Definition of cystine in US English:



  • A compound which is an oxidized dimer of cysteine and is the form in which cysteine often occurs in organic tissue.

    Chemical formula: C₆H₁₂N₂O₄S₂

    • ‘Cysteamine enters the lysosomes by a specific transporter and converts cystine to cysteine and cysteine-cysteamine mixed disulfide.’
    • ‘Cysteine in the extracellular space is mostly oxidized to cystine.’
    • ‘Stones can be composed of calcium, oxalate, urate, cystine, xanthine, phosphate, or all of these.’
    • ‘In 1812, William Hyde Wollaston found a substance in urine that he identified as a cystic oxide, and was later named cystine.’
    • ‘Zinc is required for the incorporation of cystine into keratin.’
    • ‘Decomposition of urine containing cystine or pus will have the odor of rotten eggs.’
    • ‘Glutathione conjugation uses Nacetylcysteine, cysteine, and methionine; cystine is used for sulfation; and glucuronidation requires pantothenic acid.’
    • ‘The sulfur-containing amino acids are methionine, cysteine, cystine, homocysteine, homocystine, and taurine.’
    • ‘Once inside a cell, cystine is rapidly reduced to cysteine that, as a precursor of GSH, undergoes GSH synthesis.’
    • ‘The proteins of soyabean yields all essential amino acids in adequate amounts, except methionine and cystine.’


Mid 19th century: from Greek kustis ‘bladder’ (because it was first isolated from urinary calculi) + -ine.