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Cysteine

L-Cysteine
L-Cystein - L-Cysteine.svg
L-cysteine-3D-balls2.png
L-cysteine-3D-vdW2.png
Names
IUPAC name
Cysteine
Other names
2-Amino-3-sulfhydrylpropanoic acid
Identifiers
52-90-4 YesY
52-89-1 (hydrochloride) N
3D model (Jmol) Interactive image
Interactive image
ChEBI CHEBI:15356 YesY
ChEMBL ChEMBL54943 YesY
ChemSpider 574 (Racemic) YesY
5653 (L-form) YesY
ECHA InfoCard 100.000.145
EC Number 200-158-2
E number E920 (glazing agents, ...)
4782
KEGG D00026 YesY
PubChem 5862
UNII K848JZ4886 YesY
Properties
C3H7NO2S
Molar mass 121.15 g·mol−1
Appearance white crystals or powder
Melting point 240 °C (464 °F; 513 K) decomposes
soluble
Solubility 1.5g/100g ethanol 19 degC
+9.4° (H2O, c = 1.3)
Supplementary data page
Refractive index (n),
Dielectric constantr), etc.
Thermodynamic
data
Phase behaviour
solid–liquid–gas
UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Cysteine (abbreviated as Cys or C) is a semi-essentialproteinogenic 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.

Although classified as a non-essential amino acid, in rare cases, cysteine may be essential for infants, the elderly, and individuals with certain metabolic disease or who suffer from malabsorption syndromes. Cysteine can usually be synthesized by the human body under normal physiological conditions if a sufficient quantity of methionine is available. Cysteine is catabolized in the gastrointestinal tract and blood plasma. In contrast, cystine travels safely through the GI tract and blood plasma and is promptly reduced to the two cysteine molecules upon cell entry.

Cysteine is found in most high-protein foods, including:


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Wikipedia

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