteinylglycine disulfide is one of the hydrolysis products of glutathione. Cystinylglycine disulfide is a small peptide replaced cystinylglycine in plasma from patients with homosyctinuria. (PMID: 7333014).
Hydroxyoctanoic acid medium chain substrate of the 2-hydroxy acid oxidases associated with the 3 distinct human 2-hydroxy acid oxidase genes, HAOX1, HAOX2, and HAOX3. (PMID: 10777549).
Hexadecanedioic acid mono-L-carnitine ester is an intermediate in the formation of hexadecanedioylcarnitine. Hexadecanedioic acid has been shown to be activated by ATP-Mg2+ and CoA and transported into the inner mitochondrial compartment as the mono-L-carnitine ester. (PMID: 4703570).
Isoallolithocholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Hippuric acid is an acyl glycine formed from the conjugation of benzoic acid with glycine. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction: acyl-CoA + glycine < -- > CoA + N-acylglycine. Hippuric acid is a normal component of urine and is typically increased with increased consumption of phenolic compounds (tea, wine, fruit juices). These phenols are converted into benzoic acid which is then converted into hippuric acid and excreted in the urine. Hippuric acid is the most frequently used biomarker in the biological monitoring of occupational exposure to toluene. This product of solvent biotransformation may be also found in the urine of individuals who have not been exposed to the solvent. A smaller fraction of the absorbed toluene is oxidized into aromatic compounds including ortho-cresol, which is not found in the urine of nonexposed individuals in a significant amount. The concentration of hippuric acid in the urine of individuals exposed to a low toluene concentration does not differ from that of individuals not exposed to the solvent. This has led to the conclusion that hippuric acid should not be utilized in the biological monitoring of occupational exposure to low levels of toluene in the air. Protein-bound organic acids such as hippuric acid are markedly accumulated in uremic plasma and produce defective protein binding of drugs (PMID: 9120876 , 8734460). Hippuric acid has been identified as a uremic toxin according to the European Uremic Toxin Working Group (PMID: 22626821). Hippuric acid is also found to be associated with phenylketonuria, propionic acidemia, and tyrosinemia I, which are inborn errors of metabolism. Hippuric acid is an endogenous phenolic acid metabolite detected after the consumption of whole grain.
L-pipecolic acid is a normal human metabolite present in human blood, where is present as the primary enantiomer of pipecolic acid. L-pipecolic acid is a cyclic imino acid (contains both imino (>C=NH) and carboxyl (-C(=O)-OH) functional groups) produced during the degradation of lysine, accumulates in body fluids of infants with generalized genetic peroxisomal disorders, including Zellweger syndrome (OMIM 214100), neonatal adrenoleukodystrophy (OMIM 202370), and infantile Refsum disease (OMIM 266510). L-pipecolic acid levels are also elevated in patients with chronic liver diseases. L-pipecolic acid is the substrate of delta1-piperideine-2-carboxylate reductase (EC 1.5.1.21) in the pathway of lysine degradation (PMID: 2717271, 8305590, 1050990).
Isolithocholic acid is a bile acid formed from chenodeoxycholate by bacterial action, usually conjugated with glycine or taurine. It acts as a detergent to solubilize fats for absorption and is itself absorbed. It is used as cholagogue and choleretic. A bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Isovaleric acid, is a natural fatty acid found in a wide variety of plants and essential oils. Isovaleric acid is clear colorless liquid that is sparingly soluble in water, but well soluble in most common organic solvents. It has been suggested that isovaleric acid from pilot whales, a species frequently consumed in the Faroe Islands, may be the unusual dietary factor in prolonged gestation in the population of the Faroe Islands. Previous studies suggested that was due to the high intake of n-3 polyunsaturated fatty acids has been, but fatty acid data for eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) in blood lipids of Faroese and Norwegians was reviewed in terms of the type of fish eaten (mostly lean white fish with DHA much greater than EPA); the popular lean fish, thus, probably provides too little EPA to produce a marked effect on human biochemistry (PMID 2646392). Isovaleric acid is found to be associated with isovaleric acidemia, which is an inborn error of metabolism.
Homoserine is a more reactive variant of the amino acid serine. In this variant, the hydroxyl side chain contains an additional CH2 group which brings the hydroxyl group closer to its own carboxyl group, allowing it to chemically react to form a five-membered ring. This occurs at the point that amino acids normally join to their neighbours in a peptide bond. Homoserine is therefore unsuitable for forming proteins and has been eliminated from the repertoire of amino acids used by living things. Homoserine is the final product on the C-terminal end of the N-terminal fragment following a cyanogen bromide cleavage. (wikipedia). Homoserine is also a microbial metabolite.
Levulinic acid is a crystalline keto acid prepared from levulose, inulin, starch, etc., by boiling them with dilute hydrochloric or sulfuric acids.
Glycylproline is a dipeptide composed of glycine and proline, and is an end product of collagen metabolism that is further cleaved by prolidase (EC 3.4.13.9). The resulting proline molecules are recycled into collagen or other proteins. Prolidase deficiency is a rare autosomal recessive disease characterized by chronic ulcerative dermatitis, mental retardation, frequent infections, and massive urinary excretion of iminodipeptides. Patients with this disease have reportedly decreased prolidase enzyme activity against glycylproline (Gly-Pro). The enzyme's activity against other substrates is not as affected. Some patients with prolidase deficiency have a marked urinary excretion of glycylproline. Patients with pressure sores contain significantly more urinary glycylproline than the control (PMID: 16009141, 7629169, 1536787, 10582130).
Lithocholyltaurine is a bile salt formed in the liver from lithocholic acid conjugation with taurine, usually as the sodium salt. It solubilizes fats for absorption and is itself absorbed. Lithocholic acid, a hydrophobic secondary bile acid, is well known to cause intrahepatic cholestasis. There have been extensive studies on the mechanisms of lithocholate-induced cholestasis in animals. Lithocholate diminishes both the bile acid-dependent and independent bile flow. In humans, elevated levels of lithocholic acid are found in patients with chronic cholestatic liver disease. Lithocholyltaurine impairs both the bile canalicular contractions and the canalicular bile secretion, possibly by acting directly on the canalicular membranes in lithocholyltaurine-induced cholestasis. Lithocholyltaurine induce acute cholestasis-associated with retrieval of the bile salt export pump. The bile salt export pump (BSEP) of hepatocyte secretes conjugated bile salts across the canalicular membrane in an ATP-dependent manner. Hepatic retention of bile acids may lead to liver injury by hepatocyte apoptosis and eventually deterioration of cholestatic liver diseases. One mechanism of induced apoptosis by lithocholyltaurine is the induction of transcriptional activity of AP-1 (activation protein-1). (PMID: 16981261, 15763547, 16332456, 18164257).
4-Hydroxyproline (hydroxyproline or Hyp) is a major component of the protein collagen. Hydroxyproline is produced by hydroxylation of the amino acid proline and is, therefore, a post-translationally modified, non-essential amino acid. Hydroxyproline and proline play key roles in collagen stability. In particular, they permit the sharp twisting of the collagen helix. Hydroxyproline is found in few proteins other than collagen. The only other mammalian protein which includes hydroxyproline is elastin. For this reason, hydroxyproline content has been used as an indicator to determine collagen and/or gelatin amount in tissue or biological samples. Increased serum and urine levels of hydroxyproline have been found in Paget's disease (PMID: 436278). Hydroxyproline (Hyp) content in biological fluids is used as a parameter of collagen catabolism, especially bone resorption or tissue degradation. Bedridden and elderly individuals show significantly elevated serum levels of hydroxyproline in comparison to normal, active individuals (PMID: 10706420). Elevated levels of urinary hydroxyproline are also indicative of muscle damage (PMID: 21988268). Increased reactive oxygen species (ROS) are also known to accelerate collagen degradation. Hydroxyproline levels increase in cases of depression and stress (PMID: 21483218). 4-Hydroxyproline is found to be associated with Alzheimer's disease, and also hydroxyprolinemia and iminoglycinuria which are both inborn errors of metabolism. 4-Hydroxyproline is also involved in metabolic disorders such as hyperprolinemia type I, hyperornithinemia with gyrate atrophy (HOGA), L-arginine:glycine amidinotransferase deficiency, creatine deficiency, and guanidinoacetate methyltransferase deficiency. A deficiency in ascorbic acid can result in impaired hydroxyproline formation (PubChem). trans-4-Hydroxy-L-proline is a biomarker for the consumption of processed meat.
Isovalerylglutamic acid is an unusual mtabolite that has been found in the urine of patients with Isovaleric Acidemia due to Isovaleryl-CoA Dehydrogenase Deficiency (OMMBID: The Metabolic and Molecular Bases of Inherited Disease, Ch.93: Branched Chain Organic Acidurias). and in Multiple acyl-Co A dehydrogenation deficiency (MADD) (PMID 6862997). Isovalerylglutamate is a biomarker for the consumption of cheese.
L-Threoneopterin is a catabolic product of GTP. It is synthesized by macrophages upon stimulation by interferon-gamma. It is used as a marker of HIV infection. It belongs to the chemical group known as pterins. Neopterin is a pteridine derivative present in body fluids; elevated levels result from immune system activation, malignant disease, allograft rejection, and viral infections (From Stedman, 26th ed). Neopterin also serves as a precursor in the biosynthesis of biopterin.
Hydroxypropionic porphyrin III is a porphyrin isolated only in patients with porphyria cutanea tarda. Porphyria cutanea tarda (PCT) is a metabolic disorder of haeme biosynthesis caused by decreased activity of uroporphyrinogen decarboxylase. Porphyria cutanea tarda is manifest by fragility, erosions, bullae, milia and scars on sun-exposed skin. Excess porphyrins in the skin interact with light of approximately 400 nm-wavelength radiant energy, forming reactive oxygen species. Porphyria cutanea tarda is categorized as familial, acquired or toxic. Factors that may induce clinical expression of PCT in susceptible individuals include alcohol, oestrogen, iron, polyhalogenated compounds and viral infections. Porphyria cutanea tarda is associated with an increased incidence of the haemochromatosis gene. Treatments for PCT include withdrawal of aggravating factors, phlebotomy and oral antimalarial medications. Porphyria cutanea tarda is associated with hepatic iron overload and responds to iron-reduction therapy. Porphyria cutanea tarda is the most common porphyria, followed by acute intermittent porphyria and erythropoietic protoporphyria. The molecular genetics of the porphyrias is very heterogenous. (PMID: 16315139, 7655298, 11105361).
alpha-Hydroxyisobutyric acid is a metabolite of methyl tert-butyl ether (MTBE). MTBE may be obtained through environmental exposure. MTBE is rapidly eliminated from the body, mainly through expired air as the unchanged compound. MTBE is to some extent metabolized to t-butyl alcohol (TBA) and formaldehyde and oxidized to 2-methyl-1,2-propanediol and alpha-hydroxyisobutyric acid. alpha-Hydroxyisobutyric acid has been used as an aerial bactericide.
Isobutyrylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction: acyl-CoA + glycine < -- > CoA + N-acylglycine. Isobutyrylglycine is identified in large amount in urine of patients with isobutyryl-CoA dehydrogenase deficiency. Isobutyryl-CoA dehydrogenase deficiency is a disorder caused by the deficiency of isobutyryl-CoA dehydrogenase that is involved in the catabolism of the branched-chain amino acid valine (PMID 15505379). Moreover, Isobutyrylglycine is found to be associated with ethylmalonic encephalopathy and propionic acidemia, which are also inborn errors of metabolism. Isobutyrylglycine is a biomarker for the consumption of cheese.
Cysteine-S-sulfate (SSC) is produced by reaction of inorganic sulfite and cystine by a yet unknown pathway and is a very potent NMDA-receptor agonist. Electrophysiological studies have shown that SSC displays depolarizing properties similar to glutamate. Patients affected with either Molybdenum cofactor deficiency (MOCOD, an autosomal recessive disease that leads to a combined deficiency of the enzymes sulphite oxidase, an enzyme that catalyzes the conversion of sulfite to inorganic sulfate, xanthine dehydrogenase and aldehyde oxidase) or isolated sulphite oxidase deficiency (ISOD, an extremely rare autosomal recessive disorder with identical clinical manifestations to MOCOD) excrete elevated levels of SSC. This rare disorder is associated with brain damage (seizures, spastic quadriplegia, and cerebral atrophy), mental retardation, dislocated ocular lenses, blindness, and excretion in the urine of abnormally large amounts of SSC, sulfite, and thiosulfate but no inorganic sulfate (PMID: 17764028, 15558695).
Hydroxykynurenine is a free radical generator and a bioprecursor quinolinic acid which is a endogenous excitotoxin (PMID 16697652). It is a product of enzyme kynurenine 3-monooxygenase in the tryptophan catabolism pathway (Reactome http://www.reactome.org).
Hyodeoxycholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Indoleacrylic acid (CAS: 1204-06-4), also known as indoleacrylate, IA, and IAcrA, is a member of the class of compounds known as indoles. Indoles are compounds containing an indole moiety, which consists of pyrrole ring fused to benzene to form 2,3-benzopyrrole. Indoleacrylic acid is practically insoluble (in water) and a weak acidic compound (based on its pKa). Within the cell, indoleacrylic acid is primarily located in the membrane (predicted from logP). Indoleacrylic acid is best known as a plant growth hormone (a natural auxin), whereas its biological role in animals is still unknown. A two-stage production of this compound is likely: intestinal microorganisms catabolize tryptophan to indole derivatives which are then absorbed and converted into indoleacrylic acid and its glycine conjugate, indolylacryloylglycine (IAcrGly). Indolylacryloylglycine excretion in urine is especially pronounced in some myopathies, namely in boys with Duchenne muscular dystrophy (PMID: 10707769). It has been recently found that indoleacrylic acid promotes intestinal epithelial barrier function and mitigates inflammatory responses. Stimulating indoleacrylic acid production could promote anti-inflammatory responses and have therapeutic benefits (PMID: 28704649). Urinary Indole-3-acrylate is produced by Clostridium sporogenes (PMID: 29168502). Indoleacrylic acid is also a metabolite of Peptostreptococcus (PMID: 28704649, 29168502).
Hydroxyphenylacetylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction:. acyl-CoA + glycine < -- > CoA + N-acylglycine. Hydroxyphenylacetylglycine is an endogenous human metabolite. It can be originated from the metabolism of tyramine, itself is a monoamine compound derived from the amino acid tyrosine. Hydroxyphenylacetylglycine can also be derived from the metabolism of 3,4-dihydroxyphenylalanine (L-DOPA). In the metabolism of tyrosine, this compound is involved in the reaction Hydroxyphenylacetyl-CoA + Glycine <=> Hydroxyphenylacetylglycine + CoA, catalyzed by acyltransferase enzymes (EC 2.3.1.-). Hydroxyphenylacetylglycine has been identified in human biofluids. (PMID: 14201174, 912020, 716472, 7096501, 7438429, 7438430).
Heptacarboxylporphyrin I is a bile product that arises from the conversion of Heptacarboxylporphyrinogen I to Heptacarboxylporphyrin I by porphyrinogen carboxy-lyase (EC 4.1.1.37).
Indole is an aromatic heterocyclic organic compound. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring. The participation of the nitrogen lone electron pair in the aromatic ring means that indole is not a base, and it does not behave like a simple amine. Indole is a microbial metabolite and it can be produced by bacteria as a degradation product of the amino acid tryptophan. It occurs naturally in human feces and has an intense fecal smell. At very low concentrations, however, indole has a flowery smell and is a constituent of many flower scents (such as orange blossoms) and perfumes. As a volatile organic compound, indole has been identified as a fecal biomarker of Clostridium difficile infection (PMID: 30986230). Natural jasmine oil, used in the perfume industry, contains around 2.5% of indole. Indole also occurs in coal tar. Indole has been found to be produced in a number of bacterial genera including Alcaligenes, Aspergillus, Escherichia, and Pseudomonas (PMID: 23194589, 2310183, 9680309). Indole plays a role in bacterial biofilm formation, bacterial motility, bacterial virulence, plasmid stability, and antibiotic resistance. It also functions as an intercellular signalling molecule (PMID: 26115989). Recently, it was determined that the bacterial membrane-bound histidine sensor kinase (HK) known as CpxA acts as a bacterial indole sensor to facilitate signalling (PMID: 31164470). It has been found that decreased indole concentrations in the gut promote bacterial pathogenesis, while increased levels of indole in the gut decrease bacterial virulence gene expression (PMID: 31164470). As a result, enteric pathogens sense a gradient of indole concentrations in the gut to migrate to different niches and successfully establish an infection.
2-(4-Amino-4-carboxybutyl)-1-(5-amino-5-carboxypentyl)-3,5-bis(3-amino-3-carboxypropyl)pyridinium. A rare amino acid found in elastin, formed by condensation of four molecules of lysine into a pyridinium ring.
Lactulose is a synthetic disaccharide used in the treatment of constipation and hepatic encephalopathy. It has also been used in the diagnosis of gastrointestinal disorders (From Martindale, The Extra Pharmacopoeia, 30th ed, p887). Moreover, lactulose is found to be associated with celiac disease, which is an inborn error of metabolism.
Hexacarboxylporphyrin I is a bile product that arises from the conversion of Hexacarboxylporphyrinogen I to Hexacarboxylporphyrin I by porphyrinogen carboxy-lyase (EC 4.1.1.37).
Homocarnosine is a normal human metabolite, the brain-specific dipeptide of gamma-aminobutyric acid (GABA) and histidine. (PMID 1266573). Increased concentration of CSF homocarnosine has been found in familial spastic paraplegia. (PMID 842287). Homocarnosinosis (an inherited disorder, OMIM 236130) is characterized by an elevated level of the dipeptide homocarnosine (Hca) in the Cerebrospinal fluid (CSF) and the brain and by carnosinuria and serum carnosinase deficiency, and can co-exist with paraplegia, retinitis pigmentosa, and a progressive mental deficiency. (PMID 3736769). In glial tumors of human brain the content of homocarnosine has been found to be lower than in brain tissue (PMID 1032224), while an increase in content of homocarnosine was observed in brain tissue of animals under experimental trauma of cranium. (PMID 1025883).
Hydroxyisocaproic acid is an end product of leucine metabolism in human tissues such as muscle and connective tissue. It belongs to 2-hydroxycarboxylic acid group of amino acid metabolites (PMID 6434570). Hydroxyisocaproic acid functions as an “anti-catabolite” and is widely used in the body building community. Chronic alpha-hydroxyisocaproic acid treatment of rats has been shown to improve muscle recovery after immobilization-induced atrophy (PMID: 23757407). Additionally, a 4-week hydroxyisocaproic acid supplementation of 1.5 g a day was shown to lead to increases in muscle mass during an intensive training period among soccer athletes (PMID: 20051111). Hydroxyisocaproic acid has also shown some potential as a topical antibiotic (PMID: 22483561). Elevated levels of 2-hydroxyisocaproic acid have been found in the urine of patients with dihydrolipoyl dehydrogenase (E3) deficiency (PMID: 6688766). Hydroxyisocaproic acid is also elevated in maple syrup urine disease, a genetic disorder, and has been shown to accelerate lipid peroxidation. It may also be an indicator of oxidative stress (PMID: 11894849). Hydroxyisocaproic acid has been found to be a metabolite of Lactobacillus and fungal species (http://jultika.oulu.fi/files/isbn9789526211046.pdf).
Isovalerylalanine, also known as isopentanoylalanine, belongs to the class of organic compounds known as N-acyl-L-alpha-amino acids. These are N-acylated alpha amino acids which have the L-configuration of the alpha-carbon atom. Isovalerylalanine results from the formal condensation of the carboxy group of isovaleric acid with the amino group of L-alanine. Isovalerylalanine is one of the constituents of the organic acid profile in isovaleric acidemia, it is believed to be formed by the action of the enzyme glycine N-acylase on alanine, using isovaleryl-CoA as a substrate (PMID: 6197208). Isovaleric acidemia was the first organic acid acidemia to be documented in humans. It is an autosomal recessive inborn error in the metabolism of leucine, caused by a deficiency of the mitochondrial enzyme isovaleryl-CoA dehydrogenase (IVD) that results in the accumulation isovaleryl-CoA derivatives (PMID:¬†16602101).¬†The excess of isovaleryl-CoA in plasma allows for the formation of condensation derivatives, such as isovalerylalanine which makes it one of the biomarkers for this condition.
Mesaconic acid, also known as 2-methylfumarate or citronic acid, belongs to the class of organic compounds known as methyl-branched fatty acids. These are fatty acids with an acyl chain that has a methyl branch. Usually, they are saturated and contain only one or more methyl group. However, branches other than methyl may be present. Mesaconic acid is a dicarboxylic butenoic acid, with a methyl group in position 2 and the double bound between carbons 2 and 3. Mesaconic acid was first studied for its physical properties in 1874 by Jacobus van ‚Äòt Hoff (https://web.archive.org/web/20051117102410/http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Van%27t-Hoff-1874.html). It is now known to be involved in the biosynthesis of vitamin B12 and it is also a competitor inhibitor of the reduction of fumarate.
3-Hydroxymandelic acid, also known as m-hydroxymandelate or MHMA, is a 2-hydroxy monocarboxylic acid. 3-Hydroxymandelic acid is the dehydroxylated (positions 2 and 3‚Äô) derivative of phenylacetic acid. It is a white crystalline solid that is soluble in water and polar organic solvents. It derives from a mandelic acid. Mandelic acid is a substrate or product of several biochemical processes called the mandelate pathway. Mandelate racemase interconverts the two enantiomers via a pathway that involves cleavage of the alpha-CH bond. Mandelate dehydrogenase is yet another enzyme on this pathway. Mandelate also arises from trans-cinnamate via phenylacetic acid, which is hydroxylated. Derivatives of mandelic acid, such as 3-hydroxymandelic acid, are formed as a result of metabolism of adrenaline and noradrenaline by monoamine oxidase and catechol-O-methyl transferase.
L-Xylulose (CAS: 527-50-4), also known as L-threo-2-pentulose, is a ketopentose - a monosaccharide containing five carbon atoms, including a ketone functional group. It has the chemical formula C5H10O5. L-Xylulose accumulates in the urine of pentosuria patients. Since L-xylulose is a reducing sugar like D-glucose, pentosuria patients have been wrongly diagnosed in the past to be diabetic.
Methylglutaric acid is a leucine metabolite. A large amount of methylglutaric acid is identified in urine of patients with deficiency of 3-methylglutaconyl coenzyme A hydratase (PMID 6181239). Methylglutaric acid is also found to be associated with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency, another inborn error of metabolism.
3-Hexanone, also known as 3-oxohexane or hexan-3-one, belongs to the class of organic compounds known as ketones. These are organic compounds in which a carbonyl group is bonded to two carbon atoms R2C=O (neither R may be a hydrogen atom). Ketones that have one or more alpha-hydrogen atoms undergo keto-enol tautomerization, the tautomer being an enol. 3-Hexanone is a very hydrophobic molecule, practically insoluble in water and relatively neutral. 3-Hexanone is an ether and grape tasting compound. Outside of the human body, 3-Hexanone has been detected, but not quantified in, several different foods, such as pepper (capsicum), oregon yampahs, cinnamons, cloudberries, and cardamoms. 3-Hexanone, with regard to humans, has been found to be associated with several diseases such as nonalcoholic fatty liver disease, pervasive developmental disorder not otherwise specified, autism, and perillyl alcohol administration for cancer treatment. 3-hexanone has also been linked to the inborn metabolic disorder celiac disease.
Hydroxyphenyllactic acid or 4-hydroxyphenyllactate (the L-form) is a tyrosine metabolite. The level of L-hydroxyphenyllactic acid is elevated in patients with a deficiency of the enzyme p-hydroxyphenylpyruvate oxidase (EC 1.14.2.2) (PMID: 4720815). L-hydroxyphenyllactate is present in relatively higher concentrations in the cerebrospinal fluid and urine of patients with phenylketonuria (PKU) and tyrosinemia (PMID: 3126358). However, the D-form of hydroxyphenyllactate is of bacterial origin and is also found in individuals with bacterial overgrowth or unusual gut microflora (PMID: 3126358).  Microbial hydroxyphenyllactate is likely derived from phenolic or polyphenolic compounds in the diet.  Bifidobacteria and lactobacilli produce considerable amounts of phenyllactic and p-hydroxyphenyllactic acids (PMID: 23061754).  It has also been shown that hydroxyphenyllactate decreases ROS (reactive oxygen species) production in both mitochondria and neutrophils and so hydroxyphenyllactate may function as a natural anti-oxidant (PMID: 23061754). Hydroxyphenyllactic acid is a microbial metabolite found in Acinetobacter, Bacteroides, Bifidobacteria, Bifidobacterium, Clostridium, Enterococcus, Escherichia, Eubacterium, Klebsiella, Lactobacillus, Pseudomonas and Staphylococcus (PMID: 19961416).
Hexanoylcarnitine (CAS: 6418-78-6), also known as caproylcarnitine, is an acylcarnitine. Acylcarnitines are the product of the conjugation of carnitine with acyl-coenzyme A, that allows the transport of fatty acids across mitochondrial membranes. Long or medium chain fatty acids are then oxidized in the mitochondria for energy production. The ionic nature of L-carnitine causes high water solubility which decreases with increasing chain lengths of the ester group in the acylcarnitines. Therefore, the distribution of L-carnitine and acylcarnitines in various organs is defined not only by their function but also by their physicochemical properties. Hexanoylcarnitine is a medium-chain acylcarnitine present in the urine of patients with medium-chain acyl-CoA dehydrogenase deficiency (PMID: 1635814). Hexanoylcarnitine is also found to be associated with celiac disease and glutaric aciduria II which are both inborn errors of metabolism. Numerous disorders have been described that lead to disturbances in energy production and in intermediary metabolism, which are characterized by the production and excretion of unusual acylcarnitines. A mutation in the gene coding for carnitine-acylcarnitine translocase or the OCTN2 transporter aetiologically causes a carnitine deficiency that results in poor intestinal absorption of dietary L-carnitine, its impaired reabsorption by the kidney and, consequently, in increased urinary loss of L-carnitine. Determination of the qualitative pattern of acylcarnitines can be of diagnostic and therapeutic importance. The betaine structure of carnitine requires special analytical procedures for recording. High-performance liquid chromatography (HPLC) permits screening for free and total carnitine, as well as complete quantitative acylcarnitine determination, including the long-chain acylcarnitine profile (PMID: 17508264, Monatshefte fuer Chemie (2005), 136(8), 1279-1291., Int J Mass Spectrom. 1999;188:39-52.).
Glycogen is a highly-branched polymer of about 30,000 glucose residues. The simplest structure of glycogen is made up of four units of glucose with an approximate molecular weight of 666 daltons. However, large molecules of glycogen can reach molecular weights in the order of 5 million Da. Most of the glucose units are linked together by alpha-1,4 glycosidic bonds, and approximately 1 in 12 glucose residues also form a 1,6 glycosidic bond with a second glucose, resulting in the creation of a branch. Glycogen only has one reducing end and a large number of non-reducing ends with a free hydroxyl group at carbon 4. The glycogen granules contain both glycogen and the enzymes of glycogen synthesis (glycogenesis) and degradation (glycogenolysis). The enzymes are nested between the outer branches of the glycogen molecules and act on the non-reducing ends. Therefore, the many non-reducing end-branches of glycogen facilitate its rapid synthesis and breakdown. In hypoglycemia caused by excessive insulin, liver glycogen levels are high, but the high insulin level prevents the necessary glycogenolysis to take place to maintain normal blood sugar levels. Glucagon is a common treatment for this type of hypoglycemia. Glycogen is a polysaccharide that is the principal storage form of glucose (Glc) in animal cells. Glycogen is found in the form of granules in the cytosol in many cell types. Hepatocytes (liver cells) have the highest concentration of it - up to 8% of the fresh weight in well fed state, or 100 to 120 g in an adult - giving liver a distinctive, 'starchy taste'. In the muscles, glycogen is found in a much lower concentration (1% of the muscle mass), but the total amount exceeds that in liver. Small amounts of glycogen are found in the kidneys, and even smaller amounts in certain glial cells in the brain and white blood cells.
Glycylleucine is a dipeptide composed of glycine and leucine. It is an incomplete breakdown product of protein digestion or protein catabolism. Some dipeptides are known to have physiological or cell-signaling effects although most are simply short-lived intermediates on their way to specific amino acid degradation pathways following further proteolysis. It appears to be a common substrate for glycyl-leucine dipeptidase.
Hyocholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
5-Hydroxyindoleacetic acid, also known as 5-hydroxyindole-3-acetate or 5-HIAA, belongs to the class of organic compounds known as indole-3-acetic acid derivatives. Indole-3-acetic acid derivatives are compounds containing an acetic acid (or a derivative) linked to the C3 carbon atom of an indole. 5-Hydroxyindoleacetic acid exists in all living organisms, ranging from bacteria to humans. In humans, 5-hydroxyindoleacetic acid is a breakdown product of serotonin that is excreted in the urine and it also participates in a number of enzymatic reactions. 5-hydroxyindoleacetic acid can be biosynthesized from 5-hydroxyindoleacetaldehyde; which is catalyzed by the mitochondrial enzyme aldehyde dehydrogenase. In addition, 5-hydroxyindoleacetic acid and S-adenosylmethionine can be converted into 5-methoxyindoleacetate and S-adenosylhomocysteine through its interaction with the enzyme acetylserotonin O-methyltransferase. 5-Hydroxyindoleacetic acid is also involved in the metabolism of tryptophan. 5-Hydroxyindoleacetic acid has been found to be associated with several human diseases such as brunner syndrome, friedreich's ataxia, schizophrenia, and olivopontocerebral atrophy; 5-hydroxyindoleacetic acid has also been linked to the inborn metabolic disorder sepiapterin reductase deficiency. Elevated levels of 5-hydroxyindoleacetic acid in urine (>20 uM) are indicative of appendicitis and gastroenteritis (PMID: 11462886). Serotonin and 5-Hydroxyindoleacetic acid are produced in excess amounts by carcinoid tumors, and levels of these substances may be measured in the urine to test for carcinoid tumors (NCI). 5-Hydroxyindoleacetic acid has also been found to be a product of human gut microbiota.
Hydrocinnamic acid, also known as 3-phenylpropanoic acid or dihydrocinnamic acid, belongs to the class of organic compounds known as phenylpropanoic acids. Phenylpropanoic acids are compounds with a structure containing a benzene ring conjugated to a propanoic acid (C6-C3). Phenylpropanoic acid can be prepared from cinnamic acid by hydrogenation. Hydrocinnamic acid is a sweet, balsamic, and cinnamon tasting compound. This compound is used frequently in cosmetic products such as perfumes, bath gels, detergent powders, liquid detergents, fabric softeners, and soaps as it gives off a floral scent. A characteristic reaction of phenylpropanoic acid is its cyclization to indanones. Phenylpropanoic acid is used in the food industry to preserve and maintain the original aroma quality of frozen foods. Phenylpropanoic acid is also added to food for technological purposes in a wide variety including manufacturing, processing, preparation, treatment, packaging, transportation or storage, and food additives. This compound is used as a sweetener as well to sweeten food and can be found in tabletop sweeteners.
Mannitol, or hexan-1,2,3,4,5,6-hexol (C6H8(OH)6), is an alcohol and a sugar (sugar alcohol), or a polyol, it is a stereoisomer of sorbitol and is similar to the C5 xylitol. The structure of mannitol is made of a straight chain of six carbon atoms, each of which is substituted with a hydroxyl group. Mannitol is one of the most abundant energy and carbon storage molecules in nature, it is produced by a wide range of organisms such as bacteria, fungi and plants (PMID: 19578847). In medicine, mannitol is used as a diuretic and renal diagnostic aid. Mannitol has little significant energy value as it is largely eliminated from the body before any metabolism can take place. It can be used to treat oliguria associated with kidney failure or other manifestations of inadequate renal function and has been used for determination of glomerular filtration rate. Mannitol is also commonly used as a research tool in cell biological studies, usually to control osmolarity. Mannitol has a tendency to lose a hydrogen ion in aqueous solutions, which causes the solution to become acidic. For this, it is not uncommon to add a weak base, such as sodium bicarbonate, to the solution to adjust its pH. Mannitol is a non-permeating molecule i.e., it cannot cross biological membranes. Mannitol is an osmotic diuretic agent and a weak renal vasodilator. Mannitol is found to be associated with cytochrome c oxidase deficiency and ribose-5-phosphate isomerase deficiency, which are inborn errors of metabolism. Mannitol is also a microbial metabolite found in Aspergillus, Candida, Clostridium, Gluconobacter, Lactobacillus, Lactococcus, Leuconostoc, Pseudomonas, Rhodobacteraceae, Saccharomyces, Streptococcus, Torulaspora and Zymomonas (PMID: 15240312; PMID: 29480337).
Pseudouridine, also known as psi-uridine or 5-ribosyluracil, belongs to the class of organic compounds known as nucleoside and nucleotide analogues. These are analogues of nucleosides and nucleotides, such as phosphonated nucleosides, C-glycosylated nucleoside bases, analogues where the sugar unit is a pyranose, and carbocyclic nucleosides.  Pseudouridine specifically has its uracil attached via a carbon-carbon instead of a nitrogen-carbon glycosidic bond to the ribofuranose.  It is the most prevalent of the over one hundred different modified nucleosides found in RNA (PMID: 17113994).  Pseudouridine is a solid that is soluble in water.  Pseudouridine exists in all living species, ranging from bacteria to humans, and is in all classes of RNA except mRNA.  It is formed by enzymes called pseudouridine synthases, which post-transcriptionally isomerize specific uridine residues in RNA.
N-Acetyl-9-O-lactoylneuraminic acid is a sialic acid produced by sialate 9-O-lactoyltransferases. Lactoylation of CMP-N-acetylneuraminic acid, N-acetylneuramimic acid and glycoconjugate-bound N-acetylneuramimic acid has been observed, with the glycoconjugate form being the best substrate.
N-Glycoloylganglioside GM2 is a glycosphingolipid (ceramide and oligosaccharide)or oligoglycosylceramide with one or more sialic acids (i.e. n-acetylneuraminic acid) linked on the sugar chain. It is a component the cell plasma membrane which modulates cell signal transduction events. Gangliosides have been found to be highly important in immunology. Ganglioside AII carries a net-negative charge at pH 7.0 and is acidic. Gangliosides can amount to 6% of the weight of lipids from brain, but they are found at low levels in all animal tissues.
Nonadecanoic acid, also known as n-nonadecanoic acid or nonadecylic acid or C19:0, belongs to the class of organic compounds known as long-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 13 and 21 carbon atoms, with nonadecanoic acid (its ester is called nonadecanoate) having 19 carbon atoms. Nonadecanoic acid is a very hydrophobic molecule, practically insoluble (in water). It is a solid with a melting point of 69.4¬∞C.  It can be found in bacteria, plants, and animals (including animal milk) (Nature 176:882; PMID: 14168161).  It is secreted by termites (Rhinotermes marginalis) as part of its defence mechanism (Comp. Biochem. Physiol. B 71:731).
N-Acetyl-alpha-neuraminate is a sialic acid. Sialic acids are an important family of related 9-carbon sugars acids, present on the surface of many different cells and functioning in a wide range of different biological processes. They mediate a variety of cell-cell and cell-molecule interactions in eukaryotes and can be utilized by pathogens to evade the host immune response. N-acetylneuraminic acid is the most common sialic acid, and the predominant form present in humans. It can be found as a terminal sugar on a wide range of surface glycoconjugates. A number of bacteria that can colonize humans (such as E. coli) make use of N-acetylneuraminic acid as a nutrient source.
Pregnenolone sulfate is a sulfated version of the steroid hormone known as pregnenolone. Pregnenolone sulfate belongs to the class of organic compounds known as sulfated steroids. These are sterol lipids containing a sulfate group attached to the steroid skeleton.  Pregnenolone sulfate is a neurosteroid found in the brain and central nervous system.  Pregnenolone sulfate is a metabolite synthesized from pregnenolone via sulfation.  It is known to have cognitive and memory-enhancing, antidepressant, anxiogenic, and proconvulsant effects (PMID: 21094889).  As a neurosteroid, pregnenolone sulfate modulates a variety of ion channels, transporters, and enzymes. Interestingly, as a sulfated steroid, pregnenolone sulfate is not the final- or waste-product of pregnenolone being sulfated via a phase II metabolism reaction and renally excreted, as one would presume from pharmacology textbook knowledge. Pregnenolone sulfate is also the source and thereby the starting point for subsequent steroid synthesis pathways. Recently, pregnenolone sulfate has been shown to not only be a modulator of ion channels, but it is also an activating ion channel ligand (PMID: 24084011).
Porphinehexacarboxylic acid is a porphyrinogen intermediate metabolite in the catalytic decarboxylation of the acetate groups on the rings A, B, C and D of uroporphyrinogen III to coproporphyrinogen III, a process mediated by Uroporphyrinogen decarboxylase (EC 4.1.1.37), a cytosolic haem-biosynthetic enzyme (PMID: 8424794).
Also known as GalNAc4S, this molecule is a key component of dermatan, keratan and chondroitin sulfate. It is also a substrate for the enzyme N-acteylgalactosamine-4-sulphate transferase. This molecule is found in elevated concentrations in the urine of patients suffering from muchopolysaccharidosis type III, IV and VI. Levels are typically 300-400 times normal values. GalNAc4S is thought to be derived from the action of beta-N-acetylhexosaminidase on sulphated GlcNAc or GalNAc residues at the non-reducing end of keratan sulphate, dermatan sulphate or chondroitin sulphate.
Octadecanedioic acid, also known as 1,18-octadecanedioate or octadecane-1,18-dioate, belongs to the class of organic compounds known as long-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 13 and 21 carbon atoms. In the case of octadecanedioic acid, it has carboxyl groups at both ends of the chain, not just one.  Octadecanedioic acid is a very hydrophobic molecule, practically insoluble (in water).  Octadecanedioic acid is a long-chain dicarboxylic acid normally not found in humans that has been identified in the blood serum in Reye's syndrome patients (PMID:¬†3746531).  There may also be an association with colorectal cancer (PMID: 25037050).
Propionylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction:acyl-CoA + glycine < -- > CoA + N-acylglycineThe level of propionylglycine is elevated in patients with propionic acidemia, which is an inherited deficiency of propionyl-CoA carboxylase. (Disorders of propionate and methylmalonate metabolism. In The Metabolic and Molecular Bases of Inherited Disease).
Azelaic acid (AZA) is a naturally occurring saturated nine-carbon dicarboxylic acid (COOH (CH2)7-COOH). It possesses a variety of biological actions both in vitro and in vivo. Interest in the biological activity of AZA arose originally out of studies of skin surface lipids and the pathogenesis of hypochromia in pityriasis versicolor infection. Later, it was shown that Pityrosporum can oxidize unsaturated fatty acids to C8-C12 dicarboxylic acids that are cornpetitive inhibitors of tyrosinase in vitro. Azelaic acid was chosen for further investigation and development of a new topical drug for treating hyperpigmentary disorders for the following reasons: it possesses a middle-range of antityrosinase activity, is inexpensive, and more soluble to be incorporated into a base cream than other dicarboxylic acids. Azelaic acid is another option for the topical treatment of mild to moderate inflammatory acne vulgaris. It offers effectiveness similar to that of other agents without the systemic side effects of oral antibiotics or the allergic sensitization of topical benzoyl peroxide and with less irritation than tretinoin. Azelaic acid is less expensive than certain other prescription acne preparations, but it is much more expensive than nonprescription benzoyl peroxide preparations. Whether it is safe and effective when used in combination with other agents is not known. (PMID: 7737781, 8961845).
N-Acetyl-7-O-acetylneuraminic acid is a component of glycoprotein- and glycolipid-bound sialic acids present in the human erythrocyte membrane (RBC). (PMID: 12527384). N-Acetyl-7-O-acetylneuraminic acid has been detected in basaliomas and normal human skin. (PMID: 11180001). Determination of N-Acetyl-7-O-acetylneuraminic acid in human serum has been obtained by fluorometric high-performance liquid chromatography. (PMID: 2757191).
Oxipurinol is a xanthine oxidase inhibitor. Oxipurinol is potentially used for treatment of congestive heart failure. PMID: 15139781.
Orotidine is a nucleoside formed by attaching orotic acid to a ribose ring via a beta-N1-glycosidic bond. It is a water-soluble solid.  Orotidine is found in bacteria, fungi, plants, and animals.  In humans, orotidine occurs as its 5'-phosphate (orotidylic acid), which is an intermediate in the biosynthesis of pyrimidine nucleosides (cytidine and uridine) that are found in nucleic acids (as the nucleotides containing the bases cytosine and uracil). Orotidine itself is not a component of nucleic acid.  Orotidine monophosphate (OMP) is converted to uridine monophosphate by OMP decarboxylase, which is inhibited by mononucleotide precursors.  Large amounts of orotidine are excreted in the urine of cancer patients treated with 6-azauridine, which is one such inhibitor, indicating that the subject has increased DNA synthesis due to cancer.  Orotidine was first isolated from a mutant strain of the fungus Neurospora by A. Michael Michelson, William Drell, and Herschel K. Mitchell (PMID: 14853953).
Pentacarboxylporphyrin I is a bile product that arises from the conversion of Pentacarboxylporphyrinogen I to Pentacarboxylporphyrin I by porphyrinogen carboxy-lyase (EC 4.1.1.37).
L-Octanoylcarnitine is the physiologically active form of octanoylcarnitine (PMID: 11274033). Octanoylcarnitine is detected in medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. MCAD is characterized by an intolerance to prolonged fasting, recurrent episodes of hypoglycemic coma with medium-chain dicarboxylic aciduria, impaired ketogenesis, and low plasma and tissue carnitine levels (OMIM: 201450). L-Octanoylcarnitine is also found to be associated with celiac disease and glutaric aciduria II, which are inborn errors of metabolism.
Sebacic acid is a saturated, straight-chain naturally occurring dicarboxylic acid with 10 carbon atoms. Sebacic acid is a normal urinary acid. In patients with multiple acyl-CoA-dehydrogenase deficiency (MADD), also known as glutaric aciduria type II (GAII), a group of metabolic disorders due to deficiency of either electron transfer flavoprotein or electron transfer flavoprotein ubiquinone oxidoreductase, biochemical data shows an increase in urine sebacic acid excretion. Sebacic acid is found to be associated with carnitine-acylcarnitine translocase deficiency and medium chain acyl-CoA dehydrogenase deficiency, which are inborn errors of metabolism. Sebacic acid is a white flake or powdered crystal slightly soluble in water that has been proposed as an alternative energy substrate in total parenteral nutrition. Sebacic Acid was named from the Latin sebaceus (tallow candle) or sebum (tallow) in reference to its use in the manufacture of candles. Sebacic acid and its derivatives such as azelaic acid have a variety of industrial uses as plasticizers, lubricants, hydraulic fluids, cosmetics, candles, etc. It is used in the synthesis of polyamide and alkyd resins. It is also used as an intermediate for aromatics, antiseptics and painting materials (PMID: 10556649, 1738216, 8442769, 12706375).
Monoiodothyronine is an iodothyronine metabolite. It has unknown physiological functions.
N-Acetyl-9-O-acetylneuraminic acid (alternatively 9-O-acetyl-N-acetylneuraminic acid) is an O acetylated sialic acid identified in human colon by using high-pressure liquid chromatography and gas-liquid chromatography/mass spectrometry (PMID 3623000). It also has been suggested that 9-O-acetyl-N-acetylneuraminic acid is an essential component of the cell surface receptor of influenza C virus (PMID 3700379).
Pristanic acid (2,6,10,14-tetramethylpentadecanoic acid) is a terpenoid acid present at micromolar concentrations in the plasma of healthy individuals. It is also found in the lipids from many sources such as freshwater sponges, krill, earthworms, whales, human milk fat, bovine depot fat, butterfat or Californian petroleum. It is usually present in combination with phytanic acid. In humans, pristanic acid is obtained from two sources: either directly from the diet or as the alpha oxidation product of phytanic acid. At physiological concentrations pristanic acid is a natural ligand for PPARalpha. In liver, pristanic acid is degraded by peroxisomal beta oxidation to propionyl-CoA. Together with phytanic acid, pristanic acid accumulates in several inherited disorders such as Zellweger syndrome. Pristanic acid is a branched chain fatty acid that arises from the breakdown of phytanic acid. It is present at micromolar concentrations in the plasma of healthy individuals. Pristanic acid is normally degraded by peroxisomal beta-oxidation. In patients affected with generalized peroxisomal disorders, degradation of both phytanic acid and pristanic acid is impaired owing to absence of functional peroxisomes. Pristanic acid has been found to activate the peroxisome proliferator-activated receptor {alpha} (PPAR{alpha}) in a concentration dependent manner.
N-Acetyl-4-O-acetylneuraminic acid is a component of glycoprotein- and glycolipid-bound sialic acids present in the human erythrocyte membrane (RBC). (PMID: 12527384).
SAICAR, also known as succinylaminoimidazolecarboxamide ribotide or phosphoribosylaminoimidazolesuccinocarboxamide, is a substrate for the multifunctional protein ADE2. SAICAR is an intermediate in purine metabolism. SAICAR is converted from 5-aminoimidazole-4-carboxyribonucleotide (CAIR) via phosphoribosylaminoimidazolesuccinocarboxamide synthetase (EC: 6.3.2.6) or SAICAR synthase. This enzyme catalyzes the eighth step in the biosynthesis of purine nucleotides. SAICAR (a ribotide) can lose its phosphate group leading to the appearance of a riboside known as succinylaminoimidazolecarboxamide riboside (SAICAriboside) in cerebrospinal fluid, in urine, and, to a lesser extent, in plasma. This particular riboside (called SAICAr) is characteristic of a heritable deficiency known as adenylosuccinate lyase deficiency (ADSL). On the other hand, the ribotide (SAICAR) is generally harmless and is an essential intermediate in purine metabolism. When present in sufficiently high levels, SAICAR can act as an oncometabolite. An oncometabolite is a compound that promotes tumour growth and survival. As an oncometabolite, high levels of SAICAR stimulate pyruvate kinase isoform M2 and promote cancer cell survival in glucose-limited conditions such as aerobic glycolysis (PMID: 23086999).
Oenanthic ether is an odorous substance (ester) (PMID 15474656) present in human sweat (PMID 8887339).
Phytanic acid (or 3,7,11,15-tetramethylhexadecanoic acid) is a 20-carbon branched-chain fatty acid that humans can obtain through the consumption of dairy products, ruminant animal fats, and certain fish. It is primarily formed by bacterial degradation of chlorophyll in the intestinal tract of ruminants. Unlike most fatty acids, phytanic acid cannot be metabolized by beta-oxidation (because of a methyl group in the beta position). Instead, it undergoes alpha-oxidation in the peroxisome, where it is converted into pristanic acid by the removal of one carbon. Pristanic acid can undergo several rounds of beta-oxidation in the peroxisome to form medium-chain fatty acids that can be converted into carbon dioxide and water in mitochondria. Refsum disease, an autosomal recessive neurological disorder caused by mutations in the PHYH gene, is characterized by having impaired alpha-oxidation activity. Individuals with Refsum disease accumulate large stores of phytanic acid in their blood and tissues. This frequently leads to peripheral polyneuropathy, cerebellar ataxia, retinitis pigmentosa, anosmia, and hearing loss. Therefore, chronically high levels of phytanic acid can be neurotoxic. Phytanic acid's neurotoxicity appears to lie in its ability to initiate astrocyte/neural cell death by activating the mitochondrial route of apoptosis. In particular, phytanic acid can induce the substantial generation of reactive oxygen species in isolated mitochondria as well as in intact cells. It also induces the release of cytochrome c from mitochondria.
Pterin is a chemical compound composed of a pyrazine ring and a pyrimidine ring; the pyrimidine ring has a carbonyl oxygen and an amino group. Several tautomers of pterin exist and are shown below. Pterin belongs to the pteridine family of heterocycles. -- Wikipedia.
beta-N-Acetylglucosamine is an acylaminosugar, which is an organic compound containing a sugar linked to a chain through an N-acyl group.  This compound is water-soluble.  Glycosylation with beta-N-acetylglucosamine is one of the most common post-translational modifications.  All animals and plants dynamically attach and remove beta-N-acetylglucosamine at serine and threonine residues on myriad nuclear and cytoplasmic proteins.  beta-N-Acetylglucosamine cycling, which is tightly regulated by the concerted actions of two highly-conserved enzymes, serves as a nutrient and stress sensor.  Proteins glycosylated with beta-N-acetylglucosamine can be found in almost every intracellular compartment and almost every functional class (PMID: 17460662).
Myristic acid, also known as tetradecanoic acid or C14:0, belongs to the class of organic compounds known as long-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 13 and 21 carbon atoms. Myristic acid (its ester is called myristate) is a saturated fatty acid that has 14 carbons; as such, it is a very hydrophobic molecule that is practically insoluble in water.  It exists as an oily white crystalline solid.  Myristic acid is found in all living organisms ranging from bacteria to plants to animals, and is found in most animal and vegetable fats, particularly butterfat, as well as coconut, palm, and nutmeg oils.  Industrially, myristic acid is used to synthesize a variety of flavour compounds and as an ingredient in soaps and cosmetics (Dorland, 28th ed). Within eukaryotic cells, myristic acid is also commonly conjugated to a penultimate N-terminal glycine residue in receptor-associated kinases to confer membrane localization of these enzymes (a post-translational modification called myristoylation via the enzyme N-myristoyltransferase). Myristic acid has a high enough hydrophobicity to allow the myristoylated protein to become incorporated into the fatty acyl core of the phospholipid bilayer of the plasma membrane of eukaryotic cells.  Also, this fatty acid is known because it accumulates as fat in the body; however, its consumption also impacts positively on cardiovascular health (see, for example, PMID: 15936650).  Myristic acid is named after the scientific name for nutmeg, Myristica fragrans, from which it was first isolated in 1841 by Lyon Playfair.
3-Phosphoglyceric acid, also known as 3PG, belongs to the class of organic compounds known as sugar acids and derivatives. Sugar acids and derivatives are compounds containing a saccharide unit which bears a carboxylic acid group.  3PG is the conjugate acid of glycerate 3-phosphate (GP or G3P).  It is a solid that is soluble in water.  3-Phosphoglyceric acid exists in all living species, ranging from bacteria to humans.  The glycerate is a biochemically significant metabolic intermediate in both glycolysis and the Calvin cycle. This is the first compound formed during the C3 or Calvin cycle. Glycerate 3-phosphate is also a precursor for serine, which, in turn, can create cysteine and glycine through the homocysteine cycle. Within humans, 3-phosphoglyceric acid participates in a number of enzymatic reactions. In particular, 3-phosphoglyceric acid can be biosynthesized from glyceric acid 1,3-biphosphate, which is mediated by the enzyme phosphoglycerate kinase 1. In addition, 3PG can be converted into 2-phospho-D-glyceric acid, which is catalyzed by the enzyme phosphoglycerate mutase 2.  3-phosphoglyceric acid is involved in the Warburg effect (aerobic glycolysis), a metabolic shift that is a hallmark of cancer (PMID: 29362480).
N-Butyrylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism, such as ethylmalonic encephalopathy. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13), which is an enzyme that catalyzes the chemical reaction: acyl-CoA + glycine < -- > CoA + N-acylglycine amino acids composed of glycine substituted at the nitrogen rather than the usual carbon position, resulting in the loss of hydrogen bonding donors. Polymers of these compounds are called Peptoids.
N-Glycoloylganglioside GM1 is a specific monosialoganglioside that accumulates abnormally within the nervous system due to a deficiency of GM1-b-galactosidase, resulting in GM1 gangliosidosis. (PubChem).
The hepatic pigment accumulated as a consequence of the self-catalyzed destruction of cytochrome P-450 by norethisterone (PubMed ID 284396 ).
Murocholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
N-acetylglucosamine 6-sulfate is a physiological intermediate during the degradation of keratan sulfate and it is usually hydrolyzed intralysosomally by N-acetylglucosamine-6-sulfate sulfatase. (PMID 3161730).
Porphyrins excreted in various types of porphyria (PubMed ID 5917679 ). Intermediate of haem biosynthesis (PubMed ID 1216185).
Phosphoglycolic acid is a substrate for triose-phosphate isomerase. This compound belongs to the family of Organophosphate Esters. These are organic compounds containing phosphoric acid ester functional group.
Orinapterin is a threo diastereomer of biopterin, was first isolated from human urine. Its structure was shown to be 2-amino-4(3H)-oxo-6-[(1'S,2'S)-1',2'-dihydroxypropyl]pteridine. A non-enzymatic transformation of 7,8-dihydroneopterin and 7,8-dihydrobiopterin by a mechanism analogous to keto-enol tautomerism is postulated for the formation of umanopterin and orinapterin in human body.
Normetanephrine, also known as normetadrenaline or N111, belongs to the class of organic compounds known as methoxyphenols. Methoxyphenols are compounds containing a methoxy group attached to the benzene ring of a phenol moiety.  Normetanephrine is a solid that is soluble in water.  Normetanephrine is a metabolite of norepinephrine created by action of catechol-O-methyl transferase on norepinephrine. Within humans, normetanephrine participates in a number of enzymatic reactions. In particular, normetanephrine can be converted into 3-methoxy-4-hydroxyphenylglycolaldehyde through its interaction with the enzyme amine oxidase [flavin-containing] A.  It is also involved in the metabolic disorder called transient tyrosinemia of the newborn. This compound is excreted in the urine and is found in certain tissues. It is a marker for catecholamine-secreting tumors such as pheochromocytoma (PMID: 30538672).
Propyl alcohol, also known as 1-propanol, n-propanol, or simply propanol, belongs to the class of organic compounds known as primary alcohols. Primary alcohols are compounds in which a hydroxy group is bonded to a primary carbon, with the general structure RCOH (R=alkyl, aryl). Propyl alcohol is a colourless, volatile liquid that is fully miscible with water. It has a sweet odour and an alcoholic, fermented, fusel taste. Propyl alcohol exists in all living species, ranging from bacteria to plants to humans. Propanol can be produced through fermentation of sugars by bacteria and yeast and small amounts are produced by gut microflora. Propanol has been identified as a fecal biomarker of Clostridium difficile infection (PMID: 30986230). When ingested, 1-propanol is metabolized by alcohol dehydrogenase to propionic acid leading to metabolic acidosis and an elevated anion gap (PMID: 18375643). It can be found in small amounts in alcoholic beverages such as wine. Industrially, the major use of 1-propanol is as a solvent as well as an intermediate in forming other industrially important compounds.  It is used as a carrier and extraction solvent for natural products, such as flavourings, vegetable oils, resins, waxes, and gums, and as a solvent for synthetic polymers, such as polyvinyl butyral, cellulose esters, lacquers, and PVC adhesives.  Other solvent applications include the use of 1-propanol in the polymerization and spinning of acrylonitrile, in flexographic printing inks, and in the dyeing of wool.  1-Propanol is used for both its solvent and antiseptic properties in drugs and cosmetics, such as lotions, soaps, and nail polishes (IPCS INCHEM, EHC 102). Both 1-propanol and 2-propanol are often used in hand disinfectants as they have excellent bactericidal activity.  1-Propanol is used less in industry than 2-propanol as it is more expensive and it is a toxicant that has a similar taste to ethanol, so 2-propanol is used as its unpleasant smell discourages abuse.
Phenylacetylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction:. acyl-CoA + glycine < -- > CoA + N-acylglycine. Phenylacetylglycine or PAG is a glycine conjugate of phenylacetic acid. Phenylacetic acid may arise from exposure to styrene (plastic) or through the consumption of fruits and vegetables. Phenylacetic acid is used in some perfumes, possessing a honey-like odour in low concentrations, and is also used in penicillin G production. PAG is a putative biomarker of phospholipidosis. Urinary PAG is elevated in animals exhibiting abnormal phospholipid accumulation in many tissues and may thus be useful as a surrogate biomarker for phospholipidosis. (PMID: 15764292) The presence of phenylacetylglycine in urine has been confirmed for dogs, rats and mice. However, the presence of this compound in human urine is controversial. GC-MS studies have not found this compound (PMID: 7492634) while NMR studies claimed to have identified it (PMID: 21167146). It appears that phenylacetylglycine may sometimes be mistaken for phenylacetylglutamine via NMR.
p-Hydroxymandelic acid is an acidic metabolite of p-octopamine and p-synephrine (p-phenylephrine). It is also a naturally occurring metabolite of tyramine. A specific enantiomer of p-hydroxymandelic aicd ((R)-(-)-p-hydroxymandelic -- also called pisolithin B) has been shown to exhibit antifungal properties.
Sialyllactose is an oligossaccharide found in both human breast milk and cow's milk. It is the predominant sialylated component in milk. Sialyllactose has recently been shown to inhibit the infection of HIV-1 virus. Sialyllactose is also responsible for the inhibitory activity of milk on cholera toxin.
Pentadecanoic acid, also known as pentadecylic acid or C15:0, belongs to the class of organic compounds known as long-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 13 and 21 carbon atoms. Pentadecanoic acid (its ester is called pentadecanoate) is a saturated fatty acid that has 15 carbons and is therefore a very hydrophobic molecule that is practically insoluble in water.  Pentadecanoic acid is found in plants and ruminants. Many "odd" length long-chain fatty acids, such as pentadecanoic acid, are derived from the consumption of cattle fats (milk and meat). Pentadecanoic acid constitutes 1.05% of milk fat and 0.43% of ruminant meat fat. The content of pentadecanoic acid in the subcutaneous adipose tissue of humans appears to be a good biological marker of long-term milk fat intake in free-living individuals in populations with high consumption of dairy products. (PMID: 9701185; PMID: 11238766).
Stearic acid, also known as octadecanoic acid or C18:0, belongs to the class of organic compounds known as long-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 13 and 21 carbon atoms. Stearic acid (its ester is called stearate) is a saturated fatty acid that has 18 carbons and is therefore a very hydrophobic molecule that is practically insoluble in water.  It exists as a waxy solid.  In terms of its biosynthesis, stearic acid is produced from carbohydrates via the fatty acid synthesis machinery wherein acetyl-CoA contributes two-carbon building blocks, up to the 16-carbon palmitate, via the enzyme complex fatty acid synthase (FA synthase), at which point a fatty acid elongase is needed to further lengthen it.  After synthesis, there are a variety of reactions it may undergo, including desaturation to oleate via stearoyl-CoA desaturase (PMID: 16477801).  Stearic acid is found in all living organisms ranging from bacteria to plants to animals.  It is one of the useful types of saturated fatty acids that comes from many animal and vegetable fats and oils. For example, it is a component of cocoa butter and shea butter.  It is used as a food additive, in cleaning and personal care products, and in lubricants.  Its name comes from the Greek word stear, which means ‚Äòtallow‚Äô or ‚Äòhard fat‚Äô.
Ureidosuccinic acid, also known as L-ureidosuccinate or carbamyl-L-aspartate, belongs to the class of organic compounds known as aspartic acids and derivatives. Aspartic acids and derivatives are compounds containing an aspartic acid or a derivative thereof resulting from reaction of aspartic acid at the amino group or the carboxy group, or from the replacement of any hydrogen of glycine by a heteroatom. Ureidosuccinic acid is also classified as a carbamate derivative. It is a solid that is soluble in water.  Ureidosuccinic acid exists in all living species, ranging from bacteria to plants to humans. Ureidosuccinic acid can be biosynthesized from carbamoyl phosphate and L-aspartic acid through the action of the enzyme known as aspartate carbamoyltransferase (ACTase) and serves as an intermediate in pyrimidine biosynthesis. In humans, a drop in the level of urinary ureidosuccinic acid is associated with bladder cancer (PMID: 25562196). It is also involved in the metabolic disorder called Canavan disease.
Neuraminic acids are the commonest sialic acids in nature. Most sialic acids on gangliosides share a core neuraminic acid (Neu) structure and are N-acylated at the C-5 position with either an N-acetyl or an N-glycolyl group (giving Neu5Ac or Neu5Gc, respectively). It was originally thought that unsubstituted glycosidically linked Neu did not occur in nature. However, there have been several reports suggesting its presence in gangliosides and more recently in mucin-type glycoproteins. The N- or O-substituted derivatives of neuraminic acid are collectively known as sialic acids, the predominant one being N-acetylneuraminic acid. The amino group bears either an acetyl or a glycolyl group. The hydroxyl substituents may vary considerably: acetyl, lactyl, methyl, sulfate and phosphate groups have been found. Sialic acids are found widely distributed in animal tissues. Sialic acid rich glycoproteins bind selectin in humans and other organisms. Cancer cells that can metastasize often have a lot of sialic acid rich glycoproteins. This helps these late stage cancer cells enter the blood stream. (PMID: 11884388).
Capryloylglycine is an acylglycine consisting of caprylic acid (an 8-carbon medium chain fatty acid) conjugated to glycine. Acylglycines have an aliphatic acyl chain attached to the amino group of glycine through a peptide bond. Capryloylglycine is a solid with moderate solubility in water.  Acylglycines are produced through the action of the enzyme glycine N-acyltransferase (EC 2.3.1.13).  Acylglycines are normally minor metabolites of fatty acids. However, the excretion of certain acylglycines is increased in several inborn errors of metabolism. In certain cases, the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation, including medium-chain acyl-coenzyme A (CoA) dehydrogenase (MCAD) deficiency and multiple acyl-CoA dehydrogenation defect (MAD) (PMID: 10708405). Capryloylglycine is frequently used as a cosmetic ingredient where it functions as a conditioning agent or a surfactant. It helps protect the skin‚Äôs surface from water loss and can enhance the effectiveness of cosmetic preservatives. Capryloylglycine-containing creams have been shown to inhibit hair growth in individuals suffering from hypertrichosis (PMID: 33934471), due to it inhibiting ornithine decarboxylase 1, which is present in hair follicles.
N-Glycolylneuraminic acid (Neu5Gc) is a widely expressed sialic acid found in most mammalian cells. Although humans are genetically deficient in producing Neu5Gc, small amounts are present in human cells and biofluids. Humans cannot synthesize Neu5Gc because the human gene CMAH is irreversibly mutated, though it is found in apes. This loss of the CMAH gene was estimated to have occurred two to three million years ago, just before the emergence of the genus Homo. A dietary origin of Neu5Gc was suggested by human volunteer studies. These trace amounts of Neu5Gc were determined to come from the consumption of animals in the human diet (i.e. red meats such as lamb, pork, and beef). Neu5Gc can also be found in dairy products, but to a lesser extent. Neu5Gc is not found in poultry and is found in only trace amounts in fish (Wikipedia).
Pentaporphyrin I is a porphyrin intermediate detected in liver, kidney and erythrocytes (PubMed ID 8803328 ).
Salicyluric acid is an aryl glycine conjugate formed by the body to eliminate excess salicylates, including aspirin. Aspirin is rapidly hydrolysed to salicylic acid which is further metabolized to various compounds, including salicyluric acid (SU) as well as various acyl and phenolic glucuronides, and hydroxylated metabolites. SU is the major metabolite of SA excreted in urine and it is present in the urine of people who have not taken salicylate drugs, although it has no anti-inflammatory effects in humans or in animals. More salicyluric acid (SU) is excreted in the urine of vegetarians than in non-vegetarians, primarily because fruits and vegetables are important sources of dietary salicylates. However, significantly less (10-15X) SU is excreted by vegetarians than individuals taking low-dose aspirin (PMID: 12944546). The induction of the salicyluric acid formation is one of the saturable pathways of salicylate elimination. The formation of the methyl ester of salicyluric acid is observed during the quantitation of salicyluric acid and other salicylate metabolites in urine by high-pressure liquid chromatography. This methyl ester formation causes artificially low values for salicyluric acid and high values for salicylic acid. (PMID: 6101164, 6857178). Salicyluric acid has been found to be a microbial metabolite.
N-Acetylgalactosamine 6-sulfate is found in keratan sulfate and chondroitin 6-sulfate. PMID: 12489154. Morquio syndrome is caused by an abnormal accumulation of mucopolysaccharides - in this case, keratan sulfate - in the body. Keratan sulfate is excreted in urine. The symptoms vary from patient to patient, and may include hearing loss, cataracts, skeletal dysplasia, spinal instability, and minor respiratory issues, among others. Two forms are recognized, type A and type B. Type A is a deficiency of the enzyme N-acetylgalactosamine-6-sulfate sulfatase. (Wikipedia).
Quinaldic acid, also known as quinaldate, 2-carboxyquinoline, or quinoline-2-carboxylic acid, belongs to the class of organic compounds known as quinoline carboxylic acids. These are quinolines in which the quinoline ring system is substituted by a carboxyl group at one or more positions. The quinoline ring system is a double-ring structure composed of a benzene and a pyridine ring fused at two adjacent carbon atoms. Quinaldic acid is a quinoline having a carboxy group at the 2-position. It is a solid that is moderately soluble in water with a melting point of 156¬∞C.  Quinaldic acid is a metabolite of tryptophan degradation that is formed via the kynurenine pathway; it is formed through the dehydroxylation of the intermediate kynurenic acid (PMID: 13385219). It is excreted in urine, and its urine concentration is decreased in individuals suffering from chronic alcoholism (PMID: 25754126).  Quinaldic acid has been shown to inhibit proinsulin synthesis in pancreatic islet cells (PMID: 373355).  Quinaldic acid has been shown to have anti-proliferative or anti-tumour effects and has been found to alter the expression of the p53 tumour suppressor gene as well as the phosphorylation of the p53 protein in in vitro studies (PMID: 30780127).
N-Acetylgalactosamine 4,6-disulfate (GalNAc4,6diS) is one of the sulphated N-acetylhexosamines that have been isolated from human urine. PMID: 3931626.
Neopterin, also known as monapterin, belongs to the class of organic compounds known as biopterins and derivatives. These are coenzymes containing a 2-amino-pteridine-4-one derivative and are mainly synthesized in several parts of the body, including the pineal gland.  Neopterin is a solid that is soluble in water.  Neopterin is a catabolic product of guanosine triphosphate (GTP). In humans, it is involved in pterine biosynthesis and it also serves as a precursor in the biosynthesis of biopterin, which is an essential cofactor in neurotransmitter synthesis. Neopterin has been identified as a uremic toxin according to the European Uremic Toxin Working Group (PMID: 22626821). Most uremic toxins are metabolic waste products and are normally excreted in the urine or feces.  Uremic toxins can cause kidney, liver and heart damage. They can also cause changes in mental status, such as confusion, reduced awareness, agitation, psychosis, seizures, and coma. Uremic toxins such as neopterin are actively transported into the kidneys via organic ion transporters (especially OAT3). Elevated levels of neopterin result from immune system activation, including from malignant cancer, allograft rejection, viral infection, and autoimmune disorders (PMID: 19500901).  Measurement of neopterin concentration allows estimation of the extent of oxidative stress elicited by the immune system. Neopterin concentrations usually correlate with the extent and activity of a given disease, and are also used to monitor the course of the disease. Elevated neopterin concentrations are among the best predictors of adverse outcome in patients with HIV infection, in cardiovascular disease, and in various types of cancer.
Pelargonic acid, or nonanoic acid, is a fatty acid which occurs naturally as esters is the oil of pelargonium. Synthetic esters, such as methyl nonanoate, are used as flavorings. Pelargonic acid is an organic compound composed of a nine-carbon chain terminating in a carboxylic acid. It is an oily liquid with an unpleasant, rancid odor. It is nearly insoluble in water, but well soluble in chloroform and ether. The derivative 4-nonanoylmorpholine is an ingredient in some pepper sprays.
Stearoylcarnitine, also known as acylcarnitine C18:0, is a fatty ester lipid molecule. It is found in significantly greater amounts of patients with carnitine palmitoyltransferase (CPT) II deficiency when compared to controls (PMID:15653102). Stearoylcarnitine is also found to be associated with celiac disease, another inborn error of metabolism. The carnitine palmitoyltransferase (CPT; EC 2.3.1.21) enzyme system, in conjunction with acyl-CoA synthetase and carnitine/acylcarnitine translocase, provides the mechanism whereby long-chain fatty acids are transferred from the cytosol to the mitochondrial matrix to undergo beta-oxidation (OMIM: 600650). Stearoylcarnitine is considered to be practically insoluble in water and acidic.
