S-Methylcysteine is the amino acid with the nominal formula CH3SCH2CH(NH2)CO2H.

This amino acid occurs widely in plants, including many edible vegetables.

[1] 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.

[4] Beyond its biological context, S-methylcysteine has been examined as a chelating agent.