cys·​te·​ine | \ ˈsi-stə-ˌēn How to pronounce cysteine (audio) \

Definition of cysteine

: a crystalline sulfur-containing amino acid C3H7NO2S readily oxidizable to cystine

Examples of cysteine in a Sentence

Recent Examples on the Web

The technology attaches fragments of potential small molecule drugs to another molecule that binds to cysteine, one of the amino acids that are the building blocks of proteins. Bradley J. Fikes,, "Scripps' Ben Cravatt elected to National Academy of Medicine," 16 Oct. 2017 Plants use sulfur to manufacture cysteine and methionine, two amino acids important for producing protein. Patrick Di Justo, WIRED, "What's Inside Sta-Green Planting Mix? Masterful Decomposition.," 28 July 2010 Eggs are an awesome source of cysteine, which helps break down a headache-causing toxin that's produced when your body digests alcohol. Elizabeth Narins, Cosmopolitan, "18 Expert-Tested Ways to Prevent a Hangover," 28 June 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'cysteine.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of cysteine

1884, in the meaning defined above

History and Etymology for cysteine

International Scientific Vocabulary, from cystine + -ein

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Time Traveler for cysteine

The first known use of cysteine was in 1884

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More Definitions for cysteine


cys·​teine | \ ˈsis-tə-ˌēn How to pronounce cysteine (audio) \

Medical Definition of cysteine

: a sulfur-containing amino acid C3H7NO2S occurring in many proteins and glutathione and readily oxidizable to cystine abbreviation Cys

More from Merriam-Webster on cysteine

Britannica English: Translation of cysteine for Arabic Speakers Encyclopedia article about cysteine

Comments on cysteine

What made you want to look up cysteine? Please tell us where you read or heard it (including the quote, if possible).


formidable, illustrious, or eminent

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