Cysteine, Methionine - Amino Acids Containing Sulfur


Cysteine and methionine are the only proteinogenic amino acids with functional groups containing sulfur. They are both important in the complexation of metal centers.

Especially enzyme centers with "thiophilic" metals like zinc, copper and iron often contain these amino acids. Exceptionally high concentrations of cysteine are found in the so-called metallothioneins.