Shikimate pathway

The shikimate pathway (shikimic acid pathway) is a seven step metabolic route used by bacteria, fungi, algae, parasites and plants for the biosynthesis of aromatic amino acids (phenylalanine, tyrosine, and tryptophan). This pathway is not found in animals, hence the products of this pathway represent essential amino acids that must be obtained from the animal's diet.

The first enzyme involved is the shikimate kinase, an enzyme that catalyzes the ATP-dependent phosphorylation of shikimate to form shikimate 3-phosphate. Shikimate 3-phosphate is then coupled with phosphoenol pyruvate to give 5-enolpyruvylshikimate-3-phosphate via the enzyme 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase.

Then 5-enolpyruvylshikimate-3-phosphate is transformed into chorismate by a chorismate synthase.

Prephenic acid is then synthesized by a Claisen rearrangement of chorismate by Chorismate mutase.

Prephenate is oxidatively decarboxylated with retention of the hydroxyl group to give p-hydroxyphenylpyruvate, which is transaminated using glutamate as the nitrogen source to give tyrosine and α-ketoglutarate.