cysteine
noun
cys·te·ine
ˈsi-stə-ˌēn 
: a crystalline sulfur-containing amino acid C3H7NO2S readily oxidizable to cystine
Examples of cysteine in a Sentence
Recent Examples on the Web
Passion fruit, for example, is low in methionine and cysteine.
—
Deirdre Bardolf, FOXNews.com, 10 Aug. 2025
Reintroducing cysteine to the animals’ diet reversed the weight loss, showing the effect was specifically due to cysteine deprivation.
—New Atlas, 12 July 2025
Mice that had been genetically engineered to lack the enzyme CTH that helps produce cysteine from methionine were fed a cysteine-free diet.
—New Atlas, 12 July 2025
Spot On! Advertisement Advertisement There are also 11 non-essential amino acids—alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine—that can be produced by your body.
—Stacey Colino, Time, 27 May 2025
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Deirdre Bardolf, FOXNews.com, 10 Aug. 2025
Reintroducing cysteine to the animals’ diet reversed the weight loss, showing the effect was specifically due to cysteine deprivation.
—New Atlas, 12 July 2025
Mice that had been genetically engineered to lack the enzyme CTH that helps produce cysteine from methionine were fed a cysteine-free diet.
—New Atlas, 12 July 2025
Spot On! Advertisement Advertisement There are also 11 non-essential amino acids—alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine—that can be produced by your body.
—Stacey Colino, Time, 27 May 2025
See All Example Sentences for cysteine
Cite this Entry
“Cysteine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cysteine. Accessed 19 Aug. 2025.
Copy CitationMedical Definition
cysteine
noun
cys·teine
ˈsis-tə-ˌēn
: a sulfur-containing amino acid C3H7NO2S occurring in many proteins and glutathione and readily oxidizable to cystine
—abbreviation Cys
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