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
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After our first meeting, Kay texted me his hangover regimen, which consists of capsules of N-acetyl cysteine, alpha-lipoic acid, and a supplement called Hangheal Liver Detox.
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Rebecca Mead, New Yorker, 8 Dec. 2025
In a study conducted on mice, scientists from the Massachusetts Institute of Technology (MIT) found that cysteine, a sulfur-containing amino acid, had the strongest rejuvenating effect on stem cells and early-stage intestinal cells, which are often damaged during radiation therapy for cancer.
—Deirdre Bardolf, FOXNews.com, 16 Oct. 2025
Your liver relies on amino acids from protein — like glycine, cysteine and glutamate — to make glutathione, your body’s master antioxidant.
—Lauren Mallers, Sacbee.com, 8 Oct. 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
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Rebecca Mead, New Yorker, 8 Dec. 2025
In a study conducted on mice, scientists from the Massachusetts Institute of Technology (MIT) found that cysteine, a sulfur-containing amino acid, had the strongest rejuvenating effect on stem cells and early-stage intestinal cells, which are often damaged during radiation therapy for cancer.
—Deirdre Bardolf, FOXNews.com, 16 Oct. 2025
Your liver relies on amino acids from protein — like glycine, cysteine and glutamate — to make glutathione, your body’s master antioxidant.
—Lauren Mallers, Sacbee.com, 8 Oct. 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
See All Example Sentences for cysteine
Cite this Entry
“Cysteine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cysteine. Accessed 18 Dec. 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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