Cysteine (C)

Cysteine (abbreviated as Cys or C) is a semi-essential proteinogenic amino acid with the formula HO2CCH(NH2)CH2SH. It is encoded by the codons UGU and UGC. The thiol side chain in cysteine often participates in enzymatic reactions, as a nucleophile. The thiol is susceptible to oxidization to give the disulfide derivative cystine, which serves an important structural role in many proteins. When used as a food additive, it has the E number E920.It can be seen as serine, but with one of the oxygen atoms replaced with sulfur; replacing said atom with selenium gives selenocysteine.body{zoom:85%!important;}