has part has part has role cysteine cisteina Cystein Cysteine KNApSAcK:C00001351 Wikipedia:Cysteine C CHEBI:15356 2-amino-3-sulfanylpropanoic acid KEGG:C00736 CHEBI:14061 CHEBI:4050 2-amino-3-mercaptopropanoic acid KNApSAcK:C00007323 Zystein CHEBI:23508 cysteine Cys 2-Amino-3-mercaptopropionic acid A sulfur-containing amino acid that is propanoic acid with an amino group at position 2 and a sulfanyl group at position 3. Hcys polar amino acid sulfur-containing amino acid cysteinate(1-) cysteinium alpha-amino acid cysteine zwitterion sulfanylmethyl group fundamental metabolite