InterPro domain: IPR008242

The bifunctional P-protein, which plays a central role in phenylalanine biosynthesis, contains two catalytic domains (chorismate mutase and prephenate dehydratase) and a regulatory domain (ACT). It is part of the shikimate pathway, which is present only in bacteria, fungi, and plants.

Chorismate mutase (CM; 5.4.99.5 ) catalyses the rearrangement of chorismate to prephenate, the reaction at the branch point of the biosynthetic pathway leading to the three aromatic amino acids, phenylalanine, tryptophan and tyrosine (chorismic acid is the last common intermediate, and CM leads to the L-phenylalanine/L-tyrosine branch). The chorismate mutase domain of this protein belongs to the AroQ class (prokaryotic type) [ 1 ] and has an all-helical structure. There are stand-alone versions of this domain, as well as fusions to other catalytic domains (such as prephenate dehydrogenase or DAHP synthase), or to regulatory domains.

Prephenate dehydratase (PDT; 4.2.1.51 ) converts prephenate to phenylpyruvate. In the Escherichia coli P-protein, the ACT domain has been shown to be essential for phenylalanine-mediated feedback inhibition and ligand binding [ 2 ]. It is a ligand-binding regulatory domain found primarily in enzymes and regulators of amino acid and purine metabolism [ 3 ].

1. Allosteric regulation of catalytic activity: Escherichia coli aspartate transcarbamoylase versus yeast chorismate mutase. Microbiol. Mol. Biol. Rev. 65, 404-21, table of contents
2. Regulation of phenylalanine biosynthesis. Studies on the mechanism of phenylalanine binding and feedback inhibition in the Escherichia coli P-protein. Biochemistry 38, 12212-7
3. Gleaning non-trivial structural, functional and evolutionary information about proteins by iterative database searches. J. Mol. Biol. 287, 1023-40