[ loo-seen, -sin ]
/ ˈlu sin, -sɪn /

noun Biochemistry.

a white, crystalline, water-soluble amino acid, C6H13NO2, obtained by the decomposition of proteins and made synthetically: essential in the nutrition of humans and animals. Abbreviation: Leu; Symbol: L

Origin of leucine

First recorded in 1820–30; leuc- + -ine1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for leucine

  • An experiment carried out as above without any addition of leucine gave 9732 grams of alcohol containing 040 per cent.

British Dictionary definitions for leucine


leucin (ˈluːsɪn)

/ (ˈluːsiːn) /


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

Medicine definitions for leucine


[ lōōsēn′ ]


An essential amino acid derived from the hydrolysis of protein by pancreatic enzymes during digestion and necessary for optimal growth in infants and children and for the maintenance of nitrogen balance in adults.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for leucine


[ lōōsēn′ ]

An essential amino acid. Chemical formula: C6H13NO2. See more at amino acid.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.