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Leucine (abbreviated as Leu or L) is an a-amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
 with the chemical formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 HO2CCH(NH2)CH2CH(CH3)2. It is an essential amino acid
Essential amino acid

File:BakedFish.jpgAn essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo synthesis by the organism , and therefore must be supplied in the diet....
, 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. It has an isobutyl R group. Leucine is a major component of the sub units in ferritin
Ferritin

Ferritin is a globular protein complex consisting of 24 protein subunits and is the main intracellular iron storage protein in both prokaryotes and eukaryotes, keeping it in a soluble and non-toxic form....
, astacin and other 'buffer' protein
Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
s.

n essential amino acid, leucine is not synthesized in animals, hence it must be ingested, usually as a component of proteins.






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Leucine (abbreviated as Leu or L) is an a-amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
 with the chemical formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 HO2CCH(NH2)CH2CH(CH3)2. It is an essential amino acid
Essential amino acid

File:BakedFish.jpgAn essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo synthesis by the organism , and therefore must be supplied in the diet....
, 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. It has an isobutyl R group. Leucine is a major component of the sub units in ferritin
Ferritin

Ferritin is a globular protein complex consisting of 24 protein subunits and is the main intracellular iron storage protein in both prokaryotes and eukaryotes, keeping it in a soluble and non-toxic form....
, astacin and other 'buffer' protein
Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
s.

Biosynthesis

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
Pyruvic acid

Pyruvic acid is an organic acid. It is also a ketone. It is the simplest keto acids. The carboxylate ion of pyruvic acid is known as pyruvate....
. The initial part of the pathway also leads to valine
Valine

Valine is an a-amino acid with the chemical formula HO2CCHCH2. L-Valine is one of 20 proteogenic amino acids....
. The intermediate a-ketovalerate is converted to a-isopropylmalate and then ß-isopropylmalate, which is dehydrogenated to a-ketoisocaproate, which in the final step undergoes reductive amination
Reductive amination

Reductive amination is a chemical reaction which involves the conversion of a carbonyl group to an amine, via an intermediate imine. The carbonyl group is most commonly a ketone or an aldehyde....
. Enzymes involved in a typical leucine biosynthesis include
  • Acetolactate synthase
    Acetolactate synthase

    The acetolactate synthase enzyme is a protein which in humans is encoded by the ILVBL gene. ALS catalyzes the first step in the synthesis of the branched-chain amino acids ....
    ,
  • Acetohydroxy acid isomeroreductase
    Reductase

    A reductase is an enzyme which lowers the activation energy for a Redox. ...
    ,
  • Dihydroxyacid dehydratase
    Dehydratase

    Dehydratase is an enzyme that catalyzes the removal of oxygen and hydrogen from organic compounds in the form of water. This process is also known as dehydration....
    ,
  • a-Isopropylmalate synthase
    Synthase

    In biochemistry, a synthase is an enzyme which catalyzes a synthesis process.Following the EC number classification, they belong to the group of ligases, with lyases catalysing the reverse reaction....
    ,
  • a-Isopropylmalate isomerase
    Isomerase

    In biochemistry, an isomerase is an enzyme that catalyzes the structural rearrangement of isomers. Isomerases thus catalyze reactions of the form...
    ,
  • 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. Leucine is utilized in the liver
Liver

The liver is a vital organ present in vertebrates and some other animals; it has a wide range of functions, a few of which are detoxification, protein synthesis, and production of biochemicals necessary for digestion....
, adipose tissue
Adipose tissue

In histology, adipose tissue or fat is loose connective tissue composed of adipocytes. Adipose tissue is derived from lipoblasts. Its main role is to store energy in the form of fat, although it also cushions and Thermal insulation the body....
, and muscle tissue. In adipose and muscle tissue, leucine is used in the formation of sterol
Sterol

Sterols are an important class of organic molecules. They occur naturally in plants, animals and fungi, with the most familiar type of animal sterol being cholesterol, which has been shown to contribute to high blood pressure and heart disease....
s, and the combined usage of leucine in these two tissues is seven times greater than its use in the liver.

Chemical properties

Racemic
Racemic

In chemistry, a racemic mixture, or racemate, is one that has equal Amount of substance of left- and right-handed enantiomer of a Chirality molecule....
 leucine had been subjected to circularly polarized synchrotron radiation
Synchrotron radiation

Synchrotron radiation is electromagnetic radiation, similar to cyclotron radiation, but generated by the acceleration of Ultrarelativistic limit charged particles through magnetic fields....
 in order to better understand the origin of biomolecular asymmetry. An enantiomeric enhancement of 2.6 % had been induced, indicating a photochemical origin of biomolecules' homochirality
Homochirality

Homochirality is a term used to refer to a group of molecules that possess the same sense of Chirality . Molecules involved are not necessarily the same compound, but similar groups are arranged in the same way around a central atom....
.

Food additive

As a food additive
Food additive

Food additives are substances added to food to preserve flavour or improve its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , edible salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines....
 L-Leucine has E number
E number

E numbers are number codes for food additives and are usually found on food labels throughout the European Union. The numbering scheme follows that of the International Numbering System as determined by the Codex Alimentarius committee....
 E641 and is classified as a flavour enhancer
Flavour enhancer

Flavour enhancers are commonly added to commercially produced food products to make them taste more 'savoury'.The commonly used flavour enhancers are:...
.

See also

  • Leucines
    Leucines

    The leucines describe primarily the four isomeric amino acids leucine, isoleucine, tert-Leucine and norleucine. Being compared with the four butanols, they could be classified as butyl-substituted glycines; they represent all four possible variations....
    , description of the isomers of leucine
  • Photo-reactive leucine
    Photo-reactive amino acid analog

    Photo-reactive amino acid analogs for in-vivo crosslinking of protein complexes were introduced in 2005 by researchers from the Max Planck Institute In this method, cells are grown with photoreactive diazirine analogs to leucine and methionine, which are incorporated into proteins....


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