methionine

American  

[me-thahy-uh-neen, -nin] / mɛˈθaɪ əˌnin, -nɪn /

noun

Biochemistry.

1. an amino acid, CH 3 SCH 2 CH 2 CH(NH2 )COOH, found in casein, wool, and other proteins or prepared synthetically: used as a supplement to a special diet in the prevention and treatment of certain liver diseases. Met; M

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methionine British  

/ mɛˈθaɪəˌniːn, -ˌnaɪn /

noun

1. an essential amino acid containing sulphur, which occurs in many proteins: important in methylating reactions

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methionine Scientific  

/ mə-thī′ə-nēn′ /

1. An essential amino acid. Chemical formula: C ₅ H ₁₁ NO ₂ S.

2. See more at amino acid

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Etymology

Origin of methionine

First recorded in 1925–30; blend of methyl and thionine ( def. )

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Example Sentences

See Examples For:

methionine

It’s naturally produced in our liver, kidneys and pancreas and comes from the amino acids arginine, glycine and methionine — the “building blocks of protein.”

From Los Angeles Times ● Oct. 19, 2026

“The answer may be: more methionine capacity, a reversion in polyamide spreads and another round of cost savings as the company adapts to intense competition and slow demand growth,” Bray says.

From The Wall Street Journal ● Aug. 10, 2026

Future studies will look more closely at how methionine works, whether other amino acids may produce similar or complementary effects, and how the findings might translate to people.

From Science Daily ● Jun. 1, 2026

The human body can also produce cysteine on its own by converting another amino acid called methionine in the liver.

From Science Daily ● May 21, 2026

Beans have both lysine and tryptophan, but not the amino acids cysteine and methionine, which are provided by maize.

From "1491" by Charles C. Mann

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