Rhamnose (Rham) is a naturally occurring deoxy sugar. It can be classified as either a methyl-pentose or a 6-deoxy-hexose. Rhamnose occurs in nature in its L-form as L-rhamnose (6-deoxy-L-mannose). This is unusual, since most of the naturally occurring sugars are in D-form. Rhamnose is commonly bound to other sugars in nature. It is a common glycone component of glycosides from many plants. Rhamnose is also a component of the outer cell membrane of certain bacteria. L-rhamnose is metabolized to L-Lactaldehyde, which is a branching point in the metabolic pathway of L-fucose and L-rhamnose utilization. It exists in two anomeric forms, alpha-L-rhamnose and beta-L-rhamnose. Rhamnose has been found in Klebsiella, Pseudomonas (https://link.springer.com/article/10.1007/BF00369505) (https://onlinelibrary.wiley.com/doi/abs/10.1002/ejlt.200300816).
Pyridinoline is a breakdown product of bone collagen. It can be used as a bone marker to measure osteoclastic activity.
beta-Sitosterol, a main dietary phytosterol found in plants, may have the potential for prevention and therapy for human cancer. Phytosterols are plant sterols found in foods such as oils, nuts, and vegetables. Phytosterols, in the same way as cholesterol, contain a double bond and are susceptible to oxidation, and are characterized by anti-carcinogenic and anti-atherogenic properties (PMID:13129445, 11432711). beta-Sitosterol is a phytopharmacological extract containing a mixture of phytosterols, with smaller amounts of other sterols, bonded with glucosides. These phytosterols are commonly derived from the South African star grass, Hypoxis rooperi, or from species of Pinus and Picea. The purported active constituent is termed beta-sitosterol. Additionally, the quantity of beta-sitosterol-beta-D-glucoside is often reported. Although the exact mechanism of action of beta-sitosterols is unknown, it may be related to cholesterol metabolism or anti-inflammatory effects (via interference with prostaglandin metabolism). Compared with placebo, beta-sitosterol improved urinary symptom scores and flow measures (PMID:10368239). A plant food-based diet modifies the serum beta-sitosterol concentration in hyperandrogenic postmenopausal women. This finding indicates that beta-sitosterol can be used as a biomarker of exposure in observational studies or as a compliance indicator in dietary intervention studies of cancer prevention (PMID:14652381). beta-Sitosterol induces apoptosis and activates key caspases in MDA-MB-231 human breast cancer cells (PMID:12579296).
N-Acetyl-b-D-galactosamine is an oligosaccharide residue found in the lining and glandular epithelium, the stroma and the vessels (capillary and large vessels of the human postmenopausal endometrium. (PMID: 8930627). It is suspected that N-Acetyl-b-D-galactosamine is a molecule that binds to IgA in the glomerular mesangium in Henoch-Schoenlein purpura associated nephropathy (the most common vasculitis of childhood). (PMID: 10732728).
Measurement of this acid in the urine after oral administration of histidine provides the basis for the diagnostic test of folic acid deficiency and of megaloblastic anemia of pregnancy.
Nicotinamide riboside is involved in nicotinate and nicotinamide metabolism. Nicotinamide riboside was originally identified as a nutrient in milk. It is a useful compound for the elevation of NAD+ levels in humans. Nicotinamide riboside has recently been discovered to be an NAD(+) precursor that is converted into nicotinamide mononucleotide by specific nicotinamide riboside kinases, Nrk1 and Nrk2. It has been shown that exogenous nicotinamide riboside promotes Sir2-dependent repression of recombination, improves gene silencing, and extends the lifespan of certain animal models without calorie restriction (PMID: 17482543). Supplementation in mammalian cells and mouse tissues increases NAD(+) levels and activates SIRT1 and SIRT3, culminating in enhanced oxidative metabolism and protection against high-fat diet-induced metabolic abnormalities (PMID: 22682224). Recent data suggest that nicotinamide riboside may be the only vitamin precursor that supports neuronal NAD+ synthesis (PMID: 18429699). Nicotinamide riboside kinase has an essential role in the phosphorylation of nicotinamide riboside and the cancer drug tiazofurin (PMID: 15137942).
N-alpha-Acetyl-L-citrulline, also known as N-acetylcitrulline, is an N-acetylated metabolite of citrulline that is part of the arginine biosynthetic pathway. Arginine biosynthesis is notable for its complexity and variability at the genetic level, and by its connection with several other pathways, such as pyrimidine and polyamine biosynthesis, and certain degradative pathways. The initial steps of the arginine biosynthetic pathways proceed via N-acetylated intermediates. The presumed reason for this is that the acetylation prevents the spontaneous cyclization of glutamate derivatives, which leads to proline biosynthesis. N-acetyl-L-ornithine can be transcarbamylated directly by the enzyme acetylornithine transcarbamylase, resulting in N-acetyl-L-citrulline. The enzyme acetylornithine deacetylase can accept N-acetyl-L-citrulline as a substrate and can deacetylate it into citrulline. N-alpha-Acetyl-L-citrulline is found in cases of deficiency of the urea cycle enzyme argininosuccinate synthase (EC 6.3.4.5) that leads to increased concentrations of citrulline and N-acetylcitrulline in the urine (PMID: 14633929).
Pimelic acid, also known as heptanedioic acid is a dicarboxylic acid.  Derivatives of pimelic acid are involved in the biosynthesis of the amino acid called lysine. Pimelic acid is one methylene longer than a related dicarboxylic acid, adipic acid, a precursor to many polyesters and polyamides. Pimelic acid is essential for the synthesis of biotin (also called vitamin B7). Biotin is a heterocyclic, S-containing monocarboxylic acid that is made from two precursors, alanine and pimeloyl-CoA. Biotin is important in fatty acid synthesis, branched-chain amino acid catabolism, and gluconeogenesis. Biotin is found in a wide range of foods. Likewise, intestinal bacteria synthesize biotin, which is then absorbed by the host animal. Pimelic acid (which is the precursor for pimeloyl-CoA) is synthesized in many bacteria via a head-to-tail incorporation of acetate units through a modified fatty acid synthetic pathway using O-methyl esters disguised to resemble the canonical intermediates of the fatty acid synthetic pathway (PMID:21435937). Some bacteria and yeast synthesize pimelic acid not by biosynthesis, but via cleavage of longer chain fatty acids (such as linolenic acid) via a cytochrome P450-like enzyme (PMID:28196402, 21435937, 3236079). Pimelic acid is excreted in elevated amounts in the urine of individuals with mitochondrial beta-oxidation disorders and peroxisomal beta oxidation disorders (PMID:1527989)
Monomethyl glutaric acid, also known as 4-(methoxycarbonyl)butyrate or 2-methyleneglutarate, belongs to the class of organic compounds known as fatty acid methyl esters. Fatty acid methyl esters are compounds containing a fatty acid that is esterified with a methyl group. They have the general structure RC(=O)OR', where R=fatty aliphatic tail or organyl group and R'=methyl group.
Methylhippuric acid is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction: acyl-CoA + glycine < -- > CoA + N-acylglycine. Methylhippuric acid is a metabolite of xylene which is an aromatic hydrocarbon widely used as a solvant. The amount of methylhippuric acid can be measured in urine of workers exposed to xylene (PMID 8689499).
Phenylpropionylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction: acyl-CoA + glycine < -- > CoA + N-acylglycine. The detection of phenylpropionylglycine in urine after an oral load of phenylpropionic acid can be used to diagnose deficiency of medium-chain acyl-CoA dehydrogenase, a frequent and treatable metabolic defect. (PMID 9234867).
Isopropyl alcohol, also known as isopropanol or 1-methylethanol, belongs to the class of organic compounds known as secondary alcohols. Secondary alcohols are compounds containing a secondary alcohol functional group, with the general structure HOC(R)(R') (R,R'=alkyl, aryl). It is used in the manufacture of acetone and its derivatives and as a solvent. Isopropyl alcohol exists in all living species, ranging from bacteria to humans. Isopropyl alcohol is an alcohol, bitter, and musty tasting compound. Isopropyl alcohol has also been detected, but not quantified in several different foods, such as papaya, roselles, apples, sweet cherries, and allium (onion). Isopropyl alcohol is an isomer of 1-propanol and is considered as a potentially toxic compound. Topically, it is used as an antiseptic. It is a colorless liquid having disinfectant properties.
A bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Ribonic acid (CAS: 17812-24-7) is a product of the enzyme ribose 1-dehydrogenase (NADP+) [EC 1.1.1.115] (KEGG).
Xylulose 5-phosphate (Xu-5-P) is a metabolite of the hexose monophosphate pathway that activates protein phosphatase 2A to mediate the acute effects of carbohydrate feeding on the glycolytic pathway, as well as the coordinate long-term control of the enzymes required for fatty acid and triglyceride synthesis. Xu-5-P is the signal for the coordinated control of lipogenesis. Feeding carbohydrate causes levels of liver glucose, Glucose-6-phosphate (Glc-6-P), and Fructose-6-phosphate (Fru-6-P) to rise. Elevation of Fru-6-P leads to elevation of Xu-5-P in reactions catalyzed by the near-equilibrium isomerases of the nonoxidative portion of the hexose monophosphate pathway (ribulose 5-phosphate (Ru5P) epimerase [EC 5.1.3.1], ribose 5-phosphate (Rib5P) isomerase [EC 5.3.1.6], transaldolase [EC 2.2.1.2], and transketolase [EC 2.2.1.1]). The elevation of Xu-5-P is the coordinating signal that both acutely activates phosphofructokinase [PFK; EC 2.7.1.11] in glycolysis and promotes the action of the transcription factor carbohydrate responsive element binding protein (ChREBP) to increase transcription of the genes for the enzymes of lipogenesis, the hexose monophosphate shunt, and glycolysis, all of which are required for the de novo synthesis of fat. (PMID 12721358).
Uroporphyrin is the porphyrin produced by oxidation of the methylene bridges in uroporphyrinogen. They have four acetic acid and four propionic acid side chains attached to the pyrrole rings. Uroporphyrinogen I and III are formed from polypyrryl methane in the presence of uroporphyrinogen III cosynthetase and uroporphyrin I synthetase, respectively. They can yield uroporphyrins by autooxidation or coproporphyrinogens by decarboxylation. Excessive amounts of uroporphyrin I are excreted in congenital erythropoietic porphyria, and both types I and III are excreted in porphyria cutanea tarda. Uroporphyrin I and III are the most common isomemrs. Uroporphyrin II is a rare isomer.
Histamine is an amine derived by enzymatic decarboxylation of histidine. It is a powerful stimulant of gastric secretion, a constrictor of bronchial smooth muscle, a vasodilator, and also a centrally acting neurotransmitter. Histamine can be found in Photobacterium phosphoreum and Lactobacillus (PMID:17066936). Histamine belongs to the class of organic compounds known as 2-arylethylamines. These are primary amines that have the general formula RCCNH2, where R is an organic group. High amounts of histamine have been found in spinach, oats and ryes. Another foods such as green beans, broccoli, and beetroots also contain histamine but in lower concentrations. Histamine has also been detected but not quantified in several different foods, such as groundcherries, carobs, bok choy, biscuits, and longans.
5alpha-Cholestanone, also known as 5α-cholestanone, belongs to the class of organic compounds known as cholesterols and derivatives. Cholesterols and derivatives are compounds containing a 3-hydroxylated cholestane core. Thus, 5alpha-cholestanone is considered to be a sterol lipid molecule. 5alpha-Cholestanone is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
Tetradecanedioic acid, also known as 1,14-tetradecanedioate or NSC 9504, belongs to the class of organic compounds known as long-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 13 and 21 carbon atoms. Tetradecanedioic acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
4-Methylcatechol, also known as homocatechol or toluene-3,4-diol, belongs to the class of organic compounds known as catechols. Catechols are compounds containing a 1,2-benzenediol moiety. Outside of the human body, 4-Methylcatechol is found, on average, in the highest concentration within a few different foods such as coffee and cocoa powders and in a lower concentration in beers. 4-Methylcatechol has also been detected, but not quantified in eggplants. This could make 4-methylcatechol a potential biomarker for the consumption of these foods. Recent studies have suggested that a lack of brain-derived neurotrophic factor (BDNF) in the limbic system may cause neuropathic pain (PMID:22198556). It is both a substrate and a suicide inhibitor of catechol 2,3-dioxygenase (PMID:15006807). 4-Methylcatechol is a metabolite of homoprotocatechuic acid (PMID:4974346). 4-Methylcatechol is known to induce the production of BDNF.
Tauroursodeoxycholic acid is a bile acid also known as TUDCA formed in the liver by conjugation of deoxycholate with taurine, usually as the sodium salt. TUDCA is able to prevent apoptosis and protect mitochondria from cellular elements that would otherwise interfere with energy production. One of these elements is a protein called Bax. TUDCA plays an important role in preventing Bax from being transported to the mitochondria. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Trigonelline, also known as caffearin or gynesine, belongs to the class of organic compounds known as alkaloids and derivatives. These are naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen, sulfur and more rarely other elements such as chlorine, bromine, and phosphorus. It is also found in coffee, where it may help to prevent dental caries by preventing the bacteria Streptococcus mutans from adhering to teeth. Trigonelline is an alkaloid with chemical formula C7H7NO2 and CAS number 535-83-1. Trigonelline is a product of the metabolism of niacin (vitamin B3) which is excreted in the urine. High amounts of trigonelline have been found in arabica coffee, fenugreeks, and common peas. Another foods such as yellow bell peppers, orange bellpeppers and muskmelons also contain trigonelline but in lower concentrations. Trigonelline has also been detected but not quantified in several different foods, such as rices, triticales, alfalfa, cereals and cereal products, and ryes. Trigonelline in the urine is a biomarker for the consumption of coffee, legumes and soy products.
Umanopterin is a pteridine derivative. It is identified in body fluids. An elevated level of umanopterin is associated with immune system activation, malignant diseases, allograft rejection, and viral infections (http://www.online-medical-dictionary.org/).
Ergosterol, also known as provitamin D2, belongs to the class of organic compounds known as ergosterols and derivatives. These are steroids containing ergosta-5,7,22-trien-3beta-ol or a derivative thereof, which is based on the 3beta-hydroxylated ergostane skeleton. Thus, ergosterol is considered to be a sterol lipid molecule. Ergosterol is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Ergosterol is the biological precursor to vitamin D2. It is turned into viosterol by ultraviolet light, and is then converted into ergocalciferol, which is a form of vitamin D. Ergosterol is a component of fungal cell membranes, serving the same function that cholesterol serves in animal cells. Ergosterol is not found in mammalian cell membranes.
The neurosteroid allotetrahydrodeoxycorticosterone (THDOC) is an allosteric modulator of the GABA(A) receptor. Although the role of THDOC within the brain is undefined, recent studies indicate that stress induces THDOC to levels that can activate GABA(A) receptors. These results might have significant implications for human stress-sensitive conditions such as epilepsy, post-traumatic stress disorder and depression. (PMID 12628349).
Xanthurenic acid, also known as xanthurenate or 8-hydroxykynurenic acid, is a member of the class of compounds known as quinoline carboxylic acids. Quinoline carboxylic acids are quinolines in which the quinoline ring system is substituted by a carboxyl group at one or more positions. Xanthurenic acid is slightly soluble (in water). Xanthurenic acid can be found primarily in blood, feces, and urine, as well as in human epidermis tissue. Within the cell, xanthurenic acid is primarily located in the membrane. Xanthurenic acid exists in all eukaryotes, ranging from yeast to humans. In humans, xanthurenic acid is involved in the tryptophan metabolism. Moreover, xanthurenic acid is found to be associated with citrullinemia type I, which is an inborn error of metabolism. Xanthurenic acid is a metabolite from tryptophan catabolism. It is a substrate of the enzyme methyltransferases (EC 2.1.1.-) in pathway tryptophan metabolism (KEGG).
Ribothymidine is an endogenous methylated nucleoside found in human fluids; methylated purine bases are present in higher amounts in tumor-bearing patients compared to healthy controls.DNA hypermethylation is a common finding in malignant cells and has been explored as a therapeutic target for hypomethylating agents. When chemical bonds to DNA, the DNA becomes damaged and proper and complete replication cannot occur to make the normal intended cell. A DNA adduct is an abnormal piece of DNA covalently-bonded to a cancer-causing chemical. This has shown to be the start of a cancerous cell, or carcinogenesis. DNA adducts in scientific experiments are used as bio-markers and as such are themselves measured to reflect quantitatively, for comparison, the amount of cancer in the subject. (PMID:3506820, 17044778, 17264127, 16799933).
CE(16:0), also known as cholesteryl palmitic acid, is a cholesteryl ester. A cholesteryl ester is an ester of cholesterol. Fatty acid esters of cholesterol constitute about two-thirds of the cholesterol in the plasma. Cholesterol is a sterol (a combination of steroid and alcohol) and a lipid found in the cell membranes of all body tissues and transported in the blood plasma of all animals. The accumulation of cholesterol esters in the arterial intima (the innermost layer of an artery, in direct contact with the flowing blood) is a characteristic feature of atherosclerosis. Atherosclerosis is a disease affecting arterial blood vessels. It is a chronic inflammatory response in the walls of arteries, in large part to the deposition of lipoproteins (plasma proteins that carry cholesterol and triglycerides). CE(16:0) may also accumulate in hereditary hypercholesterolemia, an inborn error of metabolism. Cholesteryl palmitate is one of the four important lipids found in the tear film. Amniotic fluid cholesteryl palmitate, as measured by thin-layer chromatography, appears to be a very sensitive and specific predictor for the risk of respiratory distress syndrome (RDS) in newborns of normal pregnancies (PMID:3405552, 16922549).
Hemin is an iron containing metalloporphyrin. Specifically, the Fe3+ oxidation product of heme is termed hemin. Hemin acts as a feed-back inhibitor on ALA synthase. Hemin also inhibits transport of ALA synthase from the cytosol (its' site of synthesis) into the mitochondria (its' site of action) as well as represses synthesis of the enzyme. Hemin is also known as a drug that is derived from processed red blood cells. Hemin for injection was known previously as hematin.
Undecanedioic acid has been found in parts of human aortas with advanced atherosclerotic lesions associated with intercellular matrix macromolecules and specifically with elastin, and may be the result of an increased hydrolysis of esters and (or) a decreased esterification. (PMID:131675). Undecanedioic acid has been found (among other unusual dicarboxylic acids) in the urine from patients under hopantenate therapy during episodes of Reye's-like syndrome. (PMID:2331533).
Tauroursocholic acid is a bile acid formed in the liver by conjugation of deoxycholate with taurine, usually as the sodium salt. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Uroporphyrin is the porphyrin produced by oxidation of the methylene bridges in uroporphyrinogen. They have four acetic acid and four propionic acid side chains attached to the pyrrole rings. Uroporphyrinogen I and III are formed from polypyrryl methane in the presence of uroporphyrinogen III cosynthetase and uroporphyrin I synthetase, respectively. They can yield uroporphyrins by autooxidation or coproporphyrinogens by decarboxylation. Excessive amounts of uroporphyrin I are excreted in congenital erythropoietic porphyria, and both types I and III are excreted in porphyria cutanea tarda. Uroporphyrin I and III are the most common isomemrs. Uroporphyrin IV is a rare isomer; Formed together with the other Uroporphyrin isomers by the nonenzymic acid-catalysed polymerisation and oxidation of Porphobilinogen (Combined Chemical Dictionary).
Suberic acid, also octanedioic acid, is a dicarboxylic acid, with formula C6H12(COOH)2. It is present in the urine of patients with fatty acid oxidation disorders (PMID 10404733). A metabolic breakdown product derived from oleic acid. Elevated levels of this unstaruated dicarboxylic acid are found in individuals with medium-chain acyl-CoA dehydrogenase deficiency (MCAD). Suberic acid is also found to be associated with carnitine-acylcarnitine translocase deficiency, malonyl-Coa decarboxylase deficiency, which are also inborn errors of metabolism.
Vinylacetylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction:. acyl-CoA + glycine < -- > CoA + N-acylglycine. Vinylacetylglycine is a human metabolite that had been identified in a GC/MS urine screen. Increased amounts of this metabolite in the urine has been linked to a metabolomic disorder termed Isovaleric acidemia. (Gas-Chromatographic Method of Analysis for Urinary Organic Acids. I. Retention indices of 155 metaboically Important Compounds; Kay Tanaka, David G. Hine, Agnes West-Dull, and Theodore B. Lynn.).
Taurodeoxycholic acid is a bile salt formed in the liver by conjugation of deoxycholate with taurine, usually as the sodium salt. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID:11316487, 16037564, 12576301, 11907135). Taurodeoxycholic acid can be found in Escherichia (PMID:30736766).
7-Methylguanine is a metabolite of DNA methylation and depurination observed in normal human biofluids; however, it has been found significantly higher in the urine of smokers than in nonsmokers. (PMID 16059882). 7-Methylguanine has been identified in the human placenta (PMID: 32033212).
1-Methylhistamine, also known as H137, belongs to the class of organic compounds known as 2-arylethylamines. These are primary amines that have the general formula RCCNH2, where R is an organic group. 1-Methylhistamine exists in all living organisms, ranging from bacteria to humans. Within humans, 1-methylhistamine participates in a number of enzymatic reactions. In particular, S-adenosylhomocysteine and 1-methylhistamine can be biosynthesized from S-adenosylmethionine and histamine; which is mediated by the enzyme histamine N-methyltransferase. In addition, 1-methylhistamine can be converted into methylimidazole acetaldehyde through its interaction with the enzyme amine oxidase [flavin-containing] a. In humans, 1-methylhistamine is involved in histidine metabolism. 1-Methylhistamine is a potentially toxic compound.
Androstanedione belongs to the class of organic compounds known as androgens and derivatives. These are 3-hydroxylated C19 steroid hormones. They are known to favor the development of masculine characteristics. They also show profound effects on scalp and body hair in humans. Thus, androstanedione is considered to be a steroid lipid molecule. Androstanedione is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
Ergocalciferol is a form of Vitamin D, also called vitamin D2. It is created from viosterol, which in turn is created when ultraviolet light activates ergosterol. Ergocalciferol is used in the treatment of hypcalcemia and in dialysis-dependent renal failure. Ergoalcifediol is a fat soluble steroid hormone precursor of vitamin D that contributes to the maintenance of normal levels of calcium and phosphorus in the bloodstream. Vitamin D2 is the form of vitamin D most commonly added to foods and nutritional supplements. Vitamin D2 must be transformed (hydroxylated) into one of two active forms via the liver or kidney. Once transformed, it binds to the vitamin D receptor that then leads to a variety of regulatory roles.
Valproic acid glucuronide is the glucuronidation product of valproic acid. Valproic acid, or 2-Propylpentanoic acid, is a chemical compound that has found clinical use as an anticonvulsant and mood-stabilizing drug, primarily in the treatment of epilepsy and bipolar disorder, but also used to treat migraine headaches and schizophrenia. In epileptics, valproic acid is used to control absence seizures, tonic-clonic seizures (grand mal), complex partial seizures, and the seizures associated with Lennox-Gastaut syndrome. Glucuronidation is a vital phase 2 metabolic (conjugative) process by which a wide range of drugs and other xenobiotics may be rendered water-soluble, detoxified and excreted. Acyl (ester) glucuronides (AGs) of carboxylic acids are potentially reactive metabolites. In particular, AGs are important phase 2 metabolites for a wide range of carboxylic acid-containing drugs. (PMID: 18201150, 17496767, 17496206).
NAD (or nicotinamide adenine dinucleotide) is used extensively in glycolysis and the citric acid cycle of cellular respiration. The reducing potential stored in NADH can be either converted into ATP through the electron transport chain or used for anabolic metabolism. ATP "energy" is necessary for an organism to live. Green plants obtain ATP through photosynthesis, while other organisms obtain it via cellular respiration (Wikipedia). NAD is a coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by a pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH) (Dorland, 27th ed).
Cortisol is a corticosteroid hormone that is involved in the response to stress; it increases blood pressure and blood sugar levels and suppresses the immune system. Synthetic cortisol, also known as hydrocortisone, is used as a drug mainly to fight allergies and inflammation. -- Wikipedia; As an oral or injectable drug, cortisol is also known as hydrocortisone. It is used as an immunosuppressive drug, given by injection in the treatment of severe allergic reactions such as anaphylaxis and angioedema, in place of prednisolone in patients who need steroid treatment but cannot take oral medication, and peri-operatively in patients on long-term steroid treatment to prevent an Addisonian crisis. -- Wikipedia.
Deoxyadenosine monophosphate (dAMP), also known as deoxyadenylic acid or deoxyadenylate in its conjugate acid and conjugate base forms, respectively, is a derivative of the common nucleic acid AMP, or adenosine monophosphate, in which the -OH (hydroxyl) group on the 2' carbon on the nucleotide's pentose has been reduced to just a hydrogen atom (hence the "deoxy-" part of the name). Additionally, the monophosphate of the name indicates that two of the phosphoryl groups of GTP have been removed, most likely by hydrolysis. It is a monomer used in DNA.
Sulfolithocholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID:11316487, 16037564, 12576301, 11907135).
5alpha-Cholestanol, also known as cholestanol or dihydrocholesterol, belongs to the class of organic compounds known as cholesterols and derivatives. Cholesterols and derivatives are compounds containing a 3-hydroxylated cholestane core. Thus, 5alpha-cholestanol is considered to be a sterol lipid molecule. 5alpha-Cholestanol is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. 5alpha-Cholestanol is a potentially toxic compound.
trans-4-hydroxycyclohexylacetic acid is a tyrosine metabolite that has been found in the urine of a patient with a defect of 4-hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27), an inborn error of metabolism. (PMID: 701419, 719903).
Tridecanoic acid, also known as N-tridecanoate or C13:0, belongs to the class of organic compounds known as long-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 13 and 21 carbon atoms. Tridecanoic acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. Tridecanoic acid is a potentially toxic compound.
Succinyladenosine (SAdo) is one of the dephosphorylated enzyme substrate that accumulates in body fluids of patients with adenylosuccinate lyase (ADSL) deficiency, the other being 5-amino-4-imidazole-N-succinocarboxamide riboside (SAICAr). ADSL is an inherited metabolic disease characterized by various degrees of psychomotor retardation (PMID 15902552). The severity of the clinical presentation correlates with a low S-Ado/SAICAr ratio in body fluids (PMID: 15571235). Normally Succinyladenosine is not found in blood or CSF but may be detected in trace amounts in urine (OMIM 103050). Succinyladenosine is also found to be associated with fumarase deficiency, another inborn error of metabolism.
Vanillactic acid, also known as vanillactate or VLA, belongs to the class of organic compounds known as phenylpropanoic acids. Phenylpropanoic acids are compounds with a structure containing a benzene ring conjugated to a propanoic acid. Vanillactic acid is a potentially toxic compound. Vanillactic acid has been linked to the inborn metabolic disorders including aromatic l-amino acid decarboxylase deficiency. Vanillactic acid is an acidic catecholamine metabolite present in normal human urine (PMID 7524950), in normal human CSF (PMID 7914240), and increased in the CSF of newborns with neonatal epileptic encephalopathy mimicking aromatic L-amino acid decarboxylase deficiency (PMID 12200739).
Uroporphyrin is the porphyrin produced by oxidation of the methylene bridges in uroporphyrinogen. Uroporphyrins have four acetic acid and four propionic acid side chains attached to their pyrrole rings. The enzyme uroporphyrinogen I synthase catalyzes the formation of hydroxymethylbilane from four molecules of porphobilinogen. Uroporphyrinogen III cosynthase then catalyzes the conversion of hydroxymethylbilane into uroporphyrinogen III. Otherwise, hydroxymethylbilane cyclizes nonenzymatically to form uroporphyrinogen I. Uroporphyrinogen I and III yield their respective uroporphyrins via autooxidation or their respective coproporphyrinogens via decarboxylation. Excessive amounts of uroporphyrin I are excreted in congenital erythropoietic porphyria, and both uroporphyrin I and uroporphyrin III are excreted in porphyria cutanea tarda. Uroporphyrin I and III are the most common isomers. Under certain conditions, uroporphyrin III can act as a phototoxin, a neurotoxin, and a metabotoxin. A phototoxin leads to cell damage upon exposure to light. A neurotoxin causes damage to nerve cells and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of porphyrins are associated with porphyrias such as porphyria variegate, acute intermittent porphyria, porphyria cutanea tarda, and hereditary coproporphyria (HCP). There are several types of porphyrias (most are inherited). Hepatic porphyrias are characterized by acute neurological attacks (seizures, psychosis, extreme back and abdominal pain, and an acute polyneuropathy), while the erythropoietic forms present with skin problems (usually a light-sensitive blistering rash and increased hair growth). The neurotoxicity of porphyrins may be due to their selective interactions with tubulin, which disrupt microtubule formation and cause neural malformations (PMID: 3441503).
Ursocholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135). Ursocholic acid is the 7 beta-hydroxyepimer of cholic acid. It induces a reduction of bile cholesterol saturation.
Cholesteryl oleate is an ester of cholesterol. Fatty acid esters of cholesterol constitute about two-thirds of the cholesterol in the plasma. Cholesterol is a sterol (a combination steroid and alcohol) and a lipid found in the cell membranes of all body tissues, and transported in the blood plasma of all animals. The accumulation of cholesterol esters in the arterial intima (the innermost layer of an artery, in direct contact with the flowing blood) is a characteristic feature of atherosclerosis. Atherosclerosis is a disease affecting arterial blood vessels. It is a chronic inflammatory response in the walls of arteries, in large part to the deposition of lipoproteins (plasma proteins that carry cholesterol and triglycerides). Cholesteryl esters, formed by the esterification of cholesterol with long-chain fatty acids, on one hand, are the means by which cholesterol is transported through the blood by lipoproteins, on the other, the way cholesterol itself can be accumulated in the cells. (PMID: 15939411).
Progesterone is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other species. Progesterone belongs to a class of hormones called progestagens, and is the major naturally occurring human progestagen. Progesterone's reproductive function serves to convert the endometrium to its secretory stage to prepare the uterus for implantation. If pregnancy does not occur, progesterone levels will decrease leading to menstruation in the human. Normal menstrual bleeding is a progesterone withdrawal bleeding. During implantation and gestation, progesterone appears to decrease the maternal immune response to allow for the acceptance of the pregnancy. Progesterone decreases contractility of the uterine musculature. The fetus metabolizes placental progesterone in the production of adrenal mineralo- and glucosteroids. A drop in progesterone levels is possibly one step that facilitates the onset of labor. In addition, progesterone inhibits lactation during pregnancy. The fall in progesterone levels following delivery is one of the triggers for milk production. Progesterone has an effect upon vaginal epithelium and cervical mucus.
Cholestenone belongs to the class of organic compounds known as cholesterols and derivatives. Cholesterols and derivatives are compounds containing a 3-hydroxylated cholestane core. Thus, cholestenone is considered to be a sterol lipid molecule. Cholestenone is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
Taurallocholic acid, also known as taurallocholate, belongs to the class of organic compounds known as taurinated bile acids and derivatives. These are bile acid derivatives containing a taurine conjugated to the bile acid moiety. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Taurallocholic acid is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Taurallocholic acid is an ethanesulfonic acid derivative of cholane.
Pyridine is a clear liquid with an odor that is sour, putrid, and fish-like. It is a relatively simple heterocyclic aromatic organic compound that is structurally related to benzene, with one CH group in the six-membered ring replaced by a nitrogen atom. Pyridine is obtained from crude coal tar or is synthesized from acetaldehyde, formaldehyde and ammonia. Pyridine is often used as a denaturant for antifreeze mixtures, for ethyl alcohol, for fungicides, and as a dyeing aid for textiles. It is a harmful substance if inhaled, ingested or absorbed through the skin. In particular, it is known to reduce male fertility and is considered carcinogenic. Common symptoms of acute exposure to pyridine include: headache, coughing, asthmatic breathing, laryngitis, nausea and vomiting. -- Wikipedia.
Valerylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction:acyl-CoA + glycine < -- > CoA + N-acylglycineValerylglycine are identified based on their liquid chromatographic-atmospheric pressure chemical ionization mass spectra (LC-APCI-MS)(PMID:8548022).
trans-Cinnamic acid, also known as (e)-cinnamic acid or phenylacrylic acid, belongs to the class of organic compounds known as cinnamic acids. These are organic aromatic compounds containing a benzene and a carboxylic acid group forming 3-phenylprop-2-enoic acid. trans-Cinnamic acid exists in all living species, ranging from bacteria to humans. trans-Cinnamic acid is a sweet, balsam, and cinnamon tasting compound. Outside of the human body, trans-Cinnamic acid is found, on average, in the highest concentration within a few different foods, such as chinese cinnamons, olives, and lingonberries and in a lower concentration in redcurrants, red raspberries, and corianders. trans-Cinnamic acid has also been detected, but not quantified in several different foods, such as common oregano, pepper (spice), fennels, pomegranates, and european cranberries. This could make trans-cinnamic acid a potential biomarker for the consumption of these foods. Cinnamic acid has been shown to be a microbial metabolite; it can be found in Alcaligenes, Brevibacterium, Cellulomonas, and Pseudomonas (PMID:16349793). trans-Cinnamic acid is a potentially toxic compound.
Tauro-b-muricholic acid is a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135).
Traumatic acid is a monounsaturated dicarboxylic acid naturally ocurring in plants. The compound was first isolated from wounded bean plants by American chemists James English Jr. and James Frederick Bonner and Dutch scientist Aire Jan Haagen-Smit in 1939. Traumatic acid is a potent wound healing agent in plants ("wound hormone") that stimulates cell division near a trauma site to form a protective callus and to heal the damaged tissue. It may also act as a growth hormone, especially in inferior plants (e.g. algae). Traumatic acid is biosynthesized in plants by non-enzimatic oxidation of traumatin (12-oxo-trans-10-dodecanoic acid), another wound hormone. At normal conditions, traumatic acid is a solid, crystalized, water insoluble substance.
Uridine diphosphate, abbreviated UDP, is a nucleotide. It is an ester of pyrophosphoric acid with the nucleoside uridine. UDP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase uracil.
Uridine diphosphate glucuronic acid is a nucleoside diphosphate sugar which serves as a source of glucuronic acid for polysaccharide biosynthesis. It may also be epimerized to UDP Iduronic acid, which donates Iduronic acid to polysaccharides. In animals, UDP glucuronic acid is used for formation of many glucosiduronides with various aglycones. The transfer of glucuronic acid from UDP-alpha-D-glucuronic acid onto a terminal galactose residue is done by beta1,3-glucuronosyltransferases, responsible for the completion of the protein-glycosaminoglycan linkage region of proteoglycans and of the HNK1 epitope of glycoproteins and glycolipids. In humans the enzyme galactose-beta-1,3-glucuronosyltransferase I completes the synthesis of the common linker region of glycosaminoglycans (GAGs) by transferring glucuronic acid (GlcA) onto the terminal galactose of the glycopeptide primer of proteoglycans. The GAG chains of proteoglycans regulate major biological processes such as cell proliferation and recognition, extracellular matrix deposition, and morphogenesis. (PMID:16815917).
Uroporphyrin is the porphyrin produced by oxidation of the methylene bridges in uroporphyrinogen. Uroporphyrins have four acetic acid and four propionic acid side chains attached to their pyrrole rings. The enzyme uroporphyrinogen I synthase catalyzes the formation of hydroxymethylbilane from four molecules of porphobilinogen. Uroporphyrinogen III cosynthase then catalyzes the conversion of hydroxymethylbilane into uroporphyrinogen III. Otherwise, hydroxymethylbilane cyclizes nonenzymatically to form uroporphyrinogen I. Uroporphyrinogen I and III yield their respective uroporphyrins via autooxidation or their respective coproporphyrinogens via decarboxylation. Excessive amounts of uroporphyrin I are excreted in congenital erythropoietic porphyria, and both uroporphyrin I and uroporphyrin III are excreted in porphyria cutanea tarda. Uroporphyrin I and III are the most common isomers. Under certain conditions, uroporphyrin I can act as a phototoxin, a neurotoxin, and a metabotoxin. A phototoxin leads to cell damage upon exposure to light. A neurotoxin causes damage to nerve cells and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of porphyrins are associated with porphyrias such as porphyria variegate, acute intermittent porphyria, porphyria cutanea tarda, and hereditary coproporphyria (HCP). There are several types of porphyrias (most are inherited). Hepatic porphyrias are characterized by acute neurological attacks (seizures, psychosis, extreme back and abdominal pain, and an acute polyneuropathy), while the erythropoietic forms present with skin problems (usually a light-sensitive blistering rash and increased hair growth). The neurotoxicity of porphyrins may be due to their selective interactions with tubulin, which disrupt microtubule formation and cause neural malformations (PMID: 3441503).
Stigmasterol is a phytosterol, meaning it is steroid derived from plants. As a food additive, phytosterols have cholesterol-lowering properties (reducing cholesterol absorption in intestines), and may act in cancer prevention. Phytosterols naturally occur in small amount in vegetable oils, especially soybean oil. One such phytosterol complex, isolated from vegetable oil, is cholestatin, composed of campesterol, stigmasterol, and brassicasterol, and is marketed as a dietary supplement. Sterols can reduce cholesterol in human subjects by up to 15%. The mechanism behind phytosterols and the lowering of cholesterol occurs as follows : the incorporation of cholesterol into micelles in the gastrointestinal tract is inhibited, decreasing the overall amount of cholesterol absorbed. This may in turn help to control body total cholesterol levels, as well as modify HDL, LDL and TAG levels. Many margarines, butters, breakfast cereals and spreads are now enriched with phytosterols and marketed towards people with high cholesterol and a wish to lower it. Stigmasterol is found to be associated with phytosterolemia, which is an inborn error of metabolism.
Threonolactone is an oxidation product of the autoxidation reaction of L-ascorbic acid.
Cholestenes are derivatives of cholestanes which have a double bond. One of the most significant cholestenes is cholecalciferol. If there are two double bonds, the molecule is known as a "cholestadienes". Examples include fusidic acid, lanosterol, and stigmasterol.--Wikipedia.
Tetrahydroneopterin is a reduced form of neopterin.
Threonic acid, also known as threonate, belongs to the class of organic compounds known as sugar acids and derivatives. Sugar acids and derivatives are compounds containing a saccharide unit which bears a carboxylic acid group. Threonic acid is a sugar acid derived from threose. The L-isomer is a metabolite of ascorbic acid (vitamin C). One study suggested that because L-threonate inhibits DKK1 expression in vitro, it may have potential in the treatment of androgenic alopecia (PMID:21034532). Threonic acid is probably derived from glycated proteins or from degradation of ascorbic acid. It is a normal component in aqueous humour and blood (PMID:10420182). Threonic acid is a substrate of L-threonate 3-dehydrogenase (EC 1.1.1.129) in the ascorbate and aldarate metabolism pathway (KEGG). It has been found to be a microbial metabolite (PMID:20615997).
Behenic acid, also docosanoic acid, is a normal carboxylic acid, a fatty acid with formula C21H43COOH. It is an important constituent of the behen oil extracted from the seeds of the Ben-oil tree, and it is so named from the Persian month Bahman when the roots of this tree were harvested. Behenic acid has been identified in the human placenta (PMID:32033212).
Ursodeoxycholic acid, also known as ursodeoxycholate or acid deoxyursocholic, belongs to the class of organic compounds known as dihydroxy bile acids, alcohols and derivatives. Dihydroxy bile acids, alcohols and derivatives are compounds containing or derived from a bile acid or alcohol, and which bears exactly two carboxylic acid groups. Ursodeoxycholic acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
Undecanoic acid, also known as N-undecylic acid or N-undecanoate, belongs to the class of organic compounds known as medium-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 4 and 12 carbon atoms. Undecanoic acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. Undecanoic acid is a potentially toxic compound.
Tetrahydrocortisol is the most powerful natural angiostatic steroid. It is involved in C21-Steroid hormone metabolism pathway (KEGG).
Ceramides, also known as N-acylsphingosines, consist of a sphingoid base linked to a fatty acid chain via the amine group. Ceramides are one of the hydrolysis byproducts of sphingomyelin via the enzyme sphingomyelinase (sphingomyelin phosphorylcholine phosphohydrolase, E.C.3.1.4.12) which has been identified in the subcellular fractions of human epidermis and many other tissues (PMID: 25935). They can also be synthesized from serine and palmitate in a de novo pathway and are regarded as important cellular signals for inducing apoptosis (PMID: 14998372). Ceramides are key to the biosynthesis of glycosphingolipids and gangliosides. Cer(d18:1/23:0), in particular, consists of a monounsaturated 18-carbon dihydroxylated sphingoid base linked to one chain of tricosanoic acid. Cer(d18:1/23:0) has been identified in the stratum corneum by reversed-phase HPLC coupled with APPI–MS (PMID: 17027012). It has been found in human blood plasma by gas-liquid chromatography on high temperature polarizable capillary columns (PMID: 2755317, 8354950).
Taurochenodesoxycholic acid is a bile acid formed in the liver by conjugation of chenodeoxycholate with taurine, usually as the sodium salt. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g. membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues (PMID: 11316487, 16037564, 12576301, 11907135). Taurochenodesoxycholic acid has been found to be a microbial metabolite.
Suberylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction: acyl-CoA + glycine < -- > CoA + N-acylglycineSuberylglycine is a dicarboxylic acid. It is formed by glycine-N-acylase catalyzed conjugation (PMID 947635). It can be used for the diagnosis of hereditary medium-chain acyl-CoA dehydrogenase deficiency (PMID 2775902). Suberylglycine is found to be associated with propionic acidemia, which is an inborn error of metabolism.
trans-Ferulic acid is a highly abundant phenolic phytochemical which is present in plant cell walls. Ferulic acid is a phenolic acid that can be absorbed by the small intestine and excreted through the urine. It is one of the most abundant phenolic acids in plants, varying from 5 g/kg in wheat bran to 9 g/kg in sugar-beet pulp and 50 g/kg in corn kernel. It occurs primarily in seeds and leaves both in its free form (albeit rarely) and covalently linked to lignin and other biopolymers. It is usually found as ester cross-links with polysaccharides in the cell wall, such as arabinoxylans in grasses, pectin in spinach and sugar beet, and xyloglucans in bamboo. It also can cross-link with proteins. Due to its phenolic nucleus and an extended side chain conjugation (carbohydrates and proteins), it readily forms a resonance-stabilized phenoxy radical which accounts for its potent antioxidant potential. Food supplementation with curcumin and ferulic acid is considered a nutritional approach to reducing oxidative damage and amyloid pathology in Alzheimer disease (PMID:17127365, 1398220, 15453708, 9878519). Ferulic acid can be found in Pseudomonas and Saccharomyces (PMID:8395165).
Isoferulic acid (CAS: 537-73-5) is a chlorogenic acid (CGA). CGAs are formed by the esterification of hydroxycinnamic acids (e.g. caffeic acid, ferulic acid, and p-coumaric acid) with quinic acid. CGAs are abundant phenolic compounds in coffee, with caffeoylquinic (CQA), feruloylquinic (FQA), and dicaffeoylquinic (diCQA) acids being the major subclasses, and coffee is the most consumed food product in the world. Isoferulic acid is present in normal human urine in concentrations of 0.05-2.07 umol/mmol creatinine at baseline, and reaches 0.2-9.6 umol/mmol creatinine in four hours after a cup of coffee, with a large inter-individual variation (PMID:17884997).
Pyrocatechol, often known as catechol or benzene-1,2-diol, is a benzenediol, with formula C6H4(OH)2. It was first prepared in 1839 by H. Reinsch by distilling catechin (the juice of Mimosa catechu). This colourless compound occurs naturally, but about 20000 tons are manufactured each year, mainly as precursors to pesticides, flavors, and fragrances. Its sulfonic acid is often present in the urine of many mammals. Small amounts of catechol occur naturally in fruits and vegetables, along with the enzyme polyphenol oxidase. Upon mixing the enzyme with the substrate and exposure to oxygen (as when a potato or apple is cut), the colorless catechol oxidizes to reddish-brown benzoquinone derivatives. The enzyme is inactivated by adding an acid, such as lemon juice, or by refrigeration. Excluding oxygen also prevents the browning reaction. Catechol melts at 28 °C and boils at 250 °C. It is employed in medicine as an expectorant. The dimethyl ether or veratrol is also used in medicine. Many other pyrocatechin derivatives have been suggested for therapeutic application. Pyrocatechol has also been found to be a microbial metabolite in Escherichia, Mycobacterium and Pseudomonas (PMID:19300498; PMID:25281236).
trans-Aconitic acid, also known as trans-aconitate or (e)-aconitic acid, belongs to the class of organic compounds known as tricarboxylic acids and derivatives. These are carboxylic acids containing exactly three carboxyl groups. trans-Aconitic acid exists in all living species, ranging from bacteria to humans. trans-Aconitic acid is a dry, musty, and nut tasting compound. Outside of the human body, trans-aconitic acid has been detected, but not quantified in several different foods, such as garden tomato fruits, root vegetables, soy beans, and rices. trans-Aconitic acid is normally present in human urine, and it has been suggested that is present in larger amounts with Reye's syndrome and organic aciduria. trans-Aconitic acid in the urine is a biomarker for the consumption of soy products. trans-Aconitic acid is a substrate of enzyme trans-Aconitic acid 2-methyltransferase (EC2.1.1.144).
Tiglylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction: acyl-CoA + glycine < -- > CoA + N-acylglycine. Tiglylglycine is an intermediate product of the catabolism of isoleucine. An elevated level of tiglylglycine is identified in urine of patients with beta-ketothiolase deficiency or with disorders of propionate metabolism (PMID 7923765). Tiglyglycine is a biomarker for the consumption of cheese.
dGDP is a derivative of the common nucleic acid GTP, or guanosine triphosphate, in which the -OH (hydroxyl) group on the 2' carbon on the nucleotide's pentose has been removed (hence the deoxy- part of the name). Additionally, the diphosphate of the name indicates that one of the phosphoryl groups of GTP has been removed, most likely by hydrolysis (Wikipedia).
Farnesyl pyrophosphate is an intermediate in the HMG-CoA reductase pathway used by organisms in the biosynthesis of terpenes and terpenoids. -- Wikipedia.
Lipoamide is a trivial name for 6,8-dithiooctanoic amide. It is 6,8-dithiooctanoic acid's functional form where the carboxyl group is attached to protein (or any other amine) by an amide linkage (containing -NH2) to an amino group. Lipoamide forms a thioester bond, oxidizing the disulfide bond, with acetaldehyde (pyruvate after it has been decarboxylated). It then transfers the acetaldehyde group to CoA which can then continue in the TCA cycle. Lipoamide is an intermediate in glycolysis/gluconeogenesis, citrate cycle (TCA cycle), alanine, aspartate and pyruvate metabolism, and valine, leucine and isoleucine degradation (KEGG:C00248). It is generated from dihydrolipoamide via the enzyme dihydrolipoamide dehydrogenase (EC:1.8.1.4) and then converted to S-glutaryl-dihydrolipoamide via the enzyme oxoglutarate dehydrogenase (EC:1.2.4.2).
5-Methylthioribose 1-phosphate belongs to the class of organic compounds known as pentoses. These are monosaccharides in which the carbohydrate moiety contains five carbon atoms. 5-Methylthioribose 1-phosphate is an intermediate in methionine biosynthesis. It is converted from 5'-deoxy-5'-methylthioadenosine by 5'-deoxy-5'-methylthioadenosine phosphorylase. Then it is converted to methionine (PMID: 2153115). In the methionine salvage pathway, 5-methylthioribose 1-phosphate isomerase (M1Pi) catalyzes the conversion of 5-methylthioribose 1-phosphate (MTR-1-P) into 5-methylthioribulose 1-phosphate (MTRu-1-P).
Hypotaurine belongs to the class of organic compounds known as sulfinic acids. Sulfinic acids are compounds containing a sulfinic acid functional group, with the general structure RS(=O)OH (R = organyl, not H). Hypotaurine exists in all living species, ranging from bacteria to humans. Within humans, hypotaurine participates in a number of enzymatic reactions. In particular, hypotaurine can be biosynthesized from cysteamine; which is catalyzed by the enzyme 2-aminoethanethiol dioxygenase. In addition, hypotaurine can be biosynthesized from 3-sulfinoalanine through its interaction with the enzyme cysteine sulfinic acid decarboxylase. In humans, hypotaurine is involved in taurine and hypotaurine metabolism.
D-myo-Inositol 1,4-bisphosphate belongs to the class of organic compounds known as inositol phosphates. Inositol phosphates are compounds containing a phosphate group attached to an inositol (or cyclohexanehexol) moiety. D-myo-Inositol 1,4-bisphosphate is an extremely weak basic (essentially neutral) compound (based on its pKa). D-myo-Inositol 1,4-bisphosphate is a substrate for several proteins including inositol polyphosphate 1-phosphatase, phosphatidylinositol 4,5-bisphosphate 5-phosphatase A, skeletal muscle and kidney enriched inositol phosphatase, and type I inositol-1,4,5-trisphosphate 5-phosphatase.
1,25-Dihydroxyvitamin D3-26,23-lactone (1,25(OH)2D3-26,23-lactone) is a vitamin D3 metabolite. The formation of 1,25(OH)2D3-26,23-lactone occurs in normocalcemic states and in situations in which 1,25(OH)2D3 has been administered. (PMID: 6324253). 1,25-dihydroxyvitamin D3 and (23S)-1,23,25-trihydroxyvitamin D3 are efficient precursors to 1,25(OH)2D3-26,23-lactone. 1,25(OH)2D3-26,23-lactone has an inhibitory action of bone resorption and the lactone ring plays a major part in its expression. (PMID: 6548386, 1666030).
10-Formyltetrahydrofolate (10-CHO-THF) is form of tetrahydrofolate that acts as a donor of formyl groups in anabolism. In particular, 10-CHO-THF is used as a substrate in a number of formyltransferase reactions. It plays an important role in purine biosynthesis, where 10-CHO-THF is a substrate for phosphoribosylaminoimidazolecarboxamide formyltransferase, as well as in the formylation of the methionyl initiator tRNA (fMet-tRNA), when 10-CHO-THF is a substrate for methionyl-tRNA formyltransferase. 10-Formyltetrahydrofolate is a substrate for Trifunctional purine biosynthetic protein adenosine-3, Bifunctional methylenetetrahydrofolate dehydrogenase/cyclohydrolase (mitochondrial), 10-formyltetrahydrofolate dehydrogenase, Folylpolyglutamate synthase (mitochondrial), Bifunctional purine biosynthesis protein PURH and C-1-tetrahydrofolate synthase (cytoplasmic).
Trehalose, also known as mycose, is a 1-alpha (disaccharide) sugar found extensively but not abundantly in nature. It is thought to be implicated in anhydrobiosis - the ability of plants and animals to withstand prolonged periods of desiccation. The sugar is thought to form a gel phase as cells dehydrate, which prevents disruption of internal cell organelles by effectively splinting them in position. Rehydration then allows normal cellular activity to be resumed without the major, generally lethal damage that would normally follow a dehydration/reyhdration cycle. Trehalose is a non-reducing sugar formed from two glucose units joined by a 1-1 alpha bond giving it the name of alpha-D-glucopyranoglucopyranosyl-1,1-alpha-D-glucopyranoside. The bonding makes trehalose very resistant to acid hydrolysis, and therefore stable in solution at high temperatures even under acidic conditions. The bonding also keeps non-reducing sugars in closed-ring form, such that the aldehyde or ketone end-groups do not bind to the lysine or arginine residues of proteins (a process called glycation). The enzyme trehalase, present but not abundant in most people, breaks it into two glucose molecules, which can then be readily absorbed in the gut. Trehalose is an important components of insects circulating fluid. It acts as a storage form of insect circulating fluid and it is important in respiration. Trehalose has also been found to be a metabolite of Burkholderia, Escherichia and Propionibacterium (PMID:12105274; PMID:25479689) (krishikosh.egranth.ac.in/bitstream/1/84382/1/88571%20P-1257.pdf).
3-Hexaprenyl-4-hydroxy-5-methoxybenzoic acid is an intermediate in the biosynthesis of Ubiquinone. It is a substrate for Hexaprenyldihydroxybenzoate methyltransferase (mitochondrial).
4-(2-Aminophenyl)-2,4-dioxobutanoic acid is a substrate for Kynurenine/alpha-aminoadipate aminotransferase mitochondrial.
The biosynthesis of tetrahydrobiopterin (BH4) from dihydroneopterin triphosphate (NH2P3) was studied in human liver extract. The phosphate-eliminating enzyme (PEE) was purified approximately 750-fold. The conversion of NH2P3 to BH4 was catalyzed by this enzyme in the presence of partially purified sepiapterin reductase, Mg2+, and NADPH. The PEE is heat stable when heated at 80°C for 5 min. It has a molecular weight of 63 000 daltons. One possible intermediate 6-(1'-hydroxy-2'-oxopropyl)5,6,7,8-tetrahydropterin(2'-oxo-tetrahydropte rin) was formed upon incubation of BH4 in the presence of sepiapterin reductase and NADP+ at pH 9.0. The reduction of this compound with NaBD4 yielded monodeutero-, threo-, and erythro-BH4; the deuterium was incorporated at the 2' position. This and the UV spectra were consistent with a 2'-oxo-tetrahydropterin structure. Dihydrofolate reductase (DHFR) catalyzed the reduction of BH2 into BH4 and was found to be specific for the pro-R-NADPH side. The sepiapterin reductase catalyzed the transfer of the pro-S hydrogen of NADPH during the reduction of sepiapterin into BH2. In the presence of crude liver extracts, the conversion of NH2P3 into BH4 requires NADPH. Two deuterium atoms were incorporated from (4S-2H)NADHP in the 1' and 2' position of the BH4 side chain. The incorporation of one hydrogen from the solvent was found at position C(6). These results are consistent with the occurrence of an intramolecular redox exchange between the pteridine nucleus and the side chain and formation of 6-pyruvoyl-5,6,7,8-tetrahydropterin(tetrahydro-1'-2'-dioxopterin) as an intermediate (PMID: 3930838).
4a-Methyl-5a-cholesta-8,24-dien-3-one is an intermediate in the Cholesterol biosynthesis pathway, in a reaction catalyzed by the enzyme 3-keto-steroid reductase [EC 1.1.1.270]. (MetaCyc Pathway: cholesterol biosynthesis).
5-Methylcytidine belongs to the class of organic compounds known as pyrimidine nucleosides. Pyrimidine nucleosides are compounds comprising a pyrimidine base attached to a ribosyl or deoxyribosyl moiety.
Dihydrolipoamide is an intermediate in glycolysis/gluconeogenesis, citrate cycle (TCA cycle), alanine, aspartate and pyruvate metabolism, and valine, leucine and isoleucine degradation (KEGG ID C00579). It is converted to lipoamide via the enzyme dihydrolipoamide dehydrogenase [EC:1.8.1.4]. Dihydrolipoamide is also a substrate of enzyme Acyltransferases [EC 2.3.1.-]. (KEGG).
S-Adenosylmethioninamine is a biological sulfonium compound known as the major biological methyl donor. It is also a donor of methylene groups, amino groups, ribosyl groups and aminopropyl groups (PMID 15130560). S-Adenosylmethioninamine is a prodcut of enzyme adenosylmethionine decarboxylase [EC 4.1.1.50] in methionine metabolism pathway (KEGG).
DL-2-Aminooctanoic acid, also known as a-aminocaprylate or alpha-aminocaprylic acid, belongs to the class of organic compounds known as alpha amino acids. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). DL-2-Aminooctanoic acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. Outside of the human body, DL-2-Aminooctanoic acid has been detected, but not quantified in cow milk.
3-succinoylpyridine is the byproduct of tobacco-specific N-nitrosamines generated by the enzyme cytochrome P 450 which catalyzes methylnitrosaminopyridylbutanone hydroxylation. (PMID: 11368333). This nicotine metabolite is commonly found in the urine of smokers. (PMID: 14581070).
Dolichyl phosphate D-mannose (DPM) is an intermediate in the biosynthesis of N-glycans. It is a substrate for dolichol-phosphate mannosyltransferase (PMID: 10835346). Dolichol-phosphate mannosyltransferase is a heterotrimeric protein embedded in the endoplasmic reticulum membrane. The first subunit of the heterotrimer appears to be the actual catalyst, and the other two subunits appear to stabilize it. More specifically, dolichol-phosphate-mannose is the donor of mannose groups in the synthesis of the dolichol pyrophosphate-linked precursor oligosaccharide in asparagine-linked glycosylation, in the synthesis of glycosyl phosphatidylinositol (GPI) anchor precursors, in protein O-mannosylation and in protein C-mannosylation. Its synthesis proceeds in two steps. First, cytosolic GDP-mannose reacts with dolichol phosphate exposed on the cytosolic face of the endoplasmic reticulum membrane to form DPM with its mannose moiety oriented toward the cytosol. The DPM molecule then flips in the endoplasmic reticulum membrane, so that its mannose moiety is in the endoplasmic reticulum lumen, accessible to the enzymes that catalyze its transfer to growing glycolipids and glycoproteins. (PMID: 11102867). Dolichyl phosphate D-mannose is also a substrate for protein O-mannosyl-transferase 2 and protein O-mannosyl-transferase 1.
16-Dehydroprogesterone, also known as delta.16-progesterone, belongs to the class of organic compounds known as 20-oxosteroids. These are steroid derivatives carrying a C=O group at the 20-position of the steroid skeleton. Thus, 16-dehydroprogesterone is considered to be a steroid lipid molecule. 16-Dehydroprogesterone is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
3-Sulfinoalanine or cysteinesulfinic acid is an N-methyl-D-aspartate agonist. It is a product of cysteine dioxygenase or CDO (EC 1.13.11.20). In humans, cysteine catabolism is tightly regulated via regulation of cysteine dioxygenase (CDO) levels in the liver, with the turnover of CDO protein being dramatically decreased when intracellular cysteine levels increase. This occurs in response to changes in the intracellular cysteine concentration via changes in the rate of CDO ubiquitination and degradation. Expressed at high levels in the liver with lower levels in the kidney, brain, and lung, cysteine dioxygenase catalyzes the addition of molecular oxygen to the sulfhydryl group of cysteine, yielding cysteinesulfinic acid. The oxidative catabolism of cysteine to cysteinesulfinate by CDO represents an irreversible loss of cysteine from the free amino acid pool. Once generated, cysteinesulfinate is shuttled into several pathways including hypotaurine/taurine synthesis, sulfite/sulfate production, and the generation of pyruvate.
Deoxycytidine triphosphate (dCTP) is a cytidine nucleotide triphosphate that is used whenever DNA is synthesized, such as in the polymerase chain reaction. e.g.:.
Phosphoribosylformylglycinamidine, also known as formylglycinamidine ribonucleotide (FGAM), is a substrate for glucosamine-6-phosphate isomerase. Phosphoribosylformylglycinamidine is found in many foods, some of which are greenthread tea, cardamom, mulberry, and carrot.
dUDP is a derivative of nucleic acid UTP, in which the -OH (hydroxyl) group on the 2' carbon on the nucleotide's pentose has been removed (hence the deoxy- part of the name). Additionally, the diphosphate of the name indicates that one of the phosphoryl groups of UTP has been removed, most likely by hydrolysis (Wikipedia).
Adenosine phosphosulfate, also known as adenylylsulfate or adenosine sulfatophosphate, belongs to the class of organic compounds known as purine ribonucleoside monophosphates. These are nucleotides consisting of a purine base linked to a ribose to which one monophosphate group is attached. Adenosine phosphosulfate exists in all living species, ranging from bacteria to humans. Within humans, adenosine phosphosulfate participates in a number of enzymatic reactions. In particular, adenosine phosphosulfate can be biosynthesized from sulfate through the action of the enzyme bifunctional 3'-phosphoadenosine 5'-phosphosulfate synthase 2. In addition, adenosine phosphosulfate can be converted into phosphoadenosine phosphosulfate; which is catalyzed by the enzyme bifunctional 3'-phosphoadenosine 5'-phosphosulfate synthase 2. In humans, adenosine phosphosulfate is involved in sulfate/sulfite metabolism. Outside of the human body, Adenosine phosphosulfate has been detected, but not quantified in several different foods, such as chia, yardlong beans, swiss chards, sapodilla, and chicory leaves. This could make adenosine phosphosulfate a potential biomarker for the consumption of these foods. An adenosine 5'-phosphate having a sulfo group attached to one the phosphate OH groups.
Oxoamide is a metabolite of Cotinine, which is a major metabolite of Nicotine.
(S)-Ureidoglycolic acid is a substrate of enzyme ureidoglycolate dehydrogenase [EC 1.1.1.154] in purine metabolism pathway (KEGG).
3-Pyridinebutanoic acid is a nicotine degradation product. It can be formed from the hydration or reduction of 4-(3-pyridyl)-3-butenoate. 3-Pyridinebutanoic acid can decompose to 3-Pyridylacetate.
Biliverdin is a green pigment formed as a byproduct of hemoglobin breakdown. It consists of four linearly connected pyrrole rings (a tetrapyrrole). Biliverdin is formed when the heme group in hemoglobin is cleaved at its alpha-methene bridge. The resulting biliverdin is then reduced to bilirubin, a yellow pigment, by the enzyme biliverdin reductase. The changing color of a bruise from deep purple to yellow over time is a graphical indicator of this reaction. Biliverdin occurs in the bile of amphibia and of birds, but not in normal human bile or serum.
N-Methylnicotinium is a nicotine degradation product arising from its methylation by S-adenosylmethionine (and subsequent conversion to S-adnonsylcysteine).
Nicotine-delta 1'-(5')-iminium ion is an intermediate in the metabolic conversion of nicotine to cotinine. This product is generated by liver enzymes.
Methacrylyl-CoA, also known as methacryloyl-CoA, belongs to the class of organic compounds known as organic pyrophosphates. These are organic compounds containing the pyrophosphate oxoanion, with the structure OP([O-])(=O)OP(O)([O-])=O. Thus, methacrylyl-CoA is considered to be a fatty ester lipid molecule. Methacrylyl-CoA is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Methacrylyl-CoA has been detected, but not quantified in, several different foods, such as beechnuts, hyacinth beans, devilfish, eggplants, and cupuaçus. This could make methacrylyl-CoA a potential biomarker for the consumption of these foods. Methacrylyl-CoA is a metabolite in the valine, leucine, and isoleucine degradation pathway and highly reacts with free thiol compounds (PMID: 14684172). Cirrhosis results in a significant decrease in 3-hydroxyisobutyryl-CoA hydrolase activity, a key enzyme in the valine catabolic pathway that plays an important role in the catabolism of a potentially toxic compound, methacrylyl-CoA, formed as an intermediate in the catabolism of valine and isobutyrate (PMID: 8938168).
Cotinineglucuronide is a natural human metabolite of Cotinine generated in the liver by UDP glucuonyltransferase. A cotinine derviative that is dervied through glucuronidation by UDP-glucuronosyltransferases (UGTs) in the liver. Glucuronidation is used to assist in the excretion of toxic substances, drugs or other substances that cannot be used as an energy source. Glucuronic acid is attached via a glycosidic bond to the substance, and the resulting glucuronide, which has a much higher water solubility than the original substance, is eventually excreted by the kidneys.
4-Imidazolone-5-propanoate is a metabolite of histidine metabolism. It is produced from urocanic acid by the enzyme urocanate hydratase [EC:4.2.1.49]. 4-Imidazolone-5-propionic acid can spontaneously decay to 4-oxoglutaramate or formylisoglutamine. It is also converted to N-forminimo-L-glutamate by the enzyme imidazolonepropionase [EC:3.5.2.7].
N-formyl-L-methionine is a L-methionine derivative in which one of the hydrogens attached to the nitrogen is replaced by a formyl group. It has a role as a metabolite. It is a proteinogenic amino acid, a N-formyl amino acid and a L-methionine derivative. It is a conjugate acid of a N-formyl-L-methioninate. N-Formyl-L-methionine belongs to the class of organic compounds known as methionine and derivatives. Methionine and derivatives are compounds containing methionine or a derivative thereof resulting from reaction of methionine at the amino group or the carboxy group, or from the replacement of any hydrogen of glycine by a heteroatom. N-Formyl-L-methionine is effective in the initiation of protein synthesis. The initiating methionine residue enters the ribosome as N-formylmethionyl-tRNA. This process occurs in Escherichia coli and other bacteria as well as in the mitochondria of eukaryotic cells.
D-4'-Phosphopantothenate is a product of the enzyme pantothenate kinase [EC 2.7.1.33] and is involved in the pantothenate and CoA biosynthesis pathway (KEGG). D-4'-Phosphopantothenate is an intermediate in coenzyme A (CoA) biosynthesis pathway. Coenzyme A is a cofactor of ubiquitous occurrence in plants, bacteria, and animals. It is needed in a large number of enzymatic reactions central to intermediary metabolism, including the oxidation of fatty acids, carbohydrates, and amino acids.
Uridine diphosphate xylose is important intermediate in the Nucleotide sugars metabolism and chondroitin sulfate biosynthesis (KEGG). The decarboxylation product of UDPglucuronic acid, which is used for formation of the xylosides of seryl hydroxyl groups in mucoprotein synthesis.
N,N-Dimethylaniline, also known as dimethylaminobenzene or dimethylphenylamine, belongs to the class of organic compounds known as dialkylarylamines. These are aliphatic aromatic amines in which the amino group is linked to two aliphatic chains and one aromatic group. N,N-dimethylaniline is a tertiary amine that is aniline in which the amino hydrogens are replaced by two methyl groups. It is a tertiary amine and a dimethylaniline. N,N-dimethylaniline appears as a yellow to brown colored oily liquid with a fishlike odor. It is less dense than water and insoluble in water. Its flash point is 150 °F, and is toxic by ingestion, inhalation, and skin absorption. N,N-Dimethylaniline was used to make dyes and as a solvent. Outside of the human body, N,N-Dimethylaniline has been detected, but not quantified in several different foods, such as common mushrooms, strawberries, feijoa, limes, and black-eyed pea.
Malyl-CoA is a substrate of enzyme malyl-CoA lyase [EC 4.1.3.24] in glyoxylate and dicarboxylate metabolism pathway (KEGG).
Succinyl-CoA is an important intermediate in the citric acid cycle, where it is synthesized from &#945;-Ketoglutarate by &#945;-ketoglutarate dehydrogenase (EC 1.2.4.2) through decarboxylation, and is converted into succinate through the hydrolytic release of coenzyme A by succinyl-CoA synthetase (EC 6.2.1.5). Succinyl-CoA may be an end product of peroxisomal beta-oxidation of dicarboxylic fatty acids; the identification of an apparently specific succinyl-CoA thioesterase (ACOT4, EC 3.1.2.3, hydrolyzes succinyl-CoA) in peroxisomes strongly suggests that succinyl-CoA is formed in peroxisomes. Acyl-CoA thioesterases (ACOTs) are a family of enzymes that catalyze the hydrolysis of the CoA esters of various lipids to the free acids and coenzyme A, thereby regulating levels of these compounds. (PMID: 16141203).
4,4-Dimethylcholesta-8,14,24-trienol is a product of the enzyme delta14-sterol reductase [EC 1.3.1.70] (KEGG). It is involved in the biosynthesis of steroids and is involved in the conversion of lanosterol to zymosterol. In particular, lanosterol 14-alpha-demethylase, catalyzes the C-14 demethylation of lanosterol to form 4,4-Dimethylcholesta-8,14,24-trienol in the ergosterol biosynthesis pathway. It is thought to be a meiosis activating sterol.
Phosphohydroxypyruvic acid is a prduct of both enzyme phosphoglycerate dehydrogenase [EC 1.1.1.95] and phosphoserine transaminase [EC 2.6.1.52] in glycine, serine and threonine metabolism pathway (KEGG). This compound belongs to the family of Organophosphate Esters. These are organic compounds containing phosphoric acid ester functional group.
25-Azacholesterol has potent hypocholesterolemic activity. (PMID 14287266) It specifically inhibits cholesterol side-chain cleavage resulting in a decrease in steroid hormone production (PMID 5165491). Azasteroids may be membrane effectors which, in the case of mitochondria, lead to changes in adenosine triphosphate levels and(or) dehydrogenase activity. Their effects on sterol metabolism, therefore, may be of secondary consideration. (PMID 994744). 25-azacholesterol can induce a myotonic state in muscles. (PMID 5009506).
3-Ketolactose is a metabolite in galactose metabolism (KEGG).
Deoxyribose 5-phosphate is a a metabolite in the pentose phosphate pathway. It can be generated from D-glyceraldehdye-3 phosphate via the enzyme 2-Deoxyribose 5-phosphate aldolase (DERA). Alternately Deoxyribose 5-phosphate can be converted to D-glyceraldehyde-3 phosphate that can then feed into the pentose phosphate pathway. Deoxyribose 5-phosphate can also be generated from 2-Deoxy-D-ribose via the enzyme Ribokinase (EC 2.7.1.15). It has been shown in a number of organisms that deoxynucleosides or deoxyriboses cause the induction of aldolases (such as DERA) involved in their catabolism, leading to the utilisation of the pentose moiety as carbon and energy source.
