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

Over seven days, the researchers adjusted the levels of methionine and cysteine in the animals' diets.

From Science Daily • Feb. 27, 2026

To promote these reactions, alternative meat developers will add browning agents, including specific amino acids such as cysteine, methionine and lysine, sugars and the vitamin thiamin.

From Salon • Nov. 25, 2024

The research published in PNAS, "Flexible B12 ecophysiology of Phaeocystis antarctica due to a fusion B12-independent methionine synthase with widespread homologues," conducted by MIT, WHOI, J.C.

From Science Daily • Feb. 5, 2024

Escherichia coli Strain A is able to grow in a minimal medium only when supplemented with methionine and biotin.

From Textbooks • Jun. 9, 2022

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