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

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 infected mice had low levels of methionine, an essential amino acid that people normally get through food.

From Science Daily • Jun. 1, 2026

They found that adding the amino acid methionine to the animals' diet protected them from wasting, blood-brain barrier problems, and death linked to inflammation.

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