Dehydroepiandrosterone sulfate or DHEA-S is the sulfated form of dehydroepiandrosterone (DHEA). This sulfation is reversibly catalyzed by sulfotransferase 2A1 (SULT2A1) primarily in the adrenals, the liver, and small intestine. In the blood, most DHEA is found as DHEA-S with levels that are about 300 times higher than those of free DHEA. Orally-ingested DHEA is converted into its sulfate when passing through the intestines and liver. Whereas DHEA levels naturally reach their peak in the early morning hours, DHEAS levels show no diurnal variation. From a practical point of view, measurement of DHEA-S is preferable to DHEA since levels are more stable. DHEA (from which DHEA-S comes from) is a natural steroid prohormone produced from cholesterol by the adrenal glands, the gonads, adipose tissue, brain, and in the skin (by an autocrine mechanism). DHEA is the precursor of androstenedione, which can undergo further conversion to produce the androgen testosterone and the estrogens estrone and estradiol. DHEA is also a potent sigma-1 agonist. Serum dehydroepiandrosterone sulfate is a classic marker for adrenarche, and subsequently for the individual hormonal milieu (PMID: 10599744). Dehydroepiandrosterone sulfate is an endogenously produced sex steroid that has been hypothesized to have anti-aging effects (PMID: 16960027). It also has been inversely associated with the development of atherosclerosis (PMID: 8956025).
Angiotensin III (AngIII) is one of the N-terminal angiotensin degradation products of angiotensin II. AngIII shares some of its properties with Ang II, including chemotaxis and production of growth factors and chemokines. AngIII generated within the brain acts within neural circuits of the central nervous system to regulate body fluid balance. The stimulation of vasopressin release by AngIII is thought to be one of the mechanisms by which AngIII controls volume homeostasis under conditions of hypovolemia, by reducing renal water loss and increasing blood pressure. Brain aminopeptidase A, the enzyme forming central AngIII, could constitute a putative central therapeutic target for the treatment of hypertension. (PMID: 17210474, 11751722, 11295571).
Angiotensin IV is one of the N-terminal angiotensin degradation products of angiotensin II. Angiotensin IV (AngIV) mediates important physiologic functions in the central nervous system, including blood flow regulation, processes underlying to learning and memory, and presents anticonvulsant activity. The presence of AngIV-specific binding sites has been identified in various mammalian tissues, including blood vessels, heart, kidney, and brain. Besides the presence of AngIV binding sites in the cardiovascular system, the major AngIV synthesizing enzymes aminopeptidase N (APN) and aminopeptidase B (APB) are also expressed in different cell types of this system. AngIV activates several protein kinases, including phosphatidylinositol 3 kinase, PI-dependent kinase-1, extracellular signal-related kinases (ERK), protein kinase B-&#945;/Akt, and p70 ribosomal S6 kinase. AngIV could contribute to vascular damage, increasing the production of monocyte chemoattractant protein-1, the main chemokine involved in monocyte recruitment, and up-regulates the expression of the adhesion molecule intercellular adhesion molecule-1 that is involved in the attachment and transmigration of circulating cells into the damaged tissue. (PMID: 17210474).
In chemistry, hydroxide is the most common name for the diatomic anion OH, consisting of oxygen and hydrogen atoms, usually derived from the dissociation of a base. It is one of the simplest diatomic ions known. Hydroxide ion is a kind of ligand. It donates one pair of electrons, behaving as a Lewis base. Examples include the aluminate ion [Al(OH)4]- and aurate ion [Au(OH)4]-.
2-Methylbutyryl-CoA (CAS: 6712-02-3), also known as alpha-methylbutyryl-coenzyme A, belongs to the class of organic compounds known as acyl-CoAs. These are organic compounds containing a coenzyme A substructure linked to an acyl chain. 2-Methylbutyryl-CoA is a strong basic compound (based on its pKa). 2-Methylbutyryl-CoA is a product of isoleucine catabolism. It is converted into tiglyl-CoA by short/branched-chain acyl-CoA dehydrogenase. 2-Methylbutyryl-CoA dehydrogenase deficiency, also known as 2-methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency or MBHD, is an inherited disorder in which the body is unable to process the amino acid isoleucine properly. It is caused by a mutation in the HADH2 gene. Untreated MBHD can lead to progressive loss of motor skills, mental retardation, and epilepsy.
2'-Deoxyguanosine 5'-monophosphate, also known as deoxyguanylic acid or 2'-deoxy-GMP, belongs to the class of organic compounds known as purine 2'-deoxyribonucleoside monophosphates. These are purine nucleotides with monophosphate group linked to the ribose moiety lacking a hydroxyl group at position 2. 2'-Deoxyguanosine 5'-monophosphate is a purine 2'-deoxyribonucleoside 5'-monophosphate having guanine as the nucleobase. It exists in all living species, ranging from bacteria to humans. Within humans, 2'-deoxyguanosine 5'-monophosphate participates in a number of enzymatic reactions. In particular, 2'-deoxyguanosine 5'-monophosphate can be converted into dGDP which is mediated by the enzyme guanylate kinase. In addition, 2'-deoxyguanosine 5'-monophosphate can be converted into deoxyguanosine through its interaction with the enzyme cytosolic purine 5'-nucleotidase. In humans, 2'-deoxyguanosine 5'-monophosphate is involved in the metabolic disorder called the gout or kelley-seegmiller syndrome pathway.
Cotinine is an alkaloid found in tobacco (Nicotiana tabacum). Cotinine belongs to the class of organic compounds known as pyrrolidinylpyridines. Pyrrolidinylpyridines are compounds containing a pyrrolidinylpyridine ring system, which consists of a pyrrolidine ring linked to a pyridine ring. It is also the predominant human metabolite of nicotine (when nicotine is inhaled or absorbed). In humans, about 70 to 80% of nicotine that is inhaled or absorbed is converted to cotinine. This transformation involves two steps. The first is mediated by a cytochrome P450 system (mainly CYP2A6 and CYP2B6) to produce nicotine iminium ion. The second step is catalyzed by aldehyde oxidase (AOX). A number of cotinine metabolites have also been structurally characterized. Indeed, it appears that most of the reported urinary metabolites of nicotine are derived from cotinine. Cotinine is widely used as a biomarker for exposure to tobacco smoke. Cotinine has an in vivo half-life of approximately 20 hours, and is typically detectable for several days (up to one week) after the use of tobacco. Similar to nicotine, cotinine binds to, activates, and desensitizes neuronal nicotinic acetylcholine receptors, though at much lower potency in comparison. It has demonstrated nootropic and antipsychotic-like effects in animal models. Cotinine treatment has also been shown to reduce depression, anxiety, and fear-related behavior as well as memory impairment in animal models of depression, PTSD, and Alzheimer's disease.
D-Fructose 2,6-bisphosphate (CAS: 77164-51-3), also known as phosphofructokinase activator, belongs to the class of organic compounds known as pentose phosphates. These are carbohydrate derivatives containing a pentose substituted by one or more phosphate groups. D-Fructose 2,6-bisphosphate is a regulatory molecule controlling the activity of the enzyme phosphofructokinase-1 or PFK1 (in mammals). PFK1, in turn, is the key regulatory enzyme in the central metabolic pathway glycolysis. D-Fructose 2,6-bisphosphate has the effect of increasing the activity of PFK1, thus increasing the rate at which the principle food molecule glucose is broken down. At the same time, this regulatory molecule also inhibits the opposing enzyme (FBPase1) in the reverse pathway (gluconeogenesis) so that the synthesis of glucose is not taking place in the same cell where glucose is being broken down (which would be wasteful).
gamma-Glutamylcysteine is a dipeptide composed of gamma-glutamate and cysteine, and is a proteolytic breakdown product of larger proteins. It belongs to the family of N-acyl-alpha amino acids and derivatives. These are compounds containing an alpha amino acid which bears an acyl group at its terminal nitrogen atom. gamma-Glutamylcysteine is an incomplete breakdown product of protein digestion or protein catabolism. Some dipeptides are known to have physiological or cell-signaling effects although most are simply short-lived intermediates on their way to specific amino acid degradation pathways following further proteolysis. gamma-Glutamylcysteine is a product of enzyme glutamate-cysteine ligase [EC 6.3.2.2] and a substrate of enzyme glutathione synthase [EC 6.3.2.3] in the glutamate metabolism pathway (KEGG).
The hypochlorite ion is ClO-. A hypochlorite compound is a chemical compound containing this group. Hypochlorite is a strong oxidant. About 28% of oxygen consumed by phagocytes upon activation participates in its generation. Hypochlorite reacts with H2O2 producing singlet oxygen (1O2) - a strong initiator of Lipid peroxidation. O-sub 2, along with H2O2 can serve as the substrate for myeloperoxidase. When this takes place, Hypochlorite is formed. Hypochlorite is able to modify antioxidants incorporated into lipoproteins such as Alpha-tocopherol, Beta-carotene, lycopene, and ubiquinol-10. It is also able to modify a number of proteins which possess antioxidant functions such as ceruloplasmin, transferrin, superoxide dismutase, and catalase. Active myeloperoxidase is found at sites of atherosclerotic damage to the arterial vessel wall in humans. Lipid peroxidation is known to contribute to the development of pathological processes, among them atherosclerosis. The present hypothesis is that blood lipoproteins modified by Lipid peroxidation play a key role in the pathogenesis of this disease. One of the possible reasons for the appearance of oxidized blood lipoproteins in blood is the interaction of native blood lipoproteins with the reactive oxygen species generated by stimulated neutrophils, monocytes and other cells. The main reaction of Hypochlorite with unsaturated lipid is probably the generation of chlorohydrins. However, this reaction is not accompanied by generation of free radicals and Lipid peroxidation. This reaction is accompanied by the production of free radicals (but not singlet oxygen), probably alkoxyl radicals, which may play a role in the initiation of Hypochlorite-induced Lipid peroxidation. (PMID: 9260000, Biofactors. 1997;6(2):181-90.).
Glyceraldehyde is a triose monosaccharide with chemical formula C3H6O3. It is the simplest of all common aldoses. It is a sweet, colourless crystalline solid that is an intermediate compound in carbohydrate metabolism. The word "glyceraldehyde" comes from combining glycerine and aldehyde, as glyceraldehyde is merely glycerine with one hydroxide changed to an aldehyde. Glyceraldehyde is produced from the action of the enzyme glyceraldehyde dehydrogenase, which converts glycerol to glyceraldehyde using NADP as a cofactor. When present at sufficiently high levels, glyceraldehyde can be a cytotoxin and a mutagen. A cytotoxin is a compound that kills cells. A mutagen is a compound that causes mutations in DNA. Glyceraldehyde is a highly reactive compound that can modify and cross-link proteins. Glyceraldehyde-modified proteins appear to be cytotoxic, depress intracellular glutathione levels, and induce reactive oxygen species (ROS) production (PMID:14981296). Glyceraldehyde has been shown to cause chromosome damage to human cells in culture and is mutagenic in the Ames bacterial test.
(S)-3-Hydroxyisobutyryl-CoA is s metabolite of 3-hydroxyisobutyryl-CoA hydrolase (EC 3.1.2.4 ) during beta-alanine metabolism (KEGG 00410), propanoate metabolism (KEGG 00640), and valine, leucine and isoleucine degradation (KEGG 00280). Deficiencies of this enzyme in valine degradation can result in hypotonia, poor feeding, motor delay, and subsequent neurological regression in infancy, episodes of ketoacidosis and Leigh-like changes in the basal ganglia on a magnetic resonance imaging scan (PMID 17160907).
Dolichyl &#946;-D-glucosyl phosphate is a polyisoprenyl phosphate monosaccharide. Biosynthesis is by Glucosyltransferase in liver mitochondria. (PubMed ID 6450044 ).
Dihydrofolic acid is a folic acid derivative acted upon by dihydrofolate reductase to produce tetrahydrofolic acid. It interacts with bacteria during cell division. It can be targeted with drug analogs to prevent nucleic acid synthesis. Dihydrofolic acid is also known by the name Dihydrofolate - more commonly Vitamin B9.
3-Methylglutaconyl-CoA is a substrate for Methylglutaconyl-CoA hydratase (mitochondrial), Methylcrotonoyl-CoA carboxylase beta chain (mitochondrial) and Methylcrotonoyl-CoA carboxylase alpha chain (mitochondrial).
Fructose 1,6-bisphosphate is fructose sugar or fructosephosphate that has been phosphorylated on carbons 1 and 6. The beta-D-form of this compound is very common in cells. The vast majority of glucose and fructose entering a cell is converted to fructose 1,6-bisphosphate at some point. Fructose 1,6-bisphosphate is a key component in the glycolysis metabolic pathway and is produced by phosphorylation of fructose 6-phosphate The enzyme phosphofructokinase uses ATP to transfer a phosphate group to fructose 6-phosphate to form fructose 1, 6-bisphosphate fructose. The enzyme aldolase splits fructose 1,6-bisphosphate into two sugars that are isomers of each other. These two sugars are dihydroxyacetone phosphate and glyceraldehyde phosphate. Fructose 1,6-bisphosphate is an allosteric activator of pyruvate kinase.
myo-Inositol 1,3,4,5-tetrakisphosphate (CAS: 102850-29-3), also known as IP4, is a second messenger responsible for mediating Ca2+ entry through the plasma membrane and mobilizing intracellular Ca2+ by acting synergistically with inositol 1,4,5-trisphosphate (IP3). Inositol 1,4,5-trisphosphate 3-kinase (IP3K, EC 2.7.1.127) phosphorylates IP3 into IP4. Evidence shows that IP4 can activate a protein with ras- and rap-GAP activity and finally inactivate the G protein. This indicates that IP4 regulates Ca2+ influx in a GTP-dependent way, which potentially links the IP3 signalling pathway to GTP-regulated signalling mechanisms. IP4 is demonstrated to be a common regulator in Ca2+ homeostasis. IP4 can bind with a high affinity to several intracellular proteins: synaptotagmin (I and II), Gap1, Btk, and centaurin-alpha and may interact with synaptotagmin to inhibit synaptic transmission. IP4 also acts as a mediator in neuronal death in the ischemic hippocampus. IP4 production is not always associated with a modification in calcium concentration, and control of calcium mobilization is not the sole function proposed for IP4. IP4 defines an essential signalling pathway for T cell precursor responsiveness and development. In the thymus, IP4 is essential during the positive and negative selection of double-positive thymocytes, and in the control of thymocyte reactivity to antigens. IP4 is also a substrate for type I inositol-1,4,5-trisphosphate 5-phosphatase, phosphatidylinositol 4,5-bisphosphate 5-phosphatase A, and skeletal muscle and kidney enriched inositol phosphatase (PMID: 15740635, 14517551).
Ubiquinol 8 is a ubiquinol in which the polyprenyl substituent is octaprenyl. Ubiquinol-8 is the reduced form of ubiquinone-8. Ubiquinone (also known as coenzyme Q) is an isoprenoid quinone that functions as an electron carrier in membranes. In eukaryotes, ubiquinone is found mostly within the inner mitochondrial membrane where it functions in respiratory electron transport, transferring two electrons from either complex I (NADH dehydrogenase) or complex II (succinate-ubiquinone reductase) to complex III (bc1 complex). The quinone nucleus of ubiquinone is derived directly from 4-hydroxybenzoate, while the isoprenoid subunits of the polyisoprenoid tail are synthesized via the methylerythritol phosphate pathway, which feeds isoprene units into the polyprenyl biosynthesis pathways. The number of isoprenoid subunits in the ubiquinone side chain varies in different species. For example, Saccharomyces cerevisiae has 6 such subunits, Escherichia coli K-12 has 8, rat and mouse have 9, and Homo sapiens has 10. Ubiquinol-8 is effective as an anti-oxidant. By donating one of its hydrogen atoms to become the free-radical semiquinone (.Q-), it can neutralize a lipid peroxyl radical. The free-radical semiquinone is then restored to a non-free-radical state by the respiratory chain Q cycle. Ubiquinol or the free-radical semiquinone can also regenerate the Vitamin E tocopheroxyl radical by electron donation (http://www.benbest.com/nutrceut/CoEnzymeQ.html).
Iodate is an iodate is a salt of iodic acid. Because it is more stable than iodide, most health authorities preferentially recommend iodate as an additive to salt for correcting iodine deficiency. Even in a low exposure, doubts have been raised whether the safety of iodate. In humans and rats, oral bioavailability of iodine from iodate is virtually equivalent to that from iodide. When given intravenously to rats, or when added to whole blood or tissue homogenates in vitro or to foodstuff, iodate is quantitatively reduced to iodide by nonenzymatic reactions, and thus becomes available to the body as iodide. Therefore, except perhaps for the gastrointestinal mucosa, exposure of tissues to iodate might be minimal. At much higher doses given intravenously (i.e., above 10 mg/kg), iodate is highly toxic to the retina. Ocular toxicity in humans has occurred only after exposure to doses of 600 to 1,200 mg per individual. Oral exposures of several animal species to high doses, exceeding the human intake from fortified salt by orders of magnitude, pointed to corrosive effects in the gastrointestinal tract, hemolysis, nephrotoxicity, and hepatic injury. Genotoxicity and carcinogenicity data for iodate are scarce or nonexistent. (PMID: 11396703).
N-Acetyl-D-Glucosamine 6-Phosphate is an intermediate in the metabolism of Aminosugars. It is a substrate for Glucosamine 6-phosphate N-acetyltransferase.
3-Hexaprenyl-4,5-Dihydroxybenzoic acid is an intermediate in the biosynthesis of Ubiquinone. It is a substrate for Hexaprenyldihydroxybenzoate methyltransferase (mitochondrial).
Linoleoyl-CoA is the acyl-CoA of linoleic acid found in the human body. It binds to and results in decreased activity of glutathione S-transferase1. It has been proposed that inhibition of mitochondrial adenine nucleotide translocator by long-chain acyl-CoA underlies the mechanism associating obesity and type 2 diabetes. Unsaturated fatty acids play an important role in the prevention of human diseases such as diabetes, obesity, cancer, and neurodegeneration. Their oxidation in vivo by acyl-CoA dehydrogenases (ACADs) catalyze the first step of each cycle of mitochondrial fatty acid beta-oxidation. ACAD-9 had maximal activity with long-chain unsaturated acyl-CoAs as substrates (PMID: 17184976, 16020546).
2-Hydroxyphenethylamine, also known as beta-phenethanolamine or 2-amino-1-phenylethanol, belongs to the class of organic compounds known as aralkylamines. These are alkylamines in which the alkyl group is substituted at one carbon atom by an aromatic hydrocarbyl group. It is the simplest member of the class of phenylethanolamines that is 2-aminoethanol bearing a phenyl substituent at the 1-position. 2-Hydroxyphenethylamine exists in all living organisms, ranging from bacteria to humans. 2-Hydroxyphenethylamine ia an amine found in the brain. It may be modulator of sympathetic functions. Its derivatives are adrenergic agonists and antagonists.
S-Lactoylglutathione is a substrate of lactoylglutathione lyase [EC 4.4.1.5] in pyruvate metabolism (KEGG). Another enzyme, glyoxalase I, synthesizes this compound by converting methylglyoxal and reduced glutathione to S-lactoylglutathione. S-D-lactoylglutathione can be hydrolysed by thiolesterases to reduced glutathione and D-lactate but also converted to N-D-lactoylcysteinylglycine and N-D-lactoylcysteine by gamma-glutamyl transferase and dipeptidase (PMID: 8632674). S-lactoylglutathione has also been shown to modulate microtubule assembly (PMID: 690442).
N-Acetylaspartylglutamate (NAAG) is a neuropeptide found in millimolar concentrations in the brain that is localized to subpopulations of glutamatergic, cholinergic, GABAergic, and noradrenergic neuronal systems. NAAG is released upon depolarization by a Ca(2+)-dependent process and is an agonist at mGluR3 receptors and an antagonist at NMDA receptors. NAAG is catabolized to N-acetylaspartate and glutamate primarily by glutamate carboxypeptidase II, which is expressed on the extracellular surface of astrocytes. The levels of NAAG and the activity of carboxypeptidase II are altered in a regionally specific fashion in several neuropsychiatric disorders (PMID:9361299). N-Acetylaspartylglutamic acid (NAAG) is a purported precursor of N-acetylaspartic acid (NAA) and is present at about one-tenth of the concentration of NAA in the brain. NAAG has been reported to activate N-methyl-D-aspartic acid (NMDA) receptors in neurons. Previous immunohistochemical studies in the vertebrate central nervous system (CNS) have suggested that NAAG is exclusively localized to neurons. Recent evidence, however, indicates that NAAG might also be localized to nonneuronal cells within the CNS. Only traces of NAA and NAAG are detectable in other tissues. Some compounds can change levels of NAA and NAAG in the brain. For example, methylphenidate increases the levels of NAA and NAAG in the cerebral cortex; amphetamine also increases NAA concentration in a mature brain by 26%, raising the possibility that other neurochemical systems might be involved in the clinical effects of stimulants (PMID:10603234).
D-Sedoheptulose 7-phosphate (CAS: 2646-35-7) is an intermediate of the pentose phosphate pathway (PPP) that has two functions: (1) the generation of NADPH for reductive syntheses and oxidative stress responses within cells, and (2) the formation of ribose residues for nucleotide and nucleic acid biosynthesis (PMID: 16055050). It is formed by transketolase and acted upon (degraded) by transaldolase. Sedoheptulose 7-phosphate can be increased in the blood of patients affected with a transaldolase deficiency, a genetic disorder (PMID: 12881455). Sedoheptulose is a ketoheptose, a monosaccharide with seven carbon atoms and a ketone functional group. It is one of the few heptoses found in nature (Wikipedia).
Selective A2 adenosine receptor agonist; potent coronary vasodilator; weak inhibitor of adenosine uptake by rat cerebral cortical synaptosomes; used as a vasodilator agent; is a potent anti-inflammatory agent, acting at its four G protein coupled receptors. Topical treatment of adenosine to foot wounds in diabetes mellitus has been shown in lab animals to drastically increase tissue repair and reconstruction. Topical administration of adenosine for use in wound healing deficiencies and diabetes mellitus in humans is currently under clinical investigation. Adenosine is a nucleoside comprised of adenine attached to a ribose (ribofuranose) moiety via a beta-N9-glycosidic bond.
Octanoyl-CoA is a substrate for Trifunctional enzyme beta subunit (mitochondrial), Acyl-coenzyme A oxidase 1 (peroxisomal), 3-ketoacyl-CoA thiolase (mitochondrial), 3-ketoacyl-CoA thiolase (peroxisomal), Nuclear receptor-binding factor 1, Acyl-CoA dehydrogenase (long-chain specific, mitochondrial), Acyl-coenzyme A oxidase 3 (peroxisomal), HPDHase, Acyl-CoA dehydrogenase (medium-chain specific, mitochondrial), Acyl-coenzyme A oxidase 2 (peroxisomal) and Peroxisomal carnitine O-octanoyltransferase.
Fructose 1-phosphate, also known as D-fructose-1-p, belongs to the class of organic compounds known as hexose phosphates. These are carbohydrate derivatives containing a hexose substituted by one or more phosphate groups. Metabolism of fructose thus essentially results in intermediates of glycolysis. The final product of glycolysis (pyruvate) may then undergo gluconeogenesis, enter the TCA cycle or be stored as fatty acids. Fructose 1-phosphate exists in all living organisms, ranging from bacteria to humans. Within humans, fructose 1-phosphate participates in a number of enzymatic reactions. In particular, fructose 1-phosphate can be biosynthesized from D-fructose through the action of the enzyme ketohexokinase. In addition, fructose 1-phosphate can be converted into dihydroxyacetone phosphate and glyceraldehyde; which is catalyzed by the enzyme fructose-bisphosphate aldolase a. Because fructokinase has a high Vmax fructose entering cells is quickly phosphorylated to fructose 1-phosphate. In humans, fructose 1-phosphate is involved in fructose intolerance, hereditary. Hypoglycemia results from inhibition of glycogenolysis and gluconeogenesis. It is generated mainly by hepatic fructokinase but is also generated in smaller amounts in the small intestinal mucosa and proximal epithelium of the renal tubule. Aldolase B converts it into glyceraldehyde and dihydroxyacetone phosphate (DHAP). Symptoms of hereditary fructose intolerance are apathy, drowsiness, sweatiness and tremulousness.
Mannose 6-phosphate, also known as alpha-D-mannose-6-p or man-6-p, belongs to the class of organic compounds known as hexose phosphates. These are carbohydrate derivatives containing a hexose substituted by one or more phosphate groups. Mannose 6-phosphate exists in all eukaryotes, ranging from yeast to humans. Within humans, mannose 6-phosphate participates in a number of enzymatic reactions. In particular, mannose 6-phosphate can be converted into fructose 6-phosphate through its interaction with the enzyme mannose-6-phosphate isomerase. In addition, mannose 6-phosphate can be biosynthesized from D-mannose through the action of the enzyme hexokinase-1. Mannose 6-phosphate is a potent competitive inhibitor of pinocytosis of human platelet beta-glucuronidase and it is a necessary component of the recognition marker on the enzyme for pinocytosis by human fibroblasts as well (PMID 908752). In humans, mannose 6-phosphate is involved in fructose intolerance, hereditary.
4-Aminobutyraldehyde is a metabolite of putrescine. It is a substrate of human liver aldehyde dehydrogenase (EC 1.2.1.3) cytoplasmic (E1) and mitochondrial (E2) isozymes (PMID 3324802).
<p>(N-acetylneuraminosyl(alpha2-6)lactosamine) is widely distributed among tissues and is involved in biological processes such as the regulation of the immune response and the progression of colon cancer. Sialylation represents one of the most frequently occurring terminations of the oligosaccharide chains of glycoproteins and glycolipids. Sialic acid is commonly found alpha,6-linked to N-acetylgalactosamine (GalNAc). The biosynthesis of the linkage is mediated by a member of the sialyltransferase family, the beta-galactoside alpha,6-sialyltransferase (EC 2.4.99.1, ST6Gal.I). Although expressed by a single gene, this enzyme shows a complex pattern of regulation which allows its tissue- and stage-specific modulation. (PMID 11425186)</p>. <p>6'-Sialyllactosamine is an oligosaccharide found in human milk. Oligosaccharides in human milk inhibit enteric pathogens <i>in vitro</i> and <i>in vivo</i>. (PMID:10683228)</p>.
Adenosyl cobyrinic acid a,c diamide is an intermediate in the metabolism of Porphyrin and chlorophyll. It is a substrate for Cob(I)yrinic acid a,c-diamide adenosyltransferase (mitochondrial).
1-Piperideine-2-carboxylic acid (P2C), also known as Δ1-pipecolic acid, is classified as a member of the tetrahydropyridines. Tetrahydropyridines are derivatives of pyridine in which two double bonds in the pyridine moiety are reduced by adding four hydrogen atoms. 1-Piperideine-2-carboxylic acid is considered to be slightly soluble (in water) and acidic. 1-Piperideine-2-carboxylic acid is an intermediate of the L-lysine metabolic pathway in the brain; the uptake of P2C into the synaptosome of the cerebral cortex was Na+ and temperature-dependent (PMID: 7654748).
Uroporphyrinogens are porphyrinogen variants in which each pyrrole ring has one acetate side chain and one propionate side chain; it is formed by condensation 4 four molecules of porphobilinogen. 4 isomers are possible but only 2 commoly are found, types I and III. Uroporphyrinogen III is a functional intermediate in heme biosynthesis while Uroporphyrinogen I is produced in an abortive side reaction.
5-Methylthioribose (CAS: 23656-67-9) belongs to the class of organic compounds known as pentoses. These are monosaccharides in which the carbohydrate moiety contains five carbon atoms. 5-Methylthioribose is an extremely weak basic (essentially neutral) compound (based on its pKa). 5-Methylthioribose exists in all living organisms, ranging from bacteria to humans. In humans, 5-methylthioribose is involved in the metabolic disorder called hypermethioninemia. Outside of the human body, 5-methylthioribose has been detected, but not quantified in, several different foods, such as alaska wild rhubarbs, common verbena, greenthread tea, pasta, and Irish moss. This could make 5-methylthioribose a potential biomarker for the consumption of these foods. 5-Methylthioribose is a metabolite of 5-methylthioribose-1-phosphate. It is a substrate of methylthioribose kinase (EC 2.7.1.100) in the methionine metabolism pathway (KEGG). It can be found in Escherichia (PMID: 4203512).
Butyryl-CoA is an intermediate in the metabolism of Butanoate. It is a substrate for Acyl-coenzyme A oxidase 3 (peroxisomal), 3-ketoacyl-CoA thiolase (mitochondrial), 3-ketoacyl-CoA thiolase (peroxisomal), Acyl-coenzyme A oxidase 1 (peroxisomal), Acyl-CoA dehydrogenase (medium-chain specific, mitochondrial), Acyl-CoA dehydrogenase (long-chain specific, mitochondrial), Acyl-coenzyme A oxidase 2 (peroxisomal), Acetyl-CoA acetyltransferase (mitochondrial), Acetyl-CoA acetyltransferase (cytosolic), Acyl-CoA dehydrogenase (short-chain specific, mitochondrial) and Trifunctional enzyme beta subunit (mitochondrial).
5-Diphosphomevalonic acid (CAS: 1492-08-6) is a metabolic intermediate in the mevalonate pathway, catalyzed by the enzyme phosphomevalonate kinase from 5-phosphomevalonate (Wikipedia).
3-Hydroxyquinine is a major metabolite of quinine. The formation of 3-hydroxyquinine is catalysed by cytochrome P450 3A4.
5a-Cholesta-8,24-dien-3-one is an intermediate in the cholesterol synthesis pathway, the by-product of the Sterol-4-alpha-carboxylate 3-dehydrogenase enzyme [EC 1.1.1.70], and the substrate of the 3-keto-steroid reductase enzyme [EC 1.1.1.270]. (BioCyc, ExPASy).
Octaprenyl diphosphate, also known as farnesylfarnesylgeraniol or OPP, belongs to the class of organic compounds known as tetraterpenoids. These are terpenoid molecules containing 10 consecutively linked isoprene units. Octaprenyl diphosphate is the precursor for the side chain of the isoprenoid quinones ubiquinone and menaquinone. It is a substrate of the enzyme trans-octaprenyltranstransferase (EC 2.5.1.11) in the steroid biosynthesis pathway.
GDP-L-fucose is a sugar nucleotide and a readily available source of fucose. Fucose is a deoxyhexose that is found in nearly all plant and animal species. The monosaccharide plays several important metabolic roles in complex carbohydrates and in glycoproteins. Fucosylated oligosaccharides are involved in cell-cell recognition, selectin-mediated leukocyte-endothelial adhesion, and mouse embryogenesis. They form the basis of the Lewis-type blood group antigens, are involved in the formation of atherosclerosis, and mediate host-bacterial interactions. A decrease in the availability of fucose is associated with leukocyte adhesion deficiency type-II disorder, and fucosylated glycoproteins have been implicated in memory processes. Fucose is made available during the synthesis of fucosylated glycolipids, oligosaccharides, and glycoproteins via a sugar nucleotide intermediate, specifically GDP-L-fucose. GTP-L-fucose pyrophosphorylase (GFPP, E. C. 2.7.7.30) catalyzes the reversible condensation of guanosine triphosphate and beta-L-fucose-1-phosphate to form the nucleotide-sugar GDP-L-fucose. The enzyme functions primarily in the mammalian liver and kidney to salvage free L-fucose during the breakdown of glycolipids and glycoproteins. (PMID: 16086588).
Carbamoyl phosphate is a precursor of both arginine and pyrimidine biosynthesis. It is a labile and potentially toxic intermediate. Carbamoyl phosphate is a molecule that is involved in ridding the body of excess nitrogen in the urea cycle, and also in the synthesis of pyrimidines. It is produced from carbon dioxide, ammonia, and phosphate (from ATP) by the enzyme carbamoyl phosphate synthase. -- Wikipedia.
Protoporphyrinogen IX is an intermediate in heme biosynthesis. It is a porphyrinogen in which two pyrrole rings each have one methyl and one propionate side chain, and the other two pyrrole rings each have one methyl and one vinyl side chain. Fifteen isomers are possible but only one, type IX, occurs naturally. Protoporphyrinogen is produced by oxidative decarboxylation of coproporphyrinogen. Under certain conditions, protoporphyrinogen IX can act as a phototoxin, a neurotoxin, and a metabotoxin. A phototoxin leads to cell damage upon exposure to light. A neurotoxin causes damage to nerve cells and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of porphyrins are associated with porphyrias such as porphyria variegate, acute intermittent porphyria, and hereditary coproporphyria (HCP). In particular, protoporphyrinogen IX is accumulated and excreted excessively in the feces in acute intermittent porphyria, protoporphyria, and variegate porphyria. There are several types of porphyrias (most are inherited). Hepatic porphyrias are characterized by acute neurological attacks (seizures, psychosis, extreme back and abdominal pain, and an acute polyneuropathy), while the erythropoietic forms present with skin problems (usually a light-sensitive blistering rash and increased hair growth). The neurotoxicity of porphyrins may be due to their selective interactions with tubulin, which disrupt microtubule formation and cause neural malformations (PMID: 3441503).
p-Anisic acid, also known as 4-anisate or draconic acid, belongs to the class of organic compounds known as p-methoxybenzoic acids and derivatives. These are benzoic acids in which the hydrogen atom at position 4 of the benzene ring is replaced by a methoxy group. p-Anisic acid is a drug. p-Anisic acid exists in all eukaryotes, ranging from yeast to humans. p-Anisic acid is a faint, sweet, and cadaverous tasting compound. Outside of the human body, p-anisic acid has been detected, but not quantified in several different foods, such as anises, cocoa beans, fennels, and german camomiles. This could make p-anisic acid a potential biomarker for the consumption of these foods. It is a white crystalline solid which is insoluble in water, highly soluble in alcohols and soluble in ether, and ethyl acetate. p-Anisic acid has antiseptic properties. It is also used as an intermediate in the preparation of more complex organic compounds. It is generally obtained by the oxidation of anethole or p-methoxyacetophenone. The term "anisic acid" often refers to this form specifically. p-Anisic acid is found naturally in anise.
N-Acetyl-b-glucosaminylamine is the product of a reaction catalyzed vy the enzyme N(4)-(beta-N-acetylglucosaminyl)-L-asparaginase [EC 3.5.1.26, Aspartylglucosaminidase, AGA]. AGA is a key enzyme in the catabolism of N-linked oligosaccharides of glycoproteins. It cleaves the asparagine from the residual N-acetylglucosamines as one of the final steps in the lysosomal breakdown of glycoproteins. Aspartylglucosaminuria (AGU) is a lysosomal disease caused by deficiency of N-aspartyl-beta-glucosaminidase. AGU is the only known lysosomal storage disease caused by an amidase deficiency. (OMIM208400).
3-Aminopropanal is a reactive aldehyde that mediates progressive neuronal necrosis and glial apoptosis. (PMID 11943872). Increased activity of polyamine oxidase catabolizes polyamines (such as spermine, spermidine and putrescine) to produce 3-aminopropanal. (PMID 15246852).
7-methylguanosine is an endogenous methylated nucleoside found in human fluids; methylated purine bases are present in higher amounts in tumor-bearing patients compared to healthy controls.DNA hypermethylation is a common finding in malignant cells and has been explored as a therapeutic target for hypomethylating agents. When chemical bonds to DNA, the DNA becomes damaged and proper and complete replication cannot occur to make the normal intended cell. A DNA adduct is an abnormal piece of DNA covalently-bonded to a cancer-causing chemical. This has shown to be the start of a cancerous cell, or carcinogenesis. DNA adducts in scientific experiments are used as bio-markers and as such are themselves measured to reflect quantitatively, for comparison, the amount of cancer in the subject. 7-Methylguanosine is a substrate for purine-nucleoside phosphorylase and Eukaryotic translation initiation factor 4E. (PMID:3506820, 17044778, 17264127, 16799933).
Glucosamine-1P is a substrate of enzyme UDP-N-acetylglucosamine diphosphorylase [EC 2.7.7.23] (KEGG).
Glyceraldehyde 3-phosphate (G3P) (CAS: 591-59-3), also known as triose phosphate, belongs to the class of organic compounds known as glyceraldehyde-3-phosphates. Glyceraldehyde-3-phosphates are compounds containing a glyceraldehyde substituted at position O3 by a phosphate group. Glyceraldehyde 3-phosphate is an extremely weak basic (essentially neutral) compound (based on its pKa). Glyceraldehyde 3-phosphate has been detected, but not quantified in, several different foods, such as sea-buckthorn berries, lingonberries, prunus (cherry, plum), quinoa, and sparkleberries. This could make glyceraldehyde 3-phosphate a potential biomarker for the consumption of these foods. Glyceraldehyde 3-phosphate is an aldotriose, an important metabolic intermediate in both glycolysis and gluconeogenesis, and in tryptophan biosynthesis. G3P is formed from fructose 1,6-bisphosphate, dihydroxyacetone phosphate (DHAP), and 1,3-bisphosphoglycerate (1,3BPG). This is the process by which glycerol (as DHAP) enters the glycolytic and gluconeogenesis pathways.
Isovaleryl-CoA is an intermediate metabolite in the catabolic pathway of leucine. The accumulation of derivatives of isovaleryl-CoA occurs in patients affected with isovaleric acidemia (IVA, OMIM: 243500), an autosomal recessive inborn error of leucine metabolism caused by a deficiency of the mitochondrial enzyme isovaleryl-CoA dehydrogenase (IVD, EC 1.3.99.10), a flavoenzyme that catalyzes the conversion of isovaleryl-CoA into 3-methylcrotonyl-CoA. IVA was the first organic acidemia recognized in humans and can cause significant morbidity and mortality. Early diagnosis and treatment with a protein-restricted diet and supplementation with carnitine and glycine are effective in promoting normal development in severely affected individuals. Both intra- and interfamilial variability have been recognized. Initially, two phenotypes with either an acute neonatal or a chronic intermittent presentation were described. More recently, a third group of individuals with mild biochemical abnormalities who can be asymptomatic have been identified through newborn screening of blood spots by tandem mass spectrometry. The majority of patients with IVA today are diagnosed pre-symptomatically through newborn screening by use of MS/MS which reveals elevations of the marker metabolite C5 acylcarnitine in dried blood spots. C5 Acylcarnitine represents a mixture of isomers (isovalerylcarnitine, 2-methylbutyrylcarnitine, and pivaloylcarnitine) (PMID: 16602101).
Stearoyl-CoA is a long-chain acyl CoA ester that acts as an intermediate metabolite in the biosynthesis of monounsaturated fatty acids; a critical committed step in the reaction is the introduction of the cis-configuration double bond into acyl-CoAs (between carbons 9 and 10). This oxidative reaction is catalyzed by the iron-containing, microsomal enzyme, stearoyl-CoA desaturase (SCD, EC 1.14.19.1). NADH supplies the reducing equivalents for the reaction, the flavoprotein is cytochrome b5-reductase and the electron carrier is the heme protein cytochrome b5. Stearoyl-CoA is converted into oleoyl-CoA and then used as a major substrate for the synthesis of various kinds of lipids including phospholipids, triglycerides, cholesteryl esters and wax esters. Oleic acid is the preferred substrate for acyl-CoA cholesterol acyltransferase (ACAT, EC 2.3.1.26) and diacylglycerol acyltransferase (DGAT, EC 2.3.1.20), the enzymes responsible for cholesteryl esters and triglycerides synthesis, respectively. In addition oleate is the major monounsaturated fatty acid in human adipose tissue and in the phospholipid of the red-blood-cell membrane. In the biosynthesis of sphinganine, stearoyl-CoA proceeds through the acyl-CoA + serine -> 3-keto-sphinganine -> sphinganine pathway, with the key enzyme being acyl-CoA serine acyltransferase (EC 2.3.1.50) to yield C20-(3-ketosphinganine) long-chain base. There is growing recognition that acyl-CoA esters could act as signaling molecules in cellular metabolism. (PMID: 12538075, 10998569, Prostaglandins Leukot Essent Fatty Acids. 2003 Feb;68(2):113-21.).
4'-Phosphopantothenoylcysteine, also known as pantothenoylcysteine 4'-phosphate, belongs to the class of organic compounds known as hybrid peptides. Hybrid peptides are compounds containing at least two different types of amino acids (alpha, beta, gamma, delta) linked to each other through a peptide bond. 4'-Phosphopantothenoylcysteine is an extremely weak basic (essentially neutral) compound (based on its pKa). Within humans, 4'-phosphopantothenoylcysteine participates in a number of enzymatic reactions. In particular, cytidine monophosphate and 4'-phosphopantothenoylcysteine can be biosynthesized from cytidine triphosphate, D-4'-phosphopantothenate, and L-cysteine through the action of the enzyme phosphopantothenate--cysteine ligase. 4'-Phosphopantothenoylcysteine (PPC) is an intermediate in the biosynthetic machinery (pathway) that converts pantothenate (vitamin B5) into coenzyme A (CoA). The enzyme phosphopantothenoylcysteine decarboxylase catalyzes the decarboxylation of PPC into 4'-phosphopantetheine. Coenzyme A is the principal acyl carrier and is required for many synthetic and degradative reactions in intermediary metabolism, and is an essential cofactor in all living systems (PMID: 15450493, 16371361, 14501115).
4-Hydroxy-4-(3-pyridyl)-butanoic acid is a nitrosonornicotine metabolite derived from tobacco smoke. (PMID: 796709). This nicotine-related compound was separated by HPLC as a cotinine metabolite in human urine and an urinary metabolites of (methylnitrosamino)(pyridyl)butanone in rats. (MID: 10362230).
Dimethylallylpyrophosphate, also known as 2-isopentenyl diphosphate or delta-prenyl diphosphoric acid, belongs to the class of organic compounds known as isoprenoid phosphates. These are prenol lipids containing a phosphate group linked to an isoprene (2-methylbuta-1,3-diene) unit. Dimethylallylpyrophosphate is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
N-Acetyl-D-mannosamine 6-phosphate is an intermediate in amino sugar metabolism and is a substrate for UDP-N-acetylglucosamine--peptide N-acetylglucosaminyltransferase, Bifunctional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase, Alpha-N-acetylglucosaminidase and Exostosin-2. It can be generated from N-acetyl-neuraminate-9-phosphate or N-acetyl-D-mannosamine.
N-Methylformamide (NMF) is one of the two major urinary biomarkers of exposure to N,N-Dimethylformamide (DMF), a compound widely used in industries because of its extensive miscibility with water and solvents. Metabolism of NMF results in the formation of N-methylcarbamoyl adducts at the N-terminal valine and lysine in blood protein globin. (PMID: 17254560, 17254560, 16289959).
2-Aminobenzoic acid, also known as anthranilic acid or O-aminobenzoate, belongs to the class of organic compounds known as aminobenzoic acids. These are benzoic acids containing an amine group attached to the benzene moiety. Within humans, 2-aminobenzoic acid participates in a number of enzymatic reactions. In particular, 2-aminobenzoic acid and formic acid can be biosynthesized from formylanthranilic acid through its interaction with the enzyme kynurenine formamidase. In addition, 2-aminobenzoic acid and L-alanine can be biosynthesized from L-kynurenine through its interaction with the enzyme kynureninase. It is a substrate of enzyme 2-Aminobenzoic acid hydroxylase in benzoate degradation via hydroxylation pathway (KEGG). In humans, 2-aminobenzoic acid is involved in tryptophan metabolism. Outside of the human body, 2-Aminobenzoic acid has been detected, but not quantified in several different foods, such as mamey sapotes, prairie turnips, rowals, natal plums, and hyacinth beans. This could make 2-aminobenzoic acid a potential biomarker for the consumption of these foods. 2-Aminobenzoic acid is a is a tryptophan-derived uremic toxin with multidirectional properties that can affect the hemostatic system. Uremic syndrome may affect any part of the body and can cause nausea, vomiting, loss of appetite, and weight loss. Chronic exposure of uremic toxins can lead to a number of conditions including renal damage, chronic kidney disease and cardiovascular disease. It can also cause changes in mental status, such as confusion, reduced awareness, agitation, psychosis, seizures, and coma.
Trehalose 6-phosphate is a substrate for Hexokinase (type I) and Tryptase beta-1. Trehalose 6-phosphate has been found to be a microbial metabolite in Escherichia, Mycobacterium and Saccharomyces (UniProt).
Inositol cyclic phosphate is a substrate for Annexin A3.
Nornicotine is an alkaloid extracted from tobacco and related to nicotine but having a lower toxicity: used as an agricultural and horticultural insecticide.
6-phosphoglucono-delta-lactone (d-6PGL) is the immediate product of the Glucose-6-phosphate dehydrogenase (G-6-PD), the first enzyme of the hexose monophosphate pathway. (PMID 3711719). The pentose-phosphate pathway provides reductive power and nucleotide precursors to the cell through oxidative and nonoxidative branches. 6-Phosphogluconolactonase is the second enzyme of the oxidative branch and catalyzes the hydrolysis of 6-phosphogluconolactones, the products of glucose 6-phosphate oxidation by glucose-6-phosphate dehydrogenase. By efficiently catalyzing the hydrolysis of d-6PGL, 6-phosphogluconolactonase prevents the reaction between d-6PGL and intracellular nucleophiles; such a reaction would interrupt the functioning of the pentose-phosphate pathway. (PMID 11457850).
5-Phosphoribosylamine is a substrate for Amidophosphoribosyltransferase and Trifunctional purine biosynthetic protein adenosine-3.
N-Acetylmannosamine, also known as beta-ManNAcc or β-ManNAc, belongs to the class of organic compounds known as acylaminosugars. These are organic compounds containing a sugar linked to a chain through N-acyl group. Within humans, N-acetylmannosamine participates in a number of enzymatic reactions. In particular, N-acetylmannosamine can be biosynthesized from N-acetyl-D-glucosamine, which is catalyzed by the enzyme N-acylglucosamine 2-epimerase. In addition, N-acetylmannosamine and uridine 5'-diphosphate can be biosynthesized from uridine diphosphate-N-acetylglucosamine; which is mediated by the enzyme bifunctional UDP-N-acetyl glucosamine 2-epimerase / N-acetylmannosamine kinase. In humans, N-acetylmannosamine is involved in the metabolic disorder called the salla disease/infantile sialic acid storage disease pathway. In the rate-limiting step of the pathway, UDP-GlcNAc is converted into ManNAc by UDP-GlcNAc 2-epimerase, encoded by the epimerase domain of GNE. Improved sialylation after the addition of ManNAc and other supporting ingredients to the culture medium not only increases manufacturing yield, but also improves therapeutic efficacy by increasing solubility, increasing half-life and reducing immunogenicity by reducing the formation of antibodies to the therapeutic glycoprotein When the GNE epimerase kinase does not function correctly in the human body thereby reducing the available ManNAc, it is reasonable to assume that treatment with ManNAc could assist with improving health benefits. There is no available therapy to treat GNE myopathy. ManNAc is the first committed biological precursor of N-acetylneuraminic acid (Neu5Ac, sialic acid).
Iminoaspartic acid is a substrate for D-aspartate oxidase.
Nicotinic acid mononucleotide, also known as nicotinate ribonucleotide, belongs to the class of organic compounds known as nicotinic acid nucleotides. These are pyridine nucleotides in which the pyridine base is nicotinic acid or a derivative thereof. Nicotinic acid mononucleotide is an extremely weak basic (essentially neutral) compound (based on its pKa). Nicotinic acid mononucleotide an intermediate in the cofactor biosynthesis and the nicotinate and nicotinamide metabolism pathways. It is a substrate for nicotinamide riboside kinase, ectonucleotide pyrophosphatase/phosphodiesterase, nicotinamide mononucleotide adenylyltransferase, 5'-nucleotidase, nicotinate-nucleotide pyrophosphorylase, and 5'(3')-deoxyribonucleotidase.
3'-Phosphoadenosine-5'-phosphosulfate. Key intermediate in the formation by living cells of sulfate esters of phenols, alcohols, steroids, sulfated polysaccharides, and simple esters, such as choline sulfate. It is formed from sulfate ion and ATP in a two-step process. This compound also is an important step in the process of sulfur fixation in plants and microorganisms.
Hydroxymethylbilane is a molecule involved in the metabolism of porphyrin. In the third step, it is generated by the enzyme porphobilinogen deaminase , and in the next step the enzyme uroporphyrinogen III synthase converts it into uroporphyrinogen III. -- Wikipedia.
Prostaglandin F2a (PGF2) is one of the earliest discovered and most common prostaglandins. It is actively biosynthesized in various organs of mammals and exhibits a variety of biological activities, including contraction of pulmonary arteries. It is used in medicine to induce labor and as an abortifacient. PGF2a binds to the Prostaglandin F2 receptor (PTGFR) which is a member of the G-protein coupled receptor family. PGF2-alpha mediates luteolysis. Luteolysis is the structural and functional degradation of the corpus luteum (CL) that occurs at the end of the luteal phase of both the estrous and menstrual cycles in the absence of pregnancy. PGF2 may also be involved in modulating intraocular pressure and smooth muscle contraction in the uterus and gastrointestinal tract sphincters. PGF2 is mainly synthesized directly from PGH2 by PGH2 9,11-endoperoxide reductase. A small amount of PGF2 is also produced from PGE2 by PGE2 9-ketoreductase. A PGF2 epimer has been reported to exhibit various biological activities, and its levels are increased in bronchoalveolar lavage fluid, plasma, and urine in patients with mastocytosis and bronchial asthma. PGF2 is synthesized from PGD2 by PGD2 11-ketoreductase. (PMID: 16475787). Prostaglandins are eicosanoids. The eicosanoids consist of the prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and lipoxins (LXs). The PGs and TXs are collectively identified as prostanoids. Prostaglandins were originally shown to be synthesized in the prostate gland, thromboxanes from platelets (thrombocytes), and leukotrienes from leukocytes, hence the derivation of their names. All mammalian cells except erythrocytes synthesize eicosanoids. These molecules are extremely potent, able to cause profound physiological effects at very dilute concentrations. All eicosanoids function locally at the site of synthesis, through receptor-mediated G-protein linked signalling pathways.
Octanal, also known as 1-caprylaldehyde or aldehyde C-8, belongs to the class of organic compounds known as medium-chain aldehydes. These are an aldehyde with a chain length containing between 6 and 12 carbon atoms. Thus, octanal is considered to be a fatty aldehyde lipid molecule. A saturated fatty aldehyde formally arising from reduction of the carboxy group of caprylic acid (octanoic acid). Octanal is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. Octanal exists in all eukaryotes, ranging from yeast to humans. Octanal is an aldehydic, citrus, and fat tasting compound. Octanal is commonly found in high concentrations in limes, caraway, and mandarin orange (clementine, tangerine) and in lower concentrations in wild carrots and carrots. Octanal has also been detected, but not quantified in several different foods, such as cherry tomato, brussel sprouts, alaska wild rhubarbs, sweet marjorams, and sunflowers.
FMNH2 is the reduced form of flavin mononucleotide. It is a substrate of the enzyme FMN reductase (EC 1.5.1.29), an enzyme that catalyzes the chemical reaction FMNH2 + NAD(P)+ <=> FMN + NAD(P)H + H+. Flavin mononucleotide (FMN), or riboflavin-5&prime;-phosphate, is a biomolecule produced from riboflavin (vitamin B2) by the enzyme riboflavin kinase and functions as prosthetic group of various oxidoreductases including NADH dehydrogenase. During a catalytic cycle, the reversible interconversion of oxidized (FMN), semiquinone (FMNH&bull;) and reduced (FMNH2) forms occurs in the various oxidoreductases. FMN is a stronger oxidizing agent than NAD and is particularly useful because it can take part in both one- and two-electron transfers.
Inositol 1,3,4-trisphosphate (CAS: 98102-63-7), also known as Ins(1,3,4)P3 or I3S, belongs to the class of organic compounds known as inositol phosphates. Inositol phosphates are compounds containing a phosphate group attached to an inositol (or cyclohexanehexol) moiety. Within humans, inositol 1,3,4-trisphosphate participates in several enzymatic reactions. In particular, inositol 1,3,4-trisphosphate can be converted into 1D-myo-inositol 1,3,4,6-tetrakisphosphate through the action of the enzyme inositol-tetrakisphosphate 1-kinase. In addition, inositol 1,3,4-trisphosphate can be converted into inositol 1,3,4,5-tetraphosphate through its interaction with the enzyme inositol-tetrakisphosphate 1-kinase. In humans, inositol 1,3,4-trisphosphate is involved in inositol metabolism. Inositol 1,3,4-trisphosphate is a specific regulator of cellular signalling.
5-Aminolevulinic acid, also known as 5-aminolevulinate or 5-amino-4-oxopentanoate, belongs to the class of organic compounds known as delta amino acids and derivatives. Delta amino acids and derivatives are compounds containing a carboxylic acid group and an amino group at the C5 carbon atom. 5-Aminolevulinic acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. 5-Aminolevulinic acid exists in all living species, ranging from bacteria to humans. 5-aminolevulinic acid can be biosynthesized from glycine and succinyl-CoA by the enzyme 5-aminolevulinate synthase. The simplest delta-amino acid in which the hydrogens at the gamma position are replaced by an oxo group. In humans, 5-aminolevulinic acid is involved in the metabolic disorder called the dimethylglycine dehydrogenase deficiency pathway. Outside of the human body, 5-Aminolevulinic acid has been detected, but not quantified in several different foods, such as american butterfish, vaccinium (blueberry, cranberry, huckleberry), amaranths, purple mangosteens, and garden cress. Used (in the form of the hydrochloride salt) in combination with blue light illumination for the treatment of minimally to moderately thick actinic keratosis of the face or scalp. It is metabolised to protoporphyrin IX, a photoactive compound which accumulates in the skin.
Allose is an aldohexose sugar. Allose is a C-3 epimer of glucose. D-allose is a rare sugar found in nature and, because of its very limited amount and of the high cost associated with its synthesis, its physiological functions remain virtually unknown (PMID 16080505). It is believed to have inhibitory effect on cancer cell proliferation (PMID 16142305), protective effects against ischemia reperfusion injury (PMID 14605979, 16716947), immunosuppressant on allogenic orthotopic liver transplantation (PMID 11120048), neuroprotective effects against retinal ischemia (PMID 16565406), suppress development of salt-induced hypertension (PMID 16148613) and an inhibitory effect on human ovarian carcinoma cells (PMID 16080505). It is a rare monosaccharide that has been isolated from the leaves of the African shrub Protea rubropilosa. It is soluble in water and practically insoluble in methanol.
2-Methylacetoacetyl-CoA belongs to the class of organic compounds known as 3-oxo-acyl CoAs. These are organic compounds containing a 3-oxo acylated coenzyme A derivative. 2-Methylacetoacetyl-CoA is a substrate for 3-hydroxyacyl-CoA dehydrogenase type II, 3-ketoacyl-CoA thiolase (mitochondrial), peroxisomal bifunctional enzyme, trifunctional enzyme beta subunit (mitochondrial), short chain 3-hydroxyacyl-CoA dehydrogenase (mitochondrial), and 3-ketoacyl-CoA thiolase (peroxisomal).
Tricosanoic acid, also known as N-tricosanoate or 22FA, belongs to the class of organic compounds known as very long-chain fatty acids. These are fatty acids with an aliphatic tail that contains at least 22 carbon atoms. Tricosanoic acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. Tricosanoic acid is a potentially toxic compound.
4-Trimethylammoniobutanoic acid, also known as gamma-butyrobetaine (GBB) or 3-dehydroxycarnitine, is a highly water-soluble derivative of gamma-aminobutyric acid (GABA). It is also a precursor of L-carnitine. It is a substrate of gamma butyrobetaine hydroxylase/dioxygenase (also known as BBOX) which catalyzes the formation of L-carnitine from gamma-butyrobetaine, the last step in the L-carnitine biosynthesis pathway. Carnitine is essential for the transport of activated fatty acids across the mitochondrial membrane during mitochondrial beta-oxidation. Numerous disorders have been described that lead to disturbances in energy production and in intermediary metabolism which are characterized by the production and excretion of unusual acylcarnitines. A mutation in the gene coding for carnitine-acylcarnitine translocase, or the OCTN2 transporter aetiologically, causes a carnitine deficiency that results in poor intestinal absorption of dietary L-carnitine, impaired reabsorption by the kidney, and increased urinary loss. Determination of the qualitative pattern of acylcarnitines can be of diagnostic and therapeutic importance. The betaine structure of carnitine requires special analytical procedures for recording. The ionic nature of L-carnitine causes a high water solubility which decreases with increasing chain length of the ester group in the acylcarnitines. Therefore, the distribution of L-carnitine and acylcarnitines in various organs is defined by their function and their physicochemical properties as well. High-performance liquid chromatography (HPLC) permits screening for free and total carnitine, as well as complete quantitative acylcarnitine determination, including the long-chain acylcarnitine profile (PMID: 17508264, Monatshefte fuer Chemie (2005), 136(8), 1279-1291., Int J Mass Spectrom. 1999;188:39-52.).
Heme O differs from the closely related heme A by having a methyl group at ring position 8 instead of the formyl group, the isoprenoid chain at position 2 is the same (Wikipedia).
GDP-mannose is a nucleoside diphosphate sugar that is important in the production of fucosylated oligosaccharides. In particular, GDP-mannose is converted to GDP-fucose, which is the fucose donor in the construction of all mammalian fucosylated glycans. GDP-mannose is transformed to GDP-fucose via three enzymatic reactions carried out by two proteins, GDP-mannose 4,6-dehydratase (GMD) and a second enzyme, GDP-keto-6-deoxymannose 3,5-epimerase, 4-reductase. GDP-mannose 4,6-dehydratase (EC 4.2.1.47) catalyzes the chemical reaction: GDP-mannose <--> GDP-4-dehydro-6-deoxy-D-mannose + H2O. The epimerase converts the GDP-4-dehydro-6-deoxy-D-mannose to GDP-fucose (PMID: 12651883). GDP-mannose is also synthesized from mannose 1-phosphate via the enzyme ATP-mannose-1-phosphate-guanyltransferase and GTP.
Trans-1,2-Dihydrobenzene-1,2-diol is an intermediate in the metabolism of Prostaglandin and leukotriene. It is a substrate for Aldo-keto reductase family 1 member C3, Aldo-keto reductase family 1 member C4, Aldo-keto reductase family 1 member C2 and Aldo-keto reductase family 1 member C1.
Keratan is a sulfated mucopolysaccharide initially isolated from bovine cornea. At least two types are known. Type I, found mostly in the cornea, contains D-galactose and D-glucosamine-6-O-sulfate as the repeating unit; type II, found in skeletal tissues, contains D-galactose and D-galactosamine-6-O-sulfate as the repeating unit.
3-Hydroxybutyryl-CoA is a substrate for Enoyl-CoA hydratase (mitochondrial), Trifunctional enzyme alpha subunit (mitochondrial) and Peroxisomal bifunctional enzyme.
Pyruvaldehyde is an organic compound used often as a reagent in organic synthesis, as a flavoring agent, and in tanning. It has been demonstrated as an intermediate in the metabolism of acetone and its derivatives in isolated cell preparations, in various culture media, and in vivo in certain animals.
2-trans,4-trans-Decadienoyl- CoA, a metabolite of unsaturated fatty acids with trans double bonds, is readily degraded by a beta-oxidation into acetyl- CoA.
4-aminophenol is considered a minor nephrotoxic metabolite of phenacetin and acetaminophen (paracetamol) in man. 4-Aminophenol can undergo autoxidations and metal-catalyzed and enzymatic oxidations in man to produce reactive oxygen species. (PMID 1713494).
Lathosterol is a a sterol (a combination steroid and alcohol) and a lipid found in the cell membranes of all body tissues, and transported in the blood plasma of all animals. It is used as an indicator of whole-body cholesterol synthesis (PMID 14511438). Plasma lathosterol levels are significantly elevated in patients with bile acid malabsorption (PMID:8777839). Lathosterol oxidase (EC 1.14.21.6) is an enzyme that catalyzes the chemical reaction 5alpha-cholest-7-en-3beta-ol + NAD(P)H + H+ + O2 cholesta-5,7-dien-3beta-ol + NAD(P)+ + 2 H2O.
2-Methyl-3-oxopropanoic acid is an intermediate in the metabolism of Propanoate. It is a substrate for 3-hydroxyisobutyrate dehydrogenase (mitochondrial), Alanine--glyoxylate aminotransferase 2 (mitochondrial) and Methylmalonate-semialdehyde dehydrogenase (mitochondrial).
5'-Methylthioadenosine, also known as MTA or thiomethyladenosine, belongs to the class of organic compounds known as 5'-deoxy-5'-thionucleosides. These are 5'-deoxyribonucleosides in which the ribose is thio-substituted at the 5'position by a S-alkyl group. 5'-Methylthioadenosine is metabolized solely by MTA-phosphorylase, to yield 5-methylthioribose-1-phosphate and adenine, a crucial step in the methionine and purine salvage pathways, respectively. 5'-Methylthioadenosine exists in all living species, ranging from bacteria to humans. 5'-Methylthioadenosine (MTA) is a naturally occurring sulfur-containing nucleoside present in all mammalian tissues. Within humans, 5'-methylthioadenosine participates in a number of enzymatic reactions. In particular, 5'-methylthioadenosine and spermidine can be biosynthesized from S-adenosylmethioninamine and putrescine through the action of the enzyme spermidine synthase. In addition, 5'-methylthioadenosine can be converted into 5-methylthioribose 1-phosphate and L-methionine; which is catalyzed by the enzyme S-methyl-5'-thioadenosine phosphorylase. It is produced from S-adenosylmethionine mainly through the polyamine biosynthetic pathway, where it behaves as a powerful inhibitory product. For instance, 5'-Methylthioadenosine has been shown to influence the regulation of gene expression, proliferation, differentiation, and apoptosis (PMID:15313459). In humans, 5'-methylthioadenosine is involved in the metabolic disorder called hypermethioninemia. Outside of the human body, 5'-Methylthioadenosine has been detected, but not quantified in several different foods, such as soursops, allspices, summer grapes, alaska wild rhubarbs, and breadfruits. Elevated excretion appears in children with severe combined immunodeficiency syndrome (SCID) (PMID:3987052). Evidence suggests that 5'-Methylthioadenosine can affect cellular processes in many ways. 5'-Methylthioadenosine can be found in human urine.
Malonyl-CoA belongs to the class of organic compounds known as acyl-CoAs. These are organic compounds containing a coenzyme A substructure linked to an acyl chain. Thus, malonyl-CoA is considered to be a fatty ester lipid molecule. Malonyl-CoA is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Within humans, malonyl-CoA participates in a number of enzymatic reactions. In particular, malonyl-CoA can be biosynthesized from acetyl-CoA; which is mediated by the enzyme acetyl-CoA carboxylase 1. In addition, malonyl-CoA can be converted into malonic acid and coenzyme A; which is catalyzed by the enzyme fatty acid synthase. Outside of the human body, malonyl-CoA has been detected, but not quantified in, several different foods, such as rapes, mamey sapotes, jew's ears, pepper (C. chinense), and Alaska wild rhubarbs. This could make malonyl-CoA a potential biomarker for the consumption of these foods. Malonyl-CoA is a coenzyme A derivative that plays a key role in fatty acid synthesis in the cytoplasmic and microsomal systems.
Cytidine 5'-monophosphate-N-acetylneuraminic acid (CMP-Neu5Ac), also known as CMP-N-acetyl-β-neuraminic acid, belongs to the class of organic compounds known as pyrimidine nucleotide sugars. These are pyrimidine nucleotides bound to a saccharide derivative through the terminal phosphate group. CMP-Neu5Ac is an extremely weak basic (essentially neutral) compound (based on its pKa). CMP-Neu5Ac donates N-acetylneuraminic acid to the terminal sugar of a ganglioside or glycoprotein.
(S)-Succinyldihydrolipoamide is a metabolite (a product as well as a substrate) in glutamate degradation.
Adenosine diphosphate ribose is a molecule formed into poly(ADP-ribose) or PAR chains by the enzyme poly ADP ribose polymerase or PARP. PARP is found in every cell nucleus. Its main role is to detect and signal single-strand DNA breaks (SSB) to the enzymatic machinery involved in the SSB repair. PARP activation is an immediate cellular response to metabolic, chemical, or radiation-induced DNA SSB damage. Once PARP detects a SSB, it binds to the DNA, and, after a structural change, begins the synthesis of a poly (ADP-ribose) chain (PAR) as a signal for the other DNA-repairing enzymes such as DNA ligase III (LigIII), DNA polymerase beta, and scaffolding proteins such as X-ray cross-complementing gene 1 (XRCC1). After repairing, the PAR chains are degraded via PAR glycohydrolase (PARG). ADP-ribose binds to and activates the TRPM2 ion channel. Adenosine diphosphate ribose is an intermediate in NAD metabolism. The enzyme NAD(P)+ nucleosidase [EC:3.2.2.6] catalyzes the production of this metabolite from nicotinamide adenine dinucleotide phosphate. This reaction is irreversible and occurs in the cytosol.
Nicotinic acid adenine dinucleotide, also known as deamido-NAD or NAAD, belongs to the class of organic compounds known as (5'->5')-dinucleotides. These are dinucleotides where the two bases are connected via a (5'->5')-phosphodiester linkage. NAAD is possibly soluble (in water) and a strong basic compound (based on its pKa). NAAD exists in all living species, ranging from bacteria to humans. L-Glutamine and NAAD can be converted into L-glutamic acid and NAD; which is catalyzed by the enzyme glutamine-dependent nad(+) synthetase. In humans, NAAD is involved in the nicotinate and nicotinamide metabolism pathway. NAAD is also involved in the metabolic disorder called succinic semialdehyde dehydrogenase deficiency. Outside of the human body, NAAD has been detected, but not quantified in, several different foods, such as japanese walnuts, cauliflowers, sparkleberries, komatsuna, and macadamia nut (m. tetraphylla). This could make NAAD a potential biomarker for the consumption of these foods. NAAD is the product of the degradation of Nicotinic acid adenine dinucleotide phosphate (NAADP) by a Ca2+-sensitive phosphatase. NAADP is a Ca2+-mobilizing second messenger which is synthesized, in response to extracellular stimuli, via the base-exchange reaction by an ADP-ribosyl cyclase (ARC) family members (such as CD38). NAADP binds to and opens Ca2+ channels on intracellular organelles, thereby increasing the intracellular Ca2+ concentration which, in turn, modulates a variety of cellular processes. Structurally, NAADP it is a dinucleotide that only differs from the house-keeping enzyme cofactor, NADP, by a hydroxyl group (replacing the nicotinamide amino group) and yet this minor modification converts it into the most potent Ca2+-mobilizing second messenger yet described. NAADP may also be broken down to 2-phosphoadenosine diphosphoribose (ADPRP) by CD38 or reduced to NAADPH.
N2-Succinyl-L-glutamic acid 5-semialdehyde is a substrate for Succinate semialdehyde dehydrogenase (mitochondrial) and Ornithine aminotransferase (mitochondrial). It can be found in Escherichia (UniProt).
6,8-Dihydroxypurine is an endogenous nucleoside found in human fluids. Purine bases are present in higher amounts in tumor-bearing patients compared to healthy controls. DNA hypermethylation is a common finding in malignant cells and has been explored as a therapeutic target for hypomethylating agents. When chemical bonds to DNA, the DNA becomes damaged and proper and complete replication cannot occur to make the normal intended cell. A DNA adduct is an abnormal piece of DNA covalently-bonded to a cancer-causing chemical. This has shown to be the start of a cancerous cell, or carcinogenesis. DNA adducts in scientific experiments are used as bio-markers and as such are themselves measured to reflect quantitatively, for comparison, the amount of cancer in the subject. (PMID: 3506820, 17044778, 17264127, 16799933).
1-Octanol, also known as octan-1-ol, is the organic compound with the molecular formula CH3(CH2)7OH. It is a fatty alcohol. Many other isomers are also known generically as octanols. Octanol is mainly produced industrially by the oligomerization of ethylene using triethylaluminium followed by oxidation of the alkylaluminium products. This route is known as the Ziegler alcohol synthesis. Octanol also occurs naturally in the form of esters in some essential oils. Octanol and water are immiscible. The distribution of a compound between water and octanol is used to calculate the partition coefficient (logP) of that molecule. Water/octanol partitioning is a good approximation of the partitioning between the cytosol and lipid membranes of living systems. Octanol is a colorless, slightly viscous liquid used as a defoaming or wetting agent. It is also used as a solvent for protective coatings, waxes, and oils, and as a raw material for plasticizers. It is also one of many compounds derived from tobacco and tobacco smoke and shown to increase the permeability of the membranes of human lung fibroblasts (PMID 7466833).
