Alanine (ALA or A)

L-Alanine is one of the 20 amino acids commonly found in proteins. Under the essential or non-essential categorization of amino acids, Alanine is a non-essential amino acid, meaning it does not need to be present in the diet.

The methyl side chain of alanine results in it being classified as an aliphatic amino acid. The more hydrophobic amino acids are usually found within a protein molecule, where they are shielded from water.

Alanine can be made by several metabolic processes. Most commonly it is made by transfer of an amine group to pyruvate (reaction 2 below). Alanine is also a product of tryptophan catabolism.

Like all the other amino acids in proteins, the L isomer of alanine is exclusively used, though D-alanine can be found as a component of bacterial cell walls. Another variant of alanine, called -alanine, has the amino group on the carbon and is found in pantothenic acid. Alanine can be formed by transamination of pyruvate and thus has close links to pathways such as glycolysis, gluconeogenesis, and the citric acid cycle.

Metabolic reactions involving alanine:

> 1. Alanine + -Ketoglutarate <=> Pyruvate + Glutamate (catalyzed by Aminotransferase).

> 2. Glutamate + Pyruvate <=> -Ketoglutarate + Alanine (catalyzed by SGPT).

One Letter Code | Three Letter Code | Molecular Wt. (Daltons) | Genetic Code Codons
A | ALA | 71.08 | GCA, GCC, GCG, GCU

Alanine is an allosteric inhibitor of glutamine synthetase, an enzyme with a central role in nitrogen metabolism in the cell. Alanine participates in transamination reactions and in the glucose-alanine cycle.

See also: Table 5.1, Genetic Code, Gluconeogenesis, Transamination in Amino Acid Metabolism (from Chapter 20), Citric Acid Cycle Intermediates in Amino Acid Metabolism (from Chapter 21), Essential Amino Acids

INTERNET LINK: Alanine Aspartate Metabolism