methionine

noun

me·​thi·​o·​nine mə-ˈthī-ə-ˌnēn How to pronounce methionine (audio)
: a crystalline sulfur-containing essential amino acid C5H11NO2S that occurs in the levorotatory form as a constituent of many proteins

Examples of methionine in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Creatine is a compound that the body makes from the amino acids arginine, glycine, and methionine. — Jessica Swirble, Verywell Health, 15 Oct. 2025 Your body makes creatine from the amino acids lysine, arginine, and methionine. — Jillian Kubala, Health, 23 Jan. 2026 Passion fruit, for example, is low in methionine and cysteine. — Deirdre Bardolf, FOXNews.com, 10 Aug. 2025 Such a meal should include a good source of protein, such as eggs, in order to stock up on or refuel depleted amino acids, including cysteine and methionine, which are building blocks for protective antioxidants. — Lauren J. Young, Scientific American, 17 Mar. 2026 See All Example Sentences for methionine

Word History

Etymology

International Scientific Vocabulary, from methyl + thion- + -ine entry 2

First Known Use

1928, in the meaning defined above

Time Traveler
The first known use of methionine was in 1928

Rhymes for methionine

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Browse Nearby Words

methionic acid
methionine
methobromide
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Cite this Entry

“Methionine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/methionine. Accessed 7 Jul. 2026.

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Medical Definition

methionine

noun
me·​thi·​o·​nine mə-ˈthī-ə-ˌnēn How to pronounce methionine (audio)
: a crystalline sulfur-containing essential amino acid C5H11NO2S that occurs in the L-form as a constituent of many proteins (as casein and egg albumin), that is important especially as a source of sulfur for the biosynthesis of cysteine and as a source of methyl groups for transmethylation reactions (as in the biosynthesis of choline, creatine, and adrenaline), and that is used as a dietary supplement for human beings and their domestic mammals and poultry and in the treatment of fatty infiltration of the liver
—abbreviation Met

More from Merriam-Webster on methionine

Britannica.com: Encyclopedia article about methionine

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