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  

/ -ˌnaɪn, mɛˈθaɪəˌniːn /

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. )

Example Sentences

For that reason, people should not start taking methionine supplements based on this study alone.

From Science Daily • Jun. 1, 2026

The team also tested whether methionine had similar effects in other conditions.

From Science Daily • Jun. 1, 2026

In models of sepsis and kidney injury, methionine again protected mice, suggesting that it could be relevant for other inflammatory disease settings.

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