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Cystine
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Diagram of an IgG immunoglobulin showing two heavy chains and two light chains connected by red and green dots representing intra-chain and inter-chain disulfide bonds, with labeled Fab and Fc regions and a note explaining the structure and cleavage points.
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Cystine

amino acid
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Cystine, a crystalline, sulfur-containing amino acid that is formed from two molecules of the amino acid cysteine. Cystine can be converted to cysteine by reduction (in this case, the addition of hydrogen). Discovered in 1810, cystine was not recognized as a component of proteins until 1899, when it was isolated from animal horn. Cystine is particularly abundant in skeletal and connective tissues and in hair, horn, and wool. The chemical structure of cystine is

cystine, chemical compound

This article was most recently revised and updated by Erik Gregersen.