[ sis-teen, -tin ]
/ ˈsɪs tin, -tɪn /

noun Biochemistry.

a crystalline amino acid, C6H12O4N2S2, occurring in most proteins, especially the keratins in hair, wool, and horn, and yielding cysteine on reduction.

Origin of cystine

1835–45; cyst- + -ine2; so called because found in the bladder Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Examples from the Web for cystine

  • Ammonia, therefore, dissolves the cystine without entering into chemical union with it.

  • This action is due chiefly to its progressive formation of calcium sulphydrate from the cystine group of the softer keratins.

    Animal Proteins|Hugh Garner Bennett

British Dictionary definitions for cystine

/ (ˈsɪstiːn, -tɪn) /


a sulphur-containing amino acid present in proteins: yields two molecules of cysteine on reduction. Formula: HOOCCH(NH 2)CH 2 SSCH 2 CH(NH 2)COOH

Word Origin for cystine

C19: see cysto- (bladder), -ine ²; named from its being discovered in a type of urinary calculus
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for cystine

[ sĭstēn′ ]


A white crystalline amino acid that is found in many proteins, especially keratin, and is the major source of metabolic sulfur.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.