leucine

American

[loo-seen, -sin] / ˈlu sin, -sɪn /

noun

Biochemistry.

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

leucine British

/ ˈluːsɪn, ˈluːsiːn /

noun

an essential amino acid found in many proteins

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

leucine Scientific

/ lo̅o̅′sēn′ /

An essential amino acid. Chemical formula: C ₆ H ₁₃ NO ₂ .
See more at amino acid

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

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

leucine

"Modulating leucine and SEL1L levels could be a strategy to boost energy production," Li added.

From Science Daily ● May 21, 2026

According to the study, leucine appears to suppress SEL1L activity.

From Science Daily ● May 21, 2026

The team found that leucine prevents the breakdown of certain proteins located on the outer surface of mitochondria.

From Science Daily ● May 21, 2026

One of these proteins is dual leucine zipper kinase, or DLK, which acts as a sensor for neuronal damage and becomes active when metabolism is disrupted.

From Science Daily ● Jan. 27, 2026

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 Roscoe Wilfred Thatcher

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023