The metabolism of S-carboxyalkylcysteines in man.

1. The ingestion of S-(2-carboxy-1-methylethyl)-, S-(2- carboxy-1-methylpropyl)-, S-(1-carboxy-2methylpropyl)- and S-(2-carboxyethyl)-L-cysteine by man was followed by the excretion in the urine of the unchanged amino acid and the N-acetylated compounds. 2. In the rat the fraction of S-(2-carboxy-1-methylethyl)-L-[U-14C]cysteine acetylated increased as the dose level decreased. 3. The significance of these results for the excretion of S-carboxyalkyl-cysteines in man is discussed.