Cysteine

l-Cysteine
	Skeletal formula of L-cysteine
Ball-and-stick model	Space-filling model
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
CAS Number	52-90-4 ; 52-89-1 (hydrochloride) ; 921-01-7 D-cysteine;
3D model (JSmol)	Interactive image; Zwitterion: Interactive image;
Abbreviations	Cys, C
ChEBI	CHEBI:15356 ;
ChEMBL	ChEMBL54943 ;
ChemSpider	574 (Racemic) ; 5653 (L-form) ;
ECHA InfoCard	100.000.145
EC Number	200-158-2;
E number	E920 (glazing agents, ...)
IUPHAR/BPS	4782;
KEGG	D00026 ;
PubChem CID	5862;
UNII	K848JZ4886 ; A9U1687S1S (hydrochloride) ;
CompTox Dashboard (EPA)	DTXSID8022876 ;
	InChI 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;
	SMILES C([C@@H](C(=O)O)N)S; Zwitterion: C([C@@H](C(=O)[O-])[NH3+])S;
Properties
Chemical formula	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	277g/L (at 25 °C)
Solubility	1.5g/100g ethanol 19 °C
Acidity (pKa)	1.71 (conjugate acid), 8.33 (thiol), 10.78
Chiral rotation ([α]D)	+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). verify (what is ?) Infobox references

Cysteine (/ˈsɪstɪiːn/;^[5] symbol Cys or C^[6]) is a semiessential^[7] proteinogenic amino acid with the formula HS−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.^[8] Cysteine is named after its discovery in urine, which comes from the urinary bladder or cyst, from Greek κύστις kýstis, "bladder".^[9]

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.^[10]^[11] The deprotonated form can generally be described by the symbol Cym as well.^[11]^[10]

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

Cysteine is encoded by the codons UGU and UGC.

^ "PubChem data".
^ Belitz, H.-D; Grosch, Werner; Schieberle, Peter (2009-02-27). Food Chemistry. Springer. ISBN 9783540699330.
^ Kirste, Burkhard (23 Jan 1998). "Cysteine Archived 2016-11-10 at the Wayback Machine". Overview of Amino Acids. Free University of Berlin Dep't. of Biology, Chemistry, and Pharmacy.
^ Weast, Robert C., ed. (1981). CRC Handbook of Chemistry and Physics (62nd ed.). Boca Raton, Florida: CRC Press. p. C-259. ISBN 0-8493-0462-8..
^ "cysteine - Definition of cysteine in English by Oxford Dictionaries". Oxford Dictionaries - English. Archived from the original on September 25, 2016. Retrieved 15 April 2018.
^ "Nomenclature and symbolism for amino acids and peptides (IUPAC-IUB Recommendations 1983)". Pure and Applied Chemistry. 56 (5): 595–624. 1984. doi:10.1351/pac198456050595.
^ "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.
^ Semenza, Evan R.; Harraz, Maged M.; Abramson, Efrat; Malla, Adarsha P.; Vasavda, Chirag; Gadalla, Moataz M.; Kornberg, Michael D.; Snyder, Solomon H.; Roychaudhuri, Robin (23 Sep 2021) [18 Aug 2021]. "D-cysteine is an endogenous regulator of neural progenitor cell dynamics in the mammalian brain". PNAS. 118 (39): e2110610118. Bibcode:2021PNAS..11810610S. doi:10.1073/pnas.2110610118. PMC 8488618. PMID 34556581.
^ Saffran, M. (April 1998). "Amino acid names and parlor games: from trivial names to a one-letter code, amino acid names have strained students' memories. Is a more rational nomenclature possible?". Biochemical Education. 26 (2): 116–118. doi:10.1016/s0307-4412(97)00167-2. ISSN 0307-4412.
^ ^a ^b "Amber Workshop - Tutorial A1 - Section 1: Do some editing of the PDB file". ambermd.org. Archived from the original on 2022-05-22. Retrieved 2022-06-02.
^ ^a ^b Lee, Jumin; Hitzenberger, Manuel; Rieger, Manuel; Kern, Nathan R.; Zacharias, Martin; Im, Wonpil (21 July 2020). "CHARMM-GUI supports the Amber force fields". The Journal of Chemical Physics. 153 (3): 035103. Bibcode:2020JChPh.153c5103L. doi:10.1063/5.0012280. PMID 32716185. S2CID 220796795.

[1] "PubChem data".

[2] Belitz, H.-D; Grosch, Werner; Schieberle, Peter (2009-02-27). Food Chemistry. Springer. ISBN 9783540699330.

[3] Kirste, Burkhard (23 Jan 1998). "Cysteine Archived 2016-11-10 at the Wayback Machine". Overview of Amino Acids. Free University of Berlin Dep't. of Biology, Chemistry, and Pharmacy.

[4] Weast, Robert C., ed. (1981). CRC Handbook of Chemistry and Physics (62nd ed.). Boca Raton, Florida: CRC Press. p. C-259. ISBN 0-8493-0462-8..

[5] "cysteine - Definition of cysteine in English by Oxford Dictionaries". Oxford Dictionaries - English. Archived from the original on September 25, 2016. Retrieved 15 April 2018.

[6] "Nomenclature and symbolism for amino acids and peptides (IUPAC-IUB Recommendations 1983)". Pure and Applied Chemistry. 56 (5): 595–624. 1984. doi:10.1351/pac198456050595.

[microbial-7] "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.

[8] Semenza, Evan R.; Harraz, Maged M.; Abramson, Efrat; Malla, Adarsha P.; Vasavda, Chirag; Gadalla, Moataz M.; Kornberg, Michael D.; Snyder, Solomon H.; Roychaudhuri, Robin (23 Sep 2021) [18 Aug 2021]. "D-cysteine is an endogenous regulator of neural progenitor cell dynamics in the mammalian brain". PNAS. 118 (39): e2110610118. Bibcode:2021PNAS..11810610S. doi:10.1073/pnas.2110610118. PMC 8488618. PMID 34556581.

[9] Saffran, M. (April 1998). "Amino acid names and parlor games: from trivial names to a one-letter code, amino acid names have strained students' memories. Is a more rational nomenclature possible?". Biochemical Education. 26 (2): 116–118. doi:10.1016/s0307-4412(97)00167-2. ISSN 0307-4412.

[:0-10] "Amber Workshop - Tutorial A1 - Section 1: Do some editing of the PDB file". ambermd.org. Archived from the original on 2022-05-22. Retrieved 2022-06-02.

[:1-11] Lee, Jumin; Hitzenberger, Manuel; Rieger, Manuel; Kern, Nathan R.; Zacharias, Martin; Im, Wonpil (21 July 2020). "CHARMM-GUI supports the Amber force fields". The Journal of Chemical Physics. 153 (3): 035103. Bibcode:2020JChPh.153c5103L. doi:10.1063/5.0012280. PMID 32716185. S2CID 220796795.

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