Cysteine (abbreviated as Cys or C)[3] is a semi-essential[4] proteinogenic amino acid with the formula HO2CCH(NH2)CH2SH>. It is encoded by the codons UGU and UGC. The thiol side chain in Cys 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.
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IUPAC name
Cysteine
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Other names
2-Amino-3-sulfhydrylpropanoic acid
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CAS Number
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52-90-4 52-89-1 (hydrochloride) |
ChEBI | CHEBI:15356 |
ChEMBL | ChEMBL54943 |
ChemSpider | 574 (Racemic) 5653 (L-form) |
EC Number | 200-158-2 |
IUPHAR/BPS
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4782 |
Jmol interactive 3D | Image Image |
KEGG | D00026 |
PubChem | 5862 |
UNII | K848JZ48867ujtytyjtyjjtyjtyrj |
InChI[show]
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SMILES[show]
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Chemical formula
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C3H7NO2S |
Molar mass | 121.15 g·mol−1 |
Appearance | white crystals or powder |
Melting point | 240 °C (464 °F; 513 K) decomposes |
Solubility in water
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soluble |
Solubility | 1.5g/100g ethanol 19 degC [1] |
Chiral rotation ([α]D)
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+9.4° (H2O, c = 1.3) |
Structure and
properties |
Refractive index (n), Dielectric constant (εr), etc. |
Thermodynamic
data |
Phase behaviour solid–liquid–gas |
Spectral data
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UV, IR, NMR, MS |