Definition of methionine in English:


Syllabification: me·thi·o·nine
Pronunciation: /məˈTHīəˌnēn


  • A sulfur-containing amino acid that is a constituent of most proteins. It is an essential nutrient in the diet of vertebrates.
    • Chemical formula: CH3S(CH2)2CH(NH2)COOH
    More example sentences
    • They fix nitrogen and so contain high quality protein, including the essential amino acids methionine and cystine.
    • The oxidation sites of alpha-crystallin are considered to be methionine, cysteine and tryptophan amino acid residues.
    • For example, eggs are high in alanine and methionine; whey protein is high in tryptophan and threonine.


1920s: from methyl + Greek theion 'sulfur'.

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a small amount; a little