Definition of cysteine in English:


Syllabification: cys·te·ine
Pronunciation: /ˈsistəˌēn, ˈsisˌtēn


  • A sulfur-containing amino acid that occurs in keratins and other proteins, often in the form of cystine, and is a constituent of many enzymes.
    • Chemical formula: HSCH2CH(NH2)COOH
    More example sentences
    • Whey proteins are also rich in the sulfur-containing amino acids cysteine and methionine.
    • The gelatinase activity was due to metalloproteinases and not cysteine or serine proteinases.
    • The integration of reduced sulphur into the amino acid cysteine is a central step in the assimilation of inorganic sulphur.


late 19th century: from cystine + -eine (variant of -ine4).

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