Mercapturic acids are condensation products formed from the coupling of cysteine with aromatic compounds.[1] They are formed as conjugates in the liver and are excreted in the urine.[1][2]
Mercapturic acids are formed as part of xenobiotic metabolism. A glutathione S-transferase first conjugates the foreign compound to glutathione, forming an adduct. The adduct is then converted to the mercapturic acid: the γ-glutamate and glycine residues in the glutathione molecule are removed by gamma-glutamyl transpeptidase and dipeptidases. In the final step, the cystine residue in the conjugate is acetylated. The mercapturic acid is then excreted.[3]
Levels of mercapturic acids in urine may be used as an indicator of exposure to, e.g., ethylene dibromide,[4] acrylamide, and terbuthylazine.[5]
Etymology
The name mercapturic acid is a combination of mercapturic and acid. The latter indicates that the compound is an acid. The former is a compound word consisting of the stem mercaptur-, coming from mercaptan, and the suffix -ic, meaning "having the character of". In sum, the name mercapturic acid means "an acid with mercaptan character/nature".[6]
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