Chain: nonpolar
Codons: ATA ATC ATT
Isoleucine (codons: ATA, ATC, ATT) is an α-amino acid that is used in the biosynthesis of proteins, specifically its L-isomer (left-handed). It contains an α-amino group, an α-carboxylic acid group, and an aliphatic branched hydrocarbon side chain, making it a nonpolar amino acid. At physiological pH (7.4), the amino group is in the protonated form (−NH₃⁺) and the carboxyl group is in the deprotonated form (−COO−).
Isoleucine is one of the 20 amino acids encoded in the standard genetic code and is essential in humans, meaning that it cannot be metabollically synthesized, and must be obtained from the diet. It is synthesized from pyruvate and alpha-ketobutyrate in other organisms such as plants and microorganisms. In catabolism, it is processed into propionyl-CoA and acetyl-CoA, which can be fed to citric acid cycle. Isoleucine is both, a ketogenic as well as glucogenic energy source.
In 1903, Felix Ehrlich isolated a compound that is an isomer of leucine from sugar beet molasses. Ehrlich also solved its structure in 1907.
Properties
Side chain: hydrophobic (nonpolar, uncharged)
Chemical formula: C₆H₁₃NO₂
Molar mass: 131.17 g/mol
Density: 1.00 g/cm³