Methyl propenyl ketone, also known as (3E)-3-penten-2-one or 2-oxo-3-pentene, belongs to the class of organic compounds known as enones. Enones are compounds containing the enone functional group, with the structure RC(=O)CR'. Thus, methyl propenyl ketone is considered to be an oxygenated hydrocarbon lipid molecule. Methyl propenyl ketone is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. Methyl propenyl ketone, with regard to humans, has been found to be associated with several diseases such as nonalcoholic fatty liver disease and ulcerative colitis. Methyl propenyl ketone has also been linked to the inborn metabolic disorder celiac disease. Methyl propenyl ketone is occasionally found as a volatile component of normal human biofluids. It is found as a volatile in the hawthorn fruit upon ripening, and also is part of the scent components of the urine of some animals. Methyl propenyl ketone is a volatile organic compound.
S-Adenosylmethionine (CAS: 29908-03-0), also known as SAM or AdoMet, is a physiologic methyl radical donor involved in enzymatic transmethylation reactions and present in all living organisms. It possesses anti-inflammatory activity and has been used in the treatment of chronic liver disease (From Merck, 11th ed). S-Adenosylmethionine is a natural substance present in the cells of the body. It plays a crucial biochemical role by donating a one-carbon methyl group in a process called transmethylation. S-Adenosylmethionine, formed from the reaction of L-methionine and adenosine triphosphate catalyzed by the enzyme S-adenosylmethionine synthetase, is the methyl-group donor in the biosynthesis of both DNA and RNA nucleic acids, phospholipids, proteins, epinephrine, melatonin, creatine, and other molecules.
N1-Acetylspermine belongs to the class of organic compounds known as acetamides. These are organic compounds with the general formula RNHC(=O)CH3, where R= organyl group. N1-Acetylspermine exists in all living species, ranging from bacteria to humans. Outside of the human body, N1-Acetylspermine has been detected, but not quantified in several different foods, such as purple lavers, jutes, yams, pineapples, and fireweeds. This could make N1-acetylspermine a potential biomarker for the consumption of these foods. N1-Acetylspermine is a polyamine that has been postulated to be an intermediate in the conversion of spermine to spermidine.
D-myo-Inositol 1,3,4,6-tetrakisphosphate, also known as Ins(1,3,4,6)P4, belongs to the class of organic compounds known as inositol phosphates. Inositol phosphates are compounds containing a phosphate group attached to an inositol (or cyclohexanehexol) moiety. D-myo-Inositol 1,3,4,6-tetrakisphosphate is an extremely strong acidic compound (based on its pKa). D-myo-Inositol 1,3,4,6-tetrakisphosphate participates in a number of enzymatic reactions. In particular, D-myo-inositol 1,3,4,6-tetrakisphosphate can be converted into D-myo-inositol 1,3,4,5,6-pentakisphosphate through the action of the enzyme inositol polyphosphate multikinase. In addition, D-myo-inositol 1,3,4,6-tetrakisphosphate can be biosynthesized from inositol 1,3,4-trisphosphate; which is mediated by the enzyme inositol-tetrakisphosphate 1-kinase. In humans, D-myo-inositol 1,3,4,6-tetrakisphosphate is involved in inositol phosphate metabolism and is a substrate for the tyrosine-protein kinase BTK.
(S)-2,3-Epoxysqualene, also known as 2,3-oxidosqualene or (S)-squalene-2,3-epoxide, belongs to the class of organic compounds known as triterpenoids. These are terpene molecules containing six isoprene units. Thus, (S)-2,3-epoxysqualene is considered to be an isoprenoid lipid molecule. (S)-2,3-Epoxysqualene is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. (S)-2,3-Epoxysqualene is an intermediate in the biosynthesis of terpenoid. It is a substrate for squalene monooxygenase and lanosterol synthase.
2(N)-methyl-norsalsolinol (NMNorsal) is a dihydroxylated tetrahydroisoquinoline derivative 2(N)-analogue of salsolinol, identified as a putative endogenous neurotoxin in patients with Parkinson's disease. A prominent blood-brain barrier (BBB) is described to exist for salsolinol, but penetration of NMNorsal occurs through the BBB into the caudate nucleus of the rat brain. There was no alteration in extracellular dopamine or 3,4-dihydroxyphenylacetic acid levels. (PMID 11924888). 2(N)-methyl-norsalsolinol was identified in L-DOPA-treated patients with Parkinson's disease and proposed to be responsible for behavioral changes. Atypical heterocyclic L-DOPA/dopamine metabolite NMNorsal is able to modify long-term regulation of serotonin and opioid receptor expression in striatum. Since the occurrence of hallucinosis or psychosis following L-DOPA treatment is related to the serotonergic system, these results probably reflect a link between NMNorsal and L-DOPA side effects in Parkinson's disease. (PMID 14607311).
Indoleacetaldehyde, also known as tryptaldehyde, belongs to the class of organic compounds known as 3-alkylindoles. 3-Alkylindoles are compounds containing an indole moiety that carries an alkyl chain at the 3-position. Indoleacetaldehyde is an extremely weak basic (essentially neutral) compound (based on its pKa). Indoleacetaldehyde exists in all living species, ranging from bacteria to humans. Within humans, indoleacetaldehyde participates in a number of enzymatic reactions. In particular, indoleacetaldehyde can be biosynthesized from tryptamine; which is mediated by the enzyme kynurenine 3-monooxygenase. In addition, indoleacetaldehyde can be converted into indoleacetic acid; which is catalyzed by the enzyme aldehyde dehydrogenase, mitochondrial. In humans, indoleacetaldehyde is involved in tryptophan metabolism. Outside of the human body, indoleacetaldehyde has been detected, but not quantified in, several different foods, such as nuts, turmerics, Alaska blueberries, summer savouries, and black raspberries. This could make indoleacetaldehyde a potential biomarker for the consumption of these foods. Indoleacetaldehyde is also a substrate for amine oxidase and 4-trimethylaminobutyraldehyde dehydrogenase.
Deoxyuridine triphosphate (dUTP) is a deoxynucleotide triphosphate (dNTP) that is chemically similar to uridine triphosphate (UTP) except that it has a deoxyribose sugar instead of a ribose sugar. DNA synthesis requires the availability of deoxynucleotide triphosphates (dTTP, dATP, dGTP, dCTP), whereas RNA synthesis requires the availability of nucleotide triphosphates (NTPs) such as TTP, ATP, GTP, and UTP. The conversion of nucleotide triphosphates (NTPs) into dNTPs can only be done in the diphosphate form. Typically, an NTP has one phosphate removed to become an NDP. This is then converted into a dNDP by an enzyme called ribonucleotide reductase and followed by the re-addition of phosphate to give a dNTP. dUTP is a substrate for several enzymes, including inosine triphosphate pyrophosphatase, deoxyuridine 5'-triphosphate nucleotidohydrolase (mitochondrial), uridine-cytidine kinase 1, nucleoside diphosphate kinase 3, nucleoside diphosphate kinase B, nucleoside diphosphate kinase 6, nucleoside diphosphate kinase (mitochondrial), nucleoside diphosphate kinase homolog 5, nucleoside diphosphate kinase A, and nucleoside diphosphate kinase 7. While UTP is routinely incorporated into RNA, dUTP is not normally incorporated into DNA. Instead, if dUTP is misincorporated into DNA, it can cause DNA damage. Therefore, dUTP can be considered as a teratogen or a mutagen. The extent of DNA damage caused by dUTP is highly dependent on the levels of the dUTP pyrophosphatase (dUTPase) and uracil-DNA glycosylase (UDG), which limits the intracellular accumulation of dUTP. Additionally, loss of viability following thymidylate synthase (TS) inhibition occurs as a consequence of the accumulation of dUTP in some cell lines and subsequent misincorporation of uracil into DNA (PMID: 11487279).
5(S)-Hydroperoxyeicosatetraenoic acid is a lipid hydroperoxide precursor of leukotrienes. The first step of biosynthesis of leukotrienes is conversion of arachidonic acid into 5(S)-hydroperoxy-6,8,11,14-(E,Z,Z,Z)-eicosatetraenoic acid [5(S)-HpETE] by 5- lipoxygenases (5-LOX). Lipid hydroperoxides undergo homolytic decomposition into bifunctional electrophiles, which react with DNA bases to form DNA adducts. These DNA modifications are proposed to be involved in the etiology of cancer, cardiovascular disease, and neurodegeneration. 5-LOX, the enzyme responsible for the formation of 5(S)-HpETE in vivo, is expressed primarily in leukocytes, including monocytes and macrophages. Studies have implicated the 5-LOX pathway as an important mediator in the pathology of atherosclerosis. (PMID: 15777099). Endogenously generated 5-hydroperoxyeicosatetraenoic acid is the preferred substrate for human leukocyte leukotriene A4 synthase activity. Thus, the arachidonic acid moiety is preferentially converted to LTA4 in a concerted reaction without dissociation of a 5-HPETE intermediate. (PMID: 3036580).
Dyspropterin, an intermediate formed from dihydroneopterin triphosphate in the biosynthetic pathway of tetrahydrobiopterin.
Diacetylchitobiosyldiphosphodolichol is an intermediate in the N-glycan biosynthesis, a series of reactions catalyzed by the enzymes chitobiosyldiphosphodolichol beta-mannosyltransferases (EC 2.4.1.141, EC 2.4.1.142). (KEGG). This compound and its corresponding enzymes are implicated in Congenital disorders of glycosylation (CDGs) , that comprise a group of multisystem diseases with mostly severe psychomotor and mental retardation. Type I CDG comprises those disorders in which there are defects that affect biosynthesis of dolichol-linked oligosaccharides in the cytosol or the endoplasmic reticulum (ER), as well as defects involving the transfer of oligosaccharides onto nascent glycoproteins. Type II CDG comprises all defects of further trimming and elongation of N-linked oligosaccharides in the ER and Golgi. (OMIM 608540).
FADH is the reduced form of flavin adenine dinucleotide (FAD). FAD is synthesized from riboflavin and two molecules of ATP. Riboflavin is phosphorylated by ATP to give riboflavin 5-phosphate (FMN). FAD is then formed from FMN by the transfer of an AMP moiety from a second molecule of ATP. FADH is generated in each round of fatty acid oxidation, and the fatty acyl chain is shortened by two carbon atoms as a result of these reactions; because oxidation is on the beta carbon, this series of reactions is called the beta-oxidation pathway. In the citric acid cycle, FADH is involved in the harvesting of high-energy electrons from carbon fuels; the citric acid cycle itself neither generates a large amount of ATP nor includes oxygen as a reactant. Instead, the citric acid cycle removes electrons from acetyl CoA and uses these electrons to form FADH.
N2-Succinyl-L-ornithine is a substrate for Ornithine aminotransferase (mitochondrial). It can be found in Escherichia (UniProt).
Plays an especially improtant role in photobiological responses. The excited states of N-formylkynurenine react to produce hydroxyl radicals.
Guanosine diphosphate, also known as 5'-GDP or 5'-diphosphate, guanosine, belongs to the class of organic compounds known as purine ribonucleoside diphosphates. These are purine ribobucleotides with diphosphate group linked to the ribose moiety. Guanosine diphosphate exists in all living species, ranging from bacteria to humans. In humans, guanosine diphosphate is involved in intracellular signalling through adenosine receptor A2B and adenosine. Outside of the human body, Guanosine diphosphate has been detected, but not quantified in several different foods, such as devilfish, java plums, green beans, almonds, and orange mints. Guanosine diphosphate is a purine ribonucleoside 5'-diphosphate resulting from the formal condensation of the hydroxy group at the 5' position of guanosine with pyrophosphoric acid.
Deoxycytidine monophosphate (dCMP), also known as deoxycytidylic acid or deoxycytidylate in its conjugate acid and conjugate base forms, respectively, is a deoxynucleotide, and one of the four monomers that make up DNA. In a DNA double helix, it will base pair with deoxyguanosine monophosphate. dCMP belongs to the class of organic compounds known as pyrimidine 2'-deoxyribonucleoside monophosphates. These are pyrimidine nucleotides with a monophosphate group linked to the ribose moiety lacking a hydroxyl group at position 2. Deficiency of the enzyme deoxycytidine kinase (EC2.7.1.74) is associated with resistance to antiviral and anticancer chemotherapeutic agents, whereas increased enzyme activity is associated with increased activation of these compounds to cytotoxic nucleoside triphosphate derivatives. dCMP exists in all living species, ranging from bacteria to humans. Within humans, dCMP participates in a number of enzymatic reactions. In particular, dCMP can be converted to dCDP by the enzyme UMP-CMP kinase 2. In addition, dCMP can be converted into deoxycytidine, which is catalyzed by the enzyme cytosolic purine 5'-nucleotidase. In humans, dCMP is involved in the metabolic disorder called ump synthase deficiency (orotic aciduria). Outside of the human body, dCMP has been detected, but not quantified in several different foods, such as turnips, garlics, agaves, garden onions, and italian sweet red peppers. dCMP is a deoxycytosine nucleotide containing one phosphate group esterified to the deoxyribose moiety in the 2'-,3'- or 5- positions.
4a-Formyl-5a-cholesta-8,24-dien-3b-ol is an intermediate in the biosynthesis of cholesterol, in a reaction catalyzed by the enzyme methylsterol monooxygenase (EC 1.14.13.72, 4,4-dimethyl-5alpha-cholest-7-en-3beta-ol,hydrogen-donor:oxygen oxidoreductase (hydroxylating)). (MetaCyc).
3-Hydroxycotinine (3HC) is the main nicotine metabolite detected in smokers urine. It is also excreted as a glucuronide conjugate (3HC-Gluc). 3HC and 3HC-Gluc account for 40-60% of the nicotine dose in urine.
The main function of coenzyme A is to carry acyl groups (such as the acetyl group) or thioesters. Acetyl-CoA is an important molecule itself. It is the precursor to HMG CoA, which is a vital component in cholesterol and ketone synthesis. (wikipedia). acetyl CoA participates in the biosynthesis of fatty acids and sterols, in the oxidation of fatty acids and in the metabolism of many amino acids. It also acts as a biological acetylating agent.
Allantoic acid is the end product of Allantoicase [EC:3.5.3.4], an enzyme involved in uric acid degradation (Purine metabolism). Although it is commonly accepted that allantoicase is lost in mammals, it has been identified in mice and humans. (PMID 11852104). A crystalline, transparent, colorless substance found in the allantoic liquid of the fetal calf. It was formerly called allantoic acid and amniotic acid.
Hydantoin-5-propionic acid is a metabolite of histidine, urinary hydantoin-5-propionic acid occur in patients with disorders of folate/ vitamin B12 metabolism (PMID: 3760095). Folic acid non-dependent excessive formiminoglutamic aciduria (Figlu-uria) is an extremely rare disorder; treatment with oral folate supplements (15 mg/day) for 3 weeks failed to reduce urinary hydantoin-5-propionic acid (PMID: 8487495).
1-Deoxy-D-xylulose 5-phosphate is a substrate for 2,4-dienoyl-CoA reductase (mitochondrial). It has been found to be a metabolite of Escherichia and Streptomyces (PMID: 10648511; PMID: 9371765).
4alpha-Methylzymosterol belongs to the class of organic compounds known as cholesterols and derivatives. Cholesterols and derivatives are compounds containing a 3-hydroxylated cholestane core. Thus, 4alpha-methylzymosterol is considered to be a sterol lipid molecule. 4alpha-Methylzymosterol is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Outside of the human body, 4alpha-methylzymosterol has been detected, but not quantified in, several different foods, such as redcurrants, sunflowers, robusta coffees, white mustards, and sesbania flowers. This could make 4alpha-methylzymosterol a potential biomarker for the consumption of these foods. 4alpha-Methylzymosterol is an intermediate in the biosynthesis of steroids. It is the seventh to last step in the synthesis of vitamin D2 and is converted from 3-keto-4-methylzymosterol via the enzyme 3-keto steroid reductase (EC 1.1.1.270). It is then converted into zymosterol.
Chlordecone alcohol is the major metabolite of Chlordecone [ an organochlorine pesticide, CAS# 143-50-0] in humans via bioreduction in the liver by Chlordecone reductase [EC: 1.1.1.225 ,CAS # 102484-73-1]. (PMID 2420999). Chlordecone treatment actively suppresses induction of 2B1 and 2B2 mRNAs in adult human hepatocytes; anti-estrogens such as Tamoxifen fail to reverse 2B1/2 mRNA induction following Chlordecone treatment of hepatocytes. (PMID 7513451). Both Chlordecone and Chlordecone alcohol alter the permeability of isolated ovine erythrocytes. (PMID 2455063).
5-Thymidylic acid (conjugate base thymidylate), also known as thymidine monophosphate (TMP), deoxythymidine monophosphate (dTMP), or deoxythymidylic acid (conjugate base deoxythymidylate), is a nucleotide that is used as a monomer in DNA. It is an ester of phosphoric acid with the nucleoside thymidine. dTMP consists of a phosphate group, the pentose sugar deoxyribose, and the nucleobase thymine. Unlike the other deoxyribonucleotides, thymidine monophosphate often does not contain the "deoxy" prefix in its name; nevertheless, its symbol often includes a "d" ("dTMP"). 5-Thymidylic acid belongs to the class of organic compounds known as pyrimidine 2'-deoxyribonucleoside monophosphates. These are pyrimidine nucleotides with a monophosphate group linked to the ribose moiety lacking a hydroxyl group at position 2. The neutral species of 5-Thymidylic acid (2'-deoxythymidine 5'-monophosphate). 5-Thymidylic acid exists in all living species, ranging from bacteria to humans. Within humans, 5-thymidylic acid participates in a number of enzymatic reactions. In particular, 5-thymidylic acid and dihydrofolic acid can be biosynthesized from dUMP and 5,10-methylene-THF by the enzyme thymidylate synthase. In addition, 5-thymidylic acid can be converted into dTDP; which is catalyzed by the enzyme thymidylate synthase. In humans, 5-thymidylic acid is involved in pyrimidine metabolism. Outside of the human body, 5-Thymidylic acid has been detected, but not quantified in several different foods, such as common buckwheats, corn salad, garden cress, squashberries, and star fruits.
L-Glutamic acid 5-phosphate is an intermediate in the urea cycle and the metabolism of amino groups. It is a substrate of aldehyde dehydrogenase 18 family, member A1 [EC:2.7.2.11 1.2.1.41] (KEGG)In citrulline biosynthesis, it is a substrate of the enzyme glutamate-5-semialdehyde dehydrogenase [EC 1.2.1.41] and in proline synthesis it is a substrate of the enzyme Glutamate 5-kinase [EC 2.7.2.11] (BioCyc).
Dopaquinone, also known as o-dopaquinone or L-dopaquinone, is a member of the class of compounds known as L-alpha-amino acids. L-alpha-amino acids are alpha-amino acids which have the L-configuration of the alpha-carbon atom. Dopaquinone is slightly soluble (in water) and a moderately acidic compound (based on its pKa). L-Dopaquinone is a metabolite of L-DOPA and a precursor of melanin. Melanin is synthesized from tyrosine by hydroxylation to dihydroxyphenylalanine (DOPA) and subsequent oxidation to dopaquinone. Both reactions are catalyzed by the enzyme tyrosinase, which is the rate-limiting step. Dopaquinone has an ortho-quinone ring, which is known to be neurotoxic and highly reactive with many other compounds (PMID: 413870). Dopaquinone typically combines with cysteine to form pheomelanin (a pigment-polymer). Alternatively, dopaquinone can be converted to leucodopachrome and eventually to eumelanin (also a pigment-polymer). Dopaquinone can be found in skin and feces. Within the cell, dopaquinone is primarily located in the cytoplasm. Dopaquinone is involved in several metabolic disorders, some of which include transient tyrosinemia, hawkinsinuria, tyrosinemia type I, and alkaptonuria. Chronically high levels of dopaquinone are associated with Parkinson's disease (PD). Many Parkinson's patients are treated with L-DOPA. However, long-term treatment with L-DOPA may actually worsen symptoms or result in neurotic and psychotic symptoms. These may be due to dopachrome and dopaquinone accumulating in the brain of L-DOPA treated patients (PMID: 19131041, PMID: 12373519).
27-Deoxy-5b-cyprinol is an intermediate in Bile acid synthesis pathway, in a sequence of reactions catalyzed by sterol 27-hydroxylase (CYP27) in the oxidation of 5 beta-cholestane-3 alpha,7 alpha,12 alpha,27-tetrol into 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid (PMID: 8496170). 5 beta-cholestane-3 alpha,7 alpha,12 alpha,25-tetrol 3-glucuronide, a metabolite of 27-Deoxy-5b-cyprinol, is the major bile alcohol component in serum from cerebrotendinous xanthomatosis patients (PMID: 7920441).
5-aminoimidazole ribonucleotide (AIR), is an intermediate of purine nucleotide biosynthesis. It is also the precursor to 4-amino-2-methyl-5-hydroxymethylpyrimidine (HMP), the first product of pyrimidine biosynthesis. This reaction is mediated by the enzyme HMP-P kinase (ThiD). HMP is a precursor of thiamine phosphate (TMP), and subsequently to thiamine pyrophosphate (TPP). TPP is an essential cofactor in all living systems that plays a central role in metabolism. (PMID: 15326535). 5-Aminoimidazole ribonucleotide is a substrate for a number of proteins including: Scaffold attachment factor B2, Multifunctional protein ADE2, Pulmonary surfactant-associated protein B, Tumor necrosis factor receptor superfamily member 25, Pulmonary surfactant-associated protein C, Serine/threonine-protein kinase Chk1, Vinexin, Trifunctional purine biosynthetic protein adenosine-3, Antileukoproteinase 1 and Scaffold attachment factor B.
Nicorette is a branded over-the-counter palliative treatment which is used to ameliorate the withdrawal effects involved in quitting smoking. Originally available as a patch for topical application, it was later made available as a nicotine gum (composed of nicotine polacrilex)lozenge, inhaler, and nasal spray. All these products contain nicotine as the active ingredient and work by delivering this into the bloodstream.
2-Aminomuconic acid is a product of the Tryptophan metabolism degradation pathway (kinurenine pathway), in a reaction catabolized by the enzyme aminocarboxymuconate semialdehyde decarboxylase [EC:4.1.1.45]. The kynurenine pathway is the major route of L-tryptophan degradation in mammals. (BioCyc).
Obtusifoliol belongs to the class of organic compounds known as ergosterols and derivatives. These are steroids containing ergosta-5,7,22-trien-3beta-ol or a derivative thereof, which is based on the 3beta-hydroxylated ergostane skeleton. Thus, obtusifoliol is considered to be a sterol lipid molecule. Obtusifoliol is found, on average, in the highest concentration within evening primroses. Obtusifoliol has also been detected, but not quantified in, several different foods, such as common chokecherries, jicama, pepper (C. frutescens), avocado, and pecan nuts. This could make obtusifoliol a potential biomarker for the consumption of these foods. Obtusifoliol is an intermediate in the biosynthesis of cholesterol: in a reaction catalyzed by the enzyme CYP51A1 (EC 1.14.13.70, sterol 14-demethylase) (PMID: 9559662). CYP51A1 is a housekeeping enzyme essential for the viability of mammals, an essential step in cholesterol biosynthesis. Sterol 14-demethylation occurs in all organisms exhibiting de novo sterol biosynthesis and CYP51A1 has been conserved throughout evolution (PMID: 8797093).
Isobutyryl-CoA is a substrate for Acyl-CoA dehydrogenase (short-chain specific, mitochondrial), Acyl-CoA dehydrogenase (medium-chain specific, mitochondrial) and Acyl-CoA dehydrogenase (long-chain specific, mitochondrial).
13,14-dihydro-15-keto PGA2 is produced via non-enzymatic dehydration of 13,14-dihydro-15-keto PGE2. PGE2 is the most common and most biologically active of the mammalian prostaglandins. It has important effects in labour and also stimulates osteoblasts to release factors which stimulate bone resorption by osteoclasts (a type of bone cell that removes bone tissue by removing the bone's mineralized matrix). (PMID: 16978535, 7384561, 7384560)Prostaglandins are eicosanoids. The eicosanoids consist of the prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and lipoxins (LXs). The PGs and TXs are collectively identified as prostanoids. Prostaglandins were originally shown to be synthesized in the prostate gland, thromboxanes from platelets (thrombocytes), and leukotrienes from leukocytes, hence the derivation of their names. All mammalian cells except erythrocytes synthesize eicosanoids. These molecules are extremely potent, able to cause profound physiological effects at very dilute concentrations. All eicosanoids function locally at the site of synthesis, through receptor-mediated G-protein linked signalling pathways.
dCDP is a substrate for Uridine-cytidine kinase 1, Nucleoside diphosphate kinase (mitochondrial), Nucleoside diphosphate kinase homolog 5, Ribonucleoside-diphosphate reductase large subunit, Nucleoside diphosphate kinase A, Nucleoside diphosphate kinase 7, Ribonucleoside-diphosphate reductase M2 chain, Nucleoside diphosphate kinase B, Nucleoside diphosphate kinase 3, Nucleoside diphosphate kinase 6 and UMP-CMP kinase.
Flavin adenine dinucleotide (FAD) is a redox-active coenzyme associated with various proteins, which is involved with several enzymatic reactions in metabolism. FAD, also known as adeflavin or flamitajin b, belongs to the class of organic compounds known as flavin nucleotides. These are nucleotides containing a flavin moiety. Flavin is a compound that contains the tricyclic isoalloxazine ring system, which bears 2 oxo groups at the 2- and 4-positions. FAD is a drug which is used to treat eye diseases caused by vitamin b2 deficiency, such as keratitis and blepharitis. FAD exists in all living species, ranging from bacteria to humans. In humans, FAD is involved in the metabolic disorder called the medium chain acyl-coa dehydrogenase deficiency (mcad) pathway. Outside of the human body, FAD has been detected, but not quantified in several different foods, such as other bread, passion fruits, asparagus, kelps, and green bell peppers. It is a flavoprotein in which the substituent at position 10 of the flavin nucleus is a 5'-adenosyldiphosphoribityl group.
N-Acetylarylamine is an odourless solid chemical of leaf or flake-like appearance. It is also known as acetanilide, N-phenylacetamide, acetanil, or acetanilid, and was formerly known by the trade name Antifebrin. N-Acetylarylamine has analgesic and fever-reducing properties; it is in the same class of drugs as acetaminophen (paracetamol). Under the name acetanilid it formerly figured in the formula of a number of patent medicines and over the counter drugs. In 1948, Julius Axelrod and Bernard Brodie discovered that acetanilide is much more toxic in these applications than other drugs, causing methemoglobinemia and ultimately doing damage to the liver and kidneys. As such, acetanilide has largely been replaced by less toxic drugs, in particular acetaminophen, which is a metabolite of acetanilide and whose use Axelrod and Brodie suggested in the same study.
Lanosterol, also known as lanosterin, belongs to the class of organic compounds known as triterpenoids. These are terpene molecules containing six isoprene units. Thus, lanosterol is considered to be a sterol lipid molecule. Lanosterol is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Lanosterol is biochemically synthesized starting from acetyl-CoA by the HMG-CoA reductase pathway. The critical step is the enzymatic conversion of the acyclic terpene squalene to the polycylic lanosterol via 2,3-squalene oxide.
Betaine aldehyde, also known as BTL, belongs to the class of organic compounds known as tetraalkylammonium salts. These are organonitrogen compounds containing a quaternary ammonium substituted with four alkyl chains. Betaine aldehyde is an extremely weak basic (essentially neutral) compound (based on its pKa). In humans, betaine aldehyde is involved in betaine metabolism. Outside of the human body, betaine aldehyde has been detected, but not quantified in, several different foods, such as sourdoughs, summer savouries, loganberries, burbots, and celery stalks. This could make betaine aldehyde a potential biomarker for the consumption of these foods. Betaine aldehyde is an intermediate in the metabolism of glycine, serine, and threonine. The human aldehyde dehydrogenase (EC 1.2.1.3) facilitates the conversion of betaine aldehyde into glycine betaine. Betaine aldehyde is a substrate for choline dehydrogenase (PMID: 12467448, 7646513).
5,6-Dihydroxyindole-2-carboxylic acid is an intermediate in the metabolism of Tyrosine. It is a substrate for Dopachrome tautomerase.
Glucosamine 6-phosphate (CAS: 3616-42-0) is normally produced in endothelial cells via de novo glucosamine synthesis by the enzyme fructose-6-phosphate amidotransferase and the modulation of this pathway by hyperglycemia and glutamine. Glutamine-fructose-6-phosphate amidotransferase (GFAT) catalyzes the first committed step in the pathway for biosynthesis of hexosamines in mammals.It is a member of the N-terminal nucleophile class of amidotransferases, GFAT transfers the amino group from the L-glutamine amide to D-fructose 6-phosphate, producing glutamic acid and glucosamine 6-phosphate. As glucosamine inhibits endothelial nitric oxide synthesis it has important implications for impaired endothelium-dependent relaxation and vascular dysfunction in diabetes mellitus (PMID:11270676, 11842094).
Spermine, also known as gerontine or musculamine, belongs to the class of organic compounds known as dialkylamines. These are organic compounds containing a dialkylamine group, characterized by two alkyl groups bonded to the amino nitrogen. The resultin N-carbamoylputrescine is acted on by a hydrolase to split off urea group, leaving putrescine. The precursor for synthesis of spermine is the amino acid ornithine. The intermediate is spermidine. Spermine is a drug. Spermine exists in all living species, ranging from bacteria to humans. 5'-methylthioadenosine and spermine can be biosynthesized from S-adenosylmethioninamine and spermidine through its interaction with the enzyme spermine synthase. Another pathway in plants starts with decarboxylation of L-arginine to produce agmatine. In humans, spermine is involved in spermidine and spermine biosynthesis. Outside of the human body, spermine is found, on average, in the highest concentration in oats. Spermine has also been detected, but not quantified in several different foods, such as sapodilla, mexican groundcherries, cloves, sourdocks, and sunflowers. This could make spermine a potential biomarker for the consumption of these foods. This decarboxylation gives putrescine. The name spermin was first used by the German chemists Ladenburg and Abel in 1888, and the correct structure of spermine was not finally established until 1926, simultaneously in England (by Dudley, Rosenheim, and Starling) and Germany (by Wrede et al.). In one pathway L-glutamine is the precursor to L-ornithine, after which the synthesis of spermine from L-ornithine follows the same pathway as in animals. Spermine is a potentially toxic compound.
Spermidine, also known as SPD, belongs to the class of organic compounds known as dialkylamines. These are organic compounds containing a dialkylamine group, characterized by two alkyl groups bonded to the amino nitrogen. Abnormal bleeding, such as bleeding spontaneously or profusely from a very minor injury can also occur. Spermidine exists in all living species, ranging from bacteria to humans. Within humans, spermidine participates in a number of enzymatic reactions. In particular, 5'-methylthioadenosine and spermidine can be biosynthesized from S-adenosylmethioninamine and putrescine by the enzyme spermidine synthase. In addition, S-adenosylmethioninamine and spermidine can be converted into 5'-methylthioadenosine and spermine through the action of the enzyme spermine synthase. In humans, spermidine is involved in spermidine and spermine biosynthesis. Outside of the human body, spermidine is found, on average, in the highest concentration within cow milk and oats. Spermidine has also been detected, but not quantified in several different foods, such as common chokecherries, watercress, agars, strawberry guava, and bog bilberries. This could make spermidine a potential biomarker for the consumption of these foods. Spermidine is consideres as an uremic toxine. Increased levels of uremic toxins can stimulate the production of reactive oxygen species. Chronic exposure to uremic toxins can lead to a number of conditions including renal damage, chronic kidney disease and cardiovascular disease. As a uremic toxin, this compound can cause uremic syndrome. Uremic toxins such as spermidine are actively transported into the kidneys via organic ion transporters (especially OAT3).
Succinic acid semialdehyde (or succinate semialdehyde) is an intermediate in the catabolism of gamma-aminobutyrate or GABA (PMID:16435183). It is formed from GABA by the action of GABA transaminase, which leads to the production of succinate semialdehyde and alanine. The resulting succinate semialdehyde is further oxidized by succinate semialdehyde dehydrogenase to become succinic acid, which also yields NADPH. Under certain situations, high levels of succinate semialdehyde can function as a neurotoxin and a metabotoxin. A neurotoxin is a compound that causes damage to the brain and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Elevated serum levels of succinate semialdehyde are found in succinic semialdehyde dehydrogenase (SSADH) deficiency (gamma-hydroxybutyric aciduria), a rare neurometabolic disorder of gamma-aminobutyric acid (GABA) degradation. Symptoms include motor delay, hypotonia, speech delay, autistic features, seizures, and ataxia. Patients also exhibit behavioural problems such as attention deficit, hyperactivity, anxiety, or aggression (PMID:18622364). Succinate semialdehyde is considered a reactive carbonyl and may lead to increased oxidative stress. This stress is believed to contribute to the formation of free radicals in the brain tissue of animal models induced with SSADH deficiency, which further leads to secondary cell damage and death. Additionally, oxidative stress may be responsible for the loss of striatal dopamine, which may contribute to the neuropathology of SSADH deficiency.
ADP-Ribosyl-L-arginine is the substrate of the protein ADP-ribosylarginine hydrolase (EC-Number 3.2.2.19 ), removing ADP-ribose from arginine residues in ADP ribosylated proteins. Arginine residues in proteins act as acceptors, catalyzing the NAD (+)-dependent activation of the enzyme adenylate cyclase (EC 4.6.1.1). (MetaCyc).
Maltotriose is a trisaccharide (three-part sugar) consisting of three glucose molecules linked with α-1,4 glycosidic bonds. It is most commonly produced by the digestive enzyme alpha-amylase (a common enzyme in human saliva) on amylose in starch. The creation of both maltotriose and maltose during this process is due to the random manner in which alpha amylase hydrolyses α-1,4 glycosidic bonds. It is the shortest chain oligosaccharide that can be classified as maltodextrin. Maltotriose belongs to the class of organic compounds known as oligosaccharides. These are carbohydrates made up of 3 to 10 monosaccharide units linked to each other through glycosidic bonds. Maltotriose is a common oligosaccharide metabolite found in human urine after maltose ingestion or infusion (PMID:6645121). Maltotriose is increased in glycogen storage disease II (OMIM: 232300) due to a mutation of the enzyme alpha-1,4-glucosidase (EC 3.2.1.20) (PMID:4286143).
Allysine (CAS: 1962-83-0), also known as 2-amino-6-oxohexanoic acid or 6-oxonorleucine, belongs to the class of organic compounds known as alpha-amino acids. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). Outside of the human body, allysine has been detected, but not quantified in, several different foods, such as winged beans, wasabi, common verbena, arrowhead, and oats. This could make allysine a potential biomarker for the consumption of these foods. Allysine is a derivative of lysine used in the production of elastin and collagen. It is produced by the actions of the enzyme lysyl oxidase in the extracellular matrix and is essential in the crosslink formation that stabilizes collagen and elastin.
Fucose 1-phosphate (CAS: 16562-58-6) belongs to the class of organic compounds known as monosaccharide phosphates. These are monosaccharides comprising a phosphate group linked to the carbohydrate unit. Fucose 1-phosphate is an intermediate in the reversible synthesis of GDP-L-fucose catalyzed by the enzyme guanosine triphosphate fucose pyrophosphorylase (GFPP, EC 2.7.7.30). The reversible reaction is magnesium-dependent, although the enzyme is partially active when cobalt or manganese is substituted. The reaction is unusual in that, of the four canonical nucleoside triphosphates, only guanosine can be utilized efficiently to form a nucleotide-sugar. Free cytosolic fucose is phosphorylated by L-fucokinase (EC 2.7.1.52) to form fucose-1-phosphate in the salvage pathway of GDP-L-fucose (PMID: 16185085, 14686921).
L-Sorbose, also known as L-sorbinose or L-xylo-hexulose, belongs to the class of organic compounds known as monosaccharides. Monosaccharides are compounds containing one carbohydrate unit not glycosidically linked to another such unit, and no set of two or more glycosidically linked carbohydrate units. Monosaccharides have the general formula CnH2nOn. L-Sorbose exists in all living species, ranging from bacteria to humans. The commercial production of vitamin C (ascorbic acid) often begins with sorbose. L-Sorbose (CAS: 87-79-6) is a ketose belonging to the group of sugars known as monosaccharides. Sorbose has been found to be a metabolite of Ketogulonicigenium (PMID:15785002).
4-(3-pyridyl)-4-oxobutyramide (POBAM) is a metabolite of nicotine and cotinine degradation. (PMID: 9512938, 13872096).
4-Fumarylacetoacetic acid is an intermediate in the metabolism of tyrosine. Fumarylacetoacetate hydrolase (FAH) is an enzyme which catalyzes the hydrolysis of 4-fumarylacetoacetate into fumarate and acetoacetate. FAH is the last enzyme in the tyrosine catabolism pathway. FAH deficiency is associated with Type 1 hereditary tyrosinemia.
Methylmalonyl-CoA is an intermediate in the metabolism of Propanoate. It is a substrate for Malonyl-CoA decarboxylase (mitochondrial), Methylmalonyl-CoA mutase (mitochondrial) and Methylmalonyl-CoA epimerase (mitochondrial).
Glyceric acid 1,3-biphosphate (CAS: 1981-49-3), also known as 1,3-bisphosphoglycerate (1,3BPG) or PGAP, is a 3-carbon organic molecule present in most, if not all living creatures. It primarily exists as a metabolic intermediate in glycolysis during respiration. 1,3BPG has been recognized as regulatory signal implicated in the control of metabolism, oxygen affinity of red cells, and other cellular functions. 1,3BPG concentration in erythrocytes changes in a number of pathological conditions, such as inherited phosphoglycerate kinase deficiency in erythrocytes (involved in the synthesis and breakdown of 1,3BPG) (PMID: 3555887). Glyceric acid 1,3-biphosphate is phosphorylated at the number 1 and 3 carbons. The result of this phosphorylation gives 1,3BPG important biological properties such as the ability to phosphorylate ADP to form the energy storage molecule ATP (Wikipedia).
Pseudouridine (5-ribosyluracil) is a ubiquitous yet enigmatic constituent of structural RNAs (transfer, ribosomal, small nuclear, and small nucleolar). Although pseudouridine (psi) was the first modified nucleoside to be discovered in RNA, and is the most abundant, its biosynthesis and biological roles have remained poorly understood since its identification as a "fifth nucleoside" in RNA. Recently, a combination of biochemical, biophysical, and genetic approaches has helped to illuminate the structural consequences of psi in polyribonucleotides, the biochemical mechanism of U-->psi isomerization in RNA, and the role of modification enzymes (psi synthases) and box H/ACA snoRNAs, a class of eukaryotic small nucleolar RNAs, in the site-specific biosynthesis of psi. Through its unique ability to coordinate a structural water molecule via its free N1-H, psi exerts a subtle but significant "rigidifying" influence on the nearby sugar-phosphate backbone and also enhances base stacking. These effects may underlie the biological role of most (but perhaps not all) of the psi residues in RNA. Certain genetic mutants lacking specific psi residues in tRNA or rRNA exhibit difficulties in translation, display slow growth rates, and fail to compete effectively with wild-type strains in mixed culture. In particular, normal growth is severely compromised in an Escherichia coli mutant deficient in a pseudouridine synthase responsible for the formation of three closely spaced psi residues in the mRNA decoding region of the 23S rRNA. Such studies demonstrate that pseudouridylation of RNA confers an important selective advantage in a natural biological context. PMID: 10902565.
Nicotine glucuronidation results in an N-quaternary glucuronide in humans. This reaction is catalyzed by uridine diphosphate-glucuronosyltransferase (UGT) enzyme(s) producing (S)-nicotine-N-beta-glucuronide (Nicotine-Gluc). About 3-5% of nicotine is converted to Nicotine-Gluc and excreted in urine in humans.
Is an intermediate in the Thymidylate kinase (EC 2.7.4.9; ATP:dTMP phosphotransferase) catalyzes the phosphorylation of dTMP (to form dTDP) in the dTTP synthesis pathway for DNA synthesis. (OMIM 188345 )
Propionyl-CoA is an intermediate in the metabolism of propanoate. Propionic aciduria is caused by an autosomal recessive disorder of propionyl coenzyme A (CoA) carboxylase deficiency (EC 6.4.1.3). In propionic aciduria, propionyl CoA accumulates within the mitochondria in massive quantities; free carnitine is then esterified, creating propionyl carnitine, which is then excreted in the urine. Because the supply of carnitine in the diet and from synthesis is limited, such patients readily develop carnitine deficiency as a result of the increased loss of acylcarnitine derivatives. This condition demands supplementation of free carnitine above the normal dietary intake to continue to remove (detoxify) the accumulating organic acids. Propionyl-CoA is a substrate for Acyl-CoA dehydrogenase (medium-chain specific, mitochondrial), Acetyl-coenzyme A synthetase 2-like (mitochondrial), Propionyl-CoA carboxylase alpha chain (mitochondrial), Methylmalonate-semialdehyde dehydrogenase (mitochondrial), Trifunctional enzyme beta subunit (mitochondrial), 3-ketoacyl-CoA thiolase (peroxisomal), Acyl-CoA dehydrogenase (long-chain specific, mitochondrial), Malonyl-CoA decarboxylase (mitochondrial), Acetyl-coenzyme A synthetase (cytoplasmic), 3-ketoacyl-CoA thiolase (mitochondrial) and Propionyl-CoA carboxylase beta chain (mitochondrial). (PMID: 10650319).
N1-Acetylspermidine is a polyamine. In many organisms, polyamines originate from L-ornithine and methionine. Ornithine decarboxylase (EC 4.1.1.17), a key enzyme in polyamine metabolism, decarboxylates L-ornithine to yield putrescine which is then converted to higher polyamines spermidine and spermine by successive addition of aminopropyl groups derived from decarboxylated S-adenosylmethionine. Aliphatic polyamines occur ubiquitously in organisms and have important functions in the stabilization of cell membranes, biosynthesis of informing molecules, cell growth and differentiation, as well as adaptation to osmotic, ionic, pH and thermal stress. These cationic substances are implicated in multiple functions, therefore it is not surprising that intracellular levels of polyamines are regulated by different mechanisms. The inhibition of polyamine metabolism has important pharmacological and therapeutic implications for the control of physiological processes, reproduction, cancer and parasitic diseases. Recent reports have suggested the idea that parasites with an high turnover of Ornithine Decarboxilase (ODC) are resistant to Difluoromethyl ornithine (DFMO, the irreversible inhibitor of ornithine decarboxylase) because they always contain a fraction of newly synthesized and active enzyme, therefore not DFMO inhibited, sufficient to produce small amounts of putrescine rapidly converted into spermidine, which can support protozoan proliferation. DFMO has proved to be curative in trypanosomiasis, coccidiosis, and certain other protozoan infections. (PMID: 15490259).
Presqualene diphosphate is an intermediate in the biosynthesis of Terpenoid. It is a substrate for Farnesyl-diphosphate farnesyltransferase.
2-aminomuconic semialdehyde is an intermediate in the oxidative metabolism of tryptophan in mammals, and takes place via the kynurenine pathway, which is also used for NAD biosynthesis in all eukaryotic organisms. 2-Aminomuconic semialdehyde is reported to be unstable and spontaneously converted to picolinic acid (regarded as metabolically inert and is excreted in the urine as a glycine conjugate), and enzymatically converted to 2-aminomuconic acid through the action of 2-aminomuconic semialdehyde dehydrogenase. (PMID: 10510494, 16267312, 14275129).
Geranyl diphosphate is the precursor of monoterpenes, a large family of natural occurring C10 compounds predominately found in plants and animals. Geranyl diphosphate is regarded as a key intermediate in the steroid, isoprene and terpene biosynthesis pathways and is used by organisms in the biosynthesis of farnesyl pyrophosphate, geranylgeranyl pyrophosphate, cholesterol, terpenes and terpenoids. (wikipedia). In humans, geranyl diphosphate synthase (GPPS) catalyzes the condensation of dimethylallyl diphosphate (DMAPP) and isopentenyl diphosphate (IPP) to form geranyl diphosphate. Animals produce IPP through the mevalonate (MVA) pathway. Isoprenoid compounds have been implicated in several human disease states including coronary heart disease, blindness, infectious hepatitis and cancer. Geranyl pyrophosphate is an intermediate in the HMG-CoA reductase pathway used by organisms in the biosynthesis of terpenes and terpenoids. -- Wikipedia.
4,4-Dimethyl-5a-cholesta-8,24-dien-3-b-ol (14-demethyllanosterol) is an intermediate in sterol biosynthesis. In particular, it is an intermediate in the conversion of lanosterol to zymosterol. 4,4-Dimethyl-5a-cholesta-8,24-dien-3-b-ol is a substrate for C-4 methyl sterol oxidase, NAD(P)-dependent steroid dehydrogenase, Cytochrome P450 51A1 and Delta(14)-sterol reductase.
Glutaconyl-CoA (CAS: 6712-05-6), also known as 4-carboxybut-2-enoyl-CoA, belongs to the class of organic compounds known as 2-enoyl CoAs. These are organic compounds containing a coenzyme A substructure linked to a 2-enoyl chain. Thus, glutaconyl-CoA is considered to be a fatty ester lipid molecule. Glutaconyl-CoA is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Glutaconyl-CoA is a substrate for glutaryl-CoA dehydrogenase.
Fatty acid elongation in mitochondria; Fatty acid metabolism.
1-Deoxy-D-xylulose is a product of the splitting up of Pyridoxine (an intermediate in Vitamin B6 metabolism) into two components (the other one being 4-Hydroxy-L-threonine). (KEGG).
2,3-Bisphosphoglycerate (CAS: 138-81-8), also known as 2,3-BPG or 2,3-diphosphoglycerate, is a three-carbon isomer of the glycolytic intermediate 1,3-bisphosphoglycerate and is present at high levels in the human red blood cell (RBC; erythrocyte) at the same molar concentration as hemoglobin. It is notable because it binds to deoxygenated hemoglobin in RBCs. In doing so, it allosterically upregulates the ability of RBCs to release oxygen near tissues that need it most. Its function was discovered in 1967 by Reinhold Benesch and Ruth Benesch.
2-Hydroxyphytanoyl-CoA is a substrate for Phytanoyl-CoA dioxygenase (peroxisomal).
Maltotetraose belongs to the class of organic compounds known as oligosaccharides. These are carbohydrates made up of 3 to 10 monosaccharide units linked to each other through glycosidic bonds. Maltotetraose exists in all living organisms, ranging from bacteria to humans. Outside of the human body, maltotetraose has been detected, but not quantified in several different foods, such as welsh onions, kales, small-leaf lindens, other bread, and romaine lettuces. Maltotetraose is a normal human oligo saccharide present in plasma, but is elevated in cases of Pompe disease (PMID 15886040).
Norcotinine is a metabolite of nicotine. It has been detected in smokers urine (about 1% of total nicotine and metabolites). Two pathways for its formation are possible, demethylation of cotinine or oxidative metabolism of nornicotine. Animal and human studies have demonstrated the existence of both of these pathways.
5-Methylthioribulose 1-phosphate is an intermediate in the methionine salvage pathway. It is a microbial metabolite produced by gut microbes during methionine generation from methylthioadenosine. The first step is the phosphorolysis of methylthioadenosine to 5-methylthioribose-1-phosphate and adenine by the enzyme 5-deoxy- 5-methylthioadenosine phosphorylase (methylthioadenosine phosphorylase); 5-methylthioribose-1-phosphate is then converted to 5-methylthioribulose-1-phosphate (PMID: 6725268). 5-Deoxy-5-methylthioadenosine (methylthioadenosine) is a metabolite of S-adenosyl-L-methionine formed during the synthesis of the polyamines, spermidine and spermine.
1-Pyrroline-5-carboxylic acid (CAS: 2906-39-0) is an enamine or an imino acid that forms upon the spontaneous dehydration of L-glutamate gamma-semialdehyde in aqueous solutions. The stereoisomer (S)-1-pyrroline-5-carboxylate is an intermediate in glutamate metabolism, arginine degradation, and proline biosynthesis and degradation. It can also be converted into or be formed from three amino acids: L-glutamate, L-ornithine, and L-proline. In particular, it is synthesized via the oxidation of proline by pyrroline-5-carboxylate reductase 1 (PYCR1) (EC 1.5.1.2) or by proline dehydrogenase (PRODH) (EC 1.5.99.8). It is hydrolyzed into L-glutamate by delta-1-pyrroline-5-carboxylate dehydrogenase (ALDH4A1) (EC 1.5.1.12). It is also one of the few metabolites that can act as a precursor to other metabolites of both the urea cycle and the tricarboxylic acid (TCA) cycle. Under certain conditions, pyrroline-5-carboxylate can act as a neurotoxin and a metabotoxin. A neurotoxin causes damage to nerve cells and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of pyrroline-5-carboxylate are associated with at least five inborn errors of metabolism, including hyperprolinemia type I, hyperprolinemia type II, iminoglycinuria, prolinemia type II, and pyruvate carboxylase deficiency. Hyperprolinemia type II results in high levels of pyrroline-5-carboxylate. People with hyperprolinemia type II have signs and symptoms that vary in severity, but they are more likely than type I to have seizures or intellectual disability. Pyrroline-5-carboxylate is highly reactive and excess quantities have been shown to cause cell death and apoptosis (PMID: 15548746).
5'-Phosphoribosyl-N-formylglycinamide, also known as FGAR or N-formyl-GAR, belongs to the class of organic compounds known as glycinamide ribonucleotides. Glycinamide ribonucleotides are compounds in which the amide N atom of glycineamide is linked to the C-1 of a ribosyl (or deoxyribosyl) moiety. FGAR is an extremely weak basic (essentially neutral) compound (based on its pKa). FGAR is a substrate for phosphoribosylformylglycinamidine synthase. It is involved in aminoimidazole ribonucleotide biosynthesis and plays a vital role in purine metabolism as well as in the conversion of glutamine to glutamate.
m-Chlorohippuric acid is an inactive metabolite of Bupropion. The formation of m-chlorobenzoic acid involves side chain cleavage of bupropion to an acidic metabolite in humans (PMID: 3107223).
Alanine is a nonessential amino acid made in the body from the conversion of the carbohydrate pyruvate or the breakdown of DNA and the dipeptides carnosine and anserine. It is highly concentrated in muscle and is one of the most important amino acids released by muscle, functioning as a major energy source. Plasma alanine is often decreased when the BCAA (Branched Chain Amino Acids) are deficient. This finding may relate to muscle metabolism. Alanine is highly concentrated in meat products and other high-protein foods like wheat germ and cottage cheese. Alanine is an important participant as well as regulator in glucose metabolism. Alanine levels parallel blood sugar levels in both diabetes and hypoglycemia, and alanine reduces both severe hypoglycemia and the ketosis of diabetes. It is an important amino acid for lymphocyte reproduction and immunity. Alanine therapy has helped dissolve kidney stones in experimental animals. Normal alanine metabolism, like that of other amino acids, is highly dependent upon enzymes that contain vitamin B6. Alanine, like GABA, taurine and glycine, is an inhibitory neurotransmitter in the brain. Alanine can be found in some Gram-positive bacteria (PMID:24752840).
Lactic acid is an organic acid. It is a chiral molecule, consisting of two optical isomers, L-lactic acid and D-lactic acid, with the L-isomer being the most common in living organisms. Lactic acid plays a role in several biochemical processes and is produced in the muscles during intense activity. D-Lactic acid is the end product of the enzyme glyoxalase II (or hydroxyacyl-glutathione hydrolase) (EC 3.1.2.6), which converts the intermediate substrate S-lactoyl-glutathione to reduced glutathione and D-lactate (OMIM: 138790). Lactic acid is a microbial metabolite found in Aerococcus, Bacillus, Carnobacterium, Corynebacterium, Enterococcus, Escherichia, Lactobacillus, Lactococcus, Leuconostoc, Oenococcus, Pediococcus, Rhizopus, Saccharomyces, Streptococcus, Tetragenococcus, Vagococcus and Weissella (PMID:26287368; PMID:26360870).
Diadenosine diphosphate is a member of the diadenosine polyphosphates. Diadenosine diphosphate is typically synthesized from ADP-ribosyl cyclases. Diadenosine polyphosphates are members of a group of dinucleoside polyphosphates that are ubiquitous, naturally occurring molecules. They form a recently identified class of compounds derived from ATP and consist of two adenosine molecules bridged by up to six phosphate groups. These compounds are stored in high concentrations in platelet dense granules and are released when platelets become activated. Some of the compounds promote platelet aggregation, while others are inhibitory. Possible roles as neurotransmitters, extracellular signalling molecules or 'alarmones' secreted by cells in response to physiologically stressful stimuli have been postulated. Recent studies suggest a role for these compounds in atrial and synaptic neurotransmission. Studies using isolated mesenteric arteries indicate an important role of phosphate chain length in determining whether diadenosine polyphosphates produce vasodilatation or vasoconstriction, but in the coronary circulation, diadenosine polyphosphates generally produce vasodilatation via mechanisms thought to involve release of NO or prostacyclin (PGI2). They produce cardiac electrophysiological effects by altering ventricular refractoriness at submicromolar concentrations and reduce heart rate. Mechanisms involving KATP channels have been proposed in addition to the involvement of P1- and P2-purinergic receptors and the specific diadenosine polyphosphate receptor identified on isolated cardiac myocytes. Clinical evidence suggests a role for diadenosine polyphosphates in hypertensive patients and those with the Chediak-Higashi syndrome. (PMID: 10434992).
D-myo-Inositol 4-phosphate, also known as inositol 4-phosphoric acid, belongs to the class of organic compounds known as inositol phosphates. Inositol phosphates are compounds containing a phosphate group attached to an inositol (or cyclohexanehexol) moiety. D-myo-Inositol 4-phosphate is an extremely weak basic (essentially neutral) compound (based on its pKa). Within humans, D-myo-inositol 4-phosphate participates in a number of enzymatic reactions. In particular, D-myo-inositol 4-phosphate can be biosynthesized from D-myo-inositol 1,4-bisphosphate through its interaction with the enzyme inositol polyphosphate 1-phosphatase. In addition, D-myo-inositol 4-phosphate can be converted into myo-inositol through its interaction with the enzyme inositol monophosphatase 1.
Guanosine cyclic 3',5'-(hydrogen phosphate). A guanine nucleotide containing one phosphate group which is esterified to the sugar moiety in both the 3'- and 5'-positions. It is a cellular regulatory agent and has been described as a second messenger. Its levels increase in response to a variety of hormones, including acetylcholine, insulin, and oxytocin and it has been found to activate specific protein kinases. (From Merck Index, 11th ed).
Phosphorus, in its common form, is a waxy white (or yellowish) solid that has a characteristic disagreeable smell similar to that of garlic. Pure forms of the element are colourless and transparent. This nonmetal is not soluble in water, but is soluble in carbon disulfide. The white allotrope ignites spontaneously in air; however, both white and red phosphorus burn in air to produce phosphorus pentoxide. Phosphorus is a key element in all known forms of life. Physiologically, it exists as an ion in the body. Inorganic phosphorus in the form of the phosphate PO43- plays a major role in biological molecules such as DNA and RNA where it forms part of the structural framework of these molecules. Living cells also utilize phosphate to transport cellular energy via adenosine triphosphate (ATP). Nearly every cellular process that uses energy gets it in the form of ATP. ATP is also important for phosphorylation, a key regulatory event in cells. Phospholipids are the main structural components of all cellular membranes. Calcium phosphate salts are used by animals to stiffen their bones. An average person contains a little less than 1 kg of phosphorus, about three quarters of which is present in bones and teeth in the form of apatite. A well-fed adult in the industrialized world consumes and excretes about 1-3 g of phosphorus per day in the form of phosphate. Phosphorus is an essential mineral macronutrient, which is studied extensively in soil conservation in order to understand plant uptake from soil systems. Due to its reactivity to air and many other oxygen containing substances, phosphorus is not found free in nature, but it is widely distributed in many different minerals. Phosphorus is found to be associated with glycerol intolerance syndrome, which is an inborn error of metabolism.
6-Phosphogluconic acid, also known as 6-phospho-D-gluconate or gluconic acid-6-phosphate, belongs to the class of organic compounds known as monosaccharide phosphates. These are monosaccharides comprising a phosphated group linked to the carbohydrate unit. 6-Phosphogluconic acid exists in all living species, ranging from bacteria to humans. Within humans, 6-phosphogluconic acid participates in a number of enzymatic reactions. In particular, 6-phosphogluconic acid can be biosynthesized from gluconolactone; which is mediated by the enzyme 6-phosphogluconolactonase. In addition, 6-phosphogluconic acid can be converted into D-ribulose 5-phosphate through the action of the enzyme 6-phosphogluconate dehydrogenase, decarboxylating. In humans, 6-phosphogluconic acid is involved in the metabolic disorder called the transaldolase deficiency pathway. Outside of the human body, 6-Phosphogluconic acid has been detected, but not quantified in several different foods, such as cascade huckleberries, common chokecherries, half-highbush blueberries, american cranberries, and okra.
4-Methylpentanal is an intermediate in the metabolism of C21-Steroid hormone. It is a substrate for Cytochrome P450 11A1 (mitochondrial).
Pyridoxine 5'-phosphate is a substrate for Pyridoxine-5'-phosphate oxidase and Pyridoxal kinase.
(13E)-11a-Hydroxy-9,15-dioxoprost-13-enoic acid is a substrate for Carbonyl reductase 1.Prostaglandins are eicosanoids. The eicosanoids consist of the prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and lipoxins (LXs). The PGs and TXs are collectively identified as prostanoids. Prostaglandins were originally shown to be synthesized in the prostate gland, thromboxanes from platelets (thrombocytes), and leukotrienes from leukocytes, hence the derivation of their names. All mammalian cells except erythrocytes synthesize eicosanoids. These molecules are extremely potent, able to cause profound physiological effects at very dilute concentrations. All eicosanoids function locally at the site of synthesis, through receptor-mediated G-protein linked signalling pathways.
D-Erythrose 4-phosphate is a phosphorylated derivative of erythrose that serves as an important intermediate in the pentose phosphate pathway. It is also used in phenylalanine, tyrosine and tryptophan biosynthesis, and it plays a role in vitamin B6 metabolism (KEGG).
Oleoyl-CoA is a substrate for Acyl-CoA desaturase and Protein FAM34A.
N'-Hydroxymethylnorcotinine is a cotinine metabolite derived from liver. Formation of norcotinine via N-demethylation of cotinine is expected to proceed via the N-hydroxymethyl intermediate, which is predicted to be relatively stable, due to the low pKa of the pyrrolidone-N moiety.
N6,N6,N6-Trimethyl-L-lysine is a methylated derivative of the amino acid lysine. It is a component of histone proteins, a precursor of carnitine and a coenzyme of fatty acid oxidation. N6,N6,N6-Trimethyl-L-lysine residues are found in a number of proteins and are generated by the action of S-adenosyl-L-methionine on exposed lysine residues. When trimethyllysine is released from cognate proteins via proteolysis, it serves as a precursor for carnitine biosynthesis. Mitochondrial 6-N-trimethyllysine dioxygenase converts 6-N-trimethyllysine to 3-hydroxy-6-N-trimethyllysine as the first step for carnitine biosynthesis. Because the subsequent carnitine biosynthesis enzymes are cytosolic, 3-hydroxy-6-N-trimethyllysine must be transported out of the mitochondria by a putative mitochondrial 6-N-trimethyllysine/3-hydroxy-6-N-trimethyllysine transporter system. Plasma -N-trimethyllysine concentrations are significantly lower in systemic carnitine deficiency patients compared to normal individuals, but no significant difference in urinary -N-trimethyllysine excretion is seen between the two groups.
Rubidium is a soft, silvery-white metallic element of the alkali metal group, present in traces amounts in human tissues and fluids. Rb-87, a naturally occurring isotope, is (slightly) radioactive. Rubidium is very soft and highly reactive, with properties similar to other elements in group 1, like rapid oxidation in air. Rubidium, particularly 87Rb, in the form of vapor, is one of the most commonly-used atomic species employed for laser cooling and Bose-Einstein condensation. Its desirable features for this application include the ready availability of inexpensive diode laser light at the relevant wavelength, and the moderate temperatures required to obtain substantial vapor pressures. Physiologically, it exists as an ion in the body. It has been found slightly increased in neoplastic human breast tissues obtained from patients at the time of mastectomy, compared to normal tissue. (PMID: 6488192, 15820728, 7324778, 9630429, 577330).
Deoxythymidine diphosphate-glucose is an intermediate in the nucleotide sugar metabolism pathway (KEGG). It is a substrate for the enzyme dTDP-D-glucose 4,6-dehydratase which catalyzes the reaction: dTDP-glucose = dTDP-4-dehydro-6-deoxy-D-glucose + H2O.
2'-Hydroxynicotine is a metabolite produced from the degradation of nicotine, an alkaloid found in the nightshade family of plants (Solanaceae), predominantly in tobacco, and in lower quantities in tomato, potato, eggplant (aubergine), and green pepper. Cytochrome P450 2A6 (EC 1.14.14.1) metabolizes nicotine via 2'-hydroxylation into 4-(methylamino)-1-(3-pyridyl)-1-butanone with 2'-hydroxynicotine as an intermediate (PMID: 11050152). 2'-Hydroxynicotine spontaneously yields nicotine-Δ1′(2′)-iminium ion, which is in equilibrium with 4-(methylamino)-1-(3-pyridyl)-1-butanone (PMID: 15734728). About 10% of nicotine and its metabolites are excreted as 4-oxo-4-(3-pyridyl)butanoate (keto acid) and 4-hydroxy-4-(3-pyridyl)butanoate (hydroxy acid) in the urine of smokers (PMID: 10548320).
2-Amino-3-carboxymuconic acid semialdehyde (CAS: 16597-58-3) is an intermediate metabolite of the tryptophan-niacin catabolic pathway. Current interest in the degradation of tryptophan is mostly due to the role of quinolinate and other metabolites in several neuropathological conditions. Quinolinate is a neurotoxin formed nonenzymatically from 2-amino-3-carboxymuconic semialdehyde in mammalian tissues. 2-Amino-3-carboxymuconic acid semialdehyde is enzymatically converted into 2-aminomuconate via 2-aminomuconic semialdehyde (PMID: 10510494, 16267312, 14275129).
Manganese is an essential trace nutrient in all forms of life. Physiologically, it. exists as an ion in the body. It is concentrated in cell mitochondria, mostly in the pituitary gland, liver, pancreas, kidney, and bone, influences the synthesis of mucopolysaccharides, stimulates hepatic synthesis of cholesterol and fatty acids, and is a cofactor in many enzymes, including arginase and alkaline phosphatase in the liver.
Leukotriene A4 (LTA4) is the first metabolite in the series of reactions leading to the synthesis of all leukotrienes. 5-Lipoxygenase (5-LO) catalyzes the two-step conversion of arachidonic acid to LTA4.The first step consists of the oxidation of arachidonic acid to the unstable intermediate 5-hydroperoxyeicosatetraenoic acid (5-HPETE), and the second step is the dehydration of 5-HPETE to form LTA4. Leukotriene A4, an unstable epoxide, is hydrolyzed to leukotriene B4 or conjugated with glutathione to yield leukotriene C4 and its metabolites, leukotriene D4 and leukotriene E4. The leukotrienes participate in host defense reactions and pathophysiological conditions such as immediate hypersensitivity and inflammation. Recent studies also suggest a neuroendocrine role for leukotriene C4 in luteinizing hormone secretion. (PMID: 10591081, 2820055). Leukotrienes are eicosanoids. The eicosanoids consist of the prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and lipoxins (LXs). The PGs and TXs are collectively identified as prostanoids. Prostaglandins were originally shown to be synthesized in the prostate gland, thromboxanes from platelets (thrombocytes), and leukotrienes from leukocytes, hence the derivation of their names. All mammalian cells except erythrocytes synthesize eicosanoids. These molecules are extremely potent, able to cause profound physiological effects at very dilute concentrations. All eicosanoids function locally at the site of synthesis, through receptor-mediated G-protein linked signalling pathways.
Palmityl-CoA is a fatty acid coenzyme derivative which plays a key role in fatty acid oxidation and biosynthesis.
Glutaryl-CoA is a substrate for 2-oxoglutarate dehydrogenase E1 component (mitochondrial), Dihydrolipoyllysine-residue succinyltransferase component of 2- oxoglutarate dehydrogenase complex (mitochondrial) and Glutaryl-CoA dehydrogenase (mitochondrial).
Diguanosine tetraphosphate is a diguanosine polyphosphate. Diguanosine polyphosphates (GpnGs) are found in human platelets, among a number of dinucleoside polyphosphates, which vary with respect to the number of phosphate groups and the nucleoside moieties; not only diguanosine polyphosphates (GpnG) are found, but also mixed dinucleoside polyphosphates containing one adenosine and one guanosine moiety (ApnG). The vasoactive nucleotides that can be detected in human plasma contain shorter (n=2-3) and longer (n=4-6) polyphosphate chains. GpnGs have not yet been characterized so far with respect to their effects on kidney vasculature. (PMID: 11159696, 11682456, 11115507).
Adenosine diphosphate (ADP), also known as adenosine pyrophosphate (APP), is an important organic compound in metabolism and is essential to the flow of energy in living cells. ADP consists of three important structural components: a sugar backbone attached to adenine and two phosphate groups bonded to the 5 carbon atom of ribose. The diphosphate group of ADP is attached to the 5’ carbon of the sugar backbone, while the adenine attaches to the 1’ carbon. ADP belongs to the class of organic compounds known as purine ribonucleoside diphosphates. These are purine ribobucleotides with diphosphate group linked to the ribose moiety. It is an ester of pyrophosphoric acid with the nucleotide adenine. Adenosine diphosphate is a nucleotide. ADP exists in all living species, ranging from bacteria to humans. In humans, ADP is involved in d4-gdi signaling pathway. ADP is the product of ATP dephosphorylation by ATPases. ADP is converted back to ATP by ATP synthases. ADP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase adenine.
Deoxythymidine triphosphate (dTTP) is one of the four nucleoside triphosphates that are used in the in vivo synthesis of DNA. Unlike the other deoxyribonucleoside triphosphates, thymidine triphosphate does not always contain the "deoxy" prefix in its name. The corresponding ribonucleoside triphosphate is called uridine triphosphate. Thymidine 5'-triphosphate, also known as TTP or DTHD5'ppp, belongs to the class of organic compounds known as pyrimidine 2'-deoxyribonucleoside triphosphates. These are pyrimidine nucleotides with a triphosphate group linked to the ribose moiety lacking a hydroxyl group at position 2. Thymidine 5'-triphosphate exists in all living species, ranging from bacteria to humans. Outside of the human body, Thymidine 5'-triphosphate has been detected, but not quantified in several different foods, such as elliott's blueberries, mamey sapotes, sesames, alliums, and sweet oranges.
Mevalonic acid-5P (CAS: 1189-94-2), also known as 5-phosphomevalonic acid, belongs to the class of organic compounds known as monoalkyl phosphates. These are organic compounds containing a phosphate group that is linked to exactly one alkyl chain. Within humans, mevalonic acid-5P participates in many enzymatic reactions. In particular, mevalonic acid-5P can be biosynthesized from mevalonate; which is mediated by the enzyme mevalonate kinase. In addition, mevalonic acid-5P can be converted into mevalonic acid-5-pyrophosphate through its interaction with the enzyme phosphomevalonate kinase. In humans, mevalonic acid-5P is involved in the mevalonate pathway. Outside of the human body, mevalonic acid-5P has been detected, but not quantified in, several different foods, such as oriental wheat, devilfish, pepper (spice), redcurrants, and star fruits. This could make mevalonic acid-5P a potential biomarker for the consumption of these foods.
4-Trimethylammoniobutanal is a substrate for Serine hydroxymethyltransferase (cytosolic), Serine hydroxymethyltransferase (mitochondrial), Aldehyde dehydrogenase (mitochondrial), Fatty aldehyde dehydrogenase, 4-trimethylaminobutyraldehyde dehydrogenase, Aldehyde dehydrogenase (dimeric NADP-preferring), Aldehyde dehydrogenase family 7 member A1, Aldehyde dehydrogenase 1A3 and Aldehyde dehydrogenase X (mitochondrial).
