AskDefine | Define leucine

Dictionary Definition

leucine n : a white crystalline amino acid occurring in proteins that is essential for nutrition; obtained by the hydrolysis of most dietary proteins

User Contributed Dictionary



  1. An essential amino acid, C6H13NO2, isomeric with isoleucine, found in most animal proteins; it is essential for growth in children.


essential amino acid; C6H13NO2
  • Spanish: leucina

Extensive Definition

Leucine (abbreviated as Leu or L) 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

Biological Uses

As a dietary supplement, leucine has been found to slow the degradation of muscle tissue by increasing the synthesis of muscle proteins. 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.


leucine in Catalan: Leucina
leucine in Czech: Leucin
leucine in Danish: Leucin
leucine in German: Leucin
leucine in Spanish: Leucina
leucine in Esperanto: Leŭcino
leucine in French: Leucine
leucine in Korean: 류신
leucine in Croatian: Leucin
leucine in Indonesian: Leusin
leucine in Italian: Leucina
leucine in Hebrew: לאוצין
leucine in Latvian: Leicīns
leucine in Luxembourgish: Leucin
leucine in Lithuanian: Leucinas
leucine in Dutch: Leucine
leucine in Japanese: ロイシン
leucine in Norwegian: Leucin
leucine in Polish: Leucyna
leucine in Portuguese: Leucina
leucine in Russian: Лейцин
leucine in Slovak: Leucín
leucine in Finnish: Leusiini
leucine in Swedish: Leucin
leucine in Turkish: Lösin
leucine in Ukrainian: Лейцин
leucine in Vlaams: Leucine
leucine in Chinese: 亮氨酸
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