leucine

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leucine

(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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.

Leucine

 

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.

REFERENCES

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.

T. S. PASKHINA

leucine

[′lü‚sēn]
(biochemistry)
C6H13O2N A monocarboxylic essential amino acid obtained by hydrolysis of protein-containing substances such as milk.
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