name= ("S")-2-amino-4-methyl-pentanoic acid
C=6 |H=13 |N=1 |O=2
mass=131.18 g/mol

Leucine (abbreviated as Leu or L) [cite web | author=IUPAC-IUBMB Joint Commission on Biochemical Nomenclature | title=Nomenclature and Symbolism for Amino Acids and Peptides | work=Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology etc | url=http://www.chem.qmul.ac.uk/iupac/AminoAcid/ | accessdate=2007-05-17] is an α-amino acid with the chemical formula HO2CCH(NH2)CH2CH(CH3)2. It is an essential amino acid, which means that humans cannot synthesise it. Its codons are UUA, UUG, CUU, CUC, CUA, and CUG. With a hydrocarbon side chain, leucine is classified as a hydrophobic amino acid.


As an essential amino acid, leucine is not synthesized in animals, hence it must be ingested, usually as a component of proteins. It is synthesized in plants and microorganisms via several steps starting from pyruvic acid. The initial part of the pathway also leads to valine. The intermediate α-ketovalerate is converted to α-isopropylmalate and then β-isopropylmalate, which is dehydrogenated to α-ketoisocaproate, which in the final step undergoes reductive amination. Enzymes involved in a typical leucine biosynthesis include [Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.]
* Acetolactate synthase,
* Acetohydroxy acid isomeroreductase,
* Dihydroxyacid dehydratase,
* α-Isopropylmalate synthase,
* α-Isopropylmalate isomerase,
* Leucine aminotransferase.

Biological Uses

As a dietary supplement, leucine has been found to slow the degradation of muscle tissue by increasing the synthesis of muscle proteins. [cite web | author=L. Combaret, et al Human Nutrition Research Centre of Clermont-Ferrand | title=A leucine-supplemented diet restores the defective postprandial inhibition of proteasome-dependent proteolysis in aged rat skeletal muscle | work=Journal of Physiology Volume 569, issue 2, p. 489-499 | url=http://jp.physoc.org/cgi/reprint/569/2/489 | accessdate=2008-03-25] Leucine is utilized in the liver, adipose tissue, and muscle tissue. In adipose and muscle tissue, leucine is used in the formation of sterols, and the combined usage of leucine in these two tissues is seven times greater than its use in the liver. [cite web | author=J. Rosenthal, et al Department of Medicine, University of Toronto, Toronto, Canada | title=Metabolic fate of leucine: A significant sterol precursor in adipose tissue and muscle | work= American Journal of Physiology Vol. 226, No. 2, p. 411-418 | url=http://ajplegacy.physiology.org/cgi/reprint/226/2/411 | accessdate=2008-03-25]

Food additive

As a food additive L-Leucine has E number E641 and is classified as a flavour enhancer.

See also

* Photo-reactive leucine


External links

* [http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/AminoAcid/Leu.html Leucine biosynthesis]
* [http://www.dietaryfiberfood.com/leucine-rich.php Leucine content in food]
* [http://www.compchemwiki.org/index.php?title=Leucine Computational Chemistry Wiki]
* [http://news.bbc.co.uk/1/hi/health/4502862.stm Leucine prevents muscle loss in rats]
* [http://www.newscientist.com/article/dn9147-why-highprotein-meat-may-curb-appetite.html Leucine helps regulate appetite in rats]
* [http://ajpendo.physiology.org/cgi/content/full/288/4/E645 Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects]

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