GDP-4-Dehydro-6-deoxy-D-mannose is an intermediate in the fucosylation of mammalian cells. The functional significance of these fucosylated glycans is unclear, although there is evidence that the sialyl Lex determinant participaates in leukocyte adhesion and trafficking processes. GDP-4-Dehydro-6-deoxy-D-mannose is generated by GDP-D-mannose-4,6-dehydratase (GMD). This compound is then converted by the FX protein (GDP-4-keto-6-D-deoxymannose epimerase/GDP-4-keto-6-L-galactose reductase) to GDP-L-fucose. (PMID: 11698403).
Isopentenyl pyrophosphate, IPP or isopentenyl diphosphate, is an intermediate in the HMG-CoA reductase pathway used by organisms in the biosynthesis of terpenes and terpenoids. IPP is formed from Mevalonate-5-pyrophosphate, in a reaction catalyzed by the enzyme mevalonate-5-pyrophosphate decarboxylase. (wikipedia).
Sphingomyelin (d18:1/18:0) or SM(d18:1/18:0) is a type of sphingolipid found in animal cell membranes, especially in the membranous myelin sheath which surrounds some nerve cell axons. It usually consists of phosphorylcholine and ceramide. SM(d18:1/18:0) consists of a sphingosine backbone and a stearic acid chain. In humans, sphingomyelin is the only membrane phospholipid not derived from glycerol. Like all sphingolipids, SM has a ceramide core (sphingosine bonded to a fatty acid via an amide linkage). In addition, it contains one polar head group, which is either phosphocholine or phosphoethanolamine. The plasma membrane of cells is highly enriched in sphingomyelin and is considered largely to be found in the exoplasmic leaflet of the cell membrane. However, there is some evidence that there may also be a sphingomyelin pool in the inner leaflet of the membrane. Moreover, neutral sphingomyelinase-2, an enzyme that breaks down sphingomyelin into ceramide, has been found to localize exclusively to the inner leaflet further suggesting that there may be sphingomyelin present there. Sphingomyelin can accumulate in a rare hereditary disease called Niemann-Pick Disease, types A and B. Niemann-Pick disease is a genetically-inherited disease caused by a deficiency in the enzyme sphingomyelinase, which causes the accumulation of sphingomyelin in spleen, liver, lungs, bone marrow, and the brain, causing irreversible neurological damage. SMs play a role in signal transduction. Sphingomyelins are synthesized by the transfer of phosphorylcholine from phosphatidylcholine to a ceramide in a reaction catalyzed by sphingomyelin synthase.
Deoxyribose 1-phosphate is an intermediate in the metabolism of Pyrimidine. It is a substrate for Purine nucleoside phosphorylase and Thymidine phosphorylase.
Hydroxypyruvic acid is an intermediate in the metabolism of Glycine, serine and threonine. It is a substrate for Serine--pyruvate aminotransferase and Glyoxylate reductase/hydroxypyruvate reductase.
2-Keto-3-deoxy-D-gluconic acid is a substrate for Fructose-bisphosphate aldolase A.
Parathion is a highly toxic cholinesterase inhibitor that is used as an acaricide and as an insecticide.
2-Methyl-3-hydroxybutyryl-CoA (CAS: 6701-38-8) belongs to the class of organic compounds known as (S)-3-hydroxyacyl-CoAs. These are organic compounds containing an (S)-3-hydroxyl acylated coenzyme A derivative. Thus, 2-methyl-3-hydroxybutyryl-CoA is considered to be a fatty ester lipid molecule. 2-Methyl-3-hydroxybutyryl-CoA is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. 2-Methyl-3-hydroxybutyryl-CoA is a substrate for 3-hydroxyacyl-CoA dehydrogenase type II, enoyl-CoA hydratase, trifunctional enzyme alpha subunit, short-chain 3-hydroxyacyl-CoA dehydrogenase, and peroxisomal bifunctional enzyme.
Retinal is a carotenoid constituent of visual pigments. It is the oxidized form of retinol which functions as the active component of the visual cycle. It is bound to the protein opsin forming the complex rhodopsin. When stimulated by visible light, the retinal component of the rhodopsin complex undergoes isomerization at the 11-position of the double bond to the cis-form; this is reversed in "dark" reactions to return to the native trans-configuration.
Phytanoyl CoA is a coenzyme A derivative of phytanic acid. Phytanic acid is present in human diet or in animal tissues where it may be derived from chlorophyll in plant extracts. Specifically it is an epimeric metabolite of the isoprenoid side chain of chlorophyll. Owing to the presence of its epimeric beta-methyl group, phytanic acid cannot be metabolized by beta-oxidation. Instead, it is metabolized in peroxisomes via alpha-oxidation to give pristanic acid, which is then oxidized by beta-oxidation. PhyH (phytanoyl-CoA 2-hydroxylase) catalyses hydroxylation of phytanoyl-CoA. Mutations of PhyH can lead to phytanic acid accumulation. High levels of phytanic acid are found in patients suffering from Refsum's syndrome. This inherited neurological disorder is characterized by an accumulation of phytanic acid in blood and tissues. Clinically it is characterized by adult onset retinitis pigmentosa, anosmia, sensory neuropathy, and phytanic acidaemia. This disorder has been found to be related to deficiency in the &#945;-oxidation pathway in the liver. (PMID: 17956235). Phytanoyl CoA and other branched-chain fatty acid CoA products are potent inducers of the peroxisome proliferator-activated receptor PPARalpha, a nuclear receptor that enhances transcription of peroxisomal enzymes mediating beta-oxidation of these potentially toxic fatty acids (PMID: 16768463). Pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase are strongly inhibited by phytanoyl-CoA. Decreased activity of these important mitochondrial metabolism complexes might therefore contribute to neurological symptoms upon accumulation of phytanic acid in Refsum disease (PMID: 16737698).
Adenosine 5' tetraphosphate, Ap4, is a natural nucleotide present in many biological systems. This nucleotide has been found as a constituent of the nucleotide pool present in the aqueous humor of a number of mammals and appears to act as a regulator of intraocular pressure (PMID: 14600249). AP4 may also play a significant role in the physiological regulation of vascular tone (PMID: 8599250). The plasma concentration of AP4 is in the nanomolar range. Technically adenosine tetraphosphate is condensation product of adenosine with tetraphosphoric acid at the 5' position. Acetyl coenzyme A (CoA) synthetase (EC 6.2.1.1) catalyzes the synthesis of adenosine 5'-tetraphosphate (P4A) and adenosine 5'-pentaphosphate (p5A) from ATP and tri- or tetrapolyphosphate (P3 or P4).
Cotinine methonium ion is a metabolite of cotinine, itself a primary metabolite of nicotine that is found in the urine of smokers; this reaction involves biological methylation of the pyridine ring of cotinine. Cotinine methonium ion was isolated and identified from human urine after cotinine administration (BioCyc).
Purine, also known as purine base or 1H-purine, belongs to the class of organic compounds known as purines and purine derivatives. These are aromatic heterocyclic compounds containing a purine moiety, which is formed a pyrimidine-ring ring fused to an imidazole ring. Two of the bases in nucleic acids, adenine and guanine, are purines. Purines from food (or from tissue turnover) are metabolised by several enzymes, including xanthine oxidase, into uric acid. Purine exists in all living species, ranging from bacteria to humans. High levels of uric acid can predispose to gout when the acid crystalises in joints; this phenomenon only happens in humans and some animal species (e.g. dogs) that lack an intrinsic uricase enzyme that can further degrade uric acid. In humans, purine is involved in thioguanine action pathway. Outside of the human body, purine is found, on average, in the highest concentration within cocoa beans. Purine has also been detected, but not quantified in several different foods, such as rapinis, plains prickly pears, blackcurrants, radish, and parsley. This could make purine a potential biomarker for the consumption of these foods. Purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring.
N-Acetyl-glucosamine 1-phosphate is an intermediate in aminosugar metabolism. It is a substrate for the enzymes phosphoglucomutase 3 [EC:5.4.2.2 and EC:5.4.2.3] and UDP-N-acteylglucosamine pyrophosphorylase 1 [EC:2.7.7.23] (KEGG). It is involved in UDP-N-acetyl-D-glucosamine biosynthesis and UDP-N-acetylgalactosamine biosynthesis (BioCyc).
3-Mercaptopyruvic acid, also known as 3-mercapto-2-oxopropanoate or beta-thiopyruvate, belongs to the class of organic compounds known as alpha-keto acids and derivatives. These are organic compounds containing an aldehyde substituted with a keto group on the adjacent carbon. 3-Mercaptopyruvic acid is an intermediate in cysteine metabolism. 3-Mercaptopyruvic acid exists in all living organisms, ranging from bacteria to humans. Within humans, 3-mercaptopyruvic acid participates in a number of enzymatic reactions. In particular, 3-mercaptopyruvic acid and cyanide can be converted into pyruvic acid and thiocyanate; which is mediated by the enzyme 3-mercaptopyruvate sulfurtransferase. In addition, 3-mercaptopyruvic acid can be biosynthesized from 3-mercaptolactic acid; which is mediated by the enzyme L-lactate dehydrogenase. It has been studied as a potential treatment for cyanide poisoning, but its half-life is too short for it to be clinically effective. In humans, 3-mercaptopyruvic acid is involved in cystinosis, ocular nonnephropathic. Outside of the human body, 3-mercaptopyruvic acid has been detected, but not quantified in several different foods, such as lima beans, spinachs, shallots, mexican groundcherries, and white lupines. This could make 3-mercaptopyruvic acid a potential biomarker for the consumption of these foods.
Pyrroline hydroxycarboxylic acid is a metabolite identified in the urine of patients with type II hyperprolinemia. (OMIM 239510). The urinary excretion of Pyrroline hydroxycarboxylic acid increased in hyperprolinemic patients but not in healthy controls during oral loading of hydroxyproline and hydroxyproline-ornithine. (PMID: 533224). Hyperprolinemia type II (HP II) is a rare inherited metabolic disease due to the deficiency of pyroline-5-carboxylate dehydrogenase. It is generally believed to be a benign condition although some patients have neurological problems such as refractory convulsions. (PMID: 15214748). The oxidation of pyrroline-carboxylate generates glutamate and pyrroline-hydroxycarboxylate, a reaction catalyzed by hydroxyproline oxidase (PMID: 500817).
Diaminopimelic acid or DAPA is a lysine-like amino acid derivative that is a key component of the bacterial cell wall. DAPA is incorporated or integrated into peptidoglycan of gram negative bacteria and is the attachment point for Braun's lipoprotein (BLP or Murein Lipoprotein). BLP is found in gram-negative cell walls and is one of the most abundant membrane proteins. BLP is bound at its C-terminal end (a lysine) by a covalent bond to the peptidoglycan layer (specifically to diaminopimelic acid molecules) and is embedded in the outer membrane by its hydrophobic head (a cysteine with lipids attached). BLP tightly links the two layers and provides structural integrity to the bacterial outer membrane. Diaminopimelic acid can be found in human urine or feces due to the lysis or enzymatic breakdown of gram negative gut microbes.
Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere. Nitrogen occurs in all living organisms. It is a constituent element of amino acids and therefore of proteins and nucleic acids (DNA and RNA). Nitrogen is found in the chemical structure of almost all neurotransmitters and is a key component of alkaloids. Specific bacteria (e.g. Rhizobium trifolium) possess nitrogenase enzymes which can fix atmospheric nitrogen into a form (ammonium ion) which is chemically useful to higher organisms. Animals use nitrogen-containing amino acids from plant sources, as starting materials for all nitrogen-compound animal biochemistry, including the manufacture of proteins and nucleic acids. Animal metabolism of NO (nitric oxide) results in production of nitrite. Animal metabolism of nitrogen in proteins generally results in excretion of urea, while animal metabolism of nucleic acids results in excretion of urea and uric acid. The characteristic odor of animal flesh decay is caused by nitrogen-containing long-chain amines, such as putrescine and cadaverine. Decay of organisms and their waste products may produce small amounts of nitrate, but most decay eventually returns nitrogen content to the atmosphere, as molecular nitrogen. The circulation of nitrogen from the atmosphere through organics and then back to the atmosphere is commonly referred to as the nitrogen cycle. Nitrogen can be measured in urine with the Kjeldahl method or by spectrophotometric methods (enzymic tests). Total urinary nitrogen is calculated based on urea urinary nitrogen quantified with these methods.
Dephospho-CoA, also known as 3'-dephospho-CoA, belongs to the class of organic compounds known as purine ribonucleoside diphosphates. These are purine ribonucleosides with a diphosphate group linked to the ribose moiety. Thus, dephospho-CoA is considered to be a fatty ester lipid molecule. Dephospho-CoA is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Outside of the human body, dephospho-CoA has been detected, but not quantified in, several different foods, such as wild leeks, summer savouries, arctic blackberries, biscuits, and persimmons. This could make dephospho-CoA a potential biomarker for the consumption of these foods. Dephospho-CoA is an intermediate in pantothenate and CoA biosynthesis. It is a substrate for bifunctional coenzyme A synthase which contains the dephospho-CoA kinase (EC 2.7.1.24). This enzyme catalyzes the final step in CoA biosynthesis: the phosphorylation of the 3'-hydroxyl group of ribose using ATP as a phosphate donor. The reaction is ATP + 3'-dephospho-CoA = ADP + CoA.
Choloyl-CoA is an intermediate metabolite in the Bile acid biosynthesis (KEGG). The conjugation of bile acids to glycine and taurine for excretion into bile occurs via a reaction catalyzed by the enzyme Bile acid-CoA:amino acid N-acyltransferase (BACAT) catalyzes.
3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) (CAS: 1553-55-5) is formed when acetyl-CoA condenses with acetoacetyl-CoA in a reaction that is catalyzed by the enzyme HMG-CoA synthase in the mevalonate pathway or mevalonate-dependent (MAD) route, an important cellular metabolic pathway present in virtually all organisms. HMG-CoA reductase (EC 1.1.1.34) inhibitors, more commonly known as statins, are cholesterol-lowering drugs that have been widely used for many years to reduce the incidence of adverse cardiovascular events. HMG-CoA reductase catalyzes the rate-limiting step in the mevalonate pathway and these agents lower cholesterol by inhibiting its synthesis in the liver and in peripheral tissues. Androgen also stimulates lipogenesis in human prostate cancer cells directly by increasing transcription of the fatty acid synthase and HMG-CoA-reductase genes (PMID: 14689582).
2-Keto-3-deoxy-6-phosphogluconic acid is a substrate for Fructose-bisphosphate aldolase A. It can be found in Achromobacter, Alcaligenes, Clostridium and Rhodobacteraceae (PMID: 5383859; PMID: 5304016) (M. Szymona and M. Doudoroff.  Carbohydrate Metabolism in Rhodopseudomonas spheroides. J. Gen. Microbiol (1960). 22: 167-183).
Diguanosine triphosphate is a diguanosine polyphosphate. Diguanosine polyphosphates (GpnGs) are found in human platelets, among a number of dinucleoside polyphosphates, which vary with respect to the number of phosphate groups and the nucleoside moieties; not only diguanosine polyphosphates (GpnG) are found, but also mixed dinucleoside polyphosphates containing one adenosine and one guanosine moiety (ApnG). The vasoactive nucleotides that can be detected in human plasma contain shorter(n=2-3) and longer(n=4-6) polyphosphate groups. GpnGs have not yet been characterized so far with respect to their effects on kidney vasculature. (PMID: 11159696, 11682456, 11115507).
Diguanosine pentaphosphate is a diguanosine polyphosphate. Diguanosine polyphosphates (GpnGs) are found in human platelets, among a number of dinucleoside polyphosphates, which vary with respect to the number of phosphate groups and the nucleoside moieties; not only diguanosine polyphosphates (GpnG) are found, but also mixed dinucleoside polyphosphates containing one adenosine and one guanosine moiety (ApnG). The vasoactive nucleotides that can be detected in human plasma contain short(n=2-3)and long(n=4-6)polyphosphate groups. GpnGs have not yet been characterized so far with respect to their effects on kidney vasculature. (PMID: 11159696, 11682456, 11115507).
Isoamyl nitrite (IAN) has been used as antianginal agents for more than 100 years. It is now established that IAN cause direct vasorelaxation through vascular generation of NO and relaxation via a cyclic guanosine monophosphate-dependent process. (PMID: 8996213). IAN is a member of the family of volatile organic nitrites that exert vasodilatory effects and have recently exhibited a considerable potential for inhalation abuse. (PMID: 9829558). All nitrovasodilators act intracellularly by a common molecular mechanism. This is characterized by the release of nitric oxide (NO). This process basically depends on the presence of oxygen as electron acceptor from the sydnonimine molecule. Organic nitrites (such as IAN) require the interaction with a mercapto group to form a S-nitrosothiol intermediate, from which finally NO radicals are liberated. In the presence of thiol compounds organic nitrites (e.g., IAN) and nitrosothiols may act as intermediary products of NO generation. (PMID: 1683227).
Sphinganine 1-phosphate is an intermediate in the metabolism of Glycosphingolipids and sphingolipids. It is a substrate for Sphingosine kinase 1, Lipid phosphate phosphohydrolase 2, Sphingosine kinase 2, Sphingosine-1-phosphate lyase 1, Lipid phosphate phosphohydrolase 1 and Lipid phosphate phosphohydrolase 3.
3-Keto-b-D-galactose is an intermediate in Galactose metabolism, N-Glycan degradation, Glycosaminoglycan degradation, glycerolipid metabolism, Sphingolipid metabolism, Glycosphingolipid biosynthesis - ganglioseries and Glycan structures - degradation through the enzyme galactosidase, beta 1 [EC:3.2.1.23], and an intermediate of Fructose and mannose metabolism, Galactose metabolism, Ascorbate and aldarate metabolism, Bile acid biosynthesis, Glycine, serine and threonine metabolism, Lysine degradation, Bisphenol A degradation, Nucleotide sugars metabolism, Linoleic acid metabolism, Tetrachloroethene degradation, and Butanoate metabolism through th enzyme retinol dehydrogenase 13 (all-trans/9-cis) [EC:1.1.1.-] (KEGG).
N-Methylphenylethanolamine is an intermediate in the metabolism of Tyrosine. It is a substrate for Phenylethanolamine N-methyltransferase.
alpha-Linolenic acid (ALA) is a polyunsaturated fatty acid (PUFA). It is a member of the group of essential fatty acids called omega-3 fatty acids. alpha-Linolenic acid, in particular, is not synthesized by mammals and therefore is an essential dietary requirement for all mammals. Certain nuts (English walnuts) and vegetable oils (canola, soybean, flaxseed/linseed, olive) are particularly rich in alpha-linolenic acid. Omega-3 fatty acids get their name based on the location of one of their first double bond. In all omega-3 fatty acids, the first double bond is located between the third and fourth carbon atom counting from the methyl end of the fatty acid (n-3). Although humans and other mammals can synthesize saturated and some monounsaturated fatty acids from carbon groups in carbohydrates and proteins, they lack the enzymes necessary to insert a cis double bond at the n-6 or the n-3 position of a fatty acid. Omega-3 fatty acids like alpha-linolenic acid are important structural components of cell membranes. When incorporated into phospholipids, they affect cell membrane properties such as fluidity, flexibility, permeability, and the activity of membrane-bound enzymes. Omega-3 fatty acids can modulate the expression of a number of genes, including those involved with fatty acid metabolism and inflammation. alpha-Linolenic acid and other omega-3 fatty acids may regulate gene expression by interacting with specific transcription factors, including peroxisome proliferator-activated receptors (PPARs) and liver X receptors (LXRs). alpha-Linolenic acid is found to be associated with isovaleric acidemia, which is an inborn error of metabolism.
Melatonin is a biogenic amine that is found in animals, plants and microbes. Aaron B. Lerner of Yale University is credited for naming the hormone and for defining its chemical structure in 1958. In mammals, melatonin is produced by the pineal gland. The pineal gland is small endocrine gland, about the size of a rice grain and shaped like a pine cone (hence the name), that is located in the center of the brain (rostro-dorsal to the superior colliculus) but outside the blood-brain barrier. The secretion of melatonin increases in darkness and decreases during exposure to light, thereby regulating the circadian rhythms of several biological functions, including the sleep-wake cycle. In particular, melatonin regulates the sleep-wake cycle by chemically causing drowsiness and. lowering the body temperature. Melatonin is also implicated in the regulation of mood,learning and memory, immune activity, dreaming, fertility and reproduction. Melatonin is also an effective antioxidant. Most of the actions of melatonin are mediated through the binding and activation of melatonin receptors. Individuals with autism spectrum disorders(ASD) may have lower than normal levels of melatonin. A 2008 study found that unaffected parents of individuals with ASD also have lower melatonin levels, and that the deficits. were associated with low activity of the ASMT gene, which encodes the last enzyme of melatonin synthesis. Reduced melatonin production has also been proposed as a likely factor in the significantly higher cancer rates in night workers.
Quantitatively, the most important metabolite of nicotine in most mammalian species is cotinine. In humans, about 70 to 80% of nicotine is converted to cotinine. 3-Hydroxycotinine (3HC) is the main nicotine metabolite detected in smokers urine. It is also excreted as a glucuronide conjugate (3HC-Gluc). 3HC and 3HC-Gluc account for 40-60% of the nicotine dose in urine.
A human metabolite taken as a putative food compound of mammalian origin.
p-Aminobenzoic acid, also known as 4-aminobenzoic acid or PABA, is an organic compound with molecular formula C7H7NO2. PABA is a white crystalline substance that is only slightly soluble in water. It consists of a benzene ring substituted with an amino group and a carboxylic acid. PABA is an essential nutrient for some bacteria and is sometimes called vitamin Bx. However, PABA is not essential for humans and it varies in its activity from other B vitamins. PABA is sometimes marketed as an essential nutrient under the premise that it can stimulate intestinal bacteria. Certain bacteria in the human intestinal tract such as E. coli generate PABA from chorismate. Humans lack the enzymes to convert PABA into folate, and therefore require folate from dietary sources such as green leafy vegetables. Although some intestinal bacteria can synthesize folate from PABA and some E. coli can synthesize folate this requires six enzymatic activities in folate synthesis which are not all done in the same bacteria. PABA used to be a common sunscreen agent until it was found to also be a sensitizer. The potassium salt of PABA is used therapeutically in fibrotic skin disorders. PABA can also be found in Acetobacter (DOI: 10.3181/00379727-52-14147).
Guanosine monophosphate (GMP), also known as 5′-guanidylic acid or guanylic acid (conjugate base guanylate), is a nucleotide that is used as a monomer in RNA. It is an ester of phosphoric acid with the nucleoside guanosine. GMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase guanine; hence it is a ribonucleoside monophosphate. Guanosine monophosphate is commercially produced by microbial fermentation. Guanosine monophosphate, also known as guanylic acid or 5'-GMP, belongs to the class of organic compounds known as purine ribonucleoside monophosphates. These are nucleotides consisting of a purine base linked to a ribose to which one monophosphate group is attached. A guanine nucleotide containing one phosphate group esterified to the sugar moiety and found widely in nature. Guanosine monophosphate exists in all living species, ranging from bacteria to humans. Within humans, guanosine monophosphate participates in a number of enzymatic reactions. In particular, guanosine triphosphate and guanosine monophosphate can be biosynthesized from diguanosine tetraphosphate through its interaction with the enzyme bis(5'-nucleosyl)-tetraphosphatase [asymmetrical]. In addition, guanosine monophosphate can be biosynthesized from guanosine diphosphate; which is mediated by the enzyme ectonucleoside triphosphate diphosphohydrolase 5. In humans, guanosine monophosphate is involved in the metabolic disorder called the lesch-nyhan syndrome (lns) pathway. Outside of the human body, guanosine monophosphate has been detected, but not quantified in several different foods, such as common cabbages, tea, winter squash, spearmints, and sugar apples.
Guaiacol is a phenolic compound with a methoxy group and is the monomethyl ether of catechol. Guaiacol is readily oxidized by the heme iron of peroxidases including the peroxidase of cyclooxygenase (COX) enzymes. It therefore serves as a reducing co-substrate for COX reactions. Guaiacol is a phenolic natural product first isolated from Guaiac resin and the oxidation of lignin. It is a yellowish aromatic oil that is now commonly derived from guaiacum or wood creosote. It is used medicinally as an expectorant, antiseptic, and local anesthetic. Guaiacol is used in traditional dental pulp sedation, and has the property of inducing cell proliferation; guaiacol is a potent scavenger of reactive oxygen radicals and its radical scavenging activity may be associated with its effect on cell proliferation. Guaiacol is also used in the preparation of synthetic vanillin. Guaiacol is also present in wood smoke, as a product of pyrolysis of lignin. Guaiacol has been found in the urine of patients with neuroblastoma and pheochromocytoma. (PMID 4344880, 16152729).
dTDP-4-oxo-6-deoxy-D-glucose belongs to the class of organic compounds known as pyrimidine nucleotide sugars. These are pyrimidine nucleotides bound to a saccharide derivative through the terminal phosphate group. Outside of the human body, dTDP-4-oxo-6-deoxy-D-glucose has been detected, but not quantified in, several different foods, such as common thymes, kumquats, cascade huckleberries, red huckleberries, and lotus. This could make dTDP-4-oxo-6-deoxy-D-glucose a potential biomarker for the consumption of these foods. dTDP-4-oxo-6-deoxy-D-glucose is a product of the enzyme TDP-glucose 4,6-dehydratase (EC 4.2.1.46) in the nucleotide sugars metabolism pathway.
3-Sulfinylpyruvic acid is a compound found in the mammalian cysteine metabolic pathway. It is the deaminated form of cysteine sulfinic acid which subsequently spontaneously reacts to form pyruvate and release sulfur dioxide (PMID: 3925121, 6822523). It is the byproduct of oxidoreductases (EC 1.4.1.-), and aspartate transaminase (EC 2.6.1.1). It is also often associated with hepatic disease, and the presence of aspartate transaminase is used in diagnostic biochemical assays of such ailments (PMID: 17310554).
Niacinamide, also known as nicotinamide (NAM), is a form of vitamin B3 found in food and used as a dietary supplement and medication. Niacinamide belongs to the class of organic compounds known as nicotinamides. These are heterocyclic aromatic compounds containing a pyridine ring substituted at position 3 by a carboxamide group. Its primary significance is in the prevention and/or cure of blacktongue and pellagra. The structure of nicotinamide consists of a pyridine ring to which a primary amide group is attached in the meta position. It is an amide of nicotinic acid. As an aromatic compound, it undergoes electrophilic substitution reactions and transformations of its two functional groups. Niacinamide and phosphoribosyl pyrophosphate can be converted into nicotinic acid mononucleotide and phosphate by the enzyme nicotinamide phosphoribosyltransferase. In humans, niacinamide is involved in the metabolic disorder called the nad+ signalling pathway (cancer). Niacinamide is an odorless tasting compound. Outside of the human body, niacinamide is found, on average, in the highest concentration within a few different foods, such as common sages, cow milk, and cocoa beans and in a lower concentration in common pea. Niacinamide has also been detected, but not quantified in several different foods, such as yardlong beans, roselles, apples, oyster mushrooms, and swiss chards. Niacinamide occurs in trace amounts mainly in meat, fish, nuts, and mushrooms, as well as to a lesser extent in some vegetables. It is commonly added to cereals and other foods. Many multivitamins contain 20–30 mg of vitamin B3 and it is also available in higher doses. Most animals cannot manufacture this compound in amounts sufficient to prevent nutritional deficiency and it therefore must be supplemented through dietary intake.
Deoxyuridine monophosphate (dUMP), also known as deoxyuridylic acid or deoxyuridylate in its conjugate acid and conjugate base forms, respectively, is a deoxynucleotide. It belongs to the class of organic compounds known as pyrimidine 2'-deoxyribonucleoside monophosphates. These are pyrimidine nucleotides with a monophosphate group linked to the ribose moiety lacking a hydroxyl group at position 2. dUMP exists in all living species, ranging from bacteria to humans. Within humans, dUMP participates in a number of enzymatic reactions. In particular, dUMP can be biosynthesized from dCMP through its interaction with the enzyme deoxycytidylate deaminase. In addition, dUMP can be biosynthesized from deoxyuridine; which is mediated by the enzyme thymidine kinase, cytosolic. In humans, dUMP is involved in pyrimidine metabolism. A pyrimidine 2'-deoxyribonucleoside 5'-monophosphate having uracil as the nucleobase. Outside of the human body, dUMP has been detected, but not quantified in several different foods, such as breadnut tree seeds, sea-buckthornberries, sour cherries, black walnuts, and common oregano.
This compound It is a byproduct of 6-pyruvoyltetrahydropterin synthase (EC 4.2.3.12), and associated with 6-Pyruvoyltetrahydropterin synthase deficiency (an autosomal recessive disorder that causes malignant hyperphenylalaninemia due to tetrahydrobiopterin deficiency). (Wikipedia).
Cotinine N-oxide is a minor metabolite of nicotine, cotinine formation being the major pathway of nicotine metabolism in smokers. Cotinine N-oxide accounts for less than 5% of the nicotine dose. Cotinine N-oxide can be reduced back to the parent amine in vivo. Nicotine is a naturally occurring alkaloid found in many plants. The principal sources of nicotine exposure are through the use of tobacco, nicotine containing gum and nicotine replacement therapies. Nicotine is an amine composed of pyridine and pyrrolidine rings. It has been shown that nicotine crosses biological membranes and the blood brain barrier easily. The absorbed nicotine is extensively metabolized in the liver to form a wide variety of metabolites including and cotinine N-oxide. Nicotine has been shown to affect a wide variety of biological functions ranging from gene expression, regulation of hormone secretion and enzyme activities. (PMID: 16359169, 15109883).
In the mammalian host, dihydrofolate biosynthesis occurs via the reduction of folic acid, whereas in plasmodia (e.g. Plasmodium berghei, a malaria parasite) the biosynthesis of 7,8-dihydropteroate, an intermediate product in dihydrofolate synthesis, occurs via the enzymic catalysis of the reaction of 2-amino-4-hydroxy-6-hydroxymethyl-7,8-dihydropteridine pyrophosphate with p-aminobenzoate. Malaria parasites synthesize their folate cofactors de novo and the antimalarial action of sulfonamides is due to their inhibiting the plasmodial dihydropteroate synthesis. The enzymes 6-hydroxymethylpterin pyrophosphokinase (EC 2.7.6.3, HPPK) and dihydropteroate synthase (EC 2.5.1.15, DHPS) catalyze sequential steps in folate biosynthesis. They are present in microorganisms but absent in mammals and therefore are especially suitable targets for antimicrobials. Sulfa drugs (sulfonamides and sulfones) currently are used as antimicrobials targeting DHPS, although resistance to these drugs is increasing. An NADPH-coupled microplate photometric assay could be used for rapid screening of chemical libraries for novel inhibitors of folate biosynthesis as the first step in developing new antimicrobial drugs targeting the folate biosynthetic pathway; in the microplate, the product of the DHPS reaction, 7,8-dihydropteroic acid, is reduced to tetrahydropteroate by excess dihydrofolate reductase (DHFR) using the cofactor NADPH (PMID: 17134675, 4354403, 3546688).
Citicoline is an essential intermediate in the biosynthetic pathway of structural phospholipids in cell membranes, particularly phosphatidylcholine. Once absorbed, citicoline is widely distributed throughout the body, crosses the blood-brain barrier and reaches the central nervous system (CNS), where it is incorporated into the membrane and microsomal phospholipid fraction. Citicoline activates biosynthesis of structural phospholipids of neuronal membranes, increases brain metabolism, and acts upon the levels of different neurotransmitters. Thus, citicoline has been experimentally shown to increase norepinephrine and dopamine levels in the CNS. Owing to these pharmacological mechanisms, citicoline has a neuroprotective effect in hypoxic and ischemic conditions, decreasing the volume of ischemic lesion, and also improves learning and memory performance in animal models of brain aging. In addition, citicoline has been shown to restore the activity of mitochondrial ATPase and membrane Na+/K+ATPase, to inhibit activation of certain phospholipases, and to accelerate reabsorption of cerebral edema in various experimental models. Citicoline has also been shown to be able to inhibit mechanisms of apoptosis associated to cerebral ischemia and in certain neurodegeneration models, and to potentiate neuroplasticity mechanisms. Citicoline is a safe drug, as shown by the toxicological tests conducted, that has no significant systemic cholinergic effects and is a well tolerated product. (PMID:17171187).
Pantetheine 4'-phosphate, or 4'-phosphopantetheine, is a metabolite in the pantothenate and coenzyme A biosynthesis pathway. It can be generated from Pantatheine (via pantothenate kinase 1) or R-4'-Phospho-pantothenoyl-L-cysteine (via phosphopantothenoylcysteine decarboxylase) or Dephospho-CoA (via 4'-phosphopantetheine adenylyl-transferase and ectonucleotide pyrophosphatase). In most mammals, coenzyme A can be hydrolyzed to pantetheine and pantothenate in the intestinal lumen via the following series of reactions: coenzyme A leads to phosphopantetheine leads to pantetheine leads to pantothenate. The conversion of 4'-phosphopantetheine (4'-PP) to dephospho-CoA, is catalyzed by 4'-phosphopantetheine adenylyl-transferase. In mammalian systems, this step may occur in the mitochondria or in the cytosol. (PMID: 1746161) It has been identified as an essential cofactor in in the biosynthesis of fatty acids, polyketides, depsipeptides, peptides, and compounds derived from both carboxylic and amino acid precursors. In particular it is a key prosthetic group of acyl carrier protein (ACP) and peptidyl carrier proteins (PCP) and aryl carrier proteins (ArCP) derived from Coenzyme A. Phosphopantetheine fulfils two demands. Firstly, the intermediates remain covalently linked to the synthases (or synthetases) in an energy-rich thiol ester linkage. Secondly, the flexibility and length of phosphopantetheine chain (approximately 2 nm) allows the covalently tethered intermediates to have access to spatially distinct enzyme active sites.
Permanganate is a permanganate is a chemical compound that contains the permanganate ion (MnO4-). Because manganese is in the +7 oxidation state, the permanganate ion is a strong oxidizer. Permanganates are salts of permanganic acid. Permanganate is a strong oxidizer, and similar to perchlorate. Being a strong oxidizer it is in common use in qualitative analysis experiments involving redox reactions (permanganometry). (wikipedia). Various anions interact with human serum transferrin to the concomitant binding of iron and a synergistic anion to form the transferrin-anion-iron complex. In vitro, permanganate was found to partially inactivate transferrin. Transferrin treated with a 3:1 molar ratio of permanganate to active sites lost 74 or 67% of its iron-binding capacity, respectively. (PMID: 3028261). In the presence of permanganate, Mn3+ was formed and chelated by transferrin at physiological pH in cows and goats. Manganese in the divalent state, either free as Mn2+ or bound to alpha2-macroglobulin, is removed from blood plasma very efficiently by the liver. However, the manganic-transferrin complex normally found in circulation is not rapidly removed from plasma. The liver can remove large amounts of excess manganous manganese which it presumably excretes; the small essential fraction of the manganese absorbed is oxidized to the trivalent state and bound to transferrin. (PMID 60137).
24-Hydroxycholesterol (24OHC) is almost exclusively formed in the brain. The enzymatic conversion of CNS cholesterol to 24OHC, which readily crosses the blood-brain barrier, is the major pathway for brain cholesterol elimination and brain cholesterol homeostasis maintenance. The enzyme mediating this conversion has been characterized at the molecular level as cholesterol 24-hydroxylase (EC 1.14.13.98, CYP46) and is mainly located in neurons. Like other oxysterols, 24OHC is efficiently converted into normal bile acids or excreted in bile in its sulfated and glucuronidated form. Levels of 24OHC in the circulation decrease with age in infants and children. In adults, however, the levels appear to be stable. There is accumulating evidence pointing toward a potentially important link between cholesterol, beta-amyloid, and Alzheimer's disease. Patients with active demyelinating diseases had increased levels of 24OHC in cerebrospinal fluid (CSF). Patients with Alzheimer's disease have slightly increased levels of 24OHC in CSF. Patients with multiple sclerosis have a tendency to have higher levels of 24OHC during active periods. (PMID: 15061359, 14574622). 24-Hydroxycholesterol has been found to accumulate in hereditary hypercholesterolemia, an inborn error of metabolism.
25,26-(OH)2D3 is a renal microsomal 25-OH-D3 metabolite, whose plasma concentration increases during vitamin D excess concomitantly with an increase in the concentration of lactone. This observation considered with the related structural features of 25,26-(OH)2D3 and lactone (both are oxidized at (C-26) suggested that 25,26(OH)2D3, a metabolite of unknown function, could be a precursor to lactone. In fact, it has been reported that functionalization of C-26 and subsequent lactone formation occurs exclusively in kidney. However, rigorous examination has unambiguously excluded 25S,26-(OH)2D3, the naturally occurring form as a significant lactone precursor. (PMID: 6286629).
This compound is a regulatory oxysterol which can alter HMG-CoA reductase activity when minor changes are made to its concentration. (PMID: 3654653).
3-Hydroxy-N6,N6,N6-trimethyl-L-lysine is found within the Lysine degration pathway; it is the byproduct of trimethyllysine dioxygenase (EC 1.14.11.8) which converts N6-Hydroxy-trimethyl-lysine to Glycine and 4-Trimethyl-ammoniobutanal. Because carnitine is the final product of the Lysine degration pathway, this compound is often associated with carnitine defiency disorders. (PMID: 16707092) The compound is also a byproduct of glycine hydroxymethyltransferase (EC 2.1.2.1) and Lyases (EC 4.1.2.-).
This compound is a reactant in the pathways: nicotine degradation II and nicotine degradation III, where it is converted into 4-(3-pyridyl)-butanoate. This is one of the hypothesized intermediate reactions of nicotine being converted to 3-pyridylacetate. (BioCyc) This compound is likely associated with nicotine accumulation disorders.
Estrone sulfate is a sulfated estrone derivative. Estrone sulfate acts as a long-lived reservoir that can be converted as needed to the more active estradiol (from estrone via 17 beta-hydroxysteroid dehydrogenase). Estrone Sulfate (E1S) is the most abundant circulating estrogen in non-pregnant women as well as normal men. Estrone is primarily synthesized from estrone sulfate. Estrone is an estrogenic hormone secreted by the ovaries and adipose tissues. Estrone is one of the three estrogens found in humans. The other two are estriol and estradiol. Estrone is the least prevalent of the three. Estradiol plays a critical role on reproductive and sexual functioning in women and it also affects other organs including the bones. Estriol is an estrogen that is prevalent primarily during pregnancy.
5'-Hydroxycotinine is a hydroxylated derivative of cotinine. Cotinine is dervied from nicotine.
Dopachrome is a cyclization product of L-DOPA and is an intermediate in the biosynthesis of melanin. Dopaquinone has an ortho-quinone ring, which is known to be neurotoxic and highly reactive with many other compounds (PMID: 413870). Dopachrome spontaneously gives rise to 5,6-dihydroxyindole (DHI) or it can be enzymatically metabolized by dopachrome tautomerase to give 5,6-dihydroxyindole-2-carboxylic acid (DHICA). DHI and its oxidation products are also toxic to cells. Many Parkinson's patients are treated with L-DOPA. However, long-term treatment with L-DOPA may actually worsen symptoms or may result in neurotic and psychotic symptoms. These may be due to dopachrome and dopaquinone accumulating in the brain of L-DOPA treated patients (PMID: 19131041, PMID: 12373519).
Agmatine ((4-aminobutyl)guanidine, NH2-CH2-CH2-CH2-CH2-NH-C(-NH2)(=NH)) is the decarboxylation product of the amino acid arginine and is an intermediate in polyamine biosynthesis. It is a putative neurotransmitter. It is synthesized in the brain, stored in synaptic vesicles, accumulated by uptake, released by membrane depolarization, and inactivated by agmatinase. Agmatine binds to 2-adrenergic receptor and imidazoline binding sites, and blocks NMDA receptors and other cation ligand-gated channels. Agmatine inhibits nitric oxide synthase (NOS), and induces the release of some peptide hormones. Treatment with exogenous agmatine exerts neuroprotective effects in animal models of neurotrauma.
Diadenosine heptaphosphate (AP7A) have been isolated in human platelets and have been postulated to play an important role in the control of vascular tone and hemostasis since it inhibits ADP-induced platelet aggregation. AP7A is a potent vasoconstrictors present in human placenta. Diadenosine polyphosphates (APnAs, n = 3-6) are a family of endogenous vasoactive purine dinucleotides which have been isolated from thrombocytes. APnAs have been demonstrated to be involved in the control of vascular tone as well as the growth of vascular smooth muscle cells and hence, possibly, in atherogenesis. APnAs isolated substances are Ap3A, Ap4A, Ap5A, and Ap6A. APnAs are naturally occurring substances that facilitate tear secretion; they are released from the corneal epithelium, they stimulate tear production and therefore they may be considered as physiological modulators of tear secretion. The APnAs were discovered in the mid-sixties in the course of studies on aminoacyl-tRNA synthetases (aaRS). APnAs have emerged as intracellular and extracellular signalling molecules implicated in the maintenance and regulation of vital cellular functions and become considered as second messengers. Great variety of physiological and pathological effects in mammalian cells was found to be associated with alterations of APnAs. APnAs are polyphosphated nucleotidic substances which are found in the CNS and are known to be released in a calcium-dependent manner from storage vesicles in brain synaptosomes. (PMID: 11212966, 12738682, 11810214, 9607303, 8922753, 11327631, 10446159).
3-Methoxytyrosine, also known as 3-O-methyldopa or vanilalanine, belongs to the class of organic compounds known as tyrosine and derivatives. Tyrosine and derivatives are compounds containing tyrosine or a derivative thereof resulting from reaction of tyrosine at the amino group or the carboxy group, or from the replacement of any hydrogen of glycine by a heteroatom. 3-Methoxytyrosine is one of the main biochemical markers for Aromatic L-amino acid decarboxylase (AADC, EC4.1.1.28) deficiency, an inborn error of metabolism that affects serotonin and dopamine biosynthesis. Chronically high levels of 3-methoxytyrosine are associated with aromatic L-amino acid decarboxylase (AADC, 28) deficiency, an inborn error of metabolism that affects serotonin and dopamine biosynthesis. 3-Methoxytyrosine is a potentially toxic compound. 3-Methoxytyrosine, with regard to humans, has been found to be associated with several diseases such as epilepsy, early-onset, vitamin b6-dependent and pyridoxamine 5-prime-phosphate oxidase deficiency; 3-methoxytyrosine has also been linked to several inborn metabolic disorders including sepiapterin reductase deficiency and aromatic l-amino acid decarboxylase deficiency.
9,10-Secoergosta-5,7,10(19),22-tetraene-3,25-diol. Biologically active metabolite of vitamin D2 which is more active in curing rickets than its parent. The compound is believed to attach to the same receptor as vitamin D2 and 25-hydroxyvitamin D3.
This compound is an intermediate in purine metabolism, where it is the byproduct of phosphoribosylaminoimidazolecarboxamide formyltransferase (EC 2.1.2.3) and IMP cyclohydrolase (EC 3.5.4.10). It is also a byproduct of Ligases (EC 6.3.4.-).
Deoxyguanosine triphosphate (dGTP) is a nucleoside triphosphate, and a nucleotide precursor used in cells for DNA synthesis. dGTP is used in the polymerase chain reaction technique, in sequencing, and in cloning. It is also the competitor of inhibition onset by acyclovir in the treatment of HSV virus. Under normal physiologic conditions, deoxyguanosine (dGuo) undergoes phosphorolysis by purine nucleoside phosphorylase (PNP, EC 2.4.2.1, an enzyme involved in the recycling of nucleosides and deoxynucleosides in cellular remodeling). However, when PNP is inhibited, deoxycytidine kinase (dCK, EC 2.7.1.74) shunts unmetabolized dGuo into deoxyguanosine triphosphate (dGTP), which accumulates and blocks DNA synthesis. Deficiency of purine nucleoside phosphorylase results in defective T-cell immunity. A correlation between the degree of T cell inhibition and the level of dCK activity has been observed. (PMID:11287638, 402573).
Dihydropteridine is a generic compound; the product of the reduction of 5,6,7,8-Tetrahydropteridine, which is catalyzed by 6,7-dihydropteridine reductase (EC 1.5.1.34). (KEGG) This compound is recognised as a cause of tetrahydrobiopterin (BH(4)) deficiency, leading to hyperphenylalaninemia (HPA) and impaired biogenic amine deficiency. (PMID: 14705166).
The phosphite ion (PO3) is a polyatomic ion with a phosphorus central atom. Its geometry is tetrahedral. Many phosphite salts, such as ammonium phosphite, are highly water soluble. Also organophosphorus compounds with the formula P(OR)3. The conjugate acid of the phosphite anion is phosphorous acid (H3PO3). Other names for this acid are orthophosphorous acid and dihydroxyphosphine oxide. H3PO3 is also sometimes referred to as phosphorus trihydroxide and trihydroxyphosphine, though these names are misleading. Phosphorous acid is a diprotic acid, since the hydrogen bonded directly to the central phosphorus atom is not ionizable. Thus, a more logical chemical formula for phosphorous acid is HPO(OH)2, since three hydroxy groups are not actually present on the acid. The acid can be synthesized hy treatment of a carboxylic acid, alcohol, or most practically water, with phosphorus tribromide or more commonly phosphorus trichloride.
Diadenosine octaphosphate (AP8A) is a diadenosine polyphosphate. Diadenosine polyphosphates (APnAs, n = 3-6) are a family of endogenous vasoactive purine dinucleotides which have been isolated from thrombocytes. APnAs have been demonstrated to be involved in the control of vascular tone as well as the growth of vascular smooth muscle cells and hence, possibly, in atherogenesis. APnAs isolated substances are Ap3A, Ap4A, Ap5A, and Ap6A. APnAs are naturally occurring substances that facilitate tear secretion; they are released from the corneal epithelium, they stimulate tear production and therefore they may be considered as physiological modulators of tear secretion. The APnAs were discovered in the mid-sixties in the course of studies on aminoacyl-tRNA synthetases (aaRS). APnAs have emerged as intracellular and extracellular signalling molecules implicated in the maintenance and regulation of vital cellular functions and become considered as second messengers. Great variety of physiological and pathological effects in mammalian cells was found to be associated with alterations of APnAs. APnAs are polyphosphated nucleotidic substances which are found in the CNS and are known to be released in a calcium-dependent manner from storage vesicles in brain synaptosomes. (PMID: 11212966, 12738682, 11810214, 9607303, 8922753).
This compound is an intermediate in N-glycan biosynthesis, and the byproduct of N-acetylglucosaminyldiphosphodolichol (EC 2.4.1.141) and UDP-N-acetylglucosamine-dolichyl-phosphate (EC 2.7.8.15). (KEGG) This compound and its corresponding enzymes are implicated in the developmental programmes of a variety of eukaryotes. (PMID: 10024536).
The sulfate ion is a polyatomic anion with the empirical formula SO42- and a molecular mass of 96.06 daltons; it consists of one central sulfur atom surrounded by four equivalent oxygen atoms in a tetrahedral arrangement. The sulfate ion carries a negative two charge and is the conjugate base of the hydrogen sulfate ion, HSO4-, which is the conjugate base of H2SO4, sulfuric acid. In inorganic chemistry, a sulfate (IUPAC-recommended spelling; also sulphate in British English) is a salt of sulfuric acid. Sulfate aerosols can act as cloud condensation nuclei and this leads to greater numbers of smaller droplets of water. Lots of smaller droplets can diffuse light more efficiently than just a few larger droplets.
Allopregnanolone is a neuroactive metabolite of progesterone and a barbiturate-like modulator of central gamma-aminobutyric acid receptors that modify a range of behaviors, including the stress response. is a steroid created in the body when progesterone, the female sex hormone, is metabolized. Typically, THP (allopregnanolone) is released in the brain in response to stress, and quiets the neural system within 30 minutes of escalation. This steroid hormone has recently been found to be responsible for the extreme mood swings found in teenagers. In adults and pre-pubescent chlidren THP normally helps soothe the activity of brain cells by binding to GABA receptors that inhibit accelerating electrical activity. However, in pubescent teenagers THP actually becomes a GABA receptor antagonist. GABA (gamma-aminobutyric acid) is the primary inhibitory neurotransmitter in the brain with most sedatives (tranquilizers, anesthetics and alcohol) acting on the GABA receptor.
Thromboxane A2 is an unstable intermediate between the prostaglandin endoperoxides and thromboxane B2. The compound has a bicyclic oxaneoxetane structure. It is a potent inducer of platelet aggregation and causes vasoconstriction. It is the principal component of rabbit aorta contracting substance (RCS).Thromboxanes are eicosanoids. The eicosanoids consist of the prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and lipoxins (LXs). The PGs and TXs are collectively identified as prostanoids. Prostaglandins were originally shown to be synthesized in the prostate gland, thromboxanes from platelets (thrombocytes), and leukotrienes from leukocytes, hence the derivation of their names. All mammalian cells except erythrocytes synthesize eicosanoids. These molecules are extremely potent, able to cause profound physiological effects at very dilute concentrations. All eicosanoids function locally at the site of synthesis, through receptor-mediated G-protein linked signalling pathways.
Guanosine tetraphosphate adenosine is a dinucleoside polyphosphate. Dinucleoside polyphosphates are an interesting group of signalling molecules that control numerous physiological functions. Diadenosine compounds, with a backbone of anything from two to seven phosphates, are known to occur naturally. Some of them have been isolated from cerebral nerve terminals and, acting via nucleoside (P1), nucleotide (P2), or dinucleotide receptors, can affect central nervous system function. Many of them have been isolated from human blood platelet secretory granules and are potentially involved in haemostatic mechanisms and peripheral control of vascular tone. Many visceral organs respond to the application of adenine dinucleotides and, although they act on receptors in the periphery that can be mainly defined as either P1 or P2, evidence is now accumulating for discrete dinucleotide receptors. In the periphery, adenine dinucleotides can be potent agonists, with diverse functions, causing contraction or relaxation of smooth muscle. Many P2X receptor proteins and P2Y receptors have been cloned and adenine dinucleotides have a variable pharmacological profile at these receptors and may be useful tools for characterising subtypes of P2X and P2Y receptors. Many extracellular roles of diadenosine polyphosphates are emerging as yet increasingly important, natural ligands for a plethora of structurally diverse mononucleotide and dinucleotide receptors. (PMID: 12772275, 7767329).
This compound is the byproduct of 3beta-hydroxy-5alpha-steroid dehydrogenase (EC 1.1.1.278). With regard to hypothermia, the compound interferes with the development of rapid tolerance to the anxiolytic effect of ethanol. (PMID: 16612485).
5beta-Cholestane-3alpha,7alpha,12alpha-triol is an intermediate in bile acid biosynthesis. 5beta-Cholestane-3alpha,7alpha,12alpha-triol is the second to last step in the synthesis of 5beta-cyprinolsulfate. It is converted from 7alpha,12alpha-dihydroxy-5beta-cholestan-3-one via enzymatic reaction, and then it is converted into 3alpha,7alpha,12alpha,26-tetrahydroxy-5beta-cholestane via the enzyme cytochrome P450 (EC 1.14.13.15). This compound inhibits la-hydroxylation (PMID: 7937829). It is the byproduct of cholestanetetraol 26-dehydrogenase (EC 1.1.1.161) and the reaction that catalyzes it is classified as a small molecule reaction (BioCyc).
The enzyme biotinidase (EC-Number 3.5.1.12 ) is involved in the recycling of the vitamin biotin, cleaving D-biotinylamides and esters, in a reaction including biotin amide and water. (PMID 1719240, 171927). Late-onset multiple carboxylase deficiency (MCD) with biotinidase deficiency is caused by mutation in the biotinidase gene. MCD is an autosomal recessive metabolic disorder characterized primarily by cutaneous and neurologic abnormalities. Symptoms result from the patient's inability to reutilize biotin, a necessary nutrient. (OMIM 253260).
Guanosine triphosphate adenosine is a dinucleoside polyphosphate. Dinucleoside polyphosphates are an interesting group of signalling molecules that control numerous physiological functions. Diadenosine compounds, with a backbone of anything from two to seven phosphates, are known to occur naturally. Some of them have been isolated from cerebral nerve terminals and, acting via nucleoside (P1), nucleotide (P2), or dinucleotide receptors, can affect central nervous system function. Many of them have been isolated from human blood platelet secretory granules and are potentially involved in haemostatic mechanisms and peripheral control of vascular tone. Many visceral organs respond to the application of adenine dinucleotides and, although they act on receptors in the periphery that can be mainly defined as either P1 or P2, evidence is now accumulating for discrete dinucleotide receptors. In the periphery, adenine dinucleotides can be potent agonists, with diverse functions, causing contraction or relaxation of smooth muscle. Many P2X receptor proteins and P2Y receptors have been cloned and adenine dinucleotides have a variable pharmacological profile at these receptors and may be useful tools for characterising subtypes of P2X and P2Y receptors. Many extracellular roles of diadenosine polyphosphates are emerging as yet increasingly important, natural ligands for a plethora of structurally diverse mononucleotide and dinucleotide receptors. (PMID: 12772275, 7767329).
Diethylthiophosphate, also known as DETP, belongs to the class of organic compounds known as thiophosphate diesters. These are organic compounds containing the thiophosphoric acid functional group or a derivative thereof, with the general structure ROP(OR')(OR'')=S, where exactly two R-groups are organyl groups. The glutathione transferase reactions produce products that are, in most cases, of low toxicity. Diethylthiophosphate is a potentially toxic compound. Acute OP intoxication results from blockage of the decomposition of synaptic acetylcholine because the pesticide covalently binds to chlolinesterase Chronic exposure to POs has neurological sequelae as well and data suggests that OP exposure alters sperm chromatin condensation (A3181, A3182, A3183, A3181). Chronic exposure to POs has neurological sequelae as well (PMID 8179040) and data suggests that OP exposure alters sperm chromatin condensation (PMID 15050412). PON1 hydrolyzes the active metabolites in several organophosphates insecticides as well as, nerve agents such as soman, sarin, and VX. Metabolism of organophosphates occurs principally by oxidation, by hydrolysis via esterases and by reaction with glutathione. Acute OP intoxication results from blockage of the decomposition of synaptic acetylcholine because the pesticide covalently binds to chlolinesterase (PMID 11991535).
Dimethylaniline-N-oxide is a substrate for Dimethylaniline monooxygenase 4, Dimethylaniline monooxygenase 3, Dimethylaniline monooxygenase 1, Dimethylaniline monooxygenase 5, Putative dimethylaniline monooxygenase 6 and Dimethylaniline monooxygenase 2.
It is noteworthy that in spite of the similarity of the reactions catalyzed by these prenyltransferases, the modes of expression of catalytic function are surprisingly different, varying according to the chain length and stereochemistry of reaction products. These enzymes are summarized and classified into four groups, as shown in Figure 13. Short-chain prenyl diphosphates synthases such as FPP and GGPP synthases require no cofactor except divalent metal ions, Mg2+ or Mn2+, which are commonly required by all prenyl diphosphate synthases. Medium-chain prenyl diphosphate synthases, including the enzymes for the synthesis of all-E-HexPP and all-E-HepPP, are unusual because they each consist of two dissociable dissimilar protein components, neither of which has catalytic activity. The enzymes for the synthesis of long-chain all-E-prenyl diphosphates, including octaprenyl (C40), nonaprenyl-(C45), and decaprenyl (C50) diphosphates, require polyprenyl carrier proteins that remove polyprenyl products from the active sites of the enzymes to maintain efficient turnovers of catalysis. The enzymes responsible for Z-chain elongation include Z,E-nonaprenyl-(C45) and Z,E-undecaprenyl (C55) diphosphate synthases, which require a phospholipid. The classification of mammalian synthases seems to be fundamentally similar to that of bacterial synthases except that no medium-chain prenyl diphosphate synthases are included. The Z-prenyl diphosphate synthase in mammalian cells is dehydrodolichyl PP synthase, which catalyzes much longer chain elongations than do bacterial enzymes. Dehydrodolichyl PP synthase will be a major target of future studies in this field in view of its involvement in glycoprotein biosynthesis. PMID: 9090291.
Tiglic acid is a monocarboxylic unsaturated organic acid. It is found in croton oil and in several other natural products. It has also been isolated from the defensive secretion of certain beetles. Tiglic acid, also known as tiglate or tiglinsaeure, belongs to the class of organic compounds known as methyl-branched fatty acids. These are fatty acids with an acyl chain that has a methyl branch. Usually, they are saturated and contain only one or more methyl group. However, branches other than methyl may be present. Tiglic acid has a double bond between the second and third carbons of the chain. Tiglic acid and angelic acid form a pair of cis-trans isomers. Tiglic acid is a volatile and crystallizable substance with a sweet, warm, spicy odour. It is used in making perfumes and flavoring agents. The salts and esters of tiglic acid are called tiglates.
Epipregnanolone, also known as 3beta-hydroxy-5beta-pregnan-20-one, belongs to the class of organic compounds known as gluco/mineralocorticoids, progestogens, and derivatives. These are steroids with a structure based on a hydroxylated prostane moiety. Thus, epipregnanolone is considered to be a steroid lipid molecule. Epipregnanolone is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Epipregnanolone is a pregnane found in the urine of pregnant women and sows. It has anesthetic, hypnotic, and sedative properties. It is a substrate of the enzyme 3beta-hydroxy-5beta-steroid dehydrogenase (EC 1.1.1.277).
Guanosine pentaphosphate adenosine is a dinucleoside polyphosphate. Dinucleoside polyphosphates are an interesting group of signalling molecules that control numerous physiological functions. Diadenosine compounds, with a backbone of anything from two to seven phosphates, are known to occur naturally. Some of them have been isolated from cerebral nerve terminals and, acting via nucleoside (P1), nucleotide (P2), or dinucleotide receptors, can affect central nervous system function. Many of them have been isolated from human blood platelet secretory granules and are potentially involved in haemostatic mechanisms and peripheral control of vascular tone. Many visceral organs respond to the application of adenine dinucleotides and, although they act on receptors in the periphery that can be mainly defined as either P1 or P2, evidence is now accumulating for discrete dinucleotide receptors. In the periphery, adenine dinucleotides can be potent agonists, with diverse functions, causing contraction or relaxation of smooth muscle. Many P2X receptor proteins and P2Y receptors have been cloned and adenine dinucleotides have a variable pharmacological profile at these receptors and may be useful tools for characterising subtypes of P2X and P2Y receptors. Many extracellular roles of diadenosine polyphosphates are emerging as yet increasingly important, natural ligands for a plethora of structurally diverse mononucleotide and dinucleotide receptors. (PMID: 12772275, 7767329).
Dihydroxyacetone phosphate is an important intermediate in lipid biosynthesis and in glycolysis. Dihydroxyacetone phosphate is found to be associated with transaldolase deficiency, which is an inborn error of metabolism. Dihydroxyacetone phosphate has been identified in the human placenta (PMID: 32033212).
3, 4-Dihydroxyphenylglycol O-sulfate is a norepinephrine metabolite, a transmitter produced by sympathetic nerves, in particular those innervating mesenteric organs. This sulfate conjugate is produced by extrahepatic tissues (mesenteric organs) and eliminated by the kidneys. (PMID: 8627312).
3-Hydroxyanthranilic acid, also known as 2-amino-3-hydroxy-benzoate or 3-ohaa, belongs to the class of organic compounds known as hydroxybenzoic acid derivatives. Hydroxybenzoic acid derivatives are compounds containing a hydroxybenzoic acid (or a derivative), which is a benzene ring bearing a carboxyl and a hydroxyl groups. 3-Hydroxyanthranilic acid is a drug. 3-Hydroxyanthranilic acid exists in all living species, ranging from bacteria to humans. Within humans, 3-hydroxyanthranilic acid participates in a number of enzymatic reactions. In particular, 3-hydroxyanthranilic acid and L-alanine can be biosynthesized from L-3-hydroxykynurenine through the action of the enzyme kynureninase. In addition, 3-hydroxyanthranilic acid can be converted into cinnavalininate through the action of the enzyme catalase. 3-Hydroxyanthranilic acid is an intermediate in the metabolism of tryptophan. In humans, 3-hydroxyanthranilic acid is involved in tryptophan metabolism. Outside of the human body, 3-hydroxyanthranilic acid has been detected, but not quantified in brassicas. This could make 3-hydroxyanthranilic acid a potential biomarker for the consumption of these foods. It is new antioxidant isolated from methanol extract of tempeh. It is effective in preventing autoxidation of soybean oil and powder, while antioxidant 6,7,4'-trihydroxyisoflavone is not.
Discovered in 1875, gallium is a trivalent metal that shares certain chemical characteristics with Fe 3+, Al3+ and In3+. An important property of gallium is its high affinity binding to transferrin, the iron transport protein in the circulation. Approximately one third of transferrin in blood is occupied by iron, leaving the remainder free to bind and transport gallium to cells that display transferrin receptors. In support of this mechanism is the finding that during radiogallium tumor imaging (Ga-67 scanning) in patients, Ga-67 in the circulation is bound almost exclusively to transferrin. A recent study examining the distribution of nonradioactive gallium in the circulation after its gastrointestinal uptake from gallium maltolate (an oral formulation of gallium) has confirmed that it binds to transferrin
3-Dehydrosphinganine is an intermediate in the metabolism of Glycosphingolipids. It is a substrate for Serine palmitoyltransferase 1 and Serine palmitoyltransferase 2.
N-Sulfo-D-glucosamine is a structurally altered form of N-acetyl-D-glucosamine (a polysaccharide found in animal tissues) by heparan sulfate N-deacetylase /N-sulfotransferase enzymes.
Acetoacetyl-CoA belongs to the class of organic compounds known as aminopiperidines. Aminopiperidines are compounds containing a piperidine that carries an amino group. Acetoacetyl-CoA is a strong basic compound (based on its pKa). In humans, acetoacetyl-CoA is involved in the metabolic disorder called the short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (HADH) pathway. Acetoacetyl-CoA is an intermediate in the metabolism of butanoate. It is a substrate for succinyl-CoA:3-ketoacid-coenzyme A transferase, hydroxymethylglutaryl-CoA synthase, short-chain 3-hydroxyacyl-CoA dehydrogenase, peroxisomal bifunctional enzyme, acetyl-CoA acetyltransferase, and 3-ketoacyl-CoA thiolase.
Octane, also known as N-oktanis a hydrocarbon and an alkane with the chemical formula C8H18, and the condensed structural formula CH3(CH2)6CH3. Octane has many structural isomers that differ by the amount and location of branching in the carbon chain. One of these isomers, 2,2,4-trimethylpentane (commonly called iso-octane) is used as one of the standard values in the octane rating scale. Octane belongs to the class of organic compounds known as alkanes. These are acyclic branched or unbranched hydrocarbons having the general formula CnH2n+2, and therefore consisting entirely of hydrogen atoms and saturated carbon atoms. Thus, octane is considered to be a hydrocarbon lipid molecule. Octane is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. Octane is an alkane and gasoline tasting compound. Outside of the human body, octane has been detected, but not quantified in several different foods, such as pepper (Capsicum annuum), celery stalks, cauliflowers, alcoholic beverages, and corns. One of the isomers, 2,2,4-trimethylpentane or isooctane, is of major importance, as it has been selected as the 100 point on the octane rating scale, with n-heptane as the zero point. Octane is an alkane with the chemical formula C8H18. Octane is a potentially toxic compound. Treatment is mainly symptomatic and supportive. It has 18 isomers. Octane ratings are ratings used to represent the anti-knock performance of petroleum-based fuels (octane is less likely to prematurely combust under pressure than heptane), given as the percentage of 2,2,4-trimethylpentane in an 2,2,4-trimethylpentane / n-heptane mixture that would have the same performance.
Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine nucleobase and the other nicotinamide. NAD exists in two forms: an oxidized and reduced form, abbreviated as NAD+ and NADH (H for hydrogen) respectively. NADH is the reduced form of NAD+, and NAD+ is the oxidized form of NADH. NAD (or nicotinamide adenine dinucleotide) is used extensively in glycolysis and the citric acid cycle of cellular respiration. The reducing potential stored in NADH can be either converted into ATP through the electron transport chain or used for anabolic metabolism. ATP "energy" is necessary for an organism to live. Green plants obtain ATP through photosynthesis, while other organisms obtain it via cellular respiration. NAD is a coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by a pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). NADP is formed through the addition of a phosphate group to the 2' position of the adenosyl nucleotide through an ester linkage.
Nicotinic acid, also known as niacin or vitamin B3, is a water-soluble vitamin whose derivatives such as NADH, NAD, NAD+, and NADP play essential roles in energy metabolism in the living cell and DNA repair. The designation vitamin B3 also includes the amide form, nicotinamide or niacinamide. Severe lack of niacin causes the deficiency disease pellagra, whereas a mild deficiency slows down the metabolism decreasing cold tolerance. The recommended daily allowance of niacin is 2-12 mg a day for children, 14 mg a day for women, 16 mg a day for men, and 18 mg a day for pregnant or breast-feeding women. It is found in various animal and plant tissues and has pellagra-curative, vasodilating, and antilipemic properties. The liver can synthesize niacin from the essential amino acid tryptophan, but the synthesis is extremely slow and requires vitamin B6; 60 mg of tryptophan are required to make one milligram of niacin. Bacteria in the gut may also perform the conversion but are inefficient.
Ribose 1-phosphate is an intermediate in the metabolism of Pyrimidine and the metabolism of Nicotinate and nicotinamide. It is a substrate for Uridine phosphorylase 2, Phosphoglucomutase, Purine nucleoside phosphorylase and Uridine phosphorylase 1. Ribose 1-phosphate can be formed from guanosine through the action of purine nucleoside phosphorylase. Ribose 1-phosphate can also act as a ribose donor in the synthesis of xanthosine as catalyzed by the same enzyme (purine nucleoside phosphorylase). The presence of guanase, which irreversibly converts guanine to xanthine, affects the overall process of guanosine transformation. As a result of this purine pathway, guanosine is converted into xanthosine, thus overcoming the lack of guanosine deaminase in mammals. The activated ribose moiety in Ribose 1-phosphate which stems from the catabolism of purine nucleosides can be transferred to uracil and, in the presence of ATP, used for the synthesis of pyrimidine nucleotides; therefore, purine nucleosides can act as ribose donors for the salvage of pyrimidine bases. (PMID: 9133638).
Vanylglycol, also known as 3-Methoxy-4-hydroxyphenylethyleneglycol (MHPG), belongs to the class of organic compounds known as methoxyphenols. Methoxyphenols are compounds containing a methoxy group attached to the benzene ring of a phenol moiety. It is synthesized from endogenous epinephrine and norepinephrine in vivo. It is found in brain, blood, CSF, and urine, where its concentrations are used to measure catecholamine turnover. Catecholamines play an important role in platelet activation and aggregation, epinephrine being the most potent one. Vanylglycol and pyrocatechol can be biosynthesized from 3,4-dihydroxyphenylglycol and guaiacol; which is catalyzed by the enzyme catechol O-methyltransferase. Vanylglycol is a O-methylated metabolite of normetanephrine. In humans, vanylglycol is involved in the metabolic disorder called tyrosinemia in newborns. Alcohol consumption increases the level of vanylglycol in urine and CSF. Vanylglycol is found normally in urine, in plasma and cerebrospinal fluid. Outside of the human body, vanylglycol has been detected, but not quantified in several different foods, such as blackcurrants, chinese bayberries, elderberries, oriental wheats, and poppies.
Pyridoxal phosphate, also known as PLP, pyridoxal 5'-phosphate or P5P, is the active form of vitamin B6. It is a coenzyme in a variety of enzymatic reactions. Pyridoxal 5'-phosphate belongs to the class of organic compounds known as pyridoxals and derivatives. Pyridoxals and derivatives are compounds containing a pyridoxal moiety, which consists of a pyridine ring substituted at positions 2,3,4, and 5 by a methyl group, a hydroxyl group, a carbaldehyde group, and a hydroxymethyl group, respectively. Pyridoxal 5'-phosphate is a drug which is used for nutritional supplementation and for treating dietary shortage or imbalance. Pyridoxal 5'-phosphate exists in all living species, ranging from bacteria to humans. In humans, pyridoxal 5'-phosphate is involved in glycine and serine metabolism. Outside of the human body, pyridoxal 5'-phosphate is found, on average, in the highest concentration within cow milk. Pyridoxal 5'-phosphate has also been detected, but not quantified in several different foods, such as soursops, italian sweet red peppers, muscadine grapes, european plums, and blackcurrants. Pyridoxal 5'-phosphate, with regard to humans, has been found to be associated with several diseases such as epilepsy, early-onset, vitamin B6-dependent, odontohypophosphatasia, pyridoxamine 5-prime-phosphate oxidase deficiency, and hypophosphatasia. Pyridoxal 5'-phosphate has also been linked to the inborn metabolic disorder celiac disease.
gamma-Tocopherol, also known as 7,8-dimethyltocol, belongs to the class of organic compounds known as tocopherols. These are vitamin E derivatives containing a saturated trimethyltridecyl chain attached to the carbon C6 atom of a benzopyran ring system. They differ from tocotrienols which contain an unsaturated trimethyltrideca-3,7,11-trien-1-yl chain. It is estimated that 50% of gamma-tocopherol is metabolized into gamma-CEHC and excreted into the urine. gamma-Tocopherol is the predominant form of vitamin E in plant seeds and derived products (e.g. nuts and vegetable oils). Unlike alpha-tocopherol, gamma-tocopherol inhibits cyclooxygenase activity and, therefore, exhibit anti-inflammatory properties (PMID: 11722951).
