Lalanine

L-alanine is an alpha-amino acid that is used in the biosynthesis of proteins. It is one of the 20 standard amino acids and is classified as a non-polar, aliphatic residue. Humans can synthesize L-alanine, so it is considered non-essential in the diet; the L-enantiomer is the form incorporated into proteins.

Chemically, L-alanine has a methyl side chain attached to the alpha carbon. Its formula is C3H7NO2 and its molecular weight is 89.09 g/mol. In solution, the carboxyl group (pKa around 2.3) is deprotonated and the amino group (pKa around 9.7) is protonated, giving an isoelectric point near pH 6.0. The alpha carbon is chiral, and the biologically active form in proteins is the L-enantiomer.

Biosynthesis and metabolism: L-alanine is formed from pyruvate by transamination with glutamate, a reaction catalyzed by alanine aminotransferase. In the glucose-alanine cycle, muscle tissue transaminates pyruvate to alanine for transport to the liver, where it is converted back to pyruvate for gluconeogenesis or energy production.

Occurrence and uses: L-alanine is abundant in many dietary proteins and is found in meat, dairy products, eggs, and many plant proteins. Beyond protein synthesis, alanine serves as a substrate in metabolic pathways. In medicine, alanine transaminase (ALT) measurements are used in liver function testing, and L-alanine is used in laboratory research and as a reagent in some culture media.

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