Cysteine
Cysteine (abbreviated as Cys or C)[1] is an α-amino acid. It has the chemical formula HO2CCH(NH2)CH2SH.
| L-Cysteine | |
|---|---|
| |
 |
 |
| IUPAC name | Cysteine |
| Other names | 2-Amino-3-sulfhydrylpropanoic acid |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
Cysteine is a semi-essential amino acid, which means that humans can make it.[2] The codons UGU and UGC code for cysteine. The thiol side chain in cysteine often does enzyme reactions as a nucleophile. The thiol oxidises to give the disulfide derivative cystine, which is important in many protein structures. When used as a food additive, cysteine has the E number E920.
Cysteine Media
(R)-Cysteine (left) and (S)-Cysteine (right) in zwitterionic form at neutral pH
Cysteine synthesis: Cystathionine beta synthase catalyzes the upper reaction and cystathionine gamma-lyase catalyzes the lower reaction.
Figure 2: Cystine (shown here in its neutral form), two cysteines bound together by a disulfide bond
References
- ↑ Nomenclature and symbolism for amino acids and peptides (IUPAC-IUB Recommendations 1983). Pure Appl. Chem. 56 (5), 1984: 595–624.
- ↑ "The primary structure of proteins is the amino acid sequence". The Microbial World. University of Wisconsin-Madison Bacteriology Department. Archived from the original on 25 May 2013. Retrieved 16 September 2012.