Cysteine to 3-Thiolpyruvic Acid

Like methionine, cysteine as an a-amino acid can undergo oxidative deamination, giving rise to jS-thiolpyruvic acid. This reaction takes places through the action of the same enzymes, the d-amino acid oxidase, and the /-amino acid oxidases, which act on methionine and which have been discussed on page 374. No facts are available on the fate of the keto acid in question which apparently does not seem to play an important role in the formation of sulfate or taurine. 

Like cysteine, cystine is both a primary substance of animal metabolism and an intermediary in the transformations in which methionine or cysteine form the starting materials. 

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