leu·​cine ˈlü-ˌsēn How to pronounce leucine (audio)
: a white crystalline essential amino acid C6H13NO2 that is obtained by the hydrolysis of dietary protein (as of eggs, soy, or fish) and plays an important role in various physiological functions (as the regulation of insulin secretion and stimulation of protein synthesis in skeletal muscle)

Example Sentences

Recent Examples on the Web EyeEm//Getty Images While both are great, cottage cheese actually has more protein gram for gram, as well as just under 3 grams of leucine per 1 cup. Matthew Kadey, Men's Health, 14 Nov. 2022 Protein Powder is enriched with leucine and BCAAs to further support your muscles during and after a workout. The Salt Lake Tribune, 1 Nov. 2022 The most prevalent mutation in this T cell epitope is an amino acid substitution of proline for leucine, denoted as YLQLRTFLL or P272L mutation. William A. Haseltine, Forbes, 17 Aug. 2022 Each serving contains 20 grams of protein and is packed with essential amino acids like leucine and isoleucine, which aid in muscle recovery. Kayla Hui, Health.com, 27 Jan. 2022 After a really hard full-body workout, Baar recommends that athletes eat 0.4 g/kg of body weight of easily digestible leucine-rich protein. Washington Post, 25 Apr. 2022 All of these high-protein options are also rich in leucine, an essential amino acid involved in the growth and repair of muscle, skin, and bone. Outside Online, 17 Feb. 2021 This insertion added the peptide GLTSKRN (glycine-leucine-threonine-serine-lysine-arginine-asparagine) between Spike protein positions 214 and 215. William A. Haseltine, Forbes, 28 Sep. 2021 In simpler terms, make half of your plate carbohydrates (about 50-60 grams) and aim for 20-30 grams of protein, including essential amino acids, such as leucine. Sarah Schlichter, Outside Online, 16 Aug. 2021 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'leucine.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History


French, from leuc- leuk-

First Known Use

1826, in the meaning defined above

Time Traveler
The first known use of leucine was in 1826

Dictionary Entries Near leucine

Cite this Entry

“Leucine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/leucine. Accessed 7 Dec. 2022.

Kids Definition



leu·​cine ˈlü-ˌsēn How to pronounce leucine (audio)
: an amino acid that is very important in the nutrition of human beings

Medical Definition



leu·​cine ˈlü-ˌsēn How to pronounce leucine (audio)
: a white crystalline essential amino acid C6H13NO2 obtained by the hydrolysis of most dietary proteins
abbreviation Leu

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