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(lo͞o`sēn), organic compund, one of the 20 amino acidsamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
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 commonly found in animal proteins. Only the l-stereooisomer appears in mammalian protein. It is one of several essential amino acids needed in the diet; the human body cannot synthesize it from simpler metabolites. Young adults need about 31 mg of this amino acid per day per kilogram (14 mg per lb) of body weight. Leucine can be degraded into simpler compounds by the enzymes of the body. Leucine contributes to the structure of proteins into which it has been incorporated by the tendency of its side chain to participate in hydrophobic interactions. Certain proteins that bind to DNA (see nucleic acidnucleic acid,
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis.
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) and may help regulate its activities, posses regions in which leucines are arranged in configurations called leucine zippers. Leucine was isolated from cheese in an impure form in 1819 and from muscle and wool in the crystalline state in 1820. It was named after the Greek word leukos [white], evidently because at that time the purification of a subtance from nature to a white, crystalline state was considered noteworthy. The stucture of leucine was established by laboratory synthesis in 1891. See isoleucineisoleucine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



aminoisocaproic acid, a mono-amino-monocar-boxylic acid; colorless crystals. Melting point, 293°-295°C (with decomposition); poorly soluble in cold water; molecular weight, 131.18.

Leucine was first isolated in 1820 from muscle tissue. The natural L-leucine is a component of all animal and plant proteins. It is classified as one of the essential amino acids: the carbon skeleton of its precursor, α-ketoisovalerianic acid, is not synthesized in the human or animal body. An absence of leucine in the food results in a negative nitrogen balance and stops growth in children. The daily leucine requirement for adults and infants is 31 mg per kg and 425 mg per kg, respectively. One of the products of leucine breakdown in the body, β-hydroxy-β-methylglutaric acid (in the form of acyl coenzyme A), is an important intermediate compound in the biosynthesis of cholesterol and other steroids. Leucine is used, together with glutamic acid, methionine, and other amino acids, in the treatment of liver diseases, anemias, and some mental disorders.


Meister, A. Biokhimiia aminokislot. Moscow, 1961. (Translated from English.)
Kagan, Z. S. “Biosintez leitsina i ego reguliatsiia u mikroorganizmov i rastenii.” Uspekhi biologicheskoi khimii, 1970, vol. 11, pp. 87–106.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


C6H13O2N A monocarboxylic essential amino acid obtained by hydrolysis of protein-containing substances such as milk.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Abbreviations aa: Amino acids Ala: Alanine Asn: Asparagine bZIP: Basic leucine zipper DOG: Delay of germination Ile: Isoleucine Leu: Leucine MFMR: Multifunctional mosaic region MRCAs: Most recent common ancestors.
Ramachandran, "Genome-wide expansion and expression divergence of the basic leucine zipper transcription factors in higher plants with an emphasis on sorghum," Journal of Integrative Plant Biology, vol.
Yamaguchi-Shinozaki, "Arabidopsis basic leucine zipper transcription factors involved in an abscisic acid-dependent signal transduction pathway under drought and high-salinity conditions," Proceedings of the National Academy of Sciences, vol.
Berberich et al., "LIP19, a basic region leucine zipper protein, is a Fos-like molecular switch in the cold signaling of rice plants," Plant and Cell Physiology, vol.
Tan et al., "Analysis of basic leucine zipper genes and their expression during bud dormancy in peach (Prunus persica)," Plant Physiology and Biochemistry, vol.
Guiltinan, "Bipartite determinants of DNA-binding specificity of plant basic leucine zipper proteins," Plant Molecular Biology, vol.
Vinson, "A heterodimerizing leucine zipper coiled coil system for examining the specificity of a position interactions: amino acids I, V, L, N, A, and K," Biochemistry, vol.
Sometimes the leucine zipper helps two different molecules link up, says Kim.
The new work also clarifies the atomic nature of so-called leucine zippers stretches of amino acids that bind two proteins into two-molecule complexes called dimers, which regulate gene activity Confirmation that leucine zippers are actually coiled coils will help scientists understand how these proteins regulate the on-and-off switching of genes, comments Steven L.

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