Title: Cystine
CAS Registry Number: 56-89-3
CAS Name: L-Cystine
Additional Names: [R-(R*,R*)]-3,3¢-dithiobis[2-aminopropanoic acid]; dicysteine; b,-dithiodialanine; a-diamino-b-dithiolactic acid; b,-diamino-b,-dicarboxydiethyl disulfide; bis(b-amino-b-carboxyethyl) disulfide
Trademarks: Gelucystine (Parke-Davis)
Molecular Formula: C6H12N2O4S2
Molecular Weight: 240.30
Percent Composition: C 29.99%, H 5.03%, N 11.66%, O 26.63%, S 26.69%
Literature References: Non-essential amino acid for human development. Formed by the dimerization of two cysteines, q.v. through the sulfur. These disulfide bridges occur both within and between polypeptides; often found in extracellular proteins. First amino acid described in 1810 by Wollaston. Isoln from horn hydrolysate: K. A. H. Mörner, Z. Physiol. Chem. 28, 595 (1899). Early chemistry and biochemistry: Amino Acids and Proteins, D. M. Greenberg, Ed. (Charles C. Thomas, Springfield, IL, 1951) 950 pp. passim; J. P. Greenstein, M. Winitz, Chemistry of the Amino Acids vols 1-3 (John Wiley and Sons, Inc., New York, 1961) pp. 1879-1928, passim. Distribution in protein: R. C. Fahey et al., J. Mol. Evol. 10, 155 (1977). Review of lysosomal transport including pathophysiology: W. Gahl in Pathophysiol. Lysosomal Transp., J. G. Thoene, Ed. (CRC Press, Boca Raton, FL, 1992) pp 45-71. Review of thermodynamics and kinetics: T. R. Ralph et al., J. Electroanal. Chem. 375, 1-15 (1994); of electrosynthesis: eidem, ibid. 17-27.
Properties: Hexagonal tablets from water, dec 260-261° (sealed tube). [a]D20 -223.4° (1.0N HCl). pK1 1; pK2 2.1; pK3 8.02; pK4 8.71 at 35°. Soly in water (g/l) at 25°: 0.112; at 50°: 0.239; at 75°: 0.523; at 100°: 1.142. Quite sol in aq solns below pH 2 or above pH 8. Soly curves: Sano, Biochem. Z. 168, 14 (1926). Insol in alc. Absorption spectrum: Marchlewski, Nowotonowna, Bull. Soc. Chim. Fr. [4] 39, 163, 166 (1926).
pKa: pK1 1; pK2 2.1; pK3 8.02; pK4 8.71 at 35°
Optical Rotation: [a]D20 -223.4° (1.0N HCl)
Derivative Type: D-Form
CAS Registry Number: 349-46-2
Properties: Crystals. [a]D20 +223° (1.0N HCl). Soly in water at 25°: 0.057 g/l.
Optical Rotation: [a]D20 +223° (1.0N HCl)
Derivative Type: DL-Form
CAS Registry Number: 923-32-0
Properties: Crystals. Soly in water at 25°: 0.057 g/l.
Derivative Type: meso-Form
CAS Registry Number: 6020-39-9
Properties: Crystals. Soly in water: 0.056 g/l.
Cytarabine Cythioate Cytidine Cytisine Cytochalasins

Cystine-skeletal.png Cystine-3D-balls.png
CAS number 56-89-3 YesY
PubChem 67678
ChemSpider 575 YesY
KEGG C01420 YesY
ChEBI CHEBI:35492 YesY
Jmol-3D images Image 1
Molecular formula C6H12N2O4S2
Molar mass 240.30 g mol−1
MSDS External MSDS
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Cystine is the amino acid formed by the oxidation of two cysteine molecules that covalently link via a disulfide bond. This organosulfur compound has the formula (SCH2CH(NH2)CO2H)2. It is a white solid that is slightly soluble in water. Human hair and skin contain approximately 10-14% cystine by mass. It was discovered in 1810 by William Hyde Wollaston but was not recognized as being derived of proteins until it was isolated from the horn of a cow in 1899.[1]