Mevalonic acid, also known as MVA, mevalonate, or hiochic 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. Mevalonic acid is a key organic compound in biochemistry. It is found in most higher organisms ranging from plants to animals. Mevalonic acid is a precursor in the biosynthetic pathway known as the mevalonate pathway that produces terpenes (in plants) and steroids (in animals). Mevalonic acid is the primary precursor of isopentenyl pyrophosphate (IPP), that is in turn the basis for all terpenoids. The production of mevalonic acid by the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, is the rate-limiting step in the biosynthesis of cholesterol (PMID: 12872277). The cholesterol biosynthetic pathway has three major steps: (1) acetate to mevalonate, (2) mevalonate to squalene, and (3) squalene to cholesterol. In the first step, which catalyzed by thiolase, two acetyl-CoA molecules form acetoacetyl-CoA and one CoA molecule is released, then the acetoacetyl-CoA reacts with another molecule of acetyl-CoA and generates 3-hydroxy-3-methylglutaryl-CoA (HMGCoA). The enzyme responsible for this reaction is 3-hydroxy-3-methylglutaryl-CoA synthase (HMG-CoA synthase): In the pathway to synthesize cholesterol, one of the HMG-CoA carboxyl groups undergoes reduction to an alcohol, releasing CoA, leading to the formation of mevalonate, a six carbon compound. This reaction is catalyzed by hydroxy-methylglutaryl-CoA reductase, In the second step (mevalonate to squalene) mevalonate receives a phosphoryl group from ATP to form 5-phosphomevalonate. This compound accepts another phosphate to generate mevalonate-5-pyrophosphate. After a third phosphorylation, the compound is decarboxylated, loses water, and generates isopentenyl pyrophosphate (IPP). Then through successive condensations, IPP forms squalene, a terpene hydrocarbon that contains 30 carbon atoms. By cyclization and other changes, this compound will finally result in cholesterol. Mevalonic acid is found, on average, in the highest concentration within a few different foods, such as apples, corns, and wild carrots and in a lower concentration in garden tomato (var.), pepper (C. frutescens), and cucumbers. Mevalonic acid has also been detected, but not quantified in, several different foods, such as sweet oranges, potato, milk (cow), cabbages, and white cabbages. This could make mevalonic acid a potential biomarker for the consumption of these foods. Plasma concentrations and urinary excretion of MVA are decreased by HMG-CoA reductase inhibitor drugs such as pravastatin, simvastatin, and atorvastatin (PMID: 8808497).