''S''-Methylcysteine is the

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

with the nominal formula CH₃SCH₂CH(NH₂)CO₂H. It is the S-methylated derivative of

cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. When present as a deprotonated catalytic residue, sometime ...

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

Biosynthesis

The amino acid is not genetically coded, but it arises by

post-translational Post-translational modification (PTM) is the covalent and generally enzymatic modification of proteins following protein biosynthesis. This process occurs in the endoplasmic reticulum and the golgi apparatus. Proteins are synthesized by ribosom ...

methylation In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These t ...

of cysteine. One pathway involves methyl transfer from alkylated DNA by zinc-cysteinate-containing repair enzymes. Beyond its biological context, it has been examined as a

chelating agent Chelation is a type of bonding of ions and molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central metal atom. These ligands are ...

References

{{DEFAULTSORT:Methylcysteine, S- Biochemistry Sulfur amino acids Thioethers Amino acid derivatives