ˈsiˌstēn, -_stēˌēn, ˈsistə̇n also siˈstēə̇n noun
( -s )
Etymology: International Scientific Vocabulary, blend of cystine and -eine; originally formed as German zystein
: a crystalline amino acid HSCH 2 CH(NH 2 )COOH occurring as a constituent of many proteins and of glutathione and readily oxidizable to cystine; β-mercapto-alanine