N-Acetyl-L-glutamic acid or N-Acetylglutamate, belongs to the class of organic compounds known as N-acyl-alpha amino acids. N-acyl-alpha amino acids are compounds containing an alpha amino acid which bears an acyl group at its terminal nitrogen atom. N-Acetyl-L-glutamate can also be classified as an alpha amino acid or a derivatized alpha amino acid. Technically, N-Acetyl-L-glutamate is a biologically available N-terminal capped form of the proteinogenic alpha amino acid L-glutamic acid. N-Acetyl-L-glutamic acid is found in all organisms ranging from bacteria to plants to animals. N-acetyl amino acids can be produced either via direct synthesis of specific N-acetyltransferases or via the proteolytic degradation of N-acetylated proteins by specific hydrolases. N-terminal acetylation of proteins is a widespread and highly conserved process in eukaryotes that is involved in protection and stability of proteins (PMID: 16465618).  About 85% of all human proteins and 68% of all yeast proteins are acetylated at their N-terminus (PMID: 21750686). Several proteins from prokaryotes and archaea are also modified by N-terminal acetylation. The majority of eukaryotic N-terminal-acetylation reactions occur through N-acetyltransferase enzymes or NAT‚Äôs (PMID: 30054468).  These enzymes consist of three main oligomeric complexes NatA, NatB, and NatC, which are composed of at least a unique catalytic subunit and one unique ribosomal anchor. The substrate specificities of different NAT enzymes are mainly determined by the identities of the first two N-terminal residues of the target protein. The human NatA complex co-translationally acetylates N-termini that bear a small amino acid (A, S, T, C, and occasionally V and G) (PMID: 30054468). NatA also exists in a monomeric state and can post-translationally acetylate acidic N-termini residues (D-, E-). NatB and NatC acetylate N-terminal methionine with further specificity determined by the identity of the second amino acid.  N-acetylated amino acids, such as N-acetylglutamate can be released by an N-acylpeptide hydrolase from peptides generated by proteolytic degradation (PMID: 16465618). In addition to the NAT enzymes and protein-based acetylation, N-acetylation of free glutamic acid can also occur. In particular, N-Acetyl-L-glutamic acid can be biosynthesized from glutamate and acetylornithine by ornithine acetyltransferase, and from glutamic acid and acetyl-CoA by the enzyme known as N-acetylglutamate synthase. N-Acetyl-L-glutamic acid is the first intermediate involved in the biosynthesis of arginine in prokaryotes and simple eukaryotes and a regulator of the urea cycle in vertebrates. In vertebrates, N-acetylglutamic acid is the allosteric activator molecule to mitochondrial carbamyl phosphate synthetase I (CPSI) which is the first enzyme in the urea cycle. It triggers the production of the first urea cycle intermediate, a compound known as carbamyl phosphate. Notably the CPSI enzyme is inactive when N-acetylglutamic acid is not present. A deficiency in N-acetyl glutamate synthase or a genetic mutation in the gene coding for the enzyme will lead to urea cycle failure in which ammonia is not converted to urea, but rather accumulated in the blood leading to the condition called Type I hyperammonemia. Excessive amounts N-acetyl amino acids can be detected in the urine with individuals with aminoacylase I deficiency, a genetic disorder (PMID: 16465618). These include N-acetylalanine (as well as N-acetylserine, N-acetylglutamine, N-acetylglutamate, N-acetylglycine, N-acetylmethionine and smaller amounts of N-acetylthreonine, N-acetylleucine, N-acetylvaline and N-acetylisoleucine. Aminoacylase I is a soluble homodimeric zinc binding enzyme that catalyzes the formation of free aliphatic amino acids from N-acetylated precursors. In humans, Aminoacylase I is encoded by the aminoacylase 1 gene (ACY1) on chromosome 3p21 that consists of 15 exons (OMIM 609924). Individuals with aminoacylase I deficiency will experience convulsions, hearing loss and difficulty feeding (PMID: 16465618). ACY1 can also catalyze the reverse reaction, the synthesis of acetylated amino acids. Many N-acetylamino acids are classified as uremic toxins if present in high abundance in the serum or plasma (PMID: 26317986; PMID: 20613759). Uremic toxins are a diverse group of endogenously produced molecules that, if not properly cleared or eliminated by the kidneys, can cause kidney damage, cardiovascular disease and neurological deficits (PMID: 18287557).