S-Methylcysteine
S-Methylcysteine is the amino acid with the nominal formula CH3SCH2CHCO2H. It is the S-methylated derivative of cysteine. This amino acid occurs widely in plants, including many edible vegetables.
Natural occurrence
S-Methylcysteine is not genetically coded, but it arises by post-translational methylation of cysteine. One pathway involves methyl transfer from alkylated DNA by zinc-cysteinate-containing repair enzymes such as methylated-DNA-protein-cysteine methyltransferase.S-Methylcysteine sulfoxide is an oxidized derivative of S-methylcysteine that is found in onions.
MetaCyc contains a list of biochemical reactions producing and consuming this substance.