3-Methylcrotonyl-CoA, also known as beta-methylcrotonyl-coenzyme A or dimethylacryloyl-CoA, belongs to the class of organic compounds known as acyl-CoAs. These are organic compounds containing a coenzyme A substructure linked to an acyl chain. Thus, 3-methylcrotonyl-CoA is considered to be a fatty ester lipid molecule. 3-Methylcrotonyl-CoA is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. 3-Methylcrotonyl-CoA is an essential metabolite for leucine metabolism, is a substrate of 3-methylcrotonyl-CoA carboxylase (EC 6.4.1.4), and is a biotin-dependent mitochondrial enzyme in the catabolism of leucine (OMIM: 609010).
Acetylphosphate, also known as acetyl-p, belongs to the class of organic compounds known as acyl monophosphates. These are organic compounds containing a monophosphate linked to an acyl group. They have the general structure R-CO-P(O)(O)OH, R=H or organyl. Since acetylphosphate synthesis is known to depend on cholinesterase activity, pseudocholinesterase was assumed to participate to a small extent in acetylphosphate synthesis by cancerous serum. It is also an intermediate in pyruvate metabolism. Acetylphosphate is a drug. Acetylphosphate exists in all living organisms, ranging from bacteria to humans. Acetylphosphate can be converted into acetic acid; which is mediated by the enzyme acylphosphatase-1. It is generated from pyruvate and the formation is catalyzed by pyruvate oxidase (EC:1.2.3.3). In humans, acetylphosphate is involved in the metabolic disorder called the pyruvate dehydrogenase complex deficiency pathway. It is generated from sulfoacetaldehyde, converted to acetyl-CoA and acetate via phosphate acetyltransferase (EC:2.3.1.8) and acetate kinase (EC:2.7.2.1) respectively. Acetylphosphate or actyl phosphate is a compound involved in taurine and hypotaurine metabolism as well as pyruvate metabolism. Cancerous serum produced 37% less acetylphosphate than normal serum.
Queuine is a highly modified derivative of guanine found in the first position of the anticodon of the transfer RNAs for asp, asn, his and tyr. The original transcripts of these tRNAs contain guanine in this position. All organisms with the exception of yeast and mycoplasma contain queuine. Bacteria synthesize queuine but it cannot be synthesized by higher mammals. Significant amounts of free queuine are present in common plant and animal food products. (PMID 9016755).
7alpha-Hydroxycholesterol is an oxysterol and can serve as a biomarker for lipid peroxidation (PMID: 17386651). Products of cholesterol oxidation accumulate within atherosclerotic plaque and have been proposed to contribute to inflammatory signalling in the diseased artery (PMID: 17364953). 7alpha-Hydroxycholesterol is a cholesterol oxide that has been described as a biomarker of oxidative stress in subjects with impaired glucose tolerance and diabetes (PMID: 16634125). 7alpha-Hydroxycholesterol has been identified in the human placenta (PMID: 32033212).
Nicotine N'-oxide (NNO) is a primary metabolite of nicotine, although only about 4-7% of nicotine absorbed by smokers is metabolized via this route. The conversion of nicotine to NNO involves a flavin-containing monooxygenase 3 (FMO3). It appears that NNO is not further metabolized to any significant extent, except by reduction back to nicotine, which may lead to recycling of nicotine in the body.
myo-Inositol 1,4,5-trisphosphate (CAS: 20298-95-7), also known as Ins(1,4,5)P3 or InsP3, is an intracellular messenger formed by the action of phospholipase C on phosphatidylinositol 4,5-bisphosphate, which is one of the phospholipids that make up the cell membrane (PMID: 22453946). It is released into the cytoplasm where it releases calcium ions from internal stores within the cell's endoplasmic reticulum. These calcium ions stimulate the activity of B kinase or calmodulin (PMID: 15189149). Its transient accumulation is due both to the enhanced metabolism via the Ca2+-calmodulin-sensitive Ins(1,4,5)P3 kinase, as well as a down-regulation of phosphatidylinositol 4,5-bisphosphate hydrolysis (PMID: 3041962). It is a major regulator of apoptotic signalling driving calcium (Ca2+) transients from the endoplasmic reticulum to mitochondria, thereby establishing a functional and physical link between these organelles. It also regulates autophagy through the interaction with Beclin 1 complex, and in particular, its inhibition/depletion strongly induces macroautophagy (PMID: 19325567). In addition, recent evidence suggests that the penetrating sperm delivers into mammalian eggs a novel isoform of phospholipase C (PLC), which promotes the formation of inositol 1,4,5-trisphosphate (PMID: 15362223).
GDP-D-rhamnose is produced in virus-infected cells. Rhamnose is components of the glycans attached to capsid protein, the pathway could circumvent a limited supply of GDP sugars by the algal host.(http://www.jbc.org/cgi/content/abstract/278/24/21559).
Guanosine diphosphate adenosine is a dinucleoside polyphosphate. Dinucleoside polyphosphates are an interesting group of signalling molecules that control numerous physiological functions. Diadenosine compounds, with a backbone of anything from two to seven phosphates, are known to occur naturally. Some of them have been isolated from cerebral nerve terminals and, acting via nucleoside (P1), nucleotide (P2), or dinucleotide receptors, can affect central nervous system function. Many of them have been isolated from human blood platelet secretory granules and are potentially involved in haemostatic mechanisms and peripheral control of vascular tone. Many visceral organs respond to the application of adenine dinucleotides and, although they act on receptors in the periphery that can be mainly defined as either P1 or P2, evidence is now accumulating for discrete dinucleotide receptors. In the periphery, adenine dinucleotides can be potent agonists, with diverse functions, causing contraction or relaxation of smooth muscle. Many P2X receptor proteins and P2Y receptors have been cloned and adenine dinucleotides have a variable pharmacological profile at these receptors and may be useful tools for characterising subtypes of P2X and P2Y receptors. Many extracellular roles of diadenosine polyphosphates are emerging as yet increasingly important, natural ligands for a plethora of structurally diverse mononucleotide and dinucleotide receptors. (PMID: 12772275, 7767329).
Aminoparathion is a highly reactive metabolite of parathion.
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene, also known as benzol or [6]annulene, belongs to the class of organic compounds known as benzene and substituted derivatives. These are aromatic compounds containing one monocyclic ring system consisting of benzene. Benzene is a natural constituent of crude oil and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon. It is sometimes abbreviated PhH. Benzene is a colorless and highly flammable liquid with a sweet smell, and is partially responsible for the aroma around petrol (gasoline) stations. It is used primarily as a precursor to the manufacture of chemicals with more complex structure, such as ethylbenzene and cumene, of which billions of kilograms are produced annually. Although a major industrial chemical, benzene finds limited use in consumer items because of its toxicity. Benzene is formally rated as a carcinogen (by IARC 1) and is also a potentially toxic compound. Benzene has been found to be associated with several diseases such as autism and pervasive developmental disorder not otherwise specified.
Diguanosine diphosphate is a diguanosine polyphosphate. Diguanosine polyphosphates (GpnGs) are found in human platelets, among a number of dinucleoside polyphosphates, which vary with respect to the number of phosphate groups and the nucleoside moieties; not only diguanosine polyphosphates (GpnG) are found, but also mixed dinucleoside polyphosphates containing one adenosine and one guanosine moiety (ApnG). The vasoactive nucleotides that can be detected in human plasma contain short (n=2-3)and long(n=4-6)polyphosphate chains. GpnGs have not yet been characterized so far with respect to their effects on kidney vasculature. (PMID: 11159696, 11682456, 11115507).
Deoxyadenosine diphosphate has been identified in the mononuclear cells of a patient affected with in inherited adenosine deaminase deficiency (OMIM 102700) (PMID 6980023), and in in mononuclear cells of hemodialyzed patients. (PMID 11461945).
Bupropion is a selective catecholamine (norepinephrine and dopamine) reuptake inhibitor. It has only a small effect on serotonin reuptake. It does not inhibit MAO. The antidepressant effect of bupropion is considered to be mediated by its dopaminergic and noradrenergic action. Bupropion has also been shown to act as a competitive alpha-3-beta-4- nicotinic antagonist, the alpha-3-beta-4-antagonism has been shown to interrupt addiction in studies of other drugs such as ibogaine. This alpha-3-beta-4-antagonism correlates quite well with the observed effect of interrupting addiction. A unicyclic, aminoketone antidepressant. The mechanism of its therapeutic actions is not well understood, but it does appear to block dopamine uptake. The hydrochloride is available as an aid to smoking cessation treatment; Bupropion is a selective catecholamine (norepinephrine and dopamine) reuptake inhibitor. It has only a small effect on serotonin reuptake. It does not inhibit MAO. The antidepressant effect of bupropion is considered to be mediated by its dopaminergic and noradrenergic action. Bupropion has also been shown to act as a competitive alpha-3-beta-4-nicotinic antagonist, the alpha-3-beta-4-antagonism has been shown to interrupt addiction in studies of other drugs such as ibogaine. This alpha-3-beta-4-antagonism correlates quite well with the observed effect of interrupting addiction. Bupropion (amfebutamone) (brand names Wellbutrin and Zyban) is an antidepressant of the aminoketone class, chemically unrelated to tricyclics or selective serotonin reuptake inhibitors (SSRIs). It is similar in structure to the stimulant cathinone, and to phenethylamines in general. It is a chemical derivative of diethylpropion, an amphetamine-like substance used as an anorectic. Bupropion is both a dopamine reuptake inhibitor and a norepinephrine reuptake inhibitor. It is often used as a smoking cessation aid.
Thiamine triphosphate is the triphosphate ester of thiamine. Thiamine triphosphate (ThTP) was previously considered to be a specific neuroactive form of thiamine. However, it was recently shown that ThTP exists in bacteria, fungi, plants and animals suggesting a much more general cellular role. In particular, it seems to play a role in response to amino acid starvation. In mammals, ThTP is hydrolyzed by a specific thiamine triphosphatase. In Leigh's disease, this compound is present in decreased amounts in the brain due to a metabolic block in its formation.
AICAR also known as ZMP is an analog of AMP that is capable of stimulating AMP-dependent protein kinase activity(AMPK). AICAR is an intermediate in the generation of inosine monophosphate. AICAR is being clinically used to treat and protect against cardiac ischemic injury. AICAR can enter cardiac cells to inhibit adenosine kinase and adenosine deaminase. It enhances the rate of nucleotide re-synthesis increasing adenosine generation from adenosine monophosphate only during conditions of myocardial ischemia. AICAR increases glucose uptake by inducing translocation of GLUT4 and/or by activating the p38 MAPK pathway.
alpha-Carboxyethyl hydrochroman (alpha-CEHC) has been identified as a major water-soluble metabolite of vitamin E, which circulates in the blood and is excreted in the urine (PMID: 12420750). About one-third of the alpha-CEHC circulating in the blood is present as alpha-CEHC glucuronide (PMID: 10552913).
Flavin mononucleotide (FMN), or riboflavin-5′-phosphate, is a biomolecule produced from riboflavin (vitamin B2) by the enzyme riboflavin kinase and functions as the prosthetic group of various oxidoreductases, including NADH dehydrogenase, as well as cofactor in biological blue-light photo receptors. During the catalytic cycle, a reversible interconversion of the oxidized (FMN), semiquinone (FMNH), and reduced (FMNH2) forms occurs in the various oxidoreductases. FMN is a stronger oxidizing agent than NAD and is particularly useful because it can take part in both one- and two-electron transfers. In its role as blue-light photo receptor, (oxidized) FMN stands out from the 'conventional' photo receptors as the signaling state and not an E/Z isomerization. It is the principal form in which riboflavin is found in cells and tissues. It requires more energy to produce, but is more soluble than riboflavin. Flavin mononucleotide belongs to the class of organic compounds known as flavin nucleotides. These are nucleotides containing a flavin moiety. Flavin is a compound that contains the tricyclic isoalloxazine ring system, which bears 2 oxo groups at the 2- and 4-positions. Flavin mononucleotide exists in all living species, ranging from bacteria to humans. Within humans, flavin mononucleotide participates in a number of enzymatic reactions. In particular, formic acid and flavin mononucleotide can be biosynthesized from FMNH2; which is catalyzed by the enzyme lanosterol 14-alpha demethylase. In addition, formic acid and flavin mononucleotide can be biosynthesized from FMNH2 through the action of the enzyme lanosterol 14-alpha demethylase. In humans, flavin mononucleotide is involved in bloch pathway (cholesterol biosynthesis). Outside of the human body, flavin mononucleotide has been detected, but not quantified in several different foods, such as mandarin orange (clementine, tangerine), horseradish tree, black elderberries, angelica, and ostrich ferns.
Tetradecanoyl-CoA (or myristoyl-CoA) is an intermediate in fatty acid biosynthesis, fatty acid elongation and the beta oxidation of fatty acids. It is also used in the myristoylation of proteins. The first pass through the beta-oxidation process starts with the saturated fatty acid palmitoyl-CoA and produces myristoyl-CoA. A total of four enzymatic steps are required, starting with VLCAD CoA dehydrogenase (Very Long Chain) activity, followed by three enzymatic steps catalyzed by enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase, and ketoacyl-CoA thiolase, all present in the mitochondria. Myristoylation of proteins is also catalyzed by the presence of myristoyl-CoA along with Myristoyl-CoA:protein N-myristoyltransferase (NMT). Myristoylation is an irreversible, co-translational (during translation) protein modification found in animals, plants, fungi and viruses. In this protein modification a myristoyl group (derived from myristioyl CoA) is covalently attached via an amide bond to the alpha-amino group of an N-terminal amino acid of a nascent polypeptide. It is more common on glycine residues but also occurs on other amino acids. Myristoylation also occurs post-translationally, for example when previously internal glycine residues become exposed by caspase cleavage during apoptosis. Myristoylation plays a vital role in membrane targeting and signal transduction in plant responses to environmental stress. Compared to other species that possess a single functional myristoyl-CoA: protein N-myristoyltransferase (NMT) gene copy, human, mouse and cow possess 2 NMT genes, and more than 2 protein isoforms.
Methylguanidine (MG) is a guanidine in which one of the amino hydrogens of guanidine itself is substituted by a methyl group.  Methylguanidine is a guanidine compound deriving from protein catabolism. It is also a product of putrefaction. Methylguanidine has a role as a metabolite, an EC 1.14.13.39 (nitric oxide synthase) inhibitor and as a uremic toxin. It has been identified as a uremic toxin according to the European Uremic Toxin Working Group (PMID:22626821). It accumulates in renal failure, however it also exhibits anti-inflammatory effects. Methylguanidine is synthesized from creatinine concomitant with the synthesis of hydrogen peroxide from endogenous substrates in peroxisomes. Recent evidence suggests that methylguanidine significantly inhibits iNOS activity and TNF- release. This means that methylguandine can attenuate the degree of inflammation and tissue damage associated with endotoxic shock.
Imidazole is an organic compound with the formula C3N2H4. It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. In chemistry, it is an aromatic heterocycle, classified as a diazole, and has non-adjacent nitrogen atoms. Imidazole is a heterocyclic aromatic organic compound. It is classified as an alkaloid. The ring system of the molecule is present in important biological building blocks such as histidine and histamine. Imidazole can act as a base and as a weak acid. Imidazole exists in two tautomeric forms with the hydrogen atom moving between the two nitrogens. Many drugs contain an imidazole ring, such as antifungal drugs and nitroimidazole. Imidazole is a 5 membered planar ring which is soluble in water and polar solvents. Imidazole is a base and an excellent nucleophile. It reacts at the NH nitrogen, attacking alkylating and acylating compounds. It is not particularly susceptible to electrophilic attacks at the carbon atoms, and most of these reactions are substitutions that keep the aromaticity intact. One can see from the resonance structure that the carbon-2 is the carbon most likely to have a nucleophile attack it, but in general nucleophilic substitutions are difficult with imidazole. Imidazole is incorporated into many important biological molecules. The most obvious is the amino acid histidine, which has an imidazole side chain. histidine is present in many proteins and enzymes and plays a vital part in the structure and binding functions of hemoglobin.
S-Acetyldihydrolipoamide is a thio-acetylated form of dihydrolipoamide. The molecule is commonly conjugated to lysine residues. The structure shown is the free form of the molecule. Pyruvate dehydrogenase complex. The reaction is 2-(alpha-hydroxyethyl)-TPP + lipoamide => S-acetyldihydrolipoamide + TPP [Homo sapiens], occuring in mitochondrial matrix. (reactome.org). S-Acetyldihydrolipoamide is an intermediate in alanine, aspartate and pyruvate metabolism and glycolysis/gluconeogenesis (KEGG:C01136). It is converted from 2-hydroxyethyl-THPP and lipoamide via the enzyme pyruvate dehydrogenase (EC:1.2.4.1). It is then converted to acetyl-CoA via the enzyme pyruvate dehydrogenase E2 component (dihydrolipoamide acetyltransferase) (EC:2.3.1.12).
3-methylthiopropionate is one of the metabolites of methionine (especially of D-methionine) and pharmacokinetics of 3-MTP in urine seems to contribute to the clinicopathological investigation of the liver cirrhosis. (PMID 3997054).
Mannitol 1-phosphate is a sugar alcohol. Mannitol 1-phosphate dehydrogenase (EC 1.1.1.17) reduces fructose 6-phosphate into mannitol 1-phosphate in the gastrointestinal tract of mammals and the mannitol cycle of organisms such as Lactobacillus plantarum, a lactic acid bacterium found in many fermented food products. Mannitol 1-phosphate is also produced in many organisms that have a range of biological interactions with humans (e.g. A. niger, A. parasiticus, B. subtilis, C. difficile, E. faecalis, E. coli, K. pneumoniae, L. salivarius, M. hyopneumoniae, M. mycoides, M. pneumoniae, P. multocida, S. typhi, S. typhimurium, S. aureus, S. pneumoniae, V. cholerae, V. parahaemolyticus, Y. pestis).
5,10-Methylene-THF is an intermediate in glycine, serine and threonine metabolism and one carbon metabolism. 5,10-CH2-THF can also be used as a coenzyme in the biosynthesis of thymidine. More specifically it is the C1-donor in the reactions catalyzed by thymidylate synthase and thymidylate synthase (FAD). It also acts as a coenzyme in the synthesis of serine from glycine via the enzyme serine hydroxymethyl transferase. 5,10-Methylene-THF is a substrate for Methylenetetrahydrofolate reductase. This enzyme converts 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. This reaction is required for the multistep process that converts the amino acid homocysteine to methionine. The body uses methionine to make proteins and other important compounds. 5,10-CH2-THF is a substrate for many enzymes including Bifunctional methylenetetrahydrofolate dehydrogenase/cyclohydrolase (mitochondrial), Aminomethyltransferase (mitochondrial), Serine hydroxymethyltransferase (mitochondrial), Methylenetetrahydrofolate reductase, C-1-tetrahydrofolate synthase (cytoplasmic), Serine hydroxymethyltransferase (cytosolic) and Thymidylate synthase.
5-Formiminotetrahydrofolic acid is a substrate for Formimidoyltransferase-cyclodeaminase.
Formamide, also known as methanamide or ameisensaeureamid, belongs to the class of organic compounds known as carboximidic acids. These are organic acids with the general formula RC(=N)-OH (R=H, organic group). Formamide, in its pure state, has been used as an alternative solvent for the electrostatic self-assembly of polymer nanofilms. Formamide exists in all living organisms, ranging from bacteria to humans. Formamide has been detected, but not quantified in several different foods, such as hyssops, rose hips, asian pears, brassicas, and green bell peppers. It has been used as a softener for paper and fiber. Inhalation of large amounts of formamide vapor may require medical attention. In the past, formamide was produced by treating formic acid with ammonia, which produces ammonium formate, which in turn yields formamide upon heating:HCOOH + NH3 → HCOO−NH+4HCOO−NH+4 → HCONH2 + H2O. Formamide is also generated by aminolysis of ethyl formate: HCOOCH2CH3 + NH3 → HCONH2 + CH3CH2OH. The current industrial process for the manufacture of formamide involves either the carbonylation of ammonia: CO + NH3 → HCONH2. An alternative two-stage process involves the ammonolysis of methyl formate, which is formed from carbon monoxide and methanol: CO + CH3OH → HCOOCH3HCO2CH3 + NH3 → HCONH2 + CH3OH. Formamide is used in the industrial production of hydrogen cyanide. Formamide has been shown to exhibit hematoxicity in animals and is considered hazardous by prolonged exposure through inhalation, oral intake and dermal absorption.
6-Hydroxydopamine, also known as 6-OHDA or oxidopamina, belongs to the class of organic compounds known as catecholamines and derivatives. Catecholamines and derivatives are compounds containing 4-(2-Aminoethyl)pyrocatechol [4-(2-aminoethyl)benzene-1,2-diol] or a derivative thereof formed by substitution. The main use for oxidopamine in scientific research is to induce Parkinsonism in laboratory animals such as mice, rats and monkeys, in order to develop and test new medicines and treatments for Parkinson's disease.  In order to induce this condition in animals, around 70% of the dopaminergic neurons in the substantia nigra of the brain must be destroyed, and this is achieved either with oxidopamine or MPTP. 6-OHDA is thought to enter the neurons via the dopamine and noradrenaline (norepinephrine) reuptake transporters. Oxidopamine toxicity in neonatal rodents is also used as an animal model for the Lesch-Nyhan syndrome. Both these agents likely destroy neurons by generating reactive oxygen species such as superoxide radical. Oxidopamine is often used in conjunction with a selective noradrenaline reuptake inhibitor (such as desipramine) to selectively destroy dopaminergic neurons.
3-Pyridylacetic acid is a breakdown product of nicotine (and other tobacco alkaloids) and is part of the nicotine degradation pathway. It is formed from 4-(3-pyridyl)-butanoate. One alkaloid in particular, myosmine, appears to be a major source for 3-pyridylacetic acid. The alkaloid myosmine is present not only in tobacco products but also in various foods. Myosmine is easily nitrosated, yielding 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB) and the esophageal tobacco carcinogen N'-nitrosonornicotine. The two major metabolites of myosmine metabolism have been identified as 3-pyridylacetic acid (20-26%) and 4-oxo-4-(3-pyridyl)butyric acid (50-60%) (PMID:16079272). 3-pyridylacetatic acid is an analog of nicotinic acid. (PMID 13898750).
Asymmetric dimethylarginine (ADMA) is a naturally occurring chemical found in blood plasma. It is a metabolic by-product of continual protein modification processes in the cytoplasm of all human cells. It is closely related to L-arginine, a conditionally-essential amino acid. ADMA interferes with L-arginine in the production of nitric oxide, a key chemical to endothelial and hence cardiovascular health. Asymmetric dimethylarginine is created in protein methylation, a common mechanism of post-translational protein modification. This reaction is catalyzed by an enzyme set called S-adenosylmethionine protein N-methyltransferases (protein methylases I and II). The methyl groups transferred to create ADMA are derived from the methyl group donor S-adenosylmethionine, an intermediate in the metabolism of homocysteine. (Homocysteine is an important blood chemical, because it is also a marker of cardiovascular disease). After synthesis, ADMA migrates into the extracellular space and thence into blood plasma. Asymmetric dimethylarginine is measured using high performance liquid chromatography. ADMA has been identified as a uremic toxin according to the European Uremic Toxin Working Group (PMID: 22626821).
Guanosine hexaphosphate adenosine is a dinucleoside polyphosphate. Dinucleoside polyphosphates are an interesting group of signalling molecules that control numerous physiological functions. Diadenosine compounds, with a backbone of anything from two to seven phosphates, are known to occur naturally. Some of them have been isolated from cerebral nerve terminals and, acting via nucleoside (P1), nucleotide (P2), or dinucleotide receptors, can affect central nervous system function. Many of them have been isolated from human blood platelet secretory granules and are potentially involved in haemostatic mechanisms and peripheral control of vascular tone. Many visceral organs respond to the application of adenine dinucleotides and, although they act on receptors in the periphery that can be mainly defined as either P1 or P2, evidence is now accumulating for discrete dinucleotide receptors. In the periphery, adenine dinucleotides can be potent agonists, with diverse functions, causing contraction or relaxation of smooth muscle. Many P2X receptor proteins and P2Y receptors have been cloned and adenine dinucleotides have a variable pharmacological profile at these receptors and may be useful tools for characterising subtypes of P2X and P2Y receptors. Many extracellular roles of diadenosine polyphosphates are emerging as yet increasingly important, natural ligands for a plethora of structurally diverse mononucleotide and dinucleotide receptors. (PMID: 12772275, 7767329).
N-Acetyllactosamine, also known as galb1-4glcnacb or lacnac, belongs to the class of organic compounds known as acylaminosugars. These are organic compounds containing a sugar linked to a chain through N-acyl group. N-Acetyllactosamine exists in all living organisms, ranging from bacteria to humans.
Diguanosine hexaphosphate is a diguanosine polyphosphate. Diguanosine polyphosphates (GpnGs) are found in human platelets, among a number of dinucleoside polyphosphates, which vary with respect to the number of phosphate groups and the nucleoside moieties; not only diguanosine polyphosphates (GpnG) are found, but also mixed dinucleoside polyphosphates containing one adenosine and one guanosine moiety (ApnG). The vasoactive nucleotides that can be detected in human plasma contains short(n=2-3) and long(n=4-6)polyphosphate chains. GpnGs have not yet been characterized so far with respect to their effects on kidney vasculature. (PMID: 11159696, 11682456, 11115507).
m-Chlorobenzoic acid is a metabolic byproduct of the drug bupropion. Bupropion is sold as Wellbutrin, or Zyban and is an atypical antidepressant that acts as a norepinephrine and dopamine reuptake inhibitor, and nicotinic antagonist. In 2007 it was the fourth-most prescribed antidepressant in the United States retail market, with 20.184 million retail prescriptions.
Pyridoxal is a pyridinecarbaldehyde that is pyridine-4-carbaldehyde bearing methyl, hydroxy and hydroxymethyl substituents at positions 2, 3 and 5 respectively. Pyridoxal, also known as pyridoxaldehyde, belongs to the class of organic compounds known as pyridoxals and derivatives. Pyridoxals and derivatives are compounds containing a pyridoxal moiety, which consists of a pyridine ring substituted at positions 2, 3, 4, and 5 by a methyl group, a hydroxyl group, a carbaldehyde group, and a hydroxymethyl group, respectively. Pyridoxal is one form of vitamin B6. Pyridoxal exists in all living species, ranging from bacteria to humans. In humans, pyridoxal is involved in glycine and serine metabolism. Pyridoxal has been detected, but not quantified in several different foods, such as sourdoughs, lichee, arctic blackberries, watercress, and cottonseeds. Some medically relevant bacteria, such as those in the genera Granulicatella and Abiotrophia, require pyridoxal for growth. This nutritional requirement can lead to the culture phenomenon of satellite growth. In in vitro culture, these pyridoxal-dependent bacteria may only grow in areas surrounding colonies of bacteria from other genera ("satellitism") that are capable of producing pyridoxal. Pridoxal has a role as a cofactor, a human metabolite, a Saccharomyces cerevisiae metabolite, an Escherichia coli metabolite and a mouse metabolite.
Cytidine diphosphate, abbreviated CDP, and also known as 5'-CDP, belongs to the class of organic compounds known as pyrimidine ribonucleoside diphosphates. These are pyrimidine ribonucleotides with diphosphate group linked to the ribose moiety. It is a cytosine nucleotide containing two phosphate groups esterified to the sugar moiety. CDP exists in all living species, ranging from bacteria to humans. In humans, CDP is involved in cardiolipin biosynthesis. Outside of the human body, CDP has been detected, but not quantified in several different foods, such as carobs, mexican oregano, evergreen huckleberries, green vegetables, and pepper (Capsicum baccatum).
Corticosterone, also known as 17-deoxycortisol, belongs to the class of organic compounds known as 21-hydroxysteroids. These are steroids carrying a hydroxyl group at the 21-position of the steroid backbone. Thus, corticosterone is considered to be a steroid lipid molecule. Corticosterone is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. In many species, including amphibians, reptiles, rodents and birds, corticosterone is a main glucocorticoid,[3] involved in regulation of energy, immune reactions, and stress responses. Corticosterone is the precursor molecule to the mineralocorticoid aldosterone, one of the major homeostatic modulators of sodium and potassium levels in vivo.
D-Ribose 5-phosphate (CAS: 4300-28-1), also known as R-5-P, belongs to the class of organic compounds known as pentose phosphates. These are carbohydrate derivatives containing a pentose substituted by one or more phosphate groups. D-Ribose 5-phosphate exists in all living species, ranging from bacteria to humans. Within humans, D-ribose 5-phosphate participates in a number of enzymatic reactions. In particular, D-ribose 5-phosphate can be biosynthesized from D-ribulose 5-phosphate; which is mediated by the enzyme ribose-5-phosphate isomerase. In addition, D-ribose 5-phosphate can be biosynthesized from D-ribose; which is catalyzed by the enzyme ribokinase. Outside of the human body, D-ribose 5-phosphate has been detected, but not quantified in cow milk and rices. D-Ribose 5-phosphate is both a product and an intermediate of the pentose phosphate pathway. The last step of the oxidative reactions in the pentose phosphate pathway is the production of ribulose 5-phosphate. D-Ribose 5-phosphate is an important intermediate metabolite in the pentose phosphate pathway and in the purine metabolism pathway. The intracellular ribose 5-phosphate concentration is an important determinant of the rate of de novo purine synthesis (PMID:6699001).
S-Formylglutathione, also known as L-gamma-glutamyl-S-formyl-L-cysteinylglycine, belongs to the class of organic compounds known as oligopeptides. These are organic compounds containing a sequence of three to ten alpha-amino acids joined by peptide bonds. S-Formylglutathione is a very strong basic compound (based on its pKa). S-Formylglutathione exists in all living species, ranging from bacteria to humans. Outside of the human body, S-formylglutathione has been detected, but not quantified in, several different foods, such as sweet marjorams, muscadine grapes, amaranths, lemon verbena, and garden tomato. This could make S-formylglutathione a potential biomarker for the consumption of these foods. S-Formylglutathione is formed from the oxidation of S-hydroxymethylglutathione by the enzyme formaldehyde dehydrogenase (FDH; EC 1.2.1.1) in the presence of NAD (PMID: 2806555).
Palmitaldehyde is an intermediate in the metabolism of Glycosphingolipid. It is a substrate for Sphingosine-1-phosphate lyase 1.
deaminated metabolite of glutamine in csf of patients with hepatic coma; intermediate in the detoxification of ammonia in brain; structure.
2-oxo-4-methylthiobutanoate, also known as 2-keto-4-methylthiobutyric acid, 2-keto-4-methylthiobutyrate or 4-(methylsulfanyl)-2-oxobutanoic acid, is a member of the class of compounds known as thia- fatty acids. Thia-fatty acids are fatty acid derivatives obtained by insertion of a sulfur atom at specific positions in the chain. Thus, 2-oxo-4-methylthiobutanoate is a fatty acid lipid molecule. 2-oxo-4-methylthiobutanoate is slightly soluble (in water) and a weakly acidic compound (based on its pKa). 2-oxo-4-methylthiobutanoate can be synthesized from L-methionine and butyric acid. 2-oxo-4-methylthiobutanoate can also be synthesized into S-adenosyl-4-methylthio-2-oxobutanoic acid. 2-oxo-4-methylthiobutanoate can be found in a number of food items such as cloves, highbush blueberries, common beets, and cashew nuts. 2-oxo-4-methylthiobutanoate can be found in urine. Within the cell, 2-oxo-4-methylthiobutanoate is primarily located in the cytoplasm and in the membrane. 2-oxo-4-methylthiobutanoate has been found in all living species, from bacteria to humans. In humans, 2-oxo-4-methylthiobutanoate is found to be involved in several metabolic disorders, some of those are S-adenosylhomocysteine (SAH) hydrolase deficiency, methylenetetrahydrofolate reductase deficiency (MTHFRD), methionine adenosyltransferase deficiency, and glycine N-methyltransferase deficiency. 4-Methylthio-2-oxobutanoic acid is the direct precursor of methional, which is a potent inducer of apoptosis in a BAF3 murine lymphoid cell line which is interleukin-3 (IL3)-dependent (PMID: 7848263).
Xanthylic acid is an important metabolic intermediate in the Purine Metabolism, and is a product or substrate of the enzymes Inosine monophosphate dehydrogenase (EC 1.1.1.205), Hypoxanthine phosphoribosyltransferase (EC 2.4.2.8), Xanthine phosphoribosyltransferase (EC 2.4.2.22), 5'-Ribonucleotide phosphohydrolase (EC 3.1.3.5), Ap4A hydrolase (EC 3.6.1.17), Nucleoside-triphosphate diphosphatase (EC 3.6.1.19), Phosphoribosylamine-glycine ligase (EC 6.3.4.1), and glutamine amidotransferase (EC 6.3.5.2). (KEGG) Xanthylic acid can also be used in quantitative measurements of the Inosine monophosphate dehydrogenase enzyme activities in purine metabolism. This measurement is important for optimal thiopurine therapy for children with acute lymphoblastic leukaemia (ALL). (PMID: 16725387).
Pyridoxamine 5'-phosphate belongs to the class of organic compounds known as pyridoxamine 5'-phosphates. These are heterocyclic aromatic compounds containing a pyridoxamine that carries a phosphate group at the 5'-position. Vitamin B6 is a water-soluble compound that was discovered in 1930s during nutrition studies on rats. The vitamin was named pyridoxine to indicate its structural homology to pyridine. Later it was shown that vitamin B6 could exist in two other, slightly different, chemical forms, termed pyridoxal and pyridoxamine. All three forms of vitamin B6 are precursors of an activated compound known as pyridoxal 5-phosphate (PLP), which plays a vital role as the cofactor of a large number of essential enzymes in the human body. Vitamin B6 is a water-soluble vitamin. The three major forms of vitamin B6 are pyridoxine (also known as pyridoxol), pyridoxal, and pyridoxamine, which are all converted in the liver to pyridoxal 5-phosphate (PLP) a cofactor in many reactions of amino acid metabolism. PLP also is necessary for the enzymatic reaction governing the release of glucose from glycogen.
Riboflavin reduced is an intermediate in the metabolism of Porphyrin and chlorophyll. It is a substrate for Flavin reductase.
Folinic acid (CAS: 58-05-9), also known as leucovorin, is a medication used to decrease the toxic effects of methotrexate (a chemotherapy agent and immune system suppressant) and pyrimethamine (Wikipedia). Folinic acid is the active metabolite of folic acid. Leucovorin is used principally as its calcium salt as an antidote to folic acid antagonists which block the conversion of folic acid to folinic acid.
1-Methylguanosine is a methylated nucleoside. It is known that some modified, especially methylated, nucleosides originating from RNA degradation are excreted in abnormal levels in the urine of patients with malignant tumours. These nucleosides have been proposed as tumour markers. Their measurement could provide a non-invasive diagnostic method, help identify different cancers, and monitor any therapeutic effects (PMID:9129323).
CDP-ethanolamine, also known as cytidine 5’-diphosphoethanolamine, belongs to the class of organic compounds known as CDP-ethanolamines. These are phosphoethanolamines that consist of an ethanolamine having a cytidine 5'-diphosphate moiety attached to the oxygen. CDP-ethanolamine is a very strong basic compound (based on its pKa). In humans, CDP-ethanolamine is involved in phosphatidylethanolamine biosynthesis. Outside of the human body, CDP-ethanolamine has been detected, but not quantified in, several different foods, such as Chinese water chestnuts, buffalo currants, red huckleberries, eggplants, and brazil nuts. This could make CDP-ethanolamine a potential biomarker for the consumption of these foods.
Phosphorylcholine, also known as choline phosphate or CHOP, belongs to the class of organic compounds known as phosphocholines. Phosphocholines are compounds containing a [2-(trimethylazaniumyl)ethoxy]phosphonic acid or derivative. The phosphate of choline, and the parent compound of the phosphorylcholine family. Phosphorylcholine exists in all living species, ranging from bacteria to humans. Within humans, phosphorylcholine participates in a number of enzymatic reactions. In particular, phosphorylcholine can be converted into choline through its interaction with the enzyme phosphoethanolamine/phosphocholine phosphatase. In addition, phosphorylcholine can be converted into CDP-choline; which is mediated by the enzyme choline-phosphate cytidylyltransferase a. In humans, phosphorylcholine is involved in phospholipid biosynthesis. Outside of the human body, phosphorylcholine has been detected, but not quantified in several different foods, such as barley, pak choy, black radish, saskatoon berries, and acorns.
3-Methylguanine is a methylated purine base. Methylated purine bases are known to be present in normal urine and to change under pathological conditions, in particular in the development of leukemia, tumors and immunodeficiency, by the altered turnover of nucleic acids typical of these diseases. (PMID 9069642).
trans-2-Octenoic acid or (2E)-oct-2-enoic acid is an olefinic fatty acid that is octanoic acid carrying a double bond at position 2 (the 2E-isomer). It has a role as an animal metabolite. It is a medium-chain fatty acid, a monounsaturated fatty acid, a straight-chain fatty acid and an olefinic fatty acid. It is a conjugate acid of a (2E)-oct-2-enoate.
Epi-coprostanol, also known as epicholestanol or presteron, belongs to the class of organic compounds known as cholesterols and derivatives. Cholesterols and derivatives are compounds containing a 3-hydroxylated cholestane core. Thus, epi-coprostanol is considered to be a sterol lipid molecule. Epi-coprostanol is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
Thymidine 3',5'-cyclic monophosphate is an intermediate in the pyrimidine metabolism. It is the product or substrate of the enzymes thymidylate synthase (EC 2.1.1.45), thymidylate synthase (FAD) (EC 2.1.1.148), thymidine kinase (EC 2.7.1.21), AMP-thymidine kinase (EC 2.7.1.114), ADP-thymidine kinase (EC 2.7.1.118), dTMP kinase (EC 2.7.4.9), T2-induced deoxynucleotide kinase (EC 2.7.4.12), 5'-nucleotidase (EC 3.1.3.5), Thymidylate 5'-phosphatase (EC 3.1.3.35), and ATP-diphosphatase (EC 3.6.1.5).
Glucose 1-phosphate (also called cori ester) is a glucose molecule with a phosphate group on the 1'-carbon. It can exist in either the α- or β-anomeric form. Glucose 1-phosphate belongs to the class of organic compounds known as monosaccharide phosphates. These are monosaccharides comprising a phosphated group linked to the carbohydrate unit. Glucose 1-phosphate is the direct product of the reaction in which glycogen phosphorylase cleaves off a molecule of glucose from a greater glycogen structure. It cannot travel down many metabolic pathways and must be interconverted by the enzyme phosphoglucomutase in order to become glucose 6-phosphate. Free glucose 1-phosphate can also react with UTP to form UDP-glucose. It can then return to the greater glycogen structure via glycogen synthase.
Phenylglyoxylic acid is one of the major urinary metabolites of toluene, o-, m- and p-xylenes, styrene and ethylbenzene. (PMID 3782394). For the biological monitoring of workers exposure to solvent used in industry, its concentration is measured in human urine samples. (PMID 2739101).
2-hydroxycaproic acid, also known as 2-hydroxyhexanoic acid is a hydroxy fatty acid that is caproic (hexanoic) acid substituted by a hydroxy group at position 2. It has a role as an animal metabolite. It derives from a hexanoic acid. It is a conjugate acid of a 2-hydroxyhexanoate. 2-hydroxycaproic acid is a branched-chain alpha-keto acid that have been reported in normal human blood (PMID:7130306) and in normal amniotic fluid (PMID:7076774). It has been found that 2-hydroxycaproic acid is the most significant metabolite found in the CSF of patients infected with Nocardia. Nocardia sp. is an uncommon cause of meningitis, and Nocardia meningitis has a clinical picture similar to that of tuberculous meningitis (PMID:3818936; PMID:20615997).
D-Xylulose (CAS: 551-84-8) is a monosaccharide containing five carbon atoms. D-Xylulose is converted from xylitol by the enzyme NAD+-linked xylitol dehydrogenase (EC 1.1.1.9) in the glucuronate pathway, the most important xylitol-handling metabolic pathway in mammals. This activity has been described in human erythrocytes. Most likely, D-xylulose (as well as D-arabinose or D-ribulose) is a precursor of the pentiol D-arabitol, since pentitols are derived from their corresponding pentose phosphate precursors via pentoses. This pathway can play a role in inherited metabolic disorders underlying the accumulation of pentitols (e.g. ribose 5-phosphate isomerase deficiency and transaldolase deficiency). Although pentitols are present in all living organisms, knowledge concerning their metabolism is limited (PMID:15234337, Mol Genet Metab. 2004 Jul;82(3):231-7.).
L-Norleucine, also known as L-aminohexanoate or caprine, belongs to the class of organic compounds known as l-alpha-amino acids. These are alpha amino acids which have the L-configuration of the alpha-carbon atom. Thus, L-norleucine is considered to be a fatty acid lipid molecule. An unnatural amino acid that is used experimentally to study protein structure and function. L-Norleucine is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. L-Norleucine exists in all eukaryotes, ranging from yeast to humans. Outside of the human body, L-Norleucine has been detected, but not quantified in cow milk. This could make L-norleucine a potential biomarker for the consumption of these foods. It binds reversibly to the kringle domain of plasminogen and blocks the binding of plasminogen to fibrin and its activation to plasmin.
m-Coumaric acid, also known as 3-coumarate, belongs to the class of organic compounds known as hydroxycinnamic acids. Hydroxycinnamic acids are compounds containing an cinnamic acid where the benzene ring is hydroxylated. m-Coumaric acid exists in all living organisms, ranging from bacteria to humans. m-Coumaric acid (CAS: 588-30-7) is a polyphenol metabolite from caffeic acid, formed by the gut microflora. Outside of the human body, m-Coumaric acid is found, on average, in the highest concentration within a few different foods, such as olives, corns, and beers. m-Coumaric acid has also been detected, but not quantified in several different foods, such as carrots, strawberries, grape wines, garden tomato, and bilberries. MCT-mediated absorption of phenolic compounds per se and their colonic metabolites would exert a significant impact on human health (PMID:16870009, 15479001, 15479001). m-Coumaric acid is transported by the monocarboxylic acid transporter (MCT). The amount of this compound in human biofluids is diet-dependant. m-Coumaric acid is detected after the consumption of whole grain.
DL-O-Phosphoserine, also known as DL-O-phosphorylserine or DL-O-serine phosphate, belongs to the class of organic compounds known as alpha amino acids. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). Serine proteases are a common type of protease. DL-O-Phosphoserine exists in all living species, ranging from bacteria to humans. Serine is one of three amino acid residues that are commonly phosphorylated by kinases during cell signalling in eukaryotes.
Etheno nucleosides are a new class of chemically modified components of nucleic acids. These base-modified nucleosides demonstrate significant biological properties, acting, among others, as antiviral or antitumor agents. One of the possible modifications of the nucleoside is their transformation into ethenonucleosides. Thus, nucleosides or their respective heterocyclic bases, possessing an exocyclic amino group, as well as a neighboring endocyclic nitrogen, can react with some bifunctional reagents (e.g., α-halocarbonyl compounds) to form products with an additional five-membered ring of the imidazole type. The ethenonucleosides basically do not occur in nature; some of the only exceptions are Y-nucleosides. Etheno modified DNA bases are generated from the carcinogens vinyl chloride and urethane, but also by reactions of DNA with products derived from lipid peroxidation (LPO) and oxidative stress via endogenous pathways. Highly variable background levels of epsilon-adducts were detected in DNA from different organs of unexposed humans and rodents. Several known cancer risk factors increased the level of these DNA lesions in target organs: elevated epsilon-adducts were found in hepatic DNA from patients with metal storage diseases, after overproduction of nitric oxide (NO) by inducible NO synthase (iNOS) in a mouse model, and in colonic polyps of familial adenomatous polyposis patients. A high omega-6-polyunsaturated fatty acid diet increased epsilon-DNA adducts in white blood cells of female subjects. (PMID:10882861).
The major progestational steroid that is secreted primarily by the corpus luteum and the placenta. Progesterone acts on the uterus, the mammary glands and the brain. It is required in embryo implantation, pregnancy maintenance, and the development of mammary tissue for milk production. Progesterone, converted from pregnenolone, also serves as an intermediate in the biosynthesis of gonadal steroid hormones and adrenal corticosteroids. Progesterone is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other species. Progesterone belongs to a class of hormones called progestagens, and is the major naturally occurring human progestagen. During implantation and gestation, progesterone appears to decrease the maternal immune response to allow for the acceptance of the pregnancy. Progesterone decreases contractility of the uterine smooth muscle. The fetus metabolizes placental progesterone in the production of adrenal mineralo- and glucosteroids. A drop in progesterone levels is possibly one step that facilitates the onset of labor. In addition progesterone inhibits lactation during pregnancy. The fall in progesterone levels following delivery is one of the triggers for milk production. Progesterone is found to be associated with pregnene hydroxylation deficiency, which is an inborn error of metabolism.
Aminopterin Syndrome Sine Aminopterin (ASSA, OMIM 600325) is an embryopathy caused by maternal treatment with the olic acid antagonist aminopterin has been recognized since 1952 when aminopterin was used as an abortifacient. The characteristic phenotype of the children who survived infancy after having been exposed to aminopterin or its methyl derivative, methotrexate, in early pregnancy included a very unusual facies, skull anomalies, and skeletal defects.(OMIM). Aminopterin is an antimetabolite drug used in treatment of cancer and autoimmune diseases. It acts by inhibiting the metabolism of folic acid. - Wikipedia. The effects of the drug on intracellular metabolic processes, due to the inhibitory action on the enzyme dihydrofolate reductase, show that the result of this inhibition is more complex and is not limited to blockade of the reduction of folic acid alone. Although rescue methods are important in prevention of lethal effects of methotrexate, some metabolic pathways are insufficiently rescued, resulting in toxic reactions following methotrexate administration.(PMID 6398629).
Guanidine is a polyamine that can function as a strong organic base existing primarily as guanidium ions at physiological pH. With a pKa of 12.5, guanidine is protonated, with a charge of +1 in physiological conditions. It is found in the urine as a normal product of protein metabolism. It has been identified as a uremic toxin according to the European Uremic Toxin Working Group (PMID: 22626821). Guanidine is also used in laboratory research as a protein denaturant. (From Martindale, the Extra Pharmacopoeia, 30th ed and Merck Index, 12th ed). Guanidine is a crystalline compound of strong alkalinity formed by the oxidation of guanine. It is used in the manufacture of plastics and explosives. -- Wikipedia.
N-Acryloylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction:. acyl-CoA + glycine < -- > CoA + N-acylglycine. N-Acryloylglycine is an acylglycines found in normal human biofluids (PMID 7364920; 912020; 7438429).
Methylsuccinic acid (CAS: 498-21-5) is a normal metabolite found in human fluids. Increased urinary levels of methylsuccinic acid (together with ethylmalonic acid) are the main biochemical measurable features in ethylmalonic encephalopathy (OMIM: 602473), a rare metabolic disorder with an autosomal recessive mode of inheritance that is clinically characterized by neuromotor delay, hyperlactic acidemia, recurrent petechiae, orthostatic acrocyanosis, and chronic diarrhea (PMID:12382164). The underlying biochemical defect involves isoleucine catabolism (PMID:9667231). Methylsuccinic acid levels were found to have decreased in the urine of animals under D-serine-induced nephrotoxicity (D-serine causes selective necrosis of the proximal straight tubules in the rat kidney) (PMID:15596249). Moreover, methylsuccinic acid is found to be associated with ethylmalonic encephalopathy, isovaleric acidemia, and medium-chain acyl-CoA dehydrogenase deficiency, which are also inborn errors of metabolism.
The prototypical tricyclic antidepressant. It has been used in major depression, dysthymia, bipolar depression, attention deficit disorders, agoraphobia, and panic disorders. It has less sedative effect than some other members of this therapeutic group. -- Pubchem; Imipramine (sold as Antideprin, Janimine, Tofranil) is an antidepressant medication, a tricyclic antidepressant of the dibenzazepine group, mainly used in the treatment of clinical depression and enuresis. -- Wikipedia.
Propranolol is a widely used non-cardioselective beta-adrenergic antagonist. Propranolol is used in the treatment or prevention of many disorders including acute myocardial infarction, arrhythmias, angina pectoris, hypertension, hypertensive emergencies, hyperthyroidism, migraine, pheochromocytoma, menopause, and anxiety. --PubChem; Propranolol is a highly lipophilic drug achieving high concentrations in the brain. The duration of action of a single oral dose is longer than the half-life indicates and may be up to 12 hours, if the single dose is high enough (e.g. 80 mg). Effective plasma concentrations are between 10-100 ng/mL. -- Wikipedia; It was the first successful beta blocker developed. Propranolol is commonly marketed by Wyeth under the trade name Inderal.
Verapamil is only found in individuals that have used or taken this drug. Verapamil is a calcium channel blocker that is a class IV anti-arrhythmia agent. [PubChem]Verapamil inhibits voltage-dependent calcium channels. Specifically, its effect on L-type calcium channels in the heart causes a reduction in ionotropy and chronotropy, thuis reducing heart rate and blood pressure. Verapamil's mechanism of effect in cluster headache is thought to be linked to its calcium-channel blocker effect, but which channel subtypes are involved is presently not known. [PubChem] Calcium channel antagonists can be quite toxic. In the management of poisoning, early recognition is critical. Calcium channel antagonists are frequently prescribed, and the potential for serious morbidity and mortality with over dosage is significant. Ingestion of these agents should be suspected in any patient who presents in an overdose situation with unexplained hypotension and conduction abnormalities. The potential for toxicity should be noted in patients with underlying hepatic or renal dysfunction who are receiving therapeutic doses. (PMID 8213877).
L-Arabitol, also known as L-arabinitol or L-lyxitol, is a member of the class of compounds known as sugar alcohols. Sugar alcohols are hydrogenated forms of carbohydrate in which the carbonyl group (aldehyde or ketone reducing sugar) has been reduced to a primary or secondary hydroxyl group. L-Arabitol is soluble in water. L-Arabitol can be found in a number of food items such as sweet potato, deerberry, moth bean, and European chestnut, which makes L-arabitol a potential biomarker for the consumption of these food products. L-Arabitol can be found in most biofluids, including urine, cerebrospinal fluid (CSF), saliva, and blood. L-Arabitol exists in all living species, ranging from bacteria to humans. Moreover, L-arabitol is found to be associated with Alzheimer's disease and ribose-5-phosphate isomerase deficiency, which is an inborn error of metabolism. L-Arabitol can be formed by the reduction of either arabinose or lyxose. L-Arabitol has been reported in pentosuric acidemia (PMID:13525419). L-Arabinosinuia has been described in a patient, presented at the age of 16 months with delayed motor development and facial dysmorphism (PMID:12359133) Congenital liver cirrhosis has been recently described in a patient with highly elevated plasma and urine levels of arabitol due to transaldolase deficiency (Inherit Metab Dis 23(Suppl. 1):172, 2000).
all-trans-Retinoic acid is an isomer of retinoic acid, the oxidized form of vitamin A. Retinoic acid functions in determining position along embryonic anterior/posterior axis in chordates. It acts through Hox genes, which ultimately controls anterior/posterior patterning in early developmental stages (PMID:17495912). It is an important regulator of gene expression during growth and development, and in neoplasms. As a drug, all-trans-retinoic acid is known as tretinoin. Tretinoin is derived from maternal vitamin A and is essential for normal growth and embryonic development. An excess of tretinoin can be teratogenic. Tretinoin is used in the treatment of psoriasis, acne vulgaris, and several other skin diseases. It has also been approved for use in promyelocytic leukemia (leukemia, promyelocytic, acute).
Tellurium is a trace element that belongs chemically to the VIa group in the periodic chemical table that has the symbol Te and atomic number 52. Tellurium is a brittle silver-white metalloid which looks like tin, and is related to selenium and sulfur. Physiologically, it exists as an ion in the body. The ingestion of tellurium compounds has been known to be associated with a garlic-like odor of the breath, thus indicating that tellurium is absorbed by the gut, metabolized by tissues, and excreted through routes other than the feces. Little is known about the Te biological activity, particularly with respect to potential chemical interactions with Se-containing components in the organism. Tellurium is a non-competitive inhibitor of squalene epoxidase and has been associated with neuropathy. Late fetal stages of prenatal development appeared uniquely sensitive to organic tellurium exposure. All tellurium compounds are highly toxic. (PMID: 17873396, 15596254, 10048717).
5-Hydroxytryptophol is a relatively minor metabolite of serotonin that is excreted primarily as the glucuronide conjugate in human urine. 5-Hydroxytryptophol becomes more important quantitatively during alcohol intoxication, when a shift in the metabolism of serotonin occurs from 5-hydroxyindole acetic acid toward increased (15-fold higher) formation of 5-hydroxytryptophol due to the inhibition of aldehyde dehydrogenase by ethanol-derived acetaldehyde. Urinary excretion of 5-hydroxytryptophol has also been shown to be markedly increased for several hours following intake of foods rich in serotonin, such as bananas. Wide interspecies variation has been reported in the metabolism serotonin to 5-hydroxytryptophol; 5-Hydroxytryptophol makes up 35% of the excreted serotonin metabolites in the rat on average and 10 to 20% in several other species. Human UDP-glucuronosyltransferase 1A6 (UGT1A6) plays a predominant role in the glucuronidation of 5-hydroxytryptophol by human liver microsomes. (PMID 15258112).
Protocatechuic acid, also known as protocatechuate or 3,4-dihydroxybenzoate, belongs to the class of organic compounds known as hydroxybenzoic acid derivatives. Hydroxybenzoic acid derivatives are compounds containing a hydroxybenzoic acid (or a derivative), which is a benzene ring bearing a carboxyl and a hydroxyl groups. The enzyme protocatechuate 3,4-dioxygenase uses 3,4-dihydroxybenzoate and O2 to produce 3-carboxy-cis,cis-muconate. Protocatechuic acid is a drug. In the analogous hardening of the cockroach ootheca, the phenolic substance concerned is protocatechuic acid. Protocatechuic acid is a mild, balsamic, and phenolic tasting compound. Outside of the human body, protocatechuic acid is found, on average, in the highest concentration in a few different foods, such as garden onions, cocoa powders, and star anises and in a lower concentration in lentils, liquors, and red raspberries. Protocatechuic acid has also been detected, but not quantified in several different foods, such as cloud ear fungus, american pokeweeds, common mushrooms, fruits, and feijoa. This could make protocatechuic acid a potential biomarker for the consumption of these foods. It is also found in Allium cepa (17,540 ppm). It is a major metabolite of antioxidant polyphenols found in green tea. Similarly, PCA was reported to increase proliferation and inhibit apoptosis of neural stem cells. In vitro testing documented antioxidant and anti-inflammatory activity of PCA, while liver protection in vivo was measured by chemical markers and histological assessment.
1,3-Dimethyluric acid is a product of theophylline metabolism in man. 1,3-Dimethyluric acid is one of the purine components in urinary calculi. Methylated purines originate from the metabolism of methylxanthines (caffeine, theophylline and theobromine). Methyluric acids are indistinguishable from uric acid by simple methods routinely used in clinical laboratories, requiring the use of high-performance liquid chromatography (HPLC). Purine derivatives in urinary calculi could be considered markers of abnormal purine metabolism. The content of a purine derivative in stone depends on its average urinary excretion in the general population, similarity to the chemical structure of uric acid, and content of the latter in stone. This suggests that purines in stones represent a solid solution with uric acid as solvent. It is also plausible that methylxanthines, ubiquitous components of the diet and drugs, are involved in the pathogenesis of urolithiasis. Caffeine is metabolized via successive pathways mainly catalyzed by CYP1A2, xanthine oxidase or N-acetyltransferase-2 to give 14 different metabolites. CYP1A2 activity shows an inter-individual variability among the population. CYP1A2, an isoform of the CYP1A cytochrome P450 super-family, is involved in the metabolism of many drugs and plays a potentially important role in the induction of chemical carcinogenesis. (PMID:11712316, 15833286, 3506820, 15013152, 4039734).
The excellent tolerability of therapeutic doses of paracetamol (acetaminophen) is a major factor in the very wide use of the drug. The major problem in the use of paracetamol is its hepatotoxicity after an overdose. Hepatotoxicity has also been reported after therapeutic doses, but critical analysis indicates that most patients with alleged toxicity from therapeutic doses have taken overdoses. Importantly, prospective studies indicate that therapeutic doses of paracetamol are an unlikely cause of hepatotoxicity in patients who ingest moderate to large amounts of alcohol (PMID: 15733027). Single doses of paracetamol are effective analgesics for acute postoperative pain and give rise to few adverse effects (PMID: 14974073). Acetaminophen (AAP) overdose and the resulting hepatotoxicity is an important clinical problem. In addition, AAP is widely used as a prototype hepatotoxin to study mechanisms of chemical-induced cell injury and to test the hepatoprotective potential of new drugs and herbal medicines. Because of its importance, the mechanisms of AAP-induced liver cell injury have been extensively investigated and controversially discussed for many years (PMID: 16863451).
Paraxanthine, also known as p-xanthine, belongs to the class of organic compounds known as xanthines. These are purine derivatives with a ketone group conjugated at carbons 2 and 6 of the purine moiety. Paraxanthine exists in all living organisms, ranging from bacteria to humans. Within humans, paraxanthine participates in a number of enzymatic reactions. In particular, paraxanthine and formaldehyde can be biosynthesized from caffeine; which is catalyzed by the enzyme cytochrome P450 1A2. In addition, paraxanthine and acetyl-CoA can be converted into 5-acetylamino-6-formylamino-3-methyluracil through its interaction with the enzyme arylamine N-acetyltransferase 2. In humans, paraxanthine is involved in caffeine metabolism.
N tau-methylhistamine is one of the histamine metabolites. N tau-methylhistamine in plasma and urine is a good parameter for histamine release, and the determination of this histamine metabolite is generally less hampered by possible artifacts (due to basophil disrupture, a very short half-life time or bacterial production) than determinations of histamine itself (PMID 2409780).
2-ethylacrylic acid is an alpha, beta-unsaturated monocarboxylic acid that is acrylic acid in which the hydrogen at position 2 is substituted by an ethyl group. It has a role as a mammalian metabolite. It derives from an acrylic acid. It is a conjugate acid of a 2-ethylacrylate. 2-Ethylacrylic acid is an intermediate metabolite in the conversion of R-2-methylbutyrate into 2-ethylhydracrylic acid, which is variably increased in defects of isoleucine oxidation at distal steps in the catabolic pathway (3-oxoacyl-CoA thiolase deficiency and methylmalonyl-CoA mutase deficiency) (PMID 1016232).
2-Hydroxyvaleric acid is an organic acid present in human biofluids. Its presence in urine has been associated with lactic acidosis, which occurs in Succinic Acidemia (OMIM 600335), a syndrome of organic acidemia associated with congenital lactic acidosis and decreased NADH-cytochrome c reductase activity. 2-Hydroxyvaleric acid presence associated with lactic acidosis has also been found in Propionyl-CoA carboxylase deficiency (OMIM 253260), or Multiple carboxylase deficiency (MCD), an autosomal recessive metabolic disorder characterized primarily by cutaneous and neurologic abnormalities. (PMID: 9389332, 1790187, 3378323, 3383430, 7313494).
2-Ketohexanoic acid is a potent insulin secretagogue (PMID 7045091). 2-Ketohexanoic acid directly inhibits the ATP-sensitive K+ channel (KATP channel) in pancreatic beta-cells (stimulated in isolated mouse islets), but it is unknown whether direct KATP channel inhibition contributes to insulin release by 2-ketohexanoic acid and related alpha-keto acid anions, which are generally believed to act via beta-cell metabolism (PMID 16014804).
2-Oxovaleric acid is an alpha-ketoacid is a metabolite usually found in human biofluids. Ketoacids have been known to play an important part in the metabolism of valine, leucine, isoleucine. 2-Oxovaleric acid presence has been determined in human blood serum and urine in numerous scientific documents, although its origin remains unclear. (PMID: 11482739, 9869358, 3235498).
3,4-Dihydroxymandelic acid, also known as DOMA or 3,4-dihydroxyphenylglycolate, belongs to the class of organic compounds known as catechols. Catechols are compounds containing a 1,2-benzenediol moiety. 3,4-Dihydroxymandelic acid exists in all living organisms, ranging from bacteria to humans. Within humans, 3,4-dihydroxymandelic acid participates in a number of enzymatic reactions. In particular, 3,4-dihydroxymandelic acid can be biosynthesized from 3,4-dihydroxymandelaldehyde through its interaction with the enzyme aldehyde dehydrogenase, dimeric nadp-preferring. In addition, 3,4-dihydroxymandelic acid and guaiacol can be converted into vanillylmandelic acid and pyrocatechol through the action of the enzyme catechol O-methyltransferase. In humans, 3,4-dihydroxymandelic acid is involved in the metabolic disorder called tyrosinemia type I. Outside of the human body, 3,4-Dihydroxymandelic acid has been detected, but not quantified in several different foods, such as yellow wax beans, soy beans, pomegranates, cucurbita (gourd), and daikon radish.
4-Aminohippuric acid is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction:. acyl-CoA + glycine < -- > CoA + N-acylglycine. Renal proximal tubules secrete various organic anions, including drugs and p-aminohippurate (PAH). Uptake of PAH from blood into tubule cells occurs by exchange with intracellular alpha-ketoglutarate and is mediated by the organic anion transporter 1. PAH exit into tubule lumen is species specific and may involve ATP-independent and -dependent transporters. (PMID 11443229). Enhanced secretion of p-aminohippuric acid occurs in Fanconi's syndrome (FS). FS is associated with numerous varieties of inherited and acquired conditions; FS is characterized by a generalized transport defect in the proximal tubules, leading to renal losses of glucose, phosphate, calcium, uric acid, amino acids, bicarbonates, and other organic compounds. (PMID 12552490).
5-methoxysalicylic acid is a methoxysalicylic acid that is salicylic acid which is carrying a methoxy group at position 5. It has a role as a bacterial metabolite and a human urinary metabolite. 5-Methoxysalicylic acid is also known as 2-hydroxy-5-methoxybenzoate or 5-methoxy-2-hydroxybenzoate and belongs to the class of organic compounds known as m-methoxybenzoic acids and derivatives. These are benzoic acids in which the hydrogen atom at position 3 of the benzene ring is replaced by a methoxy group. Outside of the human body, 5-Methoxysalicylic acid has been detected, but not quantified in herbs and spices and tea.
Benzoic acid, C6H5COOH, is a colourless crystalline solid and the simplest aromatic carboxylic acid. Benzoic acid occurs naturally free and bound as benzoic acid esters in many plant and animal species. Appreciable amounts have been found in most berries (around 0.05%). Cranberries contain as much as 300-1300 mg free benzoic acid per kg fruit. Benzoic acid is a fungistatic compound that is widely used as a food preservative. It often is conjugated to glycine in the liver and excreted as hippuric acid. Benzoic acid is a byproduct of phenylalanine metabolism in bacteria. It is also produced when gut bacteria process polyphenols (from ingested fruits or beverages). It can be found in Serratia (PMID:23061754).
Epicatechin is an antioxidant flavonoid, occurring especially in woody plants as both (+)-catechin and (-)-epicatechin (cis) forms. Catechin is a tannin peculiar to green and white tea because the black tea oxidation process reduces catechins in black tea. Catechin is a powerful, water soluble polyphenol and antioxidant that is easily oxidized. Several thousand types are available in the plant world. As many as two thousand are known to have a flavon structure and are called flavonoids. Catechin is one of them. Green tea is manufactured from fresh, unfermented tea leaves; the oxidation of catechins is minimal, and hence they are able to serve as antioxidants. Researchers believe that catechin is effective because it easily sticks to proteins, blocking bacteria from adhering to cell walls and disrupting their ability to destroy them. Viruses have hooks on their surfaces and can attach to cell walls. The catechin in green tea prevents viruses from adhering and causing harm. Catechin reacts with toxins created by harmful bacteria (many of which belong to the protein family) and harmful metals such as lead, mercury, chrome, and cadmium. From its NMR espectra, there is a doubt on 2 and 3 atoms configuration. It seems to be that they are in trans position.
Isobutyric acid is a carboxylic or short chain fatty acid with characteristic sweat-like smell. Small amount of isobutyrate is generated via microbial (gut) metabolism. Small amounts may also be found in certain foods or fermented beverages. There is anosmia (genetic inability to smell) for the odor of isobutyric acid with a frequency of about 2.5%. (OMIM 207000). Isobutyric acid is slightly soluble in water but much more soluble in ethanol, ether and organic solvents. Isobutyric acid can affect people if breathed in and may be absorbed through the skin. Contact can irritate and burn the skin and eyes. Breathing Isobutyric acid can irritate the nose, throat and lungs causing coughing, wheezing and/or shortness of breath.
D-threo-Isocitric acid, also known as isocitrate or isocitrIC ACID, belongs to the class of organic compounds known as tricarboxylic acids and derivatives. These are carboxylic acids containing exactly three carboxyl groups. D-threo-Isocitric acid exists in all living species, ranging from bacteria to humans. D-threo-Isocitric acid has been detected, but not quantified in several different foods, such as citrus, fruits, common beans, green beans, and yellow wax beans.
Methanol, also known as columbian spirit or CH3OH, belongs to the class of organic compounds known as primary alcohols. Primary alcohols are compounds comprising the primary alcohol functional group, with the general structure RCOH (R=alkyl, aryl). The target of methanol in the eye is the retina, specifically the optic disk and optic nerve. Toxicity is due to the metabolic products of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase. Methanol exists in all living organisms, ranging from bacteria to humans. Methanol is an alcoholic tasting compound. Outside of the human body, Methanol is found, on average, in the highest concentration within cow milk and sweet oranges. Methanol has also been detected, but not quantified in several different foods, such as prairie turnips, mountain yams, mentha (mint), watermelons, and pasta. Methanol is responsible for accidental, suicidal, and epidemic poisonings, resulting in death or permanent sequelae. Methanol is a potentially toxic compound. Visual disturbances develop between 18h to 48h after ingestion and range from mild photophobia and blurred vision to markedly reduced visual acuity and complete blindness. Methanol is metabolized to formaldehyde by alcohol dehydrogenase, then from that to formate by formaldehyde dehydrogenase, and then to carbon dioxide by limited H4 folate. It is the simplest alcohol, and is a light, volatile, colourless, flammable, poisonous liquid with a distinctive odor that is somewhat milder and sweeter than ethanol.
Epinephrine sulfate is found in human plasma at different levels. Glucuronidation may be an improtant pathway for catecholammine in man at rest or under sympathetic stimulation.(PMID: 6688268).
Valproic acid (VPA) is considered to be a drug of first choice and one of the most frequently-prescribed antiepileptic drugs worldwide for the therapy of generalized and focal epilepsies, including special epileptic. It is a broad-spectrum antiepileptic drug and is usually well tolerated. Rarely, serious complications may occur in some patients, including hemorrhagic pancreatitis, coagulopathies, bone marrow suppression, VPA-induced hepatotoxicity and encephalopathy, but there is still a lack of knowledge about the incidence and occurrence of these special side effects. VPA has been approved for stabilization of manic episodes in patients with bipolar disorder. It is also used to treat migraine headaches and schizophrenia. As the use of VPA increases, the number of both accidental and intentional exposures increases. This is paralleled by more reports of VPA-induced toxicity. VPA is relatively contraindicated in pregnancy due to its teratogenicity. It is a known folate antagonist, which can cause neural tube defects. Thus, folic acid supplements may alleviate teratogenic problems. Women who become pregnant whilst taking valproate should be counselled as to its risks. VPA is an inhibitor of the enzyme histone deacetylase 1 (HDAC1). HDAC1 is needed for HIV to remain in infected cells. Patients treated with valproic acid in addition to highly active antiretroviral therapy (HAART) showed a median 75% reduction in latent HIV infection. VPA is believed to affect the function of the neurotransmitter GABA (as a GABA transaminase inhibitor) in the human brain. Valproic Acid dissociates to the valproate ion in the gastrointestinal tract. (PMID: 18201150, 17496767).
