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. ==Other chemical properties==