chorismate

Chorismate is a central metabolite in the shikimate pathway, a biosynthetic route for aromatic compounds found in bacteria, fungi, plants, and some algae. Animals and humans do not possess this pathway, making chorismate a key precursor that must be obtained from diet or through symbiotic organisms.

Biosynthesis and role in metabolism: In plants and microorganisms, chorismate is produced toward the end of the shikimate pathway by the action of chorismate synthase on 5-enolpyruvylshikimate-3-phosphate, after earlier steps that combine phosphoenolpyruvate and erythrose-4-phosphate. Chorismate serves as a branching point for several essential biosynthetic routes, linking to the production of multiple aromatic compounds.

Biosynthetic branches and end products:

- Tryptophan biosynthesis begins with the conversion of chorismate to anthranilate, a precursor of tryptophan.

- Phenylalanine and tyrosine are formed via chorismate mutase-catalyzed conversion to prephenate, followed by further transformations.

- Folate (tetrahydrofolate) biosynthesis uses chorismate-derived para-aminobenzoate (pABA), formed through the actions of aminodeoxychorismate synthase and lyase.

- In many plants and some microbes, chorismate is also a precursor to salicylic acid or related phenolics via isochorismate pathways.

Regulation and importance: The shikimate pathway is feedback-inhibited by the end products phenylalanine, tyrosine, and tryptophan, helping coordinate flux toward aromatic amino acid production. Because animals lack this pathway, chorismate biosynthesis is a notable target for herbicides such as glyphosate, which inhibits an upstream enzyme (EPSP synthase) and prevents chorismate formation.

See also: chorismate mutase, anthranilate synthase, isochorismate synthase.