Thymol is a phenol obtained from thyme oil or other volatile oils. It is used as a stabilizer in pharmaceutic preparations. It has been used for its antiseptic, antibacterial, and antifungal actions, and was formerly used as a vermifuge. Thymol is a monoterpene phenol derivative of cymene, C10H13OH, isomeric with carvacrol, found in oil of thyme, and extracted as a white crystalline substance of a pleasant aromatic odor and strong antiseptic properties. It is also called "hydroxy cymene". In a 1994 report released by five top cigarette companies, thymol is one of the 599 additives to cigarettes. Its use or purpose, however, is unknown, like most cigarette additives.
Dihydroxyacetone (also known as DHA) is a ketotriose compound. Its addition to blood preservation solutions results in better maintenance of 2,3-diphosphoglycerate levels during storage. It is readily phosphorylated to dihydroxyacetone phosphate by triokinase in erythrocytes. In combination with naphthoquinones, it acts as a sunscreening agent. Dihydroxyacetone is the simplest of all ketoses and, having no chiral centre, is the only one that has no optical activity. Dihydroxyacetone is a simple non-toxic sugar. It is often derived from plant sources such as sugar beets and sugar cane, by the fermentation of glycerin. Dihydroxyacetone is a white crystalline powder which is water soluble.
3-Chlorotyrosine, a specific marker of myeloperoxidase-catalyzed oxidation, is markedly elevated in low density lipoprotein isolated from human atherosclerotic intima. (PMID 9151778). In particular, myeloperoxidase halogenates tyrosine residues in plasma proteins and and generates 3-chlorotyrosine (CY). The detection of free chlorotyrosine in blood or urine arises from the degradation of these chlorinated proteins. CY concentrations may be useful for monitoring the activation of neutrophils in asthmatic patients (PMID 15196282).
3-methyl-9H-xanthine is a 3-methylxanthine tautomer where the imidazole proton is located at the 9-position. It has a role as a metabolite. It is a tautomer of a 3-methyl-7H-xanthine. 3-Methylxanthine, also known as 3 MX or purine analog, belongs to the class of organic compounds known as xanthines. These are purine derivatives with a ketone group conjugated at carbons 2 and 6 of the purine moiety.
N,N-Dimethylformamide (DMF) is a clear liquid that has been widely used in industries as a solvent, an additive, or an intermediate because of its extensive miscibility with water and most common organic solvents. Its health effects include hepatotoxicity and male reproductoxicity, possibly linked with mitochondrial DNA (mtDNA) alterations including mtDNA common deletion (delta-mtDNA4977) and mtDNA copy number; during the biotransformation of DMF in the body, free radicals are formed, including hydroxyl radicals. The world-wide consumption of DMF in 2001 was approximately 285,000 metric tonnes and most of that was used as an industrial solvent. Overexposure to DMF could result in hepatotoxicity, alcohol intolerance, possible embryotoxicity and teratogenicity in humans and animals, and decline of human sperm motility. Based on its wide application and a wide range of toxic effects, DMF has been selected as one of the four priority compounds for human field studies by the National Toxicology Program (NTP) of the US National Institute of Environmental Health Sciences (NIEHS). The current permissible exposure limit for DMF in the working environment is 10 ppm in both USA and Taiwan. The concentrations of two major DMF metabolites in urine, N-methylformamide (U-NMF) of 15 mg/L and N-acetyl-S-(N-methylcarbamoyl) cysteine (U-AMCC) of 40 mg/L, were recommended as the biological exposure indices (BEIs) by the American Conference of Governmental Industrial Hygienists for DMF exposure in workplace. (PMID: 17254560).
Theophylline, also known as quibron TSR or uniphyl, belongs to the class of organic compounds known as xanthines. These are purine derivatives with a ketone group conjugated at carbons 2 and 6 of the purine moiety. Theophylline also binds to the adenosine A2B receptor and blocks adenosine mediated bronchoconstriction. Theophylline is a drug which is used for the treatment of the symptoms and reversible airflow obstruction associated with chronic asthma and other chronic lung diseases, such as emphysema and chronic bronchitis. Theophylline is marketed under several brand names such as Theophylline and Theochron, and it is indicated mainly for asthma, bronchospasm, and COPD. Within humans, theophylline participates in a number of enzymatic reactions. In particular, theophylline and formaldehyde can be biosynthesized from caffeine; which is mediated by the enzymes cytochrome P450 1A2, cytochrome P450 3A4, cytochrome P450 2C8, cytochrome P450 2C9, and cytochrome P450 2E1. In addition, theophylline can be converted into 1-methylxanthine and formaldehyde; which is mediated by the enzyme cytochrome P450 1A2. In humans, theophylline is involved in caffeine metabolism. Theophylline is a bitter tasting compound. Outside of the human body, Theophylline is found, on average, in the highest concentration within cocoa beans and tea. Theophylline has also been detected, but not quantified in a few different foods, such as arabica coffee, lemons, and pummelo. This could make theophylline a potential biomarker for the consumption of these foods. Theophylline is a potentially toxic compound.
m-Aminobenzoic acid (also known as 3-aminobenzoic acid or MABA) is an organic compound with the molecular formula H2NC6H4CO2H. MABA is a white solid, although commercial samples are often colored. It is only slightly soluble in water. It is soluble in acetone, boiling water, hot alcohol, hot chloroform and ether. It consists of a benzene ring substituted with an amino group and a carboxylic acid. m-Aminobenzoic acid belongs to the class of organic compounds known as aminobenzoic acids. These are benzoic acids containing an amine group attached to the benzene moiety. Outside of the human body, m-Aminobenzoic acid has been detected, but not quantified in cow milk. This could make m-aminobenzoic acid a potential biomarker for the consumption of these foods.
Menadione is a synthetic naphthoquinone without the isoprenoid side chain and biological activity, but can be converted to active vitamin K2, menaquinone, after alkylation in vivo. -- Pubchem; Despite the fact that it can serve as a precursor to various types of vitamin K, menadione is generally not used as a nutritional supplement. Large doses of menadione have been reported to cause adverse outcomes including hemolytic anemia due to G6PD deficiency, neonatal brain or liver damage, or neonatal death in some cases. Moreover, menadione supplements have been banned by the FDA because of their high toxicity. It is sometimes called vitamin K3, although derivatives of naphthoquinone without the sidechain in the 3-position cannot exert all the functions of the K vitamins. Menadione is a vitamin precursor of K2 which utilizes alkylation in the liver to yield menaquinones (MK-n, n=1-13; K2 vitamers), and hence, is better classified as a provitamin. -- Wikipedia.
alpha-Tocopherol is traditionally recognized as the most active form of vitamin E in humans and is a powerful biological antioxidant. The measurement of "vitamin E" activity in international units (IU) was based on fertility enhancement by the prevention of spontaneous abortions in pregnant rats relative to alpha-Tocopherol. Natural vitamin E exists in eight different forms or isomers: four tocopherols and four tocotrienols. In foods, the most abundant sources of vitamin E are vegetable oils such as palm oil, sunflower, corn, soybean, and olive oil. Nuts, sunflower seeds, and wheat germ are also good sources.
Aspartame is the name for an artificial, non-carbohydrate sweetener, aspartyl-phenylalanine-1-methyl ester; i.e., the methyl ester of the dipeptide of the amino acids aspartic acid and phenylalanine. It is marketed under a number of trademark names, such as Equal, and Canderel, and is an ingredient of approximately 6,000 consumer foods and beverages sold worldwide. It is commonly used in diet soft drinks, and is often provided as a table condiment. It is also used in some brands of chewable vitamin supplements. In the European Union, it is also known under the E number (additive code) E951. Aspartame is also one of the sugar substitutes used by diabetics. Upon ingestion, aspartame breaks down into several constituent chemicals, including the naturally-occurring essential amino acid phenylalanine which is a health hazard to the few people born with phenylketonuria, a congenital inability to process phenylalanine. Aspartic acid is an amino acid commonly found in foods. Approximately 40% of aspartame (by mass) is broken down into aspartic acid. Because aspartame is metabolized and absorbed very quickly (unlike aspartic acid-containing proteins in foods), it is known that aspartame could spike blood plasma levels of aspartate. Aspartic acid is in a class of chemicals known as excitotoxins. Abnormally high levels of excitotoxins have been shown in hundreds of animals studies to cause damage to areas of the brain unprotected by the blood-brain barrier and a variety of chronic diseases arising out of this neurotoxicity.
Salicylic acid is a monohydroxybenzoic acid that is benzoic acid with a hydroxy group at the ortho position. It is obtained from the bark of the white willow and wintergreen leaves. It has a role as an antiinfective agent, an antifungal agent, a keratolytic drug, an EC 1.11.1.11 (L-ascorbate peroxidase) inhibitor, a plant metabolite, an algal metabolite and a plant hormone. It is a conjugate acid of a salicylate. It is a colorless solid, it is a precursor to and a metabolite of aspirin (acetylsalicylic acid). It is a plant hormone. The name is from Latin salix for willow tree. It is an ingredient in some anti-acne products. Salts and esters of salicylic acid are known as salicylates. Salicylic acid modulates COX1 enzymatic activity to decrease the formation of pro-inflammatory prostaglandins. Salicylate may competitively inhibit prostaglandin formation. Salicylate's antirheumatic (nonsteroidal anti-inflammatory) actions are a result of its analgesic and anti-inflammatory mechanisms. Salicylic acid works by causing the cells of the epidermis to slough off more readily, preventing pores from clogging up, and allowing room for new cell growth. Salicylic acid inhibits the oxidation of uridine-5-diphosphoglucose (UDPG) competitively with nicotinamide adenosine dinucleotide and noncompetitively with UDPG. It also competitively inhibits the transferring of glucuronyl group of uridine-5-phosphoglucuronic acid to the phenolic acceptor. The wound-healing retardation action of salicylates is probably due mainly to its inhibitory action on mucopolysaccharide synthesis. Salicylic acid is biosynthesized from the amino acid phenylalanine. In Arabidopsis thaliana, it can be synthesized via a phenylalanine-independent pathway.
Ribonolactone, also known as D-ribono-1,4-lactone is a five-membered form of ribonolactone having D-configuration. It has a role as a metabolite. It is a ribonolactone and a butan-4-olide. It derives from a D-ribonic acid. Ribonolactone belongs to the class of organic compounds known as pentoses. These are monosaccharides in which the carbohydrate moiety contains five carbon atoms. Ribonolactone is a metabolite normally not detectable in human biofluids; however, it has been found in the urine of patients with neuroblastoma.
Aminocaproic acid (marketed as Amicar) is a drug used to treat bleeding disorders. It is an antifibrinolytic agent that acts by inhibiting plasminogen activators which have fibrinolytic properties. It is a derivative of the amino acid lysine. It binds reversibly to the kringle domain of plasminogen and blocks the binding of plasminogen to fibrin and its activation to plasmin.
Pteroyltriglutamic acid is a crystalline conjugate of folic acid containing three molecules of glutamic acid instead of one and having the general properties of a polypeptide. As a measure of enterocyte function, the deconjugation of Pteroylpolyglutamic acid (pteroyl-L-glutamyl-gamma-L-glutamyl-gamma-L-glutamic acid) to folic acid and subsequent active absorption was measured in 19 patients with progressive systemic sclerosis and compared with 14 controls. The absorption step of folic acid was identical in the two groups, while deconjugation of pteroyl-L-glutamyl-gamma-L-glutamyl-gamma-L-glutamic acid was significantly decreased in the patients with progressive systemic sclerosis. This observation suggests a primary epithelial defect of the small intestine in patients with progressive systemic sclerosis. (PMID 3583071). Glutamyl hydrolase cleaves the poly-g-glutamate chain folate and antifolate poly-g-glutamates. Its cellular location is lysosomal with large amts. of the enzyme constitutively secreted. The highest levels of glutamyl hydrolase mRNA in humans is found in the liver and kidney (PMID:10598552).
The physiologically active form of vitamin D. It is formed primarily in the kidney by enzymatic hydroxylation of 25-hydroxycholecalciferol (calcifediol). Its production is stimulated by low blood calcium levels and parathyroid hormone. Calcitriol increases intestinal absorption of calcium and phosphorus, and in concert with parathyroid hormone increases bone resorption.--PubChem.
3-Nitrotyrosine, also known as nitrotyrosine is a product of tyrosine nitration mediated by reactive nitrogen species such as peroxynitrite anion and nitrogen dioxide. Nitrotyrosine is identified as an indicator or marker of cell damage, inflammation as well as NO (nitric oxide) production. Nitrotyrosine is formed in the presence of the active metabolite NO. Nitrotyrosine belongs to the class of organic compounds known as tyrosine and derivatives. Tyrosine and derivatives are compounds containing tyrosine or a derivative thereof resulting from reaction of tyrosine at the amino group or the carboxy group, or from the replacement of any hydrogen of glycine by a heteroatom.
2-Aminoisobutyric acid, also known as alpha-methylalanine or a-aminoisobutanoate, belongs to the class of organic compounds known as alpha amino acids. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). 2-Aminoisobutyric acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. 2-Aminoisobutyric acid exists in all living organisms, ranging from bacteria to humans. Outside of the human body, 2-Aminoisobutyric acid has been detected, but not quantified in cow milk. Aminoisobutyric acid is a nonprotein amino acid (is an end product of pyrimidine metabolism) excreted in the urine of about 5% of healthy individuals (PMID 14806475), and high excretion is an autosomal recessive phenotype (PMID 13058271).
Omeprazole is a highly effective inhibitor of gastric acid secretion used in the therapy of stomach ulcers, dyspepsia, peptic ulcer disease , gastroesophageal reflux disease and Zollinger-Ellison syndrome. The drug inhibits the H(+)-K(+)-ATPase (H(+)-K(+)-exchanging ATPase) in the proton pump of Gastric Parietal Cells.--Pubchem. Omeprazole is one of the most widely prescribed drugs internationally and is available over the counter in some countries.
Alendronate (Fosamax, Merck) is a bisphosphonate drug used for osteoporosis and several other bone diseases. It is marketed alone as well as in combination with vitamin D (2,800 U, under the name Fosavance).
Famotidine is a histamine H2-receptor antagonist that inhibits stomach acid production, and is commonly used in the treatment of peptic ulcer disease (PUD) and gastroesophageal reflux disease (GERD/GORD). It is commonly marketed by Merck under the trade names Pepcidine and Pepcid.
1,1-Dimethylbiguanide, commonly known as metformin, is a member of the class of guanidines that is biguanide the carrying two methyl substituents at position 1. It has a role as a hypoglycemic agent, a xenobiotic and an environmental contaminant. It derives from a biguanide. It is a conjugate base of a metformin(1+). Metformin is a biguanide hypoglycemic agent used in the treatment of non-insulin-dependent diabetes mellitus not responding to dietary modification. Metformin improves glycemic control by improving insulin sensitivity and decreasing intestinal absorption of glucose. Metformin is the most popular anti-diabetic drug in the United States and one of the most prescribed drugs in the country overall, with nearly 35 million prescriptions filled in 2006 for generic metformin alone. It is also used in the treatment of polycystic ovary syndrome. It is not associated with weight gain and is taken by mouth. It is sometimes used as an off-label augment to attenuate the risk of weight gain in people who take antipsychotics as well as phenelzine.
Clotrimazole is an imidazole derivative with a broad spectrum of antimycotic activity. It inhibits biosynthesis of the sterol ergostol, an important component of fungal cell membranes. Its action leads to increased membrane permeability and apparent disruption of enzyme systems bound to the membrane. -- Pubchem; There is the potential for drug interactions with Clotrimazole if taken orally, as it is a potent, specific inhibitor of cytochrome P450 oxidase enzymes and so may alter the metabolism of other drugs. Clotrimazole is an antifungal medication commonly used in the treatment of fungal infections of both humans and animals such as vaginal yeast infections and ringworm. -- Wikipedia; An imidazole derivative with a broad spectrum of antimycotic activity. It inhibits biosynthesis of the sterol ergostol, an important component of fungal cell membranes. Its action leads to increased membrane permeability and apparent disruption of enzyme systems bound to the membrane. Clotrimazole is a potent, specific inhibitor of cytochrome P450 oxidase enzymes. Hence, it may alter the metabolism of other drugs particularly if taken orally. -- Wikipedia; Clotrimazole is an antifungal medication commonly used in the treatment of fungal infections of both humans and animals such as vaginal yeast infections and ringworm. It also used to treat athlete's foot and jock itch.
Naproxen (INN) is a non-steroidal anti-inflammatory drug (NSAID) commonly used for the reduction of mild to moderate pain, fever, inflammation and stiffness caused by conditions such as osteoarthritis, rheumatoid arthritis, psoriatic arthritis, gout, ankylosing spondylitis, injury (like fractures), menstrual cramps, tendonitis, bursitis, and the treatment of primary dysmenorrhea. Naproxen and naproxen sodium are marketed under various trade names including: Aleve, Anaprox, Naprogesic, Naprosyn, Naprelan; Naproxen is a non-steroidal anti-inflammatory drug (NSAID) commonly used for the reduction of mild to moderate pain, fever, inflammation and stiffness caused by conditions such as osteoarthritis, rheumatoid arthritis, psoriatic arthritis, gout, ankylosing spondylitis, injury (like fractures), menstrual cramps, tendonitis, bursitis, and the treatment of primary dysmenorrhea. Naproxen and naproxen sodium are marketed under various trade names including: Aleve, Anaprox, Naprogesic, Naprosyn, Naprelan. Naproxen was first marketed as the prescription drug Naprosyn in 1976 and naproxen sodium was first marketed under the trade name Anaprox in 1980. It remains a prescription-only drug in much of the world. The U.S. Food and Drug Administration (FDA) approved the use of naproxen sodium as an over-the-counter (OTC) drug in 1991, where OTC preparations are sold under the trade name Aleve. In Australia, small packets of lower-strength preparations of naproxen sodium are Schedule 2 Pharmacy Medicines; Naproxen is a member of the 2-arylpropionic acid (profen) family of NSAIDs. It is an odorless, white to off-white crystalline substance. It is lipid-soluble, practically insoluble in water with a low pH (below pH 4), while freely soluble in water at 6 pH and above. Naproxen has a melting point of 153 degree centigrade.
Atenolol is a so-called beta1-selective (or 'cardioselective') drug. That means that it exerts greater blocking activity on myocardial beta1-receptors than on beta2 ones in the lung. The beta2 receptors are responsible to keep the bronchial system open. If these receptors are blocked, bronchospasm with serious lack of oxygen in the body can result. However, due to its cardioselective properties, the risk of bronchospastic reactions if using atenolol is reduced compared to nonselective drugs as propranolol. Nonetheless, this reaction may also be encountered with atenolol, particularly with high doses. Extreme caution should be exerted if atenolol is given to asthma patients, who are particularly at risk; the dose should be as low as possible. If an asthma attack occurs, the inhalation of a beta2-mimetic antiasthmatic, such as hexoprenalin or salbutamol, will usually suppress the symptoms. Atenolol (trade name Tenormin) can be used to treat cardiovascular diseases such as hypertension, coronary heart disease, arrhythmias, and treatment of myocardial infarction after the acute event. Patients with compensated congestive heart failure may be treated with atenolol as a co medication (usually together with an ACE inhibitor, a diuretic and a digitalis-glycoside, if indicated). In patients with congestive heart failure, it reduces the need for and the consumption of oxygen of the heart muscle. It is very important to start with low doses, as atenolol reduces also the muscular power of the heart, which is an undesired effect in congestive heart failure.
Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) widely marketed under various trademarks including Act-3, Advil, Brufen, Motrin, Nuprin, and Nurofen. It is used for relief of symptoms of arthritis, primary dysmenorrhoea, and fever; Ibuprofen is an NSAID which is believed to work through inhibition of cyclooxygenase (COX), thus inhibiting prostaglandin synthesis. There are at least 2 variations of cyclooxygenase (COX-1 and COX-2), ibuprofen inhibits both COX-1 and COX-2. It appears that its analgesic, antipyretic, and anti-inflammatory activity are achieved principally through COX-2 inhibition; whereas COX-1 inhibition is responsible for its unwanted effects on platelet aggregation and the GI mucosa. As with other NSAIDs, ibuprofen inhibits platelet aggregation, but is not used therapeutically for this action since it is a minor and reversible effect. -- Wikipedia.
Ethinyl estradiol. A semisynthetic alkylated estradiol with a 17-alpha-ethinyl substitution. It has high estrogenic potency when administered orally, and is often used as the estrogenic component in oral contraceptives. -- Pubchem; estradiol (17-beta estradiol) (also oestradiol) is a sex hormone. Labelled the "female" hormone but also present in males it represents the major estrogen in humans. Critical for sexual functioning, estradiol also supports bone growth. -- Wikipedia; One of the fascinating twists to mammalian sexual differentiation is that estradiol is one of the two active metabolites of testosterone in males (the other being dihydrotestosterone). estradiol cannot be transferred readily from the circulation into the brain. Since fetuses of both sexes are exposed to similarly high levels of maternal estradiol, it can play little role in prenatal sexual differentiation. However, testosterone enters the central nervous system more freely and significant amounts are aromatized to estradiol within the brain of most male mammals, including humans. There is now much evidence that the programming of adult male sexual behavior in "lower mammals," (such as mounting rather than lordosis behavior), is largely dependent on estradiol produced in the central nervous system during prenatal life and early infancy from testosterone. We do not yet know whether this process plays a minimal or significant part in human sexual behaviors. -- Wikipedia; A synthetic form of estradiol, called ethinyl estradiol is a major component of hormonal contraceptive devices. Combined oral contraceptives contain ethinyl estradiol and a progestin, which both contribute to the inhibition of GnRH, LH, and FSH. The inhibition of these hormones accounts for the ability of combined oral contraceptives or birth control pills to prevent ovulation and thus prevent pregnancy. Other types of hormonal birth control contain only progestins and no ethinyl estradiol. -- Wikipedia.
Hydrochlorothiazide is a thiazide diuretic often considered the prototypical member of this class. It reduces the reabsorption of electrolytes from the renal tubules. This results in increased excretion of water and electrolytes, including sodium, potassium, chloride, and magnesium. It has been used in the treatment of several disorders including edema, hypertension, diabetes insipidus, and hypoparathyroidism. -- Pubchem. Hydrochlorothiazide (Apo-Hydro, Aquazide H, Microzide, Oretic), sometimes abbreviated HCT, HCTZ, or HZT is a popular diuretic drug that acts by inhibiting the kidney's ability to retain water. This reduces the volume of the blood, decreasing peripheral vascular resistance. Chlorothiazide, a carbonic anhydrase inhibitor. --Wikipedia.
Levofloxacin is a synthetic fluoroquinolone antibacterial agent that inhibits the supercoiling activity of bacterial DNA gyrase, halting DNA replication. Levofloxacin is marketed by Ortho-McNeil under the trade name Levaquin. Chemically, levofloxacin is the S-enantiomer (L-isomer) of ofloxacin. -- Wikipedia.
Ranitidine (CAS: 66357-35-5) is a non-imidazole blocker of histamine receptors that mediate gastric secretion (H2 receptors). It is used to treat gastrointestinal ulcers (PubChem). Ranitidine is a histamine H2-receptor antagonist that inhibits stomach acid production and is commonly used in the treatment of peptic ulcer disease (PUD) and gastroesophageal reflux disease (GERD). It is currently marketed by GlaxoSmithKline under the trade name Zantac (Wikipedia).
gamma-CEHC (gamma-carboxyethyl hydroxychroman) is a metabolite of vitamin E. Smokers have a significantly higher excretion level of urinary gamma-CEHC, and therefore require more vitamin E compared to non-smokers. Cigarette smoking is associated with increased oxidative stress and increased risk of degenerative disease. As the major lipophilic antioxidant, requirements for vitamin E may also be higher in smokers due to increased utilization (PMID: 15493460).
Metoprolol is a selective beta1 receptor blocker used in treatment of several diseases of the cardiovascular system. It is marketed under the brand name Lopressor by Novartis, and Toprol (in the USA); Seleken or Selokeen (elsewhere); A selective adrenergic beta-1-blocking agent with no stimulatory action. It's binding to plasma albumin is weaker than alprenolol and it may be useful in the treatment of several diseases of the cardiovascular system; Metoprolol is a selective beta1 receptor blocker used in treatment of several diseases of the cardiovascular system. It is marketed under the brand name Lopressor by Novartis, and Toprol (in the USA); Seleken or Selokeen (elsewhere); as Minax by Alphapharm (in Australia), as Betaloc by AstraZeneca and as Corvitol by Berlin-Chemie AG; A selective adrenergic beta-1-blocking agent with no stimulatory action. It's binding to plasma albumin is weaker than alprenolol and it may be useful in angina pectoris, hypertension, or cardiac arrhythmias; as Minax by Alphapharm (in Australia), as Betaloc by AstraZeneca and as Corvitol by Berlin-Chemie AG.
Furosemide or frusemide is a loop diuretic used in the treatment of congestive heart failure and edema. It is most commonly marketed by Aventis Pharma under the brand name Lasix. It has also been used to prevent thoroughbred race horses from bleeding through the nose during races. An antibiotic isolated from the fermentation broth of Fusidium coccineum. (From Merck Index, 11th ed) It acts by inhibiting translocation during protein synthesis.
Warfarin is an anticoagulant that acts by inhibiting the synthesis of vitamin K-dependent coagulation factors. Warfarin is indicated for the prophylaxis and/or treatment of venous thrombosis and its extension, pulmonary embolism, and atrial fibrillation with embolization. It is also used as an adjunct in the prophylaxis of systemic embolism after myocardial infarction. Warfarin is also used as a rodenticide.
Doxylamine is a sedating antihistamine that can be used by itself as a short-term sleep aid, in combination with other drugs as a night-time cold and allergy relief. It is a member of the ethanolamine class of antihistamines and has anti-allergy power superior to almost every other antihistamine on the market, with the exception of diphenhydramine (Benadryl). It is also the most effective over-the-counter sedative available in North America, and more sedating than some prescription hypnotics. In a study, it was found that doxylamine succinate is possibly more effective than the barbiturate, phenobarbital for use as a sedative. For this reason, doxylamine has sometimes been used off label in a manner similar to diphenhydramine for the reduction of anxiety symptoms; Doxylamine succinate is used by itself as a short-term sleep aid, in combination with other drugs as a night-time cold and allergy relief drug, and a preparation is prescribed in combination with Vitamin B6 (pyridoxine) to prevent morning sickness in pregnant women. In Commonwealth countries, doxylamine is available prepared with paracetamol/acetaminophen and codeine under the brand name Syndol or Mersyndol, as treatment for tension headache and other types of pain, or as a general OTC sleep-aid branded as Somnil, Donormyl, DSozile and Restavit containing Doxylamine Succinate only.
Salbutamol is a short-acting, selective beta2-adrenergic receptor agonist used in the treatment of asthma and COPD. It is 29 times more selective for beta2 receptors than beta1 receptors giving it higher specificity for pulmonary beta receptors versus beta1-adrenergic receptors located in the heart. Salbutamol is formulated as a racemic mixture of the R- and S-isomers. The R-isomer has 150 times greater affinity for the beta2-receptor than the S-isomer and the S-isomer has been associated with toxicity. This lead to the development of levalbuterol, the single R-isomer of salbutamol. However, the high cost of levalbuterol compared to salbutamol has deterred wide-spread use of this enantiomerically pure version of the drug. Salbutamol is generally used for acute episodes of bronchospasm caused by bronchial asthma, chronic bronchitis and other chronic bronchopulmonary disorders such as chronic obstructive pulmonary disorder (COPD). It is also used prophylactically for exercise-induced asthma
One of the Angiotensin-converting enzyme inhibitors (ACE inhibitors), orally active, that has been used in the treatment of hypertension and congestive heart failure. -- Pubchem; Lisinopril is a drug of the angiotensin converting enzyme (ACE) inhibitor class that is primarily used in treatment of hypertension, congestive heart failure and heart attacks. Historically, lisinopril was the third ACE inhibitor, after captopril and enalapril that was introduced into therapy in early 1990s. Lisinopril has a number of properties that distinguish it from other ACE inhibitors: it is hydrophilic, has long half life and tissue penetration and is not metabolized by the liver. -- Wikipedia; Lisinopril is solely excreted in urine in the unchanged form. Elimination of the drug depends on glomerular filtration and tubular excretion. Rate of lisinopril elimination decreases with old age and kidney or heart failure. There is a relation between creatinine and lisinopril clearance. With prolonged therapy dose reduction can be necessary to avoid accumulation. -- Wikipedia.
Medroxyprogesterone, or MP is a progestin (synthetic progestogen). MP is not used medically, as it is over two orders of magnitude less potent than medroxyprogesterone acetate (MPA); a derivative of MP (PMID: 16784762). MP may be formed via the metabolism of MPA. Medroxyprogesterone acetate is used to treat conditions such as absent or irregular menstrual periods, or abnormal uterine bleeding. Synthetic progestogens are widely used to simulate the effects of progesterone; a natural female sex hormone. Progesterone is essential for endometrial receptivity, embryo implantation, and the successful establishment of pregnancy. A low progesterone concentration or an insufficient response to progesterone can cause infertility and pregnancy loss (PMID: 20104424). In addition to progestagenic activity, MP is also a weak antiandrogen in vitro (PMID: 29990947). Medroxyprogesterone is only found in individuals that have used or taken MPA.
Triamterene, also known as dyrenium or ademin, belongs to the class of organic compounds known as pteridines and derivatives. These are polycyclic aromatic compounds containing a pteridine moiety, which consists of a pyrimidine fused to a pyrazine ring to form pyrimido(4,5-b)pyrazine. Triamterene is a drug. While there is a lack of randomized controlled trials evaluating the use of triamterene in the treatment of Ménière's disease, the typical treatment is 37.5 mg of triamterene with 25 mg of hydrochlorothiazide 1-2 capsules daily. triamterene can be converted into triamterene through the action of the enzyme solute carrier family 22 member 2. In humans, triamterene is involved in the metabolic disorder called the triamterene action pathway. Triamterene directly blocks the epithelial sodium channel (ENaC) on the lumen side of the kidney collecting tubule. Hepatic impairment: Use with caution in people with severe hepatic dysfunction; in cirrhosis, avoid electrolyte and acid/base imbalances that might lead to hepatic encephalopathy. The patents had expired on Dyazide in 1980, but complications arose with the introductions of generics, because the formulation of Dyazide resulted in variable batches that made it impossible for generic manufacturers to show that their versions were bioequivalent.
Brompheniramine (also known as Bromfed, Bromfenex, and Dimetane) is an antihistamine drug of the propylamine class. It is commonly available over the counter and is indicated for the treatment of the symptoms of the common cold and allergic rhinitis, such as runny nose, itchy eyes, watery eyes, and sneezing. It is a first-generation antihistamine; Brompheniramine (also known as Bromfed, Bromfenex, and Dimetane) is an antihistamine drug of the propylamine class. It is commonly available over the counter and is indicated for the treatment of the symptoms of the common cold and allergic rhinitis, such as runny nose, itchy eyes, watery eyes, and sneezing. It is a first-generation antihistamine. -- Wikipedia; Histamine H1 antagonist used in treatment of allergies, rhinitis, and urticaria.
Phenylpropanolamine is a sympathomimetic that acts mainly by causing release of norepinephrine but also has direct agonist activity at some adrenergic receptors. It is most commonly used as a nasal vasoconstrictor and an appetite depressant. -- Pubchem.
Chlorpheniramine is a histamine H1 antagonist used in allergic reactions, hay fever, rhinitis, urticaria, and asthma. It has also been used in veterinary applications. One of the most widely used of the classical antihistaminics, it generally causes less drowsiness and sedation than Promethazine. -- Pubchem; Chlorphenamine or chlorpheniramine, commonly marketed as its salt chlorphenamine maleate (Chlor- Trimeton, Piriton, Chlor- Tripolon), is a first generation antihistamine used in the prevention of the symptoms of allergic conditions such as rhinitis and urticaria.- wikipedia.
Hexacarboxylporphyrin III is a bile product that arises from the conversion of Hexacarboxylporphyrinogen III to Hexacarboxylporphyrin III by porphyrinogen carboxy-lyase (EC 4.1.1.37).
3-Hydroxyoctanoic acid (CAS: 14292-27-4) is an organic 3-hydroxy dicarboxylic acid, a metabolite of medium-chain fatty acid oxidation found in human urine. It is believed that urinary 3-hydroxy dicarboxylic acids are derived from the omega-oxidation of 3-hydroxy fatty acids and the subsequent beta-oxidation of longer-chain 3-hydroxy dicarboxylic acids. (PMID:1870421). 3-Hydroxyoctanoic acid has been identified in the human placenta (PMID: 32033212).
3-Phenylbutyric acid, also known as 3-phenylbutyrate or (RS)-3-phenylbutanoate, belongs to the class of organic compounds known as phenylpropanoic acids. Phenylpropanoic acids are compounds with a structure containing a benzene ring conjugated to a propanoic acid. Adverse effects Nearly 1/4 women may experience an adverse effect of amenorrhea or menstrual dysfunction. Sodium phenylbutyrate can act as a chemical chaperone, stabilising the mutant CFTR in the endoplasmic reticulum and allowing it to reach the cell surface. A 5g tablet or powder of sodium phenylbutyrate taken by mouth can be detected in the blood within 15 minutes, and reaches peak concentration in the bloodstream within an hour.
Heptacarboxylporphyrin III is a bile product that arises from the conversion of Heptacarboxylporphyrinogen III to Heptacarboxylporphyrin III by porphyrinogen carboxy-lyase (EC 4.1.1.37).
Substrate for erythrocyte uroporphyrinogen decarboxylase in patients with porphyria cutanea tarda (PubNed ID 1610684 ).
Intermediate in the metabolism of phytanic acid and pristanic acid.
gamma-Aminobutyryllysine, also known as N2-(4-amino-1-oxobutyl)-lysine, belongs to the class of organic compounds known as hybrid peptides. Hybrid peptides are compounds containing at least two different types of amino acids (alpha, beta, gamma, delta) linked to each other through a peptide bond. gamma-Aminobutyryllysine is a very strong basic compound (based on its pKa). gamma-Aminobutyryllysine is a dipeptide present in the human brain. This dipeptide occurs in much higher concentrations in the human brain than in the brains of lower mammals (PMID: 5559257). Adult brain and cerebrospinal fluid gamma-aminobutyryllysine levels and adult brain homocarnosine levels are higher than those found in children (PMID: 5031796).
Tin is a trace element that is required in bone formation. It has the atomic symbol Sn, atomic number 50, and atomic weight 118.71. (PubChem). Experimental studies over the last decade have suggested an association between thymus immune and homeostatic function and exogenous tin. It has been hypothesized that the thymus gland synthesizes and secretes one or more tin bearing factors that enhance immune defenses against malignancy and retard the gradual loss of immune capacity with senescence. (PMID 2195720). Physiologically, it exists as an ion in the body. Inorganic tin salts are poorly absorbed and rapidly excreted in the faeces; as a result they have a low toxicity. Only about 5 per cent is absorbed from the gastrointestinal tract, widely distributed in the body, then excreted by the kidney. Some tin is deposited in lung and bone. Some tin salts can cause renal necrosis after parenteral doses. Mutagenic studies on metallic tin and its compounds have been negative. Long-term animal carcinogenic studies have shown fewer malignant tumors in animals exposed to tin than in controls. Human volunteers developed mild signs of toxicity with tin, given in fruit juices, at a concentration of 1400 mg per litre. The WHO 1973 permissible limit for tin in tinned food is 250 micrograms per kg. The adult daily intake of tin was about 17 mg per day in 1940, but it has now decreased to about 3.5 mg, due to improvements in technique of tinning with enamel overcoat and crimped lids to minimize exposure to tin and lead solder. (PMID 3291572).
1,7-dimethylguanosine is a modified ribonucleoside. 1,7-dimethylguanosine is formed in tRNA enzymatic methylation. 1,7-Dimethylguanosine was found to be formed in high amounts in the tRNA methylation reaction at high concentrations of methylating agents.1,7-dimethylguanosine has a possible connection to chemical cancerogenesis and to the aberrant increase of tRNA methylases activity in tumor tissues. The amount of 1,7-dimethylguanosine produced by the kidney is higher than that produced by the liver. The immediate precursor in the formation of 1,7-dimethylguanosine in tRNA appears to be 1-methylguanosine. An accumulation of modified ribonucleosides appears in the serum of uremic patients. (PMID: 7046770, 6164398, 7259877, 7159514, 9607216).
Caffeic acid (CAS: 331-39-5) is a polyphenol present in normal human urine positively correlated to coffee consumption and influenced by the dietary intake of diverse types of food (PMID:16870009). Caffeic acid has been found to be a microbial metabolite of Escherichia (PMID: 28396925).
Troxilin B3 is the enzymatically formed derivative of Hepoxilin B3. Normal human epidermis incubated with exogenous AA produces 12-oxo-eicosatetraenoic acid (12-oxo-ETE), hepoxilin A3 (HxA3), and hepoxilin B3 (HxB3) through the 12- Lipoxygenase (LO) pathway. 12-LO is the major arachidonic acid (AA) oxygenation pathway in epidermal cells with total product formation generally exceeding cyclooxygenase activity. Platelet-type 12-LO has been found to be the predominant isoenzyme expressed in human and murine skin epidermis. Increased levels of nonesterified hepoxilins and trioxilins occur in the psoriatic scales. Normal human epidermis synthesized only one of the two possible 10-hydroxy epimers of HxB3 whose formation is probably catalyzed by 12-LO. Hepoxilins exert action on plasma permeability on skin, and induce a specific-receptor-dependent Ca2+ mobilization from endogenous sources and the release of AA and diacylglycerols. (PMID: 11851887).
Carbon dioxide is a colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals. Carbon dioxide is produced during respiration by all animals, fungi and microorganisms that depend on living and decaying plants for food, either directly or indirectly. It is, therefore, a major component of the carbon cycle. Additionally, carbon dioxide is used by plants during photosynthesis to make sugars which may either be consumed again in respiration or used as the raw material to produce polysaccharides such as starch and cellulose, proteins and the wide variety of other organic compounds required for plant growth and development. When inhaled at concentrations much higher than usual atmospheric levels, it can produce a sour taste in the mouth and a stinging sensation in the nose and throat. These effects result from the gas dissolving in the mucous membranes and saliva, forming a weak solution of carbonic acid. Carbon dioxide is used by the food industry, the oil industry, and the chemical industry. Carbon dioxide is used to produce carbonated soft drinks and soda water. Traditionally, the carbonation in beer and sparkling wine comes about through natural fermentation, but some manufacturers carbonate these drinks artificially.
5b-Cholestane-3a,7a,12a,23-Tetrol is a bile present in the urine samples of patients with cerebrotendinous xanthomatosis (CTX). (PMID 6883710 ).
3-Methyluric acid is a methyl derivative of uric acid, found occasionally in human urine. 3-Methyluracil is one of the purine components in urinary calculi. Methylated purines originate from the metabolism of methylxanthines (caffeine, theophylline and theobromine). Methyluric acids are indistinguishable from uric acid by simple methods routinely used in clinical laboratories, requiring the use of high-performance liquid chromatography (HPLC). Purine derivatives in urinary calculi could be considered markers of abnormal purine metabolism. The content of a purine derivative in stone depends on its average urinary excretion in the general population, similarity to the chemical structure of uric acid, and content of the latter in stone. This suggests that purines in stones represent a solid solution with uric acid as solvent. It is also plausible that methylxanthines, ubiquitous components of the diet and drugs, are involved in the pathogenesis of urolithiasis. Caffeine is metabolized via successive pathways mainly catalyzed by CYP1A2, xanthine oxidase or N-acetyltransferase-2 to give 14 different metabolites. CYP1A2 activity shows an inter-individual variability among the population. CYP1A2, an isoform of the CYP1A cytochrome P450 super-family, is involved in the metabolism of many drugs and plays a potentially important role in the induction of chemical carcinogenesis. (PMID: 11712316, 15833286, 3506820, 15013152).
3-Aminosalicylic acid is a derivative of salicylic acid, a common anti-inflammatory drug.
9-Methyluric acid is a methyl derivative of uric acid, found occasionally in human urine. 9-Methyluracil is one of the purine components in urinary calculi. Methylated purines originate from the metabolism of methylxanthines (caffeine, theophylline and theobromine). Methyluric acids are indistinguishable from uric acid by simple methods routinely used in clinical laboratories, requiring the use of high-performance liquid chromatography (HPLC). Purine derivatives in urinary calculi could be considered markers of abnormal purine metabolism. The content of a purine derivative in stone depends on its average urinary excretion in the general population, similarity to the chemical structure of uric acid, and content of the latter in stone. This suggests that purines in stones represent a solid solution with uric acid as solvent. It is also plausible that methylxanthines, ubiquitous components of the diet and drugs, are involved in the pathogenesis of urolithiasis. Caffeine is metabolized via successive pathways mainly catalyzed by CYP1A2, xanthine oxidase or N-acetyltransferase-2 to give 14 different metabolites. CYP1A2 activity shows an inter-individual variability among the population. CYP1A2, an isoform of the CYP1A cytochrome P450 super-family, is involved in the metabolism of many drugs and plays a potentially important role in the induction of chemical carcinogenesis. (PMID:11712316, 15833286, 3506820, 15013152).
2-Ethyl-2-Hydroxybutyric acid, also known as 2-ethyl-2-hydroxybutanoate or 2-et-2-hba, belongs to the class of organic compounds known as hydroxy fatty acids. These are fatty acids in which the chain bears a hydroxyl group. 2-Ethyl-2-Hydroxybutyric acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
Docosapentaenoic acid is an unsaturated fatty acid found in fish oils. It is a minor constituent of the total serum unsaturated fatty acids in humans. Docosapentaenoic acid (22n-6) is practically insoluble (in water) and a weakly acidic compound (based on its pKa). Docosapentaenoic acid (22n-6) can be found in blood and urine, as well as in human adipose tissue, fibroblasts, and platelet tissues. Within the cell, docosapentaenoic acid (22n-6) is primarily located in the membrane (predicted from logP). It can also be found in the extracellular space. In humans, docosapentaenoic acid (22n-6) is involved in alpha-linolenic acid and linoleic acid metabolism. Docosapentaenoic acid (22n-6) is found to be associated with thyroid cancer.
Trioxilin A3 is the enzymatically formed derivative of Hepoxilin A3. Normal human epidermis incubated with exogenous AA produces 12-oxo-eicosatetraenoic acid (12-oxo-ETE), hepoxilin A3 (HxA3), and hepoxilin B3 (HxB3) through the 12- Lipoxygenase (LO) pathway. 12-LO is the major arachidonic acid (AA) oxygenation pathway in epidermal cells with total product formation generally exceeding cyclooxygenase activity. Platelet-type 12-LO has been found to be the predominant isoenzyme expressed in human and murine skin epidermis. Increased levels of nonesterified hepoxilins and trioxilins occur in the psoriatic scales. Normal human epidermis synthesized only one of the two possible 10-hydroxy epimers of HxB3 whose formation is probably catalyzed by 12-LO. Hepoxilins exert action on plasma permeability on skin, and induce a specific-receptor-dependent Ca2+ mobilization from endogenous sources and the release of AA and diacylglycerols. (PMID: 11851887).
Pyrazinamide. Pyrazinamide is a drug used to treat tuberculosis in afflicted patients. The drug is largely bacteriostatic, but can be bacteriocidal on actively replicating tuberculosis bacteria. -- Wikipedia; Pyrazinamide is a generic drug and is available in a wide variety of presentations. Pyrazinamide tablets are usually 500mg and form the bulkiest part of the standard tuberculosis treatment regimen. Pyrazinamide tablets are so large that some patients find them impossible to swallow: pyrazinamide syrup is an option for these patients. -- Wikipedia; Pyrazinamide is also available as part of fixed dose combinations with other TB drugs such as isoniazid and rifampicin (Rifater is an example). -- Wikipedia; Pyrazinamide is well absorbed orally. It crosses inflamed meninges and is an essential part of the treatment of tuberculous meningitis. It is metabolised by the liver and the metabolic products are excreted by the kidneys. -- Wikipedia; Pyrazinamide is a pro-drug that stops the growth of Mycobacterium tuberculosis. M. tuberculosis has the enzyme pyrazinamidase which is only active at acidic pH. Pyrazinamidase converts pyrazinamide to the active form, pyrazinoic acid. Pyrazinoic acid inhibits the enzyme fatty acid synthetase I, which is required by the bacterium to synthesise fatty acids. Mutations of the pyrazinamidase gene (pncA) are responsible for pyrazinamide resistance in M. tuberculosis. -- Wikipedia.
6,15-diketo,13,14-dihydro-PGF1 alpha is a minor metabolite of prostacyclin (PGI2). Prostacyclin (PGI2) is one of the major vascular protectors against thrombosis and vasoconstriction, caused by thromboxane A(2). PGI2 inhibits platelet aggregation and vasoconstriction. PGI2 synthase (PGIS), a catalyst of PGI2 formation from prostaglandin H2, is widely distributed and predominantly found in vascular endothelial and smooth muscle cells. PGI2 plays an important cardioprotective role increasingly appreciated in recent years in light of adverse effects of COX-2 inhibitors in clinical trials. This cardioprotection is thought to be mediated, in part, by prostacyclin inhibition of platelet aggregation. Multiple lines of evidence suggest that prostacyclin additionally protects from cardiovascular disease by pleiotropic effects on vascular smooth muscle. PGI2 inhibits proliferation of cultured vascular SMCs by inhibiting cell cycle progression from G1 to S phase. Progression through G1 phase is regulated by the sequential activation of the G1 phase cyclin-dependent kinases (cdks). (PMID: 7000774, 6231483, 16303599, 16533160, 17073611, 17164138).
Antidiuretic hormone, also known commonly as vasopressin, is a nine amino acid peptide secreted from the posterior pituitary. Within hypothalamic neurons, the hormone is packaged in secretory vesicles with a carrier protein called neurophysin, and both are released upon hormone secretion.
(R)-Mevalonic acid-5-pyrophosphate (mevalonate 5-diphosphate) is a directly synthesized product of mevalonate phosphate that is essential for cell proliferation. (PMID 2211719). It is a substrate for mevalonate-5-diphosphate decarboxylase, the third enzyme involved in the biosynthesis of cholesterol from mevalonic acid. This enzyme catalyzes the reaction of mevalonate 5-diphosphate (MVADP) with ATP to produce isopentenyl diphosphate, ADP, CO2, and inorganic phosphate. The overall reaction involves an anti elimination of the tertiary hydroxyl and carboxyl groups. This metabolite participates both in the biosynthesis of cholesterol and fatty acid mechanism, through which interpathway regulation could take place between the cholesterol and FA cascades. (PMID 8769113 ).
3,7-Dimethyluric acid is a methyl derivative of uric acid, found occasionally in human urine. 3,7-Dimethyluric is one of the purine components in urinary calculi. Methylated purines originate from the metabolism of methylxanthines (caffeine, theophylline and theobromine). Methyluric acids are indistinguishable from uric acid by simple methods routinely used in clinical laboratories, requiring the use of high-performance liquid chromatography (HPLC). Purine derivatives in urinary calculi could be considered markers of abnormal purine metabolism. The content of a purine derivative in stone depends on its average urinary excretion in the general population, similarity to the chemical structure of uric acid, and content of the latter in stone. This suggests that purines in stones represent a solid solution with uric acid as solvent. It is also plausible that methylxanthines, ubiquitous components of the diet and drugs, are involved in the pathogenesis of urolithiasis. Caffeine is metabolized via successive pathways mainly catalyzed by CYP1A2, xanthine oxidase or N-acetyltransferase-2 to give 14 different metabolites. CYP1A2 activity shows an inter-individual variability among the population. CYP1A2, an isoform of the CYP1A cytochrome P450 super-family, is involved in the metabolism of many drugs and plays a potentially important role in the induction of chemical carcinogenesis (PMID:11712316, 15833286, 3506820, 15013152).
5'-Deoxyadenosine is an oxidized nucleoside found in the urine of normal subjects. Oxidized nucleosides represent excellent biomarkers for determining the extent of damage in genetic material, which has long been of interest in understanding the mechanism of aging, neurodegenerative diseases, and carcinogenesis. (PMID 15116424). The normal form of deoxyadenosine used in DNA synthesis and repair is 2'-deoxyadenosine where the hydroxyl group (-OH) is at the 2' position of its ribose sugar moiety. 5'-deoxyadenosine has its hydroxyl group at the 5' position of the ribose sugar.
Lacto-N-difucopentaose II is an oligosaccharide first isolated from human milk by recycling chromatography in 1988. Is resistant to enzymic hydrolysis in the gastrointestinal tract of the infant; it is postulated that they reach the large intestine where they serve as substrates for bacterial metabolism. Oligosaccharides in human milk represent a group of bioactive molecules that have evolved to be an abundant and diverse component of human milk, even though they have no direct nutritive value to the infant. (PMID 3274083, 10837303, 11787695, 14530096, 17002410).
2-Hydroxy-2-methylbutyric acid, also known as (+/-)-2-hydroxy-2-methylbutanoate or 2-methyl-2-hydroxybutyric acid, belongs to the class of organic compounds known as hydroxy fatty acids. These are fatty acids in which the chain bears a hydroxyl group. 2-Hydroxy-2-methylbutyric acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
4-Hydroxycyclohexylcarboxylic acid is a rare compound in urinary organic acid analysis. It has been found to be a metabolite of Arthrobacter (http://www.nrcresearchpress.com/doi/pdf/10.1139/m74-202).
7-Methylxanthine is a methyl derivative of xanthine, found occasionally in human urine. 7-Methylxanthine is one of the purine components in urinary calculi. Methylated purines originate from the metabolism of methylxanthines (caffeine, theophylline and theobromine). Caffeine is metabolized via successive pathways mainly catalyzed by CYP1A2, xanthine oxidase or N-acetyltransferase-2 to give 14 different metabolites, including 7-methylxanthine. CYP1A2 activity shows an inter-individual variability among the population. CYP1A2, an isoform of the CYP1A cytochrome P450 super-family, is involved in the metabolism of many drugs and plays a potentially important role in the induction of chemical carcinogenesis. Purine derivatives in urinary calculi could be considered markers of abnormal purine metabolism. The content of a purine derivative in stone depends on its average urinary excretion in the general population, similarity to the chemical structure of uric acid, and content of the latter in stone. This suggests that purines in stones represent a solid solution with uric acid as solvent. It is also plausible that methylxanthines, ubiquitous components of the diet and drugs, are involved in the pathogenesis of urolithiasis. (PMID:11712316, 15833286, 3506820, 15013152).
7a-Hydroxy-cholestene-3-one is a metabolite in bile acid synthesis. It is derived from 7a-hydroxy-cholesterol and can be further metabolized to 7a,12a,-dihydroxy-cholest-4-en-3-one. Analysis of 7a-Hydroxycholestene-3-one (HCO) in serum may serve as a novel, simple, and sensitive method for the detection of bile acid malabsorption in patients with chronic diarrhea of unknown origin (PMID 9952217).
Eicosapentaenoic acid (EPA or also icosapentaenoic acid) is an important polyunsaturated fatty acid found in fish oils. It serves as the precursor for the prostaglandin-3 and thromboxane-3 families. A diet rich in eicosapentaenoic acid lowers serum lipid concentration, reduces incidence of cardiovascular disorders, prevents platelet aggregation, and inhibits arachidonic acid conversion into the thromboxane-2 and prostaglandin-2 families. Eicosapentaenoic acid is an omega-3 fatty acid. In physiological literature, it is given the name 20:5(n-3). Its systematic chemical name is all-cis-5,8,11,14,17-icosapentaenoic acid. It also has the trivial name timnodonic acid. Chemically, EPA is a carboxylic acid with a 20-carbon chain and five cis double bonds; the first double bond is located at the third carbon from the omega end. Because of the presence of double bonds, EPS is a polyunsaturated fatty acid. Metabolically it acts as a precursor for prostaglandin-3 (which inhibits platelet aggregation), thromboxane-3, and leukotriene-5 groups. It is found in fish oils of cod liver, herring, mackerel, salmon, menhaden, and sardine. It is also found in human breast milk (Wikipedia).
Myristoleic acid, also known as 9-tetradecenoate or myristoleate, belongs to the class of organic compounds known as long-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 13 and 21 carbon atoms. Myristoleic acid is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral. Myristoleic acid exists in all eukaryotes, ranging from yeast to humans. Outside of the human body, myristoleic acid is found in the highest concentration within a few different foods, such as milk (cow), butter, and margarine-like spreads, and in a lower concentration in creams, meat bouillons, and chocolates. Myristoleic acid has also been detected, but not quantified in, several different foods, such as anchovies, loganberries, sunflowers, yellow zucchinis, and dates. This could make myristoleic acid a potential biomarker for the consumption of these foods. Myristoleic acid is a monounsaturated fatty acid that represents approximately 0.3-0.7% of the total fatty acid composition of adipose tissue triacylglycerol in humans (PMID: 10393134). It has been suggested that its effective cytotoxic (i.e. cell death inducer) activity could be used for the treatment of prostate cancer (PMID: 11304730).
Dimethylmalonic acid is a dicarboxylic acid that is malonic acid in which both methylene hydrogens have been replaced by methyl groups. It has a role as a fatty acid synthesis inhibitor. Dimethylmalonic acid, also known as 2,2-dimethylmalonate or propanedioate, belongs to the class of organic compounds known as dicarboxylic acids and derivatives. These are organic compounds containing exactly two carboxylic acid groups. Dimethylmalonic acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
Tetracosanoic acid is a C24 straight-chain saturated fatty acid. It has a role as a volatile oil component, a plant metabolite, a human metabolite and a Daphnia tenebrosa metabolite. It is a very long-chain fatty acid and a straight-chain saturated fatty acid. It is a conjugate acid of a tetracosanoate. Tetracosanoic acid, also known as N-tetracosanoate or lignoceric acid, belongs to the class of organic compounds known as very long-chain fatty acids. These are fatty acids with an aliphatic tail that contains at least 22 carbon atoms. Tetracosanoic acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. Tetracosanoic acid is a potentially toxic compound.
5-Methoxydimethyltryptamine, like all methoxydimethyltryptamines is a compound that contain the biogenic monoamine tryptamine and is substituted with one methoxy group and two methyl groups. Members of this group include several potent serotonergic hallucinogens found in several unrelated plants, skins of certain toads, and in mammalian brains. They are possibly involved in the etiology of schizophrenia. They are formed as metabolites of serotonin (5-hydroxytryptamine) or tryptamine by the enzyme indolethylamine N-methyltransferase (INMT). The physiological significance of the N-methylating pathway of indoleamine metabolism, and of the methylated end products, is unknown. Because of the known psychotropic properties of the dimethylated amines, their possible involvement in the chemical pathogenesis of mental disorders has received wide interest. The hallucinogenic actions of the methylated indoleamines, like those of LSD, are believed to be mediated through the 5HT2 receptor. (PMID 11763413).
Methionine sulfoxide belongs to the class of organic compounds known as l-alpha-amino acids. These are alpha amino acids which have the L-configuration of the alpha-carbon atom. Methionine sulfoxide exists in all living species, ranging from bacteria to humans. Within humans, methionine sulfoxide participates in a number of enzymatic reactions. In particular, methionine sulfoxide can be biosynthesized from L-methionine through its interaction with the enzyme methionine-R-sulfoxide reductase B3. In addition, methionine sulfoxide can be biosynthesized from L-methionine through the action of the enzyme methionine-R-sulfoxide reductase b2, mitochondrial. In humans, methionine sulfoxide is involved in the metabolic disorder called hypermethioninemia.
2,3-Diaminopropionic acid, also known as L-2,3-diaminopropanoate or Dpr, belongs to the class of organic compounds known as l-alpha-amino acids. These are alpha amino acids which have the L-configuration of the alpha-carbon atom. 2,3-Diaminopropionic acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. 2,3-Diaminopropionic acid (2,3-diaminopropionate) is a non-proteinogenic amino acid found in certain secondary metabolites, including zwittermicin A and tuberactinomycin.2,3-Diaminopropionate is formed by the pyridoxal phosphate (PLP) mediated amination of serine. 2,3-Diaminopropionic acid exists in all living organisms, ranging from bacteria to humans.
The formation of docosahexaenoic acid(DHA) involves the production of tetracosahexaenoic acid C24:6n-3) from dietary linolenic acid (C18:3n-3) via a series of elongation and desaturation reactions, followed by beta-oxidation of C24:6n-3 to C22:6n-3. DHA is deficient in patients lacking peroxisomes.(PMID: 11734571).
Crotonoyl-CoA (CAS: 992-67-6) is an important component in several metabolic pathways, notably fatty acid and amino acid metabolism. It is the substrate of acyl-coenzyme A oxidases 1, 2, and 3 (EC 1.3.3.6) corresponding to palmitoyl, branched-chain, and pristanoyl, respectively. In peroxisomal fatty acid beta-oxidation, these enzymes produce hydrogen peroxide. Abnormalities in this group of enzymes are linked to coma, dehydration, diabetes, fatty liver, hyperinsulinemia, hyperlipidemia, and leukodystrophy. Crotonoyl-CoA is also a substrate of a group of enzymes called acyl-coenzyme A dehydrogenases (EC 1.3.99-, 1.3.99.2, 1.3.99.3) in the metabolism of fatty acids or branched-chain amino acids in the mitochondria (PMID: 7698750). Acyl-coenzyme A dehydrogenase has been shown to contribute to kidney-associated diseases, such as adrenogential syndrome, kidney failure, kidney tubular necrosis, homocystinuria, as well as other diseases including cretinism, encephalopathy, hypoglycemia, and medium-chain acyl-CoA dehydrogenase deficiency. The gene (ACADS) also plays a role in theta oscillation during sleep. In addition, crotonoyl-CoA is the substrate of enoyl-coenzyme A hydratase (EC 4.2.1.17) in the mitochondria during lysine degradation and tryptophan metabolism as well as benzoate degradation via CoA ligation. Crotonoyl-CoA is the product of this enzyme in butanoate metabolism. Moreover, it is produced from multiple enzymes in the butanoate metabolism pathway, including 3-hydroxybutyryl-CoA dehydratase (EC 4.2.1.55), glutaconyl-CoA decarboxylase (EC 4.1.1.70), vinylacetyl-CoA delta-isomerase (EC 5.3.3.3), and trans-2-enoyl-CoA reductase (NAD+) (EC 1.3.1.44). In lysine degradation and tryptophan metabolism, crotonoyl-CoA is produced by glutaryl-coenzyme A dehydrogenase (EC 1.3.99.7). This enzyme is linked to glutaric aciduria type I, metabolic diseases, movement disorders, myelinopathy, and nervous system diseases.
4-hydroxyisovaleric acid is a metabolite of isovaleric acid that has been reported to be found in the urine of patients with isovaleric acidemia. It seems to be an intermediate product in the formation of methylsuccinic acid from isovaleric acid by omega-. oxidation.
Ubiquinone-1 is a member of the chemical class known as Polyprenylbenzoquinones. These are compounds containing a polyisoprene chain attached to a quinone at the second ring position. Ubiquione-1 has just 1 isoprene unit. Normally in humans it has 10. Ubiquinone-1 is an intermediate in the synthesis of Ubiquionone 10, which is also called Coenzyme Q (CoQ). CoQ is found in the membranes of endoplasmic reticulum, peroxisomes, lysosomes, vesicles and notably the inner membrane of the mitochondrion where it is an important part of the electron transport chain; there it passes reducing equivalents to acceptors such as Coenzyme Q : cytochrome c - oxidoreductase. CoQ is also essential in the formation of the apoptosome along with other adapter proteins. The loss of trophic factors activates pro-apoptotic enzymes, causing the breakdown of mitochondria. Because of its ability to transfer electrons and therefore act as an antioxidant, Coenzyme Q has become a valued dietary supplement. CoQ10 has been widely used for the treatment of heart disease (especially heart failure), gum diseases, and also breast cancer. The benzoquinone portion of Coenzyme Q10 is synthesized from amino acids, while the isoprene sidechain is synthesized from acetyl CoA through the mevalonate pathway. The mevalonate pathway is used for the first steps of cholesterol biosynthesis.
Butyrylcarnitine, also known as (3R)-3-(butyryloxy)-4-(trimethylammonio)butanoate or L-carnitine butyryl ester, is classified as a member of the acylcarnitines. Acylcarnitines are organic compounds containing a fatty acid with the carboxylic acid attached to carnitine through an ester bond. Butyrylcarnitine is considered to be practically insoluble (in water) and acidic. Butyrylcarnitine is elevated in patients with short-chain acyl-CoA dehydrogenase (SCAD) deficiency, in infants with acute acidosis and generalized muscle weakness, and in middle-aged patients with chronic myopathy localized in muscle (OMIM: 201470).
Cystathionine ketimine (CT) is a cyclic amino acid that was found to have a priming effect on superoxide generation in human neutrophils (PMID: 10708546). D-Cystathionine ketimine and L-cystathionine ketimine enhance superoxide generation by human neutrophils in two different manners. D-Cystathionine ketimine enhanced seryl phosphorylation of 16.5-kDa protein in human neutrophils, while L-cystathionine ketimine enhanced tyrosyl phosphorylation of 45-kDa protein (PMID: 10049498). Cystathionine ketimine was found in the urine of a cystathioninuria patient (PMID: 8373176).
4-Carboxyphenylglycine is a group I metabotropic glutamate receptor (mGlu) antagaonist by blocking the cystine/glutamate exchanger. In addition, it has modulating effect on the central action of NMDA receptor antagonist. It plays a role in synaptic plasticity and excitability, long term potentiation and long term depression.
1-Phenylethylamine, or alpha-phenethylamine, is an amine. Individual enantiomers of this basic compound are useful for performing chiral resolution of acidic compounds by forming diastereomeric salts. -- Wikipedia.
Phytol is a natural linear diterpene alcohol which is used in the preparation of vitamins E and K1. It is also a decomposition product of chlorophyll. It is an oily liquid that is nearly insoluble in water, but soluble in most organic solvents. -- Wikipedia.
3'-hydroxy-Caroten-3-one is a carotenoid found in human fluids. Carotenoids are isoprenoid molecules that are widespread in nature and are typically seen as pigments in fruits, flowers, birds and crustacea. Animals are unable to synthesise carotenoids de novo, and rely upon the diet as a source of these compounds. Over recent years there has been considerable interest in dietary carotenoids with respect to their potential in alleviating age-related diseases in humans. This attention has been mirrored by significant advances in cloning most of the carotenoid genes and in the genetic manipulation of crop plants with the intention of increasing levels in the diet. Studies have shown an inverse relationship between the consumption of certain fruits and vegetables and the risk of epithelial cancer. Since carotenoids are among the micronutrients found in cancer preventive foods, detailed qualitative and quantitative determination of these compounds, particularly in fruits and vegetables and in human plasma, have recently become increasingly important. (PMID: 1416048, 15003396).
Glycinamidoribotide conversion to N-formylglycinamide ribonucleotide is the third reaction of the de novo purine biosynthesis, a reaction catalyzed by the enzyme Glycinamide ribonucleotide transformylase (EC 2.1.2.2), with concomitant conversion of 10-formyltetrahydrofolate to tetrahydrofolate. (PMID: 9143358). Glycineamideribotide formation is stimulated by Luteinizing hormone (LH) and Chorionic gonadotropin (HCG) via activation of Glc-6-P-dehydrogenase (EC 1.1.1.49). (PMID: 4366083).
Adipic acid (IUPAC systematic name: hexanedioic acid) is a chemical compound of the class of carboxylic acids. Adipic acid is prepared from various fats using oxidation.By far the main use of adipic acid is as monomer for the production of nylon by a polycondensation reaction with hexamethylene diamine forming 6,6-nylon, the most common form of nylon. --Wikipedia.
Imidazol-4-ylacetic acid is a monocarboxylic acid that is acetic acid in which one of the methyl hydrogens has been replaced by an imidazol-4-yl group. It has a role as a mouse metabolite. It is a monocarboxylic acid and a member of imidazoles. It derives from an acetic acid. It is a conjugate acid of an imidazol-4-ylacetate. It is a tautomer of an imidazol-5-ylacetic acid and a 2H-imidazol-4-ylacetic acid. Imidazoleacetic acid, also known as 4(5)-imidazoleacetate or IAA, belongs to the class of organic compounds known as imidazolyl carboxylic acids and derivatives. These are organic compounds containing a carboxylic acid chain (of at least 2 carbon atoms) linked to an imidazole ring. Imidazoleacetic acid exists in all living organisms, ranging from bacteria to humans. imidazoleacetic acid can be biosynthesized from imidazole-4-acetaldehyde through its interaction with the enzyme aldehyde dehydrogenase, mitochondrial. In humans, imidazoleacetic acid is involved in histidine metabolism. Outside of the human body, Imidazoleacetic acid has been detected, but not quantified in several different foods, such as chinese cinnamons, jostaberries, vanilla, butternut squash, and red rices. Imidazoleacetic acid is a potentially toxic compound. Imidazoleacetic acid is a metabolite product of Histamine metabolism.
2,3-dimethyl-3-hydroxyglutaric acid has been found excreted in the urine by a patient with beta-ketothiolase deficiency. (PMID 6133567).
1,9-Dimethyluric acid is a methyl derivative of uric acid, found occasionally in human urine. 1,9-Methyluracil is one of the purine components in urinary calculi. Methylated purines originate from the metabolism of methylxanthines (caffeine, theophylline and theobromine). Methyluric acids are indistinguishable from uric acid by simple methods routinely used in clinical laboratories, requiring the use of high-performance liquid chromatography (HPLC). Purine derivatives in urinary calculi could be considered markers of abnormal purine metabolism. The content of a purine derivative in stone depends on its average urinary excretion in the general population, similarity to the chemical structure of uric acid, and content of the latter in stone. This suggests that purines in stones represent a solid solution with uric acid as solvent. It is also plausible that methylxanthines, ubiquitous components of the diet and drugs, are involved in the pathogenesis of urolithiasis. Caffeine is metabolized via successive pathways mainly catalyzed by CYP1A2, xanthine oxidase or N-acetyltransferase-2 to give 14 different metabolites. CYP1A2 activity shows an inter-individual variability among the population. CYP1A2, an isoform of the CYP1A cytochrome P450 super-family, is involved in the metabolism of many drugs and plays a potentially important role in the induction of chemical carcinogenesis. (PMID:11712316, 15833286, 3506820, 15013152).
8-Dehydrocholesterol (8-DHC) elevated concentration is one of the diagnostic biochemical hallmarks of classical Smith-Lemli-Opitz syndrome (SLOS). Plasma 8-DHC could be only marginally elevated. (PMID: 16435228). Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive condition caused by a defect in cholesterol synthesis (caused by a deficit of 3beta-hydroxysterol-Delta7 reductase). Affected children often have malformations and mental retardation. Autistic behaviors also are evident. In children, the baseline cholesterol, 8-DHC levels, and cholesterol levels following supplementation does not correlate with the presence or severity of autistic symptoms. (PMID: 16761297). Accumulation of 8-dehydrocholesterol in Amniotic fluid is diagnostic for SLOS. (PMID 16231320).
Increases in plasma dopamine sulfate and urinary dopamine suggest that dopamine sulfate may be generated via DOPA sulfate and urinary dopamine may originate from circulating DOPA. DOPA sulfate may be an alternative source of dopamine sulfate. Urinary dopamine progressively increased in the course of metyrosine treatment, and this, along with the increase of the dopamine metabolite, dihydroxyphenylethanol, and plasma dopamine sulfate, occurred in the absence of any change in plasma dopamine.(PMID: 1969915).
Ureidoisobutyric acid, also known as 3-ureidoisobutyrate or beta-UBA, belongs to the class of organic compounds known as ureas. Ureas are compounds containing two amine groups joined by a carbonyl (C=O) functional group. Ureidoisobutyric acid is an extremely weak basic (essentially neutral) compound (based on its pKa). Ureidoisobutyric acid exists in all living organisms, ranging from bacteria to humans. Within humans, ureidoisobutyric acid participates in a number of enzymatic reactions. In particular, ureidoisobutyric acid can be biosynthesized from dihydrothymine through its interaction with the enzyme dihydropyrimidinase. Outside of the human body, ureidoisobutyric acid has been detected, but not quantified in, several different foods, such as bread, squashberries, black elderberries, black crowberries, and climbing beans. This could make ureidoisobutyric acid a potential biomarker for the consumption of these foods. Ureidoisobutyric acid is increased in the urine of patients with beta-ureidopropionase (EC 3.5.1.6) deficiency (PMID: 12271438), a genetic disorder. Ureidoisobutyric acid can be used to predict a patient's individual phenotypes of enzyme deficiencies in pyrimidine metabolism when associated with a risk for severe toxicity against the antineoplastic agent 5-fluorouracil (PMID: 12798197).
