Mercapturic acid formation from glutathione conjugates in the body involves processing in which organ?

• A. In the liver
• B. In the kidney
• C. In the intestine
• D. In the brain

Answer: (B)

Mercapturic acids are produced through the glutathione detoxification pathway, and the final steps occur in the kidney. While glutathione conjugation can start in the liver, the conversion to mercapturic acid requires trimming of the gamma-glutamyl and glycine residues and acetylation in the renal proximal tubule. Gamma‑glutamyl transpeptidase removes the gamma-glutamyl group, aminopeptidases release glycine to give a cysteine conjugate, and N-acetyltransferase acetylates it to form the mercapturic acid (N-acetylcysteine conjugate), which is then excreted in urine. Thus, the kidney is the site where mercapturic acid formation predominantly occurs.