A white crystalline amino acid, C6H12N2O4S2, formed from the disulfide linkage of two cysteines during folding of many proteins, especially keratin, and stabilizing the tertiary structure of the protein.
[From its discovery in bladder stones.]
cystine
Dictionary:
cys·tine (sĭs'tēn')  |
n.
A white crystalline amino acid, C6H12N2O4S2, formed from the disulfide linkage of two cysteines during folding of many proteins, especially keratin, and stabilizing the tertiary structure of the protein.
A white crystalline amino acid, C6H12N2O4S2, formed from the disulfide linkage of two cysteines during folding of many proteins, especially keratin, and stabilizing the tertiary structure of the protein.
| 5min Related Video: cystine |
| Chemistry Dictionary: cystine |
A molecule resulting from the oxidation reaction between the sulphydryl (–SH) groups of two cysteine molecules (see amino acid). This often occurs between adjacent cysteine residues in polypeptides. The resultant disulphide bridges (–S-S–) are important in stabilizing the structure of protein molecules.
| Food and Nutrition: cystine |
The dimer of cysteine produced when its sulphydryl group (—SH) is oxidized forming a disulphide (—S—S—) bridge. Such disulphide bridges are especially important in maintaining the structure of proteins, and also in the rôle of the tripeptide glutathione as an antioxidant.
| Veterinary Dictionary: cystine |
A naturally occurring amino acid, an important sulfur-containing component of the protein molecule. It is sometimes found in the urine and in the kidneys in the form of minute hexagonal crystals, frequently forming cystine calculus in the bladder.
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- c. calculi — see cystine uroliths.
| Wikipedia: Cystine |
| Cystine | |
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| Identifiers | |
| CAS number | 56-89-3  |
| Properties | |
| Molecular formula | C6H12N2O4S2 |
| Molar mass | 240.3 g mol−1 |
| Hazards | |
| MSDS | External MSDS |
| (what is this?) (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Cystine is a dimeric amino acid formed by the oxidation of two cysteine residues which covalently link to make a disulfide bond. This organosulfur compound has the formula (SCH2CH(NH2)CO2H)2. It is a colorless solid, and melts at 247-249 °C. 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] Through formation of disulfide bonds within and between protein molecules, cystine is a significant determinant of the tertiary structure of most proteins. Disulfide bonding, along with hydrogen bonding and hydrophobic interactions is partially responsible for the formation of the gluten matrix in bread. Human hair contains approximately 5% cystine by mass.[2]
Properties and nutritional aspects
The disulfide link is readily reduced to give the corresponding thiol, cysteine. This reaction is typically effected with thiols such as mercaptoethanol or dithiothreitol.
- (SCH2CH(NH2)CO2H)2 + 2 RSH → 2 HSCH2CH(NH2)CO2H + RSSR
For this reason, the nutritional benefits and sources of cystine are identical to those for the more common cysteine. Disulfide bonds cleave more rapidly at higher temperatures.[3].
See also
References
- ^ "cystine." Encyclopædia Britannica. 2007. Encyclopædia Britannica Online. 27 July 2007 www.britannica.com/eb/article-9028437/cystine
- ^ Gortner, R. A.; W. F. Hoffman, W. F. (1941), "l-Cystine", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV1P0194; Coll. Vol. 1: 194
- ^ M.A. Aslaksena, O.H. Romarheima, T. Storebakkena and A. Skrede (28 June 2006). "Evaluation of content and digestibility of disulfide bonds and free thiols in unextruded and extruded diets containing fish meal and soybean protein sources". Animal Feed Science and Technology 128 (3-4): 320–330. doi:.
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Chemistry Dictionary. A Dictionary of Chemistry. Sixth Edition. Copyright © Market House Books Ltd, 2008. All rights reserved. Read more |
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| Food and Nutrition. A Dictionary of Food and Nutrition. Copyright © 1995, 2003, 2005 by A. E. Bender and D. A. Bender. All rights reserved. Read more |
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| Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more |
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| Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Cystine". Read more |
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- What normal crystal do cystine crystals resemble?
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Mentioned in
- Nitroprusside (in medicine)
- cystinosis (medicine)
- cysteine
- methionine
- 2-mercaptopropionylglycine
- aminoaciduria
- Cystinuria: Diagnosis
- isomerase
- keratin (biochemistry)
- penicillamine (pharmacology)
