cystine
American Heritage Dictionary:
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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.
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.
[From its discovery in bladder stones.]
Oxford Dictionary of Chemistry:
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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.
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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.
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the trivial name for dicysteine; β,β′-dithiodialanine; α,α′-diamino-β,β′-dithiobis(propionic acid); (R*,R′*)-3,3′-dithiobis(2-aminopropanoic acid);
HOOC−CH(NH2)−CH2−S−S−CH2−CH(NH2)−COOH;
a di(α-amino acid) with two chiral centres, formed by the oxidation of cystein. L-Cysteine,
(R,R′)-3,3′-dithiobis(2-aminopropanoic acid), is found in peptide linkage in proteins, having been formed by post-translational oxidation of cysteine. In mammals it is a nonessential dietary amino acid and is glucogenic. As it is somewhat insoluble in neutral aqueous solutions, it sometimes forms urinary stones. meso-Cystine, (R,S′)-3,3′-dithiobis(2-aminopropanoic acid), is the internally compensated achiral diastereoisomer, in which d- and l-half-molecules are combined. See also note at cysteine.
| cystic fibrosis transmembrane conductance regulator, cystic fibrosis, cysteyl | |
| cystine knot, cystinosin, cystinosis |
Saunders Veterinary Dictionary:
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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 on Answers.com:
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Cystine
Not to be confused with cysteine.
| Cystine | |
|---|---|
 |
 |
| Identifiers | |
| CAS number | 56-89-3  |
| PubChem | 67678 |
| ChemSpider | 575 |
| UNII | 48TCX9A1VT |
| KEGG | C01420 |
| ChEBI | CHEBI:35492 |
| ChEMBL | CHEMBL366563 |
| Jmol-3D images | Image 1 |
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|
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| Properties | |
| Molecular formula | C6H12N2O4S2 |
| Molar mass | 240.3 g mol−1 |
| Hazards | |
| MSDS | External MSDS |
 (verify) (what is:  / ?)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 that covalently link to make a disulfide bond. This organosulfur compound has the formula (SCH2CH(NH2)CO2H)2. It is a white 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
- Cystinuria
- Cystinosis
- Cysteine
- Lanthionine, similar with mono-sulfide link
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:10.1016/j.anifeedsci.2005.11.008.
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American Heritage 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.
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Oxford Dictionary of Chemistry
A Dictionary of Chemistry. Sixth Edition. Copyright © Market House Books Ltd, 2008. All rights reserved.
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Oxford Food & Nutrition Dictionary
A Dictionary of Food and Nutrition. Copyright © 1995, 2003, 2005 by A. E. Bender and D. A. Bender. All rights reserved.
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Oxford Dictionary of Biochemistry
Oxford University Press. Oxford Dictionary of Biochemistry and Molecular Biology © 1997, 2000, 2006 All rights reserved.
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Saunders 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.
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