leucine

American  

[loo-seen, -sin] / ˈlu sin, -sɪn /

noun

Biochemistry.

1. a white, crystalline, water-soluble amino acid, C 6 H 13 NO 2 , obtained by the decomposition of proteins and made synthetically: essential in the nutrition of humans and animals. Leu; L

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leucine British  

/ ˈluːsɪn, ˈluːsiːn /

noun

1. an essential amino acid found in many proteins

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leucine Scientific  

/ lo̅o̅′sēn′ /

1. An essential amino acid. Chemical formula: C ₆ H ₁₃ NO ₂ .

2. See more at amino acid

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Etymology

Origin of leucine

First recorded in 1820–30; leuc- + -ine ¹

Compare meaning

How does leucine compare to similar and commonly confused words? Explore the most common comparisons:

• isoleucine vs. leucine

Example Sentences

The researchers found that leucine helps protect certain proteins on the outer membrane of mitochondria from breaking down.

From Science Daily • Nov. 3, 2025

He says that some US consumers are now seeking out beta-lactoglobulin, which is high in the amino acid leucine, rather than non-specific whey protein.

From BBC • Oct. 6, 2025

This was not the feared 226L mutation: The amino acid had changed to a histidine instead of leucine.

From Science Magazine • Dec. 5, 2024

Lo and behold, when they switched a glutamine to a leucine at position 226, it no longer bound to the bird receptors, but instead exclusively to those of humans.

From Los Angeles Times • Dec. 5, 2024

Hydrolysis by acids indicates that it contains leucine and tyrosine, two amino-acids which are constituents of proteins, along with other bodies of unknown composition.

From The Chemistry of Plant Life by Thatcher, Roscoe Wilfred