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Topic summary

Cysteine

Cysteine
Names IUPAC name
Cysteine
Systematic IUPAC name
2-Amino-3-sulfanylpropanoic acid
Other names
  • 2-Amino-3-sulfhydrylpropanoic acid
  • 2-Amino-3-mercaptopropanoic acid
Identifiers
3D model (JSmol)
Abbreviations Cys, C ChEBI
ChEMBL
ChemSpider
ECHA InfoCard100.000.145EC Number
  • 200-158-2
E numberE920 (glazing agents, ...)
KEGG
UNII
  • InChI=1S/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)
    Key: XUJNEKJLAYXESH-UHFFFAOYSA-N
  • InChI=1/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)/t2-/m0/s1
    Key: XUJNEKJLAYXESH-REOHCLBHBU
  • InChI=1/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)
    Key: XUJNEKJLAYXESH-UHFFFAOYAC
  • C([C@@H](C(=O)O)N)S
  • Zwitterion: C([C@@H](C(=O)[O-])[NH3+])S
Properties C3H7NO2SMolar mass121.15 g·mol Appearance white crystals or powder Melting point240 °C (464 °F; 513 K) decomposes 277g/L (at 25 °C) Solubility1.5g/100g ethanol 19 °C Acidity (pKa) 1.71 (conjugate acid), 8.33 (thiol), 10.78 +9.4° (H2O, c = 1.3) Supplementary data page Cysteine (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Cysteine (; symbol Cys or C) is a semiessential proteinogenic amino acid with the formulaHS−CH2−CH(NH2)−COOH. The thiol side chain in cysteine enables the formation of disulfide bonds, and often participates in enzymatic reactions as a nucleophile. Cysteine is chiral, but both D- and L-cysteine are found in nature. L‑Cysteine is a protein monomer in all biota, and D-cysteine acts as a signaling molecule in mammalian nervous systems. Cysteine is named after its discovery in urine, which comes from the urinary bladder or cyst, from Greek κύστις kýstis, "bladder".

The thiol is susceptible to oxidation to give the disulfide derivative cystine, which serves an important structural role in many proteins. In this case, the symbol Cyx is sometimes used. The deprotonated form can generally be described by the symbol Cym as well.

When used as a food additive, cysteine has the E number E920.

Cysteine is encoded by the codons UGU and UGC.

Wikipedia source