Formation of 8-hydroxyguanine (8-OHG), a mutagenic base which is a marker for OH-mediated DNA damage, requires peroxidase and halides and occurs in the presence of transition metal chelators (DTPA +/- desferrioxamine), and is inhibited by catalase, superoxide dismutase (SOD), and scavengers of hypohalous acids. (PMID 10820020). 8-Hydroxyguanine is an oxidative stress marker for diagnosis of Alzheimer's disease (AD). (PMID 15977989).
Homolanthionine is formed from homocysteine and homoserine by a condensation analogous to that normally leading to cystathionine. The only other known occurrence of homolanthionine in nature is in a methionine-requiring mutant strain of Escherichia coli. Patients with homocystinuria excrete small amounts of L-homolanthionine in their urine.
4-Hydroxycinnamic acid, also known as p-Coumaric acid, is a coumaric acid in which the hydroxy substituent is located at C-4 of the phenyl ring. It has a role as a plant metabolite. It is a conjugate acid of a 4-coumarate. p-coumaric acid is an organic compound that is a hydroxy derivative of cinnamic acid. There are three isomers of coumaric acid: o-coumaric acid, m-coumaric acid, and p-coumaric acid, that differ by the position of the hydroxy substitution of the phenyl group. p-Coumaric acid is the most abundant isomer of the three in nature. p-Coumaric acid exists in two forms trans-p-coumaric acid and cis-p-coumaric acid. It is a crystalline solid that is slightly soluble in water, but very soluble in ethanol and diethyl ether. 4-Hydroxycinnamic acid belongs to the class of organic compounds known as hydroxycinnamic acids. Hydroxycinnamic acids are compounds containing an cinnamic acid where the benzene ring is hydroxylated. 4-Hydroxycinnamic acid exists in all living species, ranging from bacteria to humans. Outside of the human body, 4-Hydroxycinnamic acid is found, on average, in the highest concentration within a few different foods, such as pepper (Capsicum frutescens), pineapples, and sunflowers and in a lower concentration in spinachs, kiwis, and sweet oranges. 4-Hydroxycinnamic acid has also been detected, but not quantified in several different foods, such as wild rices, soursops, garden onions, hyssops, and avocado.
The chlorate anion has the formula ClO3&#8722. In this case, the chlorine atom is in the +5 oxidation state. "Chlorate" can also refer to chemical compounds containing this anion; chlorates are the salts of chloric acid. "Chlorate", when followed by a roman numeral in parenthesis, e.g. chlorate(VII), refers to a particular oxyanion of chlorine. As predicted by VSEPR, chlorate anions have trigonal pyrimidal structures. Chlorates are powerful oxidizers and should be kept away from organics or easily oxidized materials. Chlorates were once widely used in pyrotechnics, though their use has fallen due to their instability. Most pyrotechnic applications which used chlorates in the past now use perchlorates instead (Wikipedia). Chlorates are inorganic salts of chloric acid that contain the ClO3- ion. Chlorate is a selective inhibitor of the synthesis of the high energy donor of sulfate 3'-phosphoadenosine 5'-phosphosulfate (PAPS). High endothelial venules (HEVs) are specialized post-capillary venules found in lymphoid tissues, that support high levels of lymphocyte extravasation from the blood; sulfation is key to the uniqueness of the HEV ligands and PAPS synthesis is required for sulfation. (PMID: 9498065). Chlorate is a sulfate analogue that has been found to be a potent and nontoxic inhibitor of sulfation. Tyrosine sulfation is a widespread posttranslational modification that occurs in the trans Golgi in a reaction catalyzed by tyrosylprotein sulfotransferase. Tyrosine sulfation has been found to be irreversible, resulting in a life-long alteration in the phenotype of the secretory proteins. The intracellular transport kinetics of a secretory protein and the biological activity of certain neuropeptides have been found to be affected by this modification. (PMID: 3288098). Na chlorate intoxication can occur mainly through poisoning by herbicides containing chlorate salts. (PMID: 10831921, 2239069).
N(6)-Methyllysine is a naturally occurring amino acid found in human biofluids. N-monomethyl-lysine is generated by metabolic transmethylation of endogenous lysine. Lysine methylation displays the highest degree of complexity among known covalent histone modifications, with each site of methylation regulating the association of different effector molecules. The versatility of lysine methylation marks is perhaps best exemplified by modifications implicated in transcriptional regulation as well as being required for double-strand break repair in several organisms. Identification of the numerous biological functions encoded by histone lysine methylation is a major area of research interest, as these mechanisms are intimately associated with cellular senescence, genomic instability, and leukemogenesis. While multiple sites of lysine methylation have been linked with gene activation, each modification is distributed to unique positions across the active gene. (PMID: 17030614, 1122639, 15756599, 3111294).
2-Pyrrolidinone is a lactam cyclization product of gamma-aminobutyric acid (GABA) (PMID 10332870). Vigabatrin (VGB, an antiepileptic drug) increases human brain gamma-aminobutyric acid (GABA) and the related metabolites, including 2-pyrrolidinone. Patients taking VGB are expected to have an increase of these metabolites (PMID 10403220, 10840398). 2-Pyrrolidone is an organic compound consisting of a five-membered lactam. It is a colorless liquid which is used in industrial settings as a high-boiling non-corrosive polar solvent for a wide variety of applications. It is miscible with a wide variety of other solvents including water, ethanol, diethyl ether, chloroform, benzene, ethyl acetate and carbon disulfide.
4-Methoxycinnamic acid, also known as para-methoxycinnamate or O-methyl-p-coumarate, belongs to the class of organic compounds known as cinnamic acids. These are organic aromatic compounds containing a benzene and a carboxylic acid group forming 3-phenylprop-2-enoic acid. Outside of the human body, 4-Methoxycinnamic acid is found, on average, in the highest concentration within turmerics. 4-Methoxycinnamic acid has also been detected, but not quantified in cow milk and wild celeries. This could make 4-methoxycinnamic acid a potential biomarker for the consumption of these foods.
3-Phenylpropionylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 2.3.1.13) which is an enzyme that catalyzes the chemical reaction:acyl-CoA + glycine < -- > CoA + N-acylglycineUrinary excretion of 3-phenylpropionylglycine is a diagnostic marker for medium-chain acyl-CoA dehydrogenase deficiency. 3-phenylpropionylglycine is derived from 3-phenylpropionic acid, a product of anaerobic bacterial metabolism in the gut. (PMID 1541011).
5-Phenylvaleric acid, also known as delta-phenylvalerate or benzenepentanoic-acid, is a monocarboxylic acid that is valeric acid substituted by a phenyl group at the delta-position. It is a monocarboxylic acid and a member of benzenes. It derives from a valeric acid. 5-Phenylvaleric acid belongs to the class of organic compounds known as medium-chain fatty acids. These are fatty acids with an aliphatic tail that contains between 4 and 12 carbon atoms.
8-hydroxyguanosine (8-OHG) is a marker for measuring the rate of oxidative damage to nucleic acids and lipids. Production of reactive oxygen species (ROS) damage proteins, lipid membranes, and nucleic acids (DNA and RNA), all critical functional components of living cells. The progressive accumulation of unrepaired free radical damage over time is believed to be a major contributor to the aging process and to a variety of age-related chronic diseases. Generation of most free radicals is a 'side effect' of normal metabolic processes, especially mitochondrial production of ROS, including superoxide anion, hydrogen peroxide, and hydroxyl radical, coincident to oxidative metabolism. (PMID 14607529). 8-OHG (marker of oxidative damage to RNA) was found in the cerebral cortex in three of six cases of neuropathologically examined autopsy of subacute sclerosing panencephalitis patients. Subacute sclerosing panencephalitis is caused by persistent brain infection of mutated measles virus, showing inflammation, neuronal loss, and demyelination. (PMID 12546425). The concentration of 8-OHG in CSF in Parkinson's disease (PD) patients is approximately three-fold that in controls. The concentration of 8-OHG in CSF decreased significantly with the duration of disease. However, the concentration of 8-OHG in serum was not significantly altered in PD patients compared to that in controls. (PMID 12499051).
Dihydroxyfumaric acid is a known generator of superoxide anions and by hydroxyl free radicals. Dihydroxyfumarate exposure can cause insulin inhibitory effects. It can spontaneously convert to hydroxypyruvate or to oxaloglycolate.
Maleylacetoacetic acid, also known as 4-maleylacetoacetate, is an intermediate in the metabolism of tyrosine. Homogentisate 1,2-dioxygenase (HGD) is the enzyme which catalyzes the conversion of homogentisate into 4-maleylacetoacetate. HGD is involved in the catabolism of aromatic rings, more specifically in the breakdown of the amino acids tyrosine and phenylalanine.
Histidylproline diketopiperazine is a cyclic dipeptide initially described in both the hypothalamus and cerebral tissues, has been detected in various sites outside the central nervous system, including the gastrointestinal tract and, more specifically, the endocrine pancreas. Histidylproline diketopiperazine belongs to the family of Dioxopiperazines. These are compounds containing a piperazine ring bearing two ketone groups.
Tiglyl-CoA is a metabolite in the degradation of isoleucine to propionic acid pathway. A defect in the conversion of tiglyl-CoA to alpha-methyl-beta-hydroxybutyryl-CoA, results in episodic abdominal pain and acidosis in patients with Tiglic acidemia (OMIM 275190).
o-Cresol is a minor urinary metabolite of toluene, O-cresol is a cresol that is phenol substituted by a methyl group at position 2. It is a minor urinary metabolite of toluene. It has a role as a human xenobiotic metabolite. It is widely used chemical with neurotoxicological properties (PMID:15687000). o-Cresol is used commercially as a disinfectant. Exposure may occur by inhalation, by cutaneous adsorption or by oral ingestion. o-Cresol denature and precipitate cellular proteins and thus may rapidly cause poisoning. o-Cresol is metabolized by conjugation and oxidation. Ingestion of o-Cresol cause intense burning of mouth and throat, followed by marked abdominal pain and distress. The minimum lethal dose of cresol by mouth is about 2 g (PMID 15040915). o-Cresol is a microbial metabolite that can be found in Pseudomonas. Besides, o-Cresol is one of the chemical compounds found in castoreum. This compound is gathered from the beaver's castor glands and found in the white cedar consumed by the beavers. Together with many other compounds, o-cresol is traditionally extracted from coal tar, the volatile materials obtained in the production of coke from coal. A similar source material is petroleum residues. These residue contains a few percent by weight of phenol and isomeric cresols. In addition to the materials derived from these natural sources, about two thirds of the Western world's supply is produced by methylation of phenol using methanol.
Monoisobutyl phthalic acid is a phthalate metabolite that has been found in human meconium and in semen (PMID: 16970347), saliva (PMID: 15995852), and urine (PMID: 15113553). Phthalate esters are a family of multifunctional compounds widely used as plasticizers, solvents, or additives in many diverse products such as poly(vinyl chloride) (PVC) materials, pharmaceuticals and medical devices, pesticides, lubricants, and personal care products. Humans have been exposed to phthalates through the manufacture, ubiquitous use, and disposal of PVC materials and other phthalate-containing products. (PMID: 16970347).
(R) Pristanoyl-CoA is converted by alpha-methylacyl-CoA racemase (E.C. 5.1.99.4) (S) pristanoyl-CoA, which is then degraded via peroxisomal beta-oxidation. Deficiency in this enzyme results in neuropathy, hypogonadism of adult onset; and in infant, defective bile acid synthesis has been observed. Pristanoyl-CoA is the substrate of propionyl-CoA C(2)-trimethyltridecanoyltransferase (E.C.2.3.1.154). It is the substrate of peroxisomal pristanoyl-CoA oxidase (E.C.1.3.3.6). A genetic disorder called Zellweger syndrome (OMIM: 214100), also known as neonatal adrenoleukodystrophy, NALD) is the result of a lack of pristanoyl-CoA oxidase, and the subsequent accumulation of phytanic acid and pristanic acid.
12-hydroxydodecanoic acid is the substrate of the human glutathione-dependent formaldehyde dehydrogenase (EC1.1.1.1). The enzyme that catalyzes the conversion of alcohols to aldehydes is a zinc-containing dimeric enzyme responsible for the oxidation of long-chain alcohols and omega-hydroxy fatty acids. (OMIM). The human glutathione-dependent formaldehyde dehydrogenase is unique among the structurally studied members of the alcohol dehydrogenase family in that it follows a random bi kinetic mechanism forming a binary complex, and a ternary complex with NAD+. (PMID 12196016).
O-6-deoxy-a-L-galactopyranosyl-(1->2)-O-b-D-galactopyranosyl-(1->3)-2-(acetylamino)-2-deoxy-D-Galactose is a milk oligosaccharide alditol derived from mucin glycoprotein detected with High-performance anion exchange-chromatography. (PMID: 1799211). This oligosaccharide alditol is also found in purified human bronchial mucins. (PMID: 1337867) This O-glycan is present in normal human mucins along the intestinal tract. (PMID: 15361072).
Plasma norepinephrine sulfate increases after sympathetic nervous system activation by an exhausting incremental exercise test and remain elevated up to 2 h after exercise. (PMID: 8330610). Human platelets contribute to the formation of plasma norepinephrine sulfate by norepinephrine uptake, intraplatelet sulfoconjugation and release of norepinephrine sulfate. (PMID: 7968241). Higher concentrations of norepinephrine sulfate in portal venous than arterial plasma indicate substantial production of norepinephrine by mesenteric organs. (PMID: 8627312). Intravenously infused norepinephrine is sulfoconjugated in humans, indicating that a major part of NE is sulfoconjugated in blood or at sites easily accessible from blood. (PMID: 12020748).
Heptacosanoic acid is a fatty acid found in follicular casts (the abnormal impactation of a sebaceous follicle) implicated as the preclinical lesion of acne vulgaris. (PMID: 2940302). Heptacosanoic acid is one of the fatty acids found that contribute to a significant increase in the microviscosity of erythrocyte membranes in patients affected with adrenoleukodystrophy (ALD) and adrenomyeloneuropathy (AMN). (PMID: 6874949). Heptacosanoic acid has been found in the adrenal cortex and brain, in adrenoleukodystrophy and Zellweger syndrome in humans. (PMID: 3806133). Heptacosanoic acid has been found in blood and tissues of patients with different genetic peroxisomal disorder (Refsum's disease, X-linked adrenoleukodystrophy, neonatal adrenoleukodystrophy or Zellweger syndrome). (PMID: 2474624).
N-Acetylputrescine is a polyamine commonly occurring excreted in normal human urine (PMID 7775374). N-Acetylputrescine is the most abundant of all polyamines both in normal individuals and in patients with leukemia (PMID 9464484). N-Acetylputrescine is the N-acetylated form of the naturally occurring polyamine called putrescine. The N-acetylation is mediated by the enzyme diamine N-acetyltransferase. Putrescine is related to cadaverine (another polyamine). Both are produced by the breakdown of amino acids in living and dead organisms and both are toxic in large doses. Putrescine and cadaverine are largely responsible for the foul odor of putrefying flesh, but also contribute to the odor of such processes as bad breath and bacterial vaginosis. Putrescine is also found in semen. Putrescine attacks s-adenosyl methionine and converts it to spermidine. Spermidine in turn attacks another s-adenosyl methionine and converts it to spermine. Putrescine is synthesized in small quantities by healthy living cells by the action of ornithine decarboxylase. N-Acetylputrescine can be found in Corynebacterium as well (PMID:25919117).
6-Lactoyltetrahydropterin is a putative intermediate in the de novo synthesis of tetrahydrobiopterin (BH4) pathway, in a reaction involving the enzyme sepiapterin reductase (E.C. 1.1.1.153) in human liver. In brain, an enzyme distinct from sepiapterin reductase catalyzes the TPNH-dependent reduction of 6-pyruvoyl-tetrahydropterin to 6-lactoyl-tetrahydropterin. (PMID: 4004850). In brain, the expression of other enzymes involved in BH4 biosynthesis includes aldose reductase, carbonyl reductase, GTP-cyclohydrolase I, and 6-pyruvoyltetrahydrobiopterin. Sepiapterin reductase expression is increased in Parkinson's disease brain tissue. (PMID: 17270157).
O-b-D-galactopyranosyl-(1->3)-O-[O-b-D-galactopyranosyl-(1->4)-2-(acetylamino)-2-deoxy-b-D-glucopyranosyl-(1->6)]-2-(acetylamino)-2-deoxy- D-Galactose is a milk oligosaccharide alditol derived from mucin glycoprotein detected with High-performance anion exchange-chromatography. (PMID: 1799211). Forms part of carbohydrate chains linked to human kappa-casein from mature milk. (PMID: 3342257). A neutral oligosaccharides from human milk of O-linked glycoproteins having blood group A and H activities. (PMID: 1904864).
Erucic acid is a 22-carbon, monounsaturated omega-9 fatty acid found mainly in the Brassica family of plants such as canola, rapeseed, wallflower seed, mustard seed as well as Brussels spouts and broccoli. Some Brassica cultivars can have up to 40 to 50 percent of their oil recovered as erucic acid. Erucic acid is also known as cis-13-docosenoic acid. The trans isomer is known as brassidic acid. Erucic acid occurs in nature only along with bitter-tasting compounds. Erucic acid has many of the same uses as mineral oils but with the advantage that it is more readily bio-degradable. Its high tolerance to temperature makes it suitable for transmission oil. Erucic acid‚Äôs ability to polymerize and dry means it can be - and is - used as a binder for oil paints. Increased levels of eicosenoic acid (20:Ln9) and erucic acid (22:1N9) have been found in the red blood cell membranes of autistic subjects with developmental regression (PMID: 16581239 ). Erucic acid is broken down long-chain acyl-coenzyme A (CoA) dehydrogenase, which is produced in the liver. This enzyme breaks this long chain fatty acid into shorter-chain fatty acids. Human infants have relatively low amounts of this enzyme and because of this, babies should not be given foods high in erucic acid. Food-grade rapeseed oil (also known as canola oil) is regulated to a maximum of 2% erucic acid by weight in the US and 5% in the EU, with special regulations for infant food. Canola was bred from rapeseed cultivars of B. napus and B. rapa at the University of Manitoba, Canada. Canola oil is derived from a variety of rapeseed that is low in erucic acid.
4-Hydroxy-2-ketoglutaric acid is a substrate for Fructose-bisphosphate aldolase A.
O-2-(acetylamino)-2-deoxy-a-D-galactopyranosyl-(1->3)-O-[6-deoxy-a-L-galactopyranosyl-(1->2)]-O-b-D-galactopyranosyl-(1->3)-O-2-(acetylamino)-2-deoxy-b-D-glucopyranosyl-(1->3)-O-b-D-galactopyranosyl-(1->4)-D-Glucose is a fucose-containing oligosaccharide found in human milk. (PMID: 11308023). Is a blood group specific oligosaccharide from feces of a blood group A breast-fed infant. (PMID: 6513935).
4-methoxyphenylacetic acid is a monocarboxylic acid that is phenylacetic acid carrying a 4-methoxy substituent. It is used as an intermediate for pharmaceuticals and other organic synthesis. It has been found to inhibit the germination of cress and lettuce seeds. It has a role as a plant metabolite, a plant growth retardant and an Aspergillus metabolite. It is a monocarboxylic acid and a monomethoxybenzene. 4-Methoxyphenylacetic acid, also known as 4-methoxybenzeneacetate or 2-(p-anisyl)acetic acid, belongs to the class of organic compounds known as anisoles. These are organic compounds containing a methoxybenzene or a derivative thereof. 4-Methoxyphenylacetic acid is a 4-O-Methylated catecholamine metabolite found in normal human urine, cerebrospinal fluid and brain tissue.
2,2-dimethylsuccinic acid is an alpha,omega-dicarboxylic acid that is succinic acid substituted by two methyl groups at positions 2 and 2 respectively. It derives from a succinic acid. 2,2-Dimethylsuccinic acid, also known as 2,2-dimethylbutanedioate, belongs to the class of organic compounds known as methyl-branched fatty acids. These are fatty acids with an acyl chain that has a methyl branch. Usually, they are saturated and contain only one or more methyl group. However, branches other than methyl may be present. 2,2-Dimethylsuccinic acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
The chlorite ion is ClO2-. A chlorite (compound) is a compound that contains this group, with chlorine in oxidation state +3. Chlorites are also known as salts of chlorous acid.
The cyanate ion is an anion consisting of one oxygen atom, one carbon atom, and one nitrogen atom, [OCN], in that order. The cyanate ion possesses 1 unit of negative charge, borne mainly by the nitrogen atom. In organic compounds the cyanate group is a functional group. The cyanate ion is an ambident nucleophile in nucleophilic substitution because it can react to form an alkyl cyanate R-OCN (exception) or an alkyl isocyanate R-NCO (rule). Aryl cyanates (C6H5OCN) can be formed by a reaction of phenol with cyanogen chloride (ClCN) in the presence of a base. The cyanate ion is relatively non-toxic in comparison with cyanides. Use of this fact is made in cyanide decontamination processes where a permanganate oxidation converts toxic cyanide to safer cyanate. Cyanate can be decomposed by the enzyme cyanate lyase (or cyanase), which is found in bacteria and plants. In particular cyanate can be decomposed to carbamate (ammonia) and carbon dioxide. Alternately the same enzyme can be used to synthesize cyanate using carbamate and carbon dioxide.
Petroselinic acid, also known as (6Z)-Octadecenoic acid, is an 18-carbon unsaturated fatty acid that occurs naturally in several animal and vegetable fats and oils. It is a white powder and is commercially available. In chemical terms, petroselinic acid is classified as a monounsaturated omega-12 fatty acid, abbreviated as 18:1 cis-6. Petroselinic acid is a positional isomer of oleic acid. The term "petroselinic" means related to, or derived from, oil of Petroselinum, or oil of parsley. Petroselinic acid was first isolated from parsley seed oil in 1909. Petroselinic acid occurs in high amounts in plants in the Apiaceae family (a family of mostly aromatic flowering plants named after the genus Apium and commonly known as the celery, carrot or parsley family), Araliaceae (a family of flowering plants composed of about 43 genera and around 1500 species consisting of primarily woody plants and some herbaceous plants), Griselinia (Griseliniaceae) and in Garryaceae. The occurrence of petroselinic acid as the major fatty acid is used in chemosystematics as a proof of a close relationship of several families within the Apiales as well as within the Garryales. Petroselonic acid has been found in coriander (Coriandrum sativum) and cumin (Cuminum cyminum) and caraway seeds. In addition, petroselinic acid has been found in minor amounts in several fats of plant and animal origin, including in human sources. Petroselinic acid is an important oleochemical material for the food, cosmetics, chemistry and pharmaceutical industry (PMID: 16604360) as it can be easily processed into lauric and adipinic acid.
Bisnorcholic acid is one of a number of short side bile acids found in the urine from patients with cerebrotendinous xanthomatosis (CTX). The presence these short side bile acids in urine of the CTX patients suggests that bile alcohols may be further degraded to these bile acids. (PMID: 2079611).
Syringic acid, also known as syringate or cedar acid, belongs to the class of organic compounds known as gallic acid and derivatives. Gallic acid and derivatives are compounds containing a 3,4,5-trihydroxybenzoic acid moiety. Outside of the human body, Syringic acid is found, on average, in the highest concentration within a few different foods, such as common walnuts, swiss chards, and olives and in a lower concentration in apples, tarragons, and peanuts. Syringic acid has also been detected, but not quantified in several different foods, such as sweet marjorams, silver lindens, bulgurs, annual wild rices, and barley. This could make syringic acid a potential biomarker for the consumption of these foods. Syringic acid is correlated with high antioxidant activity and inhibition of LDL oxidation. Research suggests that phenolics from wine may play a positive role against oxidation of low-density lipoprotein (LDL), which is a key step in the development of atherosclerosis. Syringic acid is a phenol present in some distilled alcohol beverages. It is also a product of microbial (gut) metabolism of anthocyanins and other polyphenols that have been consumed (in fruits and alcoholic beverages - PMID:18767860). Syringic acid is also a microbial metabolite that can be found in Bifidobacterium (PMID:24958563).
Adenosylcobalamin is one of two metabolically active forms synthesized upon ingestion of vitamin B12 and is the predominant form in the liver; it acts as a coenzyme in the reaction catalyzed by methylmalonyl-CoA mutase. A cobalamin (cbl) derivative in which the substituent is deoxyadenosyl. It is one of two metabolically active forms synthesized upon ingestion of vitamin B12 and is the predominant form in the liver; it acts as a coenzyme in the reaction catalyzed by methylmalonyl-CoA mutase (MCM; E.C. 5.4.99.2). Inborn errors of vitamin B12 metabolism are autosomal recessive disorders and have been classified into nine distinct complementation classes. Disorders affecting adenosylcobalamin cause methylmalonic acidemia and metabolic acidosis. Methylmalonyl-CoA mutase catalyzes the conversion of L-methylmalonyl-CoA to succinyl-CoA and uses adenosylcobalamin (AdoCbl) as a cofactor. Cbl must be transported into mitochondria, reduced and adenosylated before it can be utilized by MCM. (PMID: 17011224).
N-isovalerylsarcosine is a minor but characteristic constituent of the organic acid profile in isovaleric acidemia. They are assumed to be formed from isovaleryl-CoA by action of the enzyme acyl-CoA:glycine N-acyltransferase [EC 2.3.1.13] on sarcosine. (PMID: 6197208).
N tau-ribosylhistidine (His-R) is a histidine derivative found in the urine of histidinemic patients (histidinemia is an autosomal recessive metabolic disorder characterized by increased levels of histidine in blood, urine, and cerebrospinal fluid). The enzymes responsible for the formation of His-R are NAD (P) + nucleosidase [EC 3.2.2.5], nucleotide pyrophosphatase [EC 3.5.1.9] and 5'-nucleotidase [EC 3.1.3.5] (PMID: 2992472).
Isovaleryl glucuronide has been identified in the urine of patients with isovaleric acidemia made possible by using gas chromatograph-mass spectrometry (GC-MS). Isovaleryl glucuronide is more likely to be excreted when the amount of urinary 3-hydroxyisovaleric acid excretion is high. Isovaleryl glucuronide is more likely to be excreted when the amount of urinary 3-hydroxyisovaleric acid excretion is high. (PMID: 6547525). Isovaleric acidemia is caused by mutation in the isovaleryl CoA dehydrogenase gene and is closely related to maple syrup urine disease. It presents in two forms: the acute neonatal form, leading to massive metabolic acidosis from the first days of life and rapid death and a chronic form in which periodic attacks of severe ketoacidosis occur with asymptomatic intervening periods. (OMIM 243500).
3-Fucosyllactose is a milk oligosaccharide isolated in 1958 (PMID: 13546862), and that was also isolated for the first time from the urine of a blood group O, nonsecretor, woman during pregnancy and lactation in 1977 (PMID: 838696). Is resistant to enzymic hydrolysis in the gastrointestinal tract of the infant; it is postulated that they reach the large intestine where they serve as substrates for bacterial metabolism. (PMID 10837303).
Malonylcarnitine is a metabolite that accumulates with specific disruption of fatty-acid oxidation caused by the impaired entry of long-chain acylcarnitine esters into the mitochondria and failure of the mitochondrial respiratory chain at complex 11 and malonyl-CoA decarboxylase (EC 4.1.1.9) deficiency (OMIM: 248360). Malonylcarnitine has also been found to accumulate in some newborns with medium-chain acyl-CoA dehydrogenase (EC 1.3.99.3) deficiency (OMIM: 201450). (PMID:11558490, 15303003, 12651823).
3-Indolebutyric acid is an indolic tryptophan metabolite occasionally found in human urine. (PMID:7130309). 3-Indolebutyric acid is a plasma and urinary tryptophan-related metabolite related to metabolic and skin diseases. (PMID:15206797). Plasma levels of tryptophan metabolites in the umbilical vein and artery are significantly higher than those in the maternal vein. (PMID:1506727). 3-Indolebutyric acid has been shown to accelerated glucose uptake in the rat diaphragm. (PMID:6025019). 3-Indolebutyric acid is also a microbial netabolite, urinary indole-3-butyrate is produced by Clostridia sp. (PMID:6630445).
4-Ethylbenzoic acid is a man-made organic chemical relatively resistant to physical, chemical, or biological degradation, and constitutes an environmental burden. (PMID 3468623). It is also one of the compounds derived from tobacco and tobacco smoke. (PMID 7466833).
2-Fucosyllactose (Fuc-a( 1->2)Galb(1->4)Glc) is an oligosaccharide first found in milk in the 1950s, and a well established isolation technique was found in 1972 (PMID: 5012321). It has been used as an acceptor substrate in assays of the blood group A and B gene specified glycosyltransferases since. (PMID 6894927).
6-Methyladenine is a methylated adenine residue. The formation of internal 6-methyladenine (m6A) residues in eucaryotic messenger RNA (mRNA) is a postsynthetic modification in which S-adenosyl-L-methionine (SAM) serves as the methyl donor. 6-Methyladenine residues have also been localized to heterogeneous nuclear RNA (HnRNA), and for the most part these residues are conserved during mRNA processing. Although the biological significance of internal adenine methylation in eucaryotic mRNA remains unclear, a great deal of research has indicated that this modification may be required for mRNA transport to the cytoplasm, the selection of splice sites or other RNA processing reactions. The presence of m6A residues increases the in vitro translation efficiency of dihydrofolate reductase; an inhibition of m6A residues in dihydrofolate reductase transcripts significantly alters their rate of translation. m6A is found in many human fluids: oviductal fluid, blood plasma and urine (PMID:1551452, 8925412, 10481270, 16083005, 16684535, 3506820, 3728186).
N-Palmitoylethanolamide (PEA) is present in the tissues of most mammals. It was initially described as an agonist of the type 2 cannabinoid receptor (CB2), although it is now universally recognized that PEA is in fact incapable of binding to cannabinoid receptors, or at least not to the known receptors. In addition to its anti-inflammatory activity, PEA also produces analgesia, neuroprotection, and possesses anti-epileptic properties. It also reduces gastrointestinal motility and cancer cell proliferation, as well as protecting the vascular endothelium in the ischemic heart. The physiological stimuli that regulate PEA levels in mammalian tissues are largely unknown, however, multiple studies indicate that this lipid accumulates during cellular stress, particularly following tissue injury. For example, PEA increases post-mortem in the pig brain. Similar elevations in PEA levels have been observed in the ischemic brain and PEA is also up-regulated in response to ultraviolet-B irradiation in mouse epidermal cells. Adipose tissue is highly implicated in the systemic secretion of IL-6 and leptin, and human mature adipocytes are able to secrete large quantity of PEA. Human adipose tissue can be subjected to modulation of its inflammatory state by lipopolysaccharide (LPS). LPS strongly inhibits adipose cell leptin release, with PEA acting as a potentiator of this inhibitory effect. These actions are not linked to a reduction in leptin gene transcription. Thus, PEA does not have an anti-inflammatory role in the secretion of IL-6 via NFkappaB at the adipocyte level, but instead seems to act at the heart of the LPS-stimulated pathway, which, independently of NFkappaB, inhibits the secretion of leptin. (PMID: 16884908).
Glutamic gamma-semialdehyde is the metabolic precursor for proline biosynthesis. The conversion from L-Glutamate, an ATP- and NADPH-dependent reaction, is catalyzed by the enzyme Delta-1-pyrroline-5-carboxylate synthetase (P5CS) (OMIM 138250). L-Glutamic-gamma-semialdehyde can also be converted to or be formed from the amino acids L-ornithine (EC 2.6.1.13) and L-proline (EC 1.5.99.8 and EC 1.5.1.2). It is also one of the few metabolites that can be a precursor to other metabolites of both the urea cycle and the citric acid cycle (BioCyc).
Phthalic acid is an aromatic dicarboxylic acid, with formula C6H4(COOH)2. Phthalic acid is used mainly in the form of the anhydride to produce other chemicals such as dyes, perfumes, saccharin, phthalates and many other useful products. Phthalic acid, when found in tissues or biofluids arises from exposure to these phthalate products. Phthalate is an environmental chemical of heightened public concern because reports of its potential risk to male reproductive health (PMID 16804814), being significantly associated with reduced sperm concentration to pesticide concentration in men's urine (PMID 16804812). Within the reproductive tract, the male is exquisitely vulnerable to the effects of anti-androgens during development due the reliance on the synthesis and action of androgens for the masculinization of the male reproductive tract. The ability of phthalates to suppress androgen synthesis during development and to induce testicular dysgenesis together with cryptorchidism and hypospadias has raised considerable concern. (PMID 15016950).
Methylcysteine is one of the identified number of bioactive substances in garlic that are water soluble (PMID 16484549). It has been suggested that the use of these organosulfur agents derived from garlic could protect partially oxidized and glycated LDL or plasma against further oxidative and glycative deterioration, which might benefit patients with diabetic-related vascular diseases (PMID 15161248). It may also exert some chemopreventive effects on chemical carcinogenesis. However, it should be borne in mind that may also demonstrate promotion potential, depending on the organ examined (PMID 9591199). Methylcystein is a biomarker for the consumption of dried and cooked beans.
3'-hydroxysepiapterin is found in high concentration in the urine of patients with DHBS(dihydrobiopterin synthetase) deficiency.(PMID: 7005193).
Constituent of collagen and the antibiotic Telomycin (Combined Chemical Dictionary).
Bisdemethoxycurcumin is a curcuminoid, a component of tumeric. Tumeric is a spice that comes from the root Curcuma longa, a member of the ginger family, Zingaberaceae. It is bright yellow and has been used as a coloring agent in food in the United States. In India, it has been used for centuries as a spice and a food preservative, and also for its various medicinal properties. In Ayurveda (Indian traditional medicine), tumeric has been used for its medicinal properties for various indications and through different routes of administration. It has been used topically on the skin for wounds, blistering diseases such as pemphigus and herpes zoster, for parasitic skin infections, and for acne. It has been used via oral administration for the common cold, liver diseases, urinary tract diseases, and as a blood purifier. For chronic rhinitis and coryza, it has been used via inhalation. The average intake of tumeric in the diet in India is approximately 2 to 2.5 g in a 60 kg individual. This corresponds to an intake of approximately 60 to 100 mg of curcumin daily. The Food and Drug Administration has classified tumeric among substances Generally Recognized as Safe (GRAS). A large number of in vitro and animal studies have been conducted to evaluate the effect of curcumin on inflammation. It has been found to act at various different levels of the arachadonic acid inflammatory cascade and through effects on various enzymes and cytokines. (PMID: 12676044).
8-isoprostaglandin PGF2beta is an isoprostane. Isoprostanes are arachidonic acid metabolites produced by peroxidative attack of membrane lipids. These accumulate to substantial levels in many clinical conditions characterized in part by accumulation of free radicals and reactive oxygen species, including asthma, hypertension and ischemia-reperfusion injury. For this reason, they are frequently used as markers of oxidative stress; however, many are now finding that these molecules are not inert, but in fact evoke powerful biological responses in an increasing array of cell types. In many cases, these biological effects can account in part for the various features and manifestations of those clinical conditions. Thus, it may be possible that the isoprostanes are playing somewhat of a causal role in those disease states. (PMID: 14504139)Prostaglandins are eicosanoids. The eicosanoids consist of the prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and lipoxins (LXs). The PGs and TXs are collectively identified as prostanoids. Prostaglandins were originally shown to be synthesized in the prostate gland, thromboxanes from platelets (thrombocytes), and leukotrienes from leukocytes, hence the derivation of their names. All mammalian cells except erythrocytes synthesize eicosanoids. These molecules are extremely potent, able to cause profound physiological effects at very dilute concentrations. All eicosanoids function locally at the site of synthesis, through receptor-mediated G-protein linked signalling pathways.
Oleamide is an amide of the fatty acid oleic acid. It is an endogenous substance: it occurs naturally in the body of animals. It accumulates in the cerebrospinal fluid during sleep deprivation and induces sleep in animals. It is being studied as a potential medical treatment for mood and sleep disorders, and cannabinoid-regulated depression. The mechanism of action of oleamide's sleep inducing effects is an area of current research. It is likely that oleamide interacts with multiple neurotransmitter systems. Oleamide is structurally related to the endogenous cannabinoid anandamide, and has the ability to bind to the CB1 receptor as a full agonist.
Monoethyl phthalate (mEtP) is a metabolite, or breakdown product, of diethyl phthalate, used in perfume, cologne, deodorant, soap, shampoo, lotion, and other personal care products, particularly those containing fragrance.
Carnosol is a naturally occurring phenolic diterpene found in rosemary (Rosemarinus officinalis, Labiatae). It has been known that an extract of rosemary leaves contains high antioxidative activity. Ninety percent of this antioxidative activity can be attributed to carnosol and carnosic acid. Carnosic acid is easily converted to carnosol by oxidation. Carnosol has multiple beneficial medicinal effects including anti-inflammatory, anti-microbial and anti-cancer activities in various disease models. Carnosol may possess important neuroprotective effects against rotenone-induced DA neuronal damage. Naturally occurring antioxidants reduce the risk of neurodegenerative diseases. In addition, carnosol and carnosic acid promoted the synthesis of nerve growth factor in glial cells. Carnosol-mediated neuroprotection in DA neurons is involved in the attenuation of caspase-3 activity, which was induced by rotenone. Furthermore, carnosol-mediated tyrosine hydroxylase (TH) increase, which is dependent on the Raf-mitogen-activated protein kinase (MEK)-extracellular signal-regulated kinase (ERK)1/2 signaling pathway, is responsible for the neuroprotection in SN4741 DA cells. (PMID: 17047462). Carnosol, a phenolic diterpene compound of the labiate herbs rosemary and sage, is an activator of the human peroxisome proliferator-activated receptor gamma (PPARgamma), a ligand activated transcription factor, belonging to the metazoan family of nuclear hormone receptors. Activation of PPARgamma increases the transcription of enzymes involved in primary metabolism, leading to lower blood levels of fatty acids and glucose. Hence, PPARgamma represents the major target for the glitazone type of drugs currently being used clinically for the treatment of type 2 diabetes. (PMID: 16858665).
1,3,7-Trimethyluric acid is a methyl derivative of uric acid, found occasionally in human urine. 1,3,7-Trimethyluracil is one of the purine components in urinary calculi. Methylated purines originate from the metabolism of methylxanthines (caffeine, theophylline and theobromine). Methyluric acids are indistinguishable from uric acid by simple methods routinely used in clinical laboratories, requiring the use of high-performance liquid chromatography (HPLC). Purine derivatives in urinary calculi could be considered markers of abnormal purine metabolism. The content of a purine derivative in stone depends on its average urinary excretion in the general population, similarity to the chemical structure of uric acid, and content of the latter in stone. This suggests that purines in stones represent a solid solution with uric acid as solvent. It is also plausible that methylxanthines, ubiquitous components of the diet and drugs, are involved in the pathogenesis of urolithiasis. Caffeine is metabolized via successive pathways mainly catalyzed by CYP1A2, xanthine oxidase or N-acetyltransferase-2 to give 14 different metabolites. CYP1A2 activity shows an inter-individual variability among the population. CYP1A2, an isoform of the CYP1A cytochrome P450 super-family, is involved in the metabolism of many drugs and plays a potentially important role in the induction of chemical carcinogenesis. (PMID:11712316, 15833286, 3506820, 15013152).
Apigenin is a plant-derived flavonoid that has significant promise as a skin cancer chemopreventive agent. Apigenin inhibits the expression of involucrin (hINV), a marker of keratinocyte differentiation, is increased by differentiating agents via a protein kinase Cdelta (PKCdelta), Ras, MEKK1, and MEK3 cascade that increases AP1 factor level and AP1 factor binding to DNA elements in the hINV promoter. Apigenin suppresses the 12-O-tetradeconylphorbol-13-acetate-dependent increase in AP1 factor expression and binding to the hINV promoter. Apigenin also inhibits the increase in promoter activity observed following overexpression of PKCdelta, constitutively active Ras, or MEKK1. The suppression of PKCdelta activity is associated with reduced phosphorylation of PKCdelta-Y311. Activation of hINV promoter activity by the green tea polyphenol, (-)-epigellocathecin-3-gallate, is also inhibited by apigenin, suggesting that the two chemopreventive agents can produce opposing actions in keratinocytes (PMID: 16982614). Apigenin, a flavone abundantly found in fruits and vegetables, exhibits antiproliferative, anti-inflammatory, and antimetastatic activities through poorly defined mechanisms. This flavonoid provides selective activity to promote caspase-dependent-apoptosis of leukemia cells and uncover an essential role of PKCdelta during the induction of apoptosis by apigenin (PMID: 16844095). Apigenin markedly induces the expression of death receptor 5 (DR5) and synergistically acts with exogenous soluble recombinant human tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to induce apoptosis in malignant tumor cells. On the other hand, apigenin-mediated induction of DR5 expression is not observed in normal human peripheral blood mononuclear cells. Moreover, apigenin does not sensitize normal human peripheral blood mononuclear cells to TRAIL-induced apoptosis (PMID: 16648565).
27-Nor-5b-cholestane-3a,7a,12a,24,25-pentol is a bile alchohol present in urine of healthy humans.
3-Mercaptolactic acid is a thiol that has been confirmed to be found in urine (PMID 8852041).
2,4-Diamino-6-hydroxypyrimidine (DAHP) is a selective inhibitor of GTP cyclohydrolase I (GTPCH) that restricts the de novo synthesis of tetrahydrobiopterin (BH4) or the BH4 precursor in vascular smooth muscle cells (VSMC). (PMID 12883322). 2,4-Diamino-6-hydroxypyrimidine also inhibits nitric oxide (NO) in both Interferon-gamma (IFN-gamma) and antigen (Ag)/IgE (Ag/IgE) systems, increasing Mast cells (MC) degranulation. (PMID 14514683). Sepiapterin, a precursor to tetrahydrobiopterin in the salvage pathway, completely reverses the effect of 2,4-diamino-6-hydroxypyrimidine on neuronal NO-synthase (nNOS) ubiquitylation. (PMID 16216381).
Monomethyl phthalate is a metabolite, or breakdown product, of dimethyl phthalate, used in insect repellant, plastic, and as a rocket propellant.
8-iso-PGF3alpha is an isoprostane with an antiaggregatory action in human blood. Isoprostanes (IsoPs) are formed in vivo from the free radical-catalyzed peroxidation of arachidonate independent of cyclooxygenase (COX). Although the structures of these compounds are very similar to COX-derived prostaglandins (PGs), an important distinction between IsoPs and PGs is that IsoP bicycloendoperoxide intermediates contain side chains that are predominantly (>90%) oriented cis in relation to the prostane ring because the generation of these intermediates is favored kinetically. In contrast to other types of prostanoids, E2/D2-IsoPs are beta-hydroxyketone-containing compounds that can undergo reversible keto-enol tautomerization under both acidic and basic conditions, allowing rearrangement of the side chains that are initially cis to the more stable trans-configuration. (PMID: 12746435).
Threonine dehydrogenase catalyzes the oxidation of threonine by NAD+ to glycine and acetyl-CoA, but when the ratio acetyl-CoA/CoA increases in nutritional deprivation (e.g., in diabetes) the enzyme produces aminoacetone (Chem. Res. Toxicol., 14 (9), 1323 -1329, 2001). Aminoacetone is thought to be a substrate for SSAO (semicarbazide-sensitive amine oxidase), leading to the production of the toxic product methylglyoxal (Journal of Chromatography B. Volume 824, Issues 1-2 , 25 September 2005, Pages 116-122 ).
S-(3-Oxo-3-carboxy-n-propyl)cysteine, abbreviated as OCPC, is a cystathionine mono-oxo acid metabolite found in the urine of a cystathioninuria patient (PMID: 8373176).
trans-3-Decenoyl-CoA is an intermediate in fatty acid metabolism. trans-3-Decenoyl-CoA is the substrate of medium-chain acyl-CoA dehydrogenase (MCAD, EC 1.3.99.3) MCAD acts on C4-C16 acyl-CoAs with its peak activity toward medium-chain (C6-C12) substrates. MCAD is a key enzyme for the beta-oxidation of fatty acids. MCAD deficiency is caused by mutation in the medium-chain acyl-CoA dehydrogenase gene (ACADM; OMIM 607008). Inherited deficiency of medium-chain acyl-CoA dehydrogenase is characterized by intolerance to prolonged fasting, recurrent episodes of hypoglycemic coma with medium-chain dicarboxylic aciduria, impaired ketogenesis, and low plasma and tissue carnitine levels. The disorder may be severe, and even fatal, in young patients. It has been reported that between 19 and 25% of patients with undiagnosed deficiency of MCAD die during their first episode of metabolic decompensation. (PMID: 15850406).
The active metabolite of Folic acid, is used principally as its calcium salt as an antidote to folic acid antagonists which block the conversion of folic acid to folinic acid. Folic acid, a water-soluble B-complex vitamin, is found in foods such as liver, kidneys, yeast, and leafy, green vegetables. Folic acid is used to diagnose folate deficiency and to treat topical sprue and megaloblastic and macrocytic anemias, hematologic complications resulting from a deficiency in folic acid. A member of the vitamin B family that stimulates the hematopoietic system. It is present in the liver and kidney and is found in mushrooms, spinach, yeast, green leaves, and grasses (poaceae). Folic acid is used in the treatment and prevention of folate deficiencies and megaloblastic anemia.
N-Methyl-a-aminoisobutyric acid, also known as 2-(methylamino)isobutyrate or AMAIB, belongs to the class of organic compounds known as alpha amino acids. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). N-Methyl-a-aminoisobutyric acid is a drug. N-Methyl-a-aminoisobutyric acid is a metabolite that is actively incorporated into the cell by the actions of Interleukin 1-beta and Interleukin 6 via sodium dependent transport systems (PMID 16202926).
1,3-Dimethyluracil is a methyl derivative of uric acid, found occasionally in human urine. 1,3-Dimethyluracil is one of the purine component in urinary calculi. Methylated purines originate from the metabolism of methylxanthines (caffeine, theophylline and theobromine). Methyluric acids are indistinguishable from uric acid by simple methods routinely used in clinical laboratories, requiring the use of high-performance liquid chromatography (HPLC). Purine derivatives in urinary calculi could be considered markers of abnormal purine metabolism. The content of a purine derivative in stone depends on its average urinary excretion in the general population, similarity to the chemical structure of uric acid, and content of the latter in stone. This suggests that purines in stones represent a solid solution with uric acid as solvent. It is also plausible that methylxanthines, ubiquitous components of the diet and drugs, are involved in the pathogenesis of urolithiasis. (PMID:11712316, 15833286, 3506820).
cis-4-Decenoyl-CoA is an intermediate of linoleic acid catabolism, degraded by a mitochondrial 4-enoyl-CoA reductase. (PMID: 729581). There are two 2,4-dienoyl-CoA reductases (formerly called 4-enoyl-CoA reductase) in liver, one in mitochondria and another one in peroxisomes. Isolated peroxisomes metabolize 4-cis-decenoyl-CoA via the 2,4-dienoyl-CoA reductase pathway. (PMID: 7263650).
5-Methyltetrahydropteroylpentaglutamate is a naturally occurring folate coenzyme; binds to an inhibits glyxine N-methyltransferase to regulate the availability of methyl groups in the liver (Journal of Biological Chemistry 264 (16): 9638-9642 JUN 5 1989 ).
3 hydroxycoumarin is a metabolite of coumarin. In particular, coumarin is metabolized by CYP3A4 to form 3-hydroxycoumarin (PMID 17286538).
O-b-D-glucopyranosyl-(1->3)-O-2-(acetylamino)-2-deoxy-b-D-glucopyranosyl-(1->3)-O-[6-deoxy-a-L-galactopyranosyl-(1->4)]-O-b-D-galactopyranosyl-(1->4)-O-[6-deoxy-a-L-galactopyranosyl-(1->3)]-D-Glucose is a lactose-derived oligosaccharide naturally found in human milk detected without prior derivatization or reduction by high-pH anion-exchange chromatography and pulsed amperometric detection (HPAEC-PAD). (PMID: 8953162).
Dimethyl sulfoxide (DMSO) is a key dipolar aprotic solvent. It is less toxic than other members of this class: dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, HMPA. Dimethyl sulfoxide is the chemical compound (CH3)2SO. This colorless liquid is an important "dipolar aprotic solvent." It is readily miscible in a wide range of organic solvents as well as water. It has a distinctive property of penetrating the skin very readily, allowing the handler to taste it. Some describe it as an "oyster-like" taste, others claim it tastes like garlic. DMSO is also employed as a rinsing agent in the electronics industry and, in its deuterated form (DMSO-d6), is a useful solvent in NMR due to its ability to dissolve a wide range of chemical compounds and its minimal interference with the sample signals. In cryobiology DMSO has been used as a cryoprotectant and is still an important constituent of cryoprotectant vitrification mixtures used to preserve organs, tissues, and cell suspensions. It is particularly important in the freezing and long-term storage of embryonic stem cells and hematopoietic stem cell, which are often frozen in a mixture of 10% DMSO and 90% fetal calf serum. As part of an autologous bone marrow transplant the DMSO is re-infused along with the patient's own hematopoietic stem cell. Dimethyl sulfoxide is a by-product of wood pulping. One of the leading suppliers of DMSO is the Gaylord company in the USA. DMSO is frequently used as solvent in a number of chemical reactions. In particular it is an excellent reaction solvent for SN2 alkylations: it is possible to alkylate indoles with very high yields using potassium hydroxide as the base and a similar reaction also occurs with phenols. DMSO can be reacted with methyl iodide to form a sulfoxonium ion which can be reacted with sodium hydride to form a sulfur ylide. The methyl groups of DMSO are somewhat acidic in character (pKa=35) due to the stabilization of the resultant anions by the sulfoxide group.
11-cis-retinal is a retinal having 2E,4Z,6E,8E-double bond geometry. It has a role as a chromophore, a human metabolite and a mouse metabolite. It is a diterpene derived from the carotenoid vitamin A which functions as the active component of the visual cycle. It is the prosthetic group of rhodopsin. When stimulated by visible light, rhodopsin transforms this cis-isomer of retinal to the trans-isomer (11-trans-retinal). This transformation straightens-out the bend of the retinal molecule and causes a change in the shape of rhodopsin triggering the visual process. A series of energy-requiring enzyme-catalyzed reactions convert the 11-trans-retinal back to the cis-isomer. 11-cis-retinal functions in the retina in the transduction of light into the neural signals necessary for vision. 11-cis-retinal, while attached to opsin in rhodopsin is isomerized to all-trans-retinal by light. This is the event that triggers the nerve impulse to the brain which allows for the perception of light. All-trans-retinal is then released from opsin and reduced to all-trans-retinol. All-trans-retinol is isomerized to 11-cis-retinol in the dark, and then oxidized to 11-cis-retinal. 11-cis-retinal recombines with opsin to re-form rhodopsin. Night blindness or defective vision at low illumination results from a failure to resynthesize 11-cis retinal rapidly.
Complex steroid in human breast milk that inhibits hepatic glucuronyl transferase (PMID: 4246186).
27-Norcholestanehexol is a bile alcohol. Bile alcohols have been found to be present as minor components in the bile and urine in healthy subjects. Bile alcohols are end products for cholesterol elimination as well as major biliary constituents; in mammals, cholesterol is metabolized by additional enzymes that ultimately transform it to bile acids. Bile alcohols are preferentially excreted as glucuronides into the urine, which constitute about 10% of total bile acids. The excretion of glucuronidated bile alcohols in urine is suggested to reflect an alternative metabolism of intermediates in the normal biosynthesis of bile acids. (PMID: 6548247, 11718684).
First activated by a fatty acyl-CoA ligase activity, can then be converted to chenodeoxycholic acid by peroxisome rich fractions from rat and human liver (J Lipid Res. 1988 Aug;29(8):997-1004, PMID 3183523 ).
Harderoporphyrinogen is an intermediate in the conversion of coproporphyrinogen III and protoporphyrinogen IX.
Trihydroxycoprostanoic acid is excreted in the urine of patients with Zellweger syndrome (PMID 7347441), a genetic disorder. The oxidation trihydroxycoprostanic acid is deficient in liver homogenates from patients with peroxisomal diseases (PMID 2576087). Trihydroxycoprostanoic acid is found to be associated with adrenoleukodystrophy (ALD), which is also an inborn error of metabolism.
3-methylbutyrolactone is lactone of 4-hydroxyisovaleric acid and it has been found in the urine of patients with isovaleric acidemia, an autosomal recessive genetic disorder of the enzyme isovaleryl-CoA dehydrogenase (PMID 6452974; PMID 6616835). Isovaleric acidemia is closely related to the genetic metabolic disorder Maple syrup urine disease.
Superoxide is the anionic form O2. It is important as the product of the one-electron reduction of dioxygen (oxygen gas), which occurs widely in nature. With one unpaired electron, the superoxide ion is a free radical. It is also paramagnetic. The biological toxicity of superoxide is due to its capacity to inactivate iron-sulfur cluster containing enzymes (which are critical in a wide variety of metabolic pathways), thereby liberating free iron in the cell, which can undergo fenton-chemistry and generate the highly reactive hydroxyl radical. In its HO2 form, superoxide can also initiate lipid peroxidation of polyunsaturated fatty acids. It also reacts with carbonyl compounds and halogenated carbons to create toxic peroxy radicals. As such, superoxide is a main cause of oxidative stress. Highly reactive compounds produced when oxygen is reduced by a single electron. In biological systems, they may be generated during the normal catalytic function of a number of enzymes and during the oxidation of hemoglobin to Methemoglobin. Because superoxide is toxic, nearly all organisms living in the presence of oxygen contain isoforms of the superoxide scavenging enzyme, superoxide dismutase, or SOD. SOD is an extremely efficient enzyme; it catalyzes the neutralization of superoxide nearly as fast as the two can diffuse together spontaneously in solution. Genetic inactivation ("knockout") of SOD produces deleterious phenotypes in organisms ranging from bacteria to mice. The latter species dies around 21 days after birth if the mitochondrial variant of SOD (Mn-SOD) is inactivated, and suffers from multiple pathologies, including reduced lifespan, liver cancer, muscle atrophy, cataracts and female infertility when the cytoplasmic (Cu, Zn -SOD) variant is inactivated. With one unpaired electron, the superoxide ion is a free radical and therefore paramagnetic. In living organisms, superoxide dismutase protects the cell from the deleterious effects of superoxides.
S-(2-carboxypropyl)-Cysteamine enhances the procoagulant activity of factor VIII-East Hartford, a dysfunctional protein due to a light chain thrombin cleavage site mutation (PMID 1569180). S-(2-carboxypropyl)-Cysteamine is known to modify mutant proteins with an arg-to-cys substitution (PMID 1569181).
Malonyl-CoA semialdehyde is involved in the propanoate metabolism pathway. Malonyl-CoA semialdehyde can be reversibly produced from malonyl-CoA and 3-hydroxy-propionyl-CoA. Malonic semialdehyde is formed in the alternative pathway of propionate metabolism and in the catabolism of beta-alanine. Studies of these pathways in cultured cells from a patient with mitochondrial malonyl-CoA decarboxylase deficiency indicate that malonic semialdehyde is directly converted into acetyl-CoA in man. (PMID: 6418146).
Glycylprolylhydroxyproline is a tripeptide that has been found in urine and blood serum (PMID: 5134921). In growing children, higher level excretion of urinary hydroxyproline peptides (including glycylprolylhydroxyproline) has been observed (PMID: 14105582).
N1,N12-Diacetylspermine is a polyamine commonly occurring in normal human urine (PMID 7775374). It has been reported that urinary N1,N12-Diacetylspermine can be used as a marker to efficiently detect colorectal and breast cancers at early stages (PMID 15837752). N1,N12-Diacetylspermine has been identified in the human placenta (PMID: 32033212).
Solerol, also known as 4,5-dihydroxyhexanoic acid lactone, is a volatile component originally identified in extracts of grape wines and numerous fruits, with aroma being among the most important factors in determining wine character and quality (PMID: 11052736 ). Solerol (4,5-dihydroxyhexanoic acid lactone) also appears to be a marker for Succinic semialdehyde dehydrogenase (SSADH) deficiency and probably arises from the reaction of succinic semialdehyde with an intermediate in the pyruvate dehydrogenase pathway (PMID: 3126356 ). SSADH is a disorder that arises from a defect in gamma-aminobutyric acid catabolism, resulting in the accumulation of gamma-hydroxybutyric acid (GHB), 2,4-dihydroxybutyric acid, adipic acid as well as elevated levels of 4,5-dihydroxyhexanoic acid, and 4,5-dihydroxyhexanoic acid lactone and causing neurological and cognitive disorders of varying severity (PMID: 3126356 ). Children with SSADH deficiency usually manifest with developmental delay, behavioral symptoms, language dysfunction, seizures, hypotonia, extrapyramidal symptoms, and ataxia (PMID: 32055132).
Ethylmethylacetic acid, also known as alpha-methyl butyric acid or a-methyl butyrate, belongs to the class of organic compounds known as methyl-branched fatty acids. These are fatty acids with an acyl chain that has a methyl branch. Usually, they are saturated and contain only one or more methyl group. However, branches other than methyl may be present. Ethylmethylacetic acid is a very hydrophobic molecule, practically insoluble in water, and relatively neutral.
Cis-8,11,14,17-Eicosatetraenoic acid is an eicosanoid present in marine lipids, a minor n-3 polyunsaturated fatty acid (PUFA) which is a position isomer of 20:4n-6. n-3 PUFA contained in marine lipids appear to have a protective effect against coronary heart disease and thrombosis. Human platelets metabolize 8,11,14,17-eicosatetraenoic acid primarily into 12-hydroxy-8,10,14,17-eicosatetraenoic acid. The eicosanoids are a diverse family of molecules that have powerful effects on cell function. They are best known as intercellular messengers, having autocrine and paracrine effects following their secretion from the cells that synthesize them. The diversity of possible products that can be synthesized from eicosatrienoic acid is due, in part to the variety of enzymes that can act on it. Studies have placed many, but not all, of these enzymes at or inside the nucleus. In some cases, the nuclear import or export of eicosatrienoic acid-processing enzymes is highly regulated. Furthermore, nuclear receptors that are activated by specific eicosanoids are known to exist. Taken together, these findings indicate that the enzymatic conversion of eicosatrienoic acid to specific signaling molecules can occur in the nucleus, that it is regulated, and that the synthesized products may act within the nucleus. PMID: 3109494, 8142566, 16574479, 15896193, 10037447). Trans fatty acids are characteristically produced during industrial hydrogenation of plant oils.
3a,7a,12a-Trihydroxy-5b-cholestanoyl-CoA is an intermediate in the Bile acid biosynthesis pathway (KEGG). C27-bile acyl-CoAs are converted to their (S)-stereoisomers by the enzyme Alpha-methylacyl-CoA racemase (OMIM 604489).
Peroxynitrite is a potent oxidant synthesized by the cell during its normal metabolism. The peroxynitrite anion (ONOO-) is a reactive species produced in the reaction between the superoxide anion (O2*-) and nitric oxide (*NO). Peroxynitrite (ONOO-) is a strong oxidation and nitration agent, which damages DNA, proteins and other cellular structures. ONOO- is involved in several pathological conditions such as inflammation, arteriosclerosis, and neurodegenerative and cardiovascular disorders. ONOO- inhibits different steps of blood platelet activation and causes the depletion of platelet thiols. (PMID 15647782).
5b-Cholestane-3a,7a,12a,25,26-pentol is a bile alcohol. Bile alcohols have been found to be present as minor components in the bile and urine in healthy subjects. Bile alcohols are end products for cholesterol elimination as well as major biliary constituents; in mammals, cholesterol is metabolized by additional enzymes that ultimately transform it to bile acids. Bile alcohols are preferentially excreted as glucuronides into the urine, which constitute about 10% of total bile acids. Large amounts of bile alcohols have been found to be excreted into the bile and urine in patients with cerebrotendinous xanthomatosis (CTX), a rare inherited lipid storage disease. (PMID: 11718684).
Phytoene, also known as 7,7',8,8',11,11',12,12'-octahydrocarotene, is a carotenoid found in human fluids. Carotenoids are isoprenoid molecules that are widespread in nature and are typically seen as pigments in fruits, flowers, birds, and crustacea. Animals are unable to synthesize carotenoids de novo, and rely upon the diet as a source of these compounds. Over recent years there has been considerable interest in dietary carotenoids with respect to their potential in alleviating age-related diseases in humans. This attention has been mirrored by significant advances in cloning most of the carotenoid genes and in the genetic manipulation of crop plants with the intention of increasing levels in the diet. Studies have shown an inverse relationship between the consumption of certain fruits and vegetables and the risk of epithelial cancer. Since carotenoids are among the micronutrients found in cancer-preventive foods, detailed qualitative and quantitative determination of these compounds, particularly in fruits and vegetables and in human plasma, have recently become increasingly important (PMID: 1416048, 15003396).
Phenylephrine is an alpha-adrenergic agonist used as a mydriatic, nasal decongestant, and cardiotonic agent (PubChem). Phenylephrine is used as a decongestant, available as an oral medicine or as a nasal spray. Phenylephrine is not the most common over-the-counter (OTC) decongestant (wikipedia).
Docosahexaenoic acid (DHA) is an omega-3 essential fatty acid. Chemically, DHA is a carboxylic acid with a 22-carbon chain and six cis- double bonds with the first double bond located at the third carbon from the omega end. DHA is most often found in fish oil. It is a major fatty acid in sperm and brain phospholipids, especially in the retina. Dietary DHA can reduce the level of blood triglycerides in humans, which may reduce the risk of heart disease (Wikipedia). Docosahexaenoic acid is found to be associated with isovaleric acidemia, which is an inborn error of metabolism.
Incorporated into the benzoyl moiety of urinary hippuric acid.
3-trans,5-cis-Octadienoyl-CoA is a metabolite formed during the beta-oxidation of unsaturated fatty acids with double bonds extending from odd-numbered carbon atoms by mitochondrial delta 3,delta 2-enoyl-CoA isomerase (EC 5.3.3.8) from 2-trans-5-cis-octadienoyl-CoA. 2-trans-5-cis-octadienoyl-CoA is formed by medium-chain acyl-CoA dehydrogenase (EC 1.3.99.3) from 5-cis-Octenoyl-CoA, a putative metabolite of linolenic acid.(PMID 1495956).
Hypogeic acid is a fatty acids found in human milk Approximately 50% of the dietary calories in human milk are supplied to new-borns as fat. More than 98% of this milk fat is in the form of triglycerides, which contain fatty acid glycerol esters. Fatty acid composition in human milk changes in colostrum, transitional milk and mature milk. Knowledge of fatty acid composition of human milk is of importance for the manufacture of infant formulas, determination of the influence of diet in fatty acid composition of human milk and changes in composition with lactation. (CAN 136:246580, AN 2002:67899).
N8-Acetylspermidine is a polyamine. The polyamines, found in virtually all living organisms, are a ubiquitous group of compounds that appear to play a vital role in many cellular processes involving nucleic acids including cell growth and differentiation. Acetylation on the terminal nitrogen adjacent to the 4-carbon chain produces N8-acetylspermidine. This reaction is catalyzed by spermidine N8-acetyltransferase and does not result in the conversion of spermidine to putrescine. Instead, the product undergoes deacetylation. This acetyltransferase appears to be associated with chromatin in the cell nucleus and has been reported to be the same as (or related to) the enzyme(s) responsible for histone acetylation. N8-Acetylspermidine does not accumulate in tissues but rather appears to be rapidly deacetylated back to spermidine by a relatively specific cytosolic deacetylase, N8-acetylspermidine deacetylase. The function of this N8-acetylation/deacetylation pathway in cellular processes is not understood clearly, but several observations have suggested a role in cell growth and differentiation (PMID: 12093478).
5,6-Epoxy-8,11,14-eicosatrienoic acid is an Epoxyeicosatrienoic acid (EET), a metabolite of arachidonic acid. The epoxyeicosatrienoic acids (EETs) are endogenous lipid mediators produced by P450 epoxygenases and metabolized through multiple pathways including soluble epoxide hydrolase (sEH). The cytochrome P-450 (P450) monooxygenase pathway includes enzymes of the CYP1A, CYP2B, CYP2C, CYP2E, and CYP2J subfamilies that catalyze the formation of four regioisomeric products, 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid. EETs are produced in brain and perform important biological functions, including protection from ischemic injury. Both light flashes and direct glial stimulation produce vasodilatation mediated by EETs. EETs may be involved in the development of hypertension and endothelial dysfunction in DOCA-salt rats, but not in excessive collagen deposition or electrophysiological abnormalities. EETs have vasodilator and natriuretic effect. Blockade of EET formation is associated with salt-sensitive hypertension. (PMID: 17494091, 17468203, 17434916, 17406062, 17361113).
Carotene-3,3'-dione is a carotenoid found in human fluids. Carotenoids are isoprenoid molecules that are widespread in nature and are typically seen as pigments in fruits, flowers, birds and crustacea. Animals are unable to synthesise carotenoids de novo, and rely upon the diet as a source of these compounds. Over recent years there has been considerable interest in dietary carotenoids with respect to their potential in alleviating age-related diseases in humans. This attention has been mirrored by significant advances in cloning most of the carotenoid genes and in the genetic manipulation of crop plants with the intention of increasing levels in the diet. Studies have shown an inverse relationship between the consumption of certain fruits and vegetables and the risk of epithelial cancer. Since carotenoids are among the micronutrients found in cancer preventive foods, detailed qualitative and quantitative determination of these compounds, particularly in fruits and vegetables and in human plasma, have recently become increasingly important. (PMID: 1416048, 15003396).
N-acetyl-S-(3-oxo-3-carboxy-n-propyl)cysteine is a cystathione metabolite found in the urine of patients with cystathionuria (PMID 8750604 ).
Varanic acid is a bile acid that will accumulate in patients with deficiencies in the peroxisomal d-bifunctional protein. The final steps in bile acid biosynthesis take place in peroxisomes and involve oxidative cleavage of the side chain of C27-5beta-cholestanoic acids leading to the formation of the primary bile acids cholic acid and chenodeoxycholic acid. The enoyl-CoA hydratase and beta-hydroxy acyl-CoA dehydrogenase reactions involved in the chain shortening of C27-5beta-cholestanoic acids are catalyzed by peroxisomal d-bifunctional protein. (PMID: 9831634).
7a,12a-Dihydroxy-cholestene-3-one is an intermediate in bile acid synthesis; is considerably higher in patients with cerebrotendinous xanthomatosis (CTX) than in the normal liver. (PMID 7017048).
(3R,3'R,6'R,9-cis)-beta,epsilon-Carotene-3,3'-diol is a carotenoid found in human fluids such as serum and breast milk (PMID: 9164160). Carotenoids are isoprenoid molecules that are widespread in nature and are typically seen as pigments in fruits, flowers, birds and crustacea. Animals are unable to synthesise carotenoids de novo, and rely upon the diet as a source of these compounds. Over recent years there has been considerable interest in dietary carotenoids with respect to their potential in alleviating age-related diseases in humans. This attention has been mirrored by significant advances in cloning most of the carotenoid genes and in the genetic manipulation of crop plants with the intention of increasing levels in the diet. Studies have shown an inverse relationship between the consumption of certain fruits and vegetables and the risk of epithelial cancer. Since carotenoids are among the micronutrients found in cancer preventive foods, detailed qualitative and quantitative determination of these compounds, particularly in fruits and vegetables and in human plasma, have recently become increasingly important (PMID: 1416048, 15003396).
Desaminotyrosine, also known as 4-hydroxyphenylpropionic acid, is a normal constituent of human urine. It is a product of tyrosine metabolism; its concentration in urine increases in patients with gastrointestinal diseases. Desaminotyrosine is a major phenolic acid breakdown product of proanthocyanidin metabolism (PMID:15315398). Urinary desaminotyrosine is produced by Clostridium sporogenes and C. botulinum (PMID:29168502). Desaminotyrosine is also found in Acinetobacter, Bacteroides, Bifidobacteria, Bifidobacterium, Clostridium, Enterococcus, Escherichia, Eubacterium, Klebsiella, Lactobacillus, Pseudomonas, and Staphylococcus (PMID:29168502, 28393285, 19961416). Desaminotyrosine is a phenolic acid metabolite formed by the gut microflora detected after the consumption of whole grain.