Isoleucine biosynthesis begins with L-threonine from the threonine biosynthesis pathway. L-threonine interacts with a threonine dehydratase biosynthetic releasing water, a hydrogen ion and (2Z)-2-aminobut-2-enoate. This compound is isomerized into a 2-iminobutanoate which interacts with water and a hydrogen ion spontaneously, resulting in the release of ammonium and 2-ketobutyric acid. This compound reacts with pyruvic acid and hydrogen ion through an acetohydroxybutanoate synthase / acetolactate synthase 2 resulting in carbon dioxide and (S)-2-Aceto-2-hydroxybutanoic acid. The latter compound is reduced by an NADPH driven acetohydroxy acid isomeroreductase releasing NADP and acetohydroxy acid isomeroreductase. The latter compound is dehydrated by a dihydroxy acid dehydratase resulting in 3-methyl-2-oxovaleric acid.This compound reacts in a reversible reaction with L-glutamic acid through a Branched-chain-amino-acid aminotransferase resulting in oxoglutaric acid and L-isoleucine.

Isoleucine Biosynthesis References