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|Section2= |Section3= }} Cystine is the amino acid with the formula (SCH2CH(NH2)CO2H)2. It is a white solid that is slightly soluble in water. Each molecule of cystine is made from two molecules of cysteine, another sulfur-containing amino acid that, as its name suggests, is very similar to cystine, with which it can be interconverted. It serves two biological functions, a site of redox reactions and a mechanical linkage that allows proteins to retain their 3-dimensional structure.〔Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.〕 It is a nonessential amino acid, which means that humans manufacture it. ==Formation and reactions== It is common in many foods such as eggs, meat, dairy products, and whole grains as well as skin, horns and hair. It was not recognized as being derived of proteins until it was isolated from the horn of a cow in 1899.〔"cystine". ''Encyclopædia Britannica''. 2007. Encyclopædia Britannica Online. 27 July 2007 (www.britannica.com/eb/article-9028437/cystine )〕 Human hair and skin contain approximately 10–14% cystine by mass. It was discovered in 1810 by William Hyde Wollaston. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「cystine」の詳細全文を読む スポンサード リンク
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