InterPro domain: IPR008238

Chorismate mutase (CM) is a regulatory enzyme ( 5.4.99.5 ) required for biosynthesis of the aromatic amino acids phenylalanine and tyrosine. CM catalyzes the Claisen rearrangement of chorismate to prephenate, which can subsequently be converted to precursors of either L-Phe or L-Tyr. In bifunctional enzymes the CM domain can be fused to a prephenate dehydratase (P-protein for Phe biosynthesis), to a prephenate dehydrogenase (T-protein, for Tyr biosynthesis), or to 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) synthase ( 2.5.1.54 ). Besides these prokaryotic bifunctional enzymes, monofunctional CMs occur in prokaryotes as well as in fungi, plants and nematode worms [ 1 ].

The type I or AroH class of CM is represented by Bacillus subtilis aroH, a monofunctional, nonallosteric, homotrimeric enzyme characterized by its pseudo-alpha/beta-barrel 3D structure. Each monomer folds into a 5-stranded mixed beta-sheet packed against an alpha-helix and a 3-10 helix. The core is formed by a closed barrel of mixed beta-sheets surrounded by helices. The interfaces between adjacent subunits form three equivalent clefts that harbor the active sites [ 2 ].

The type II or AroQ class of CM has a completely different all-helical 3D structure, represented by the CM domain of the bifunctional Escherichia coli P-protein. This type is named after the Enterobacter agglomerans monofunctional CM encoded by the aroQ gene [ 3 ]. All CM domains from bifunctional enzymes as well as most monofunctional CMs belong to this class, including archaeal CM.

Eukaryotic CM from plants and fungi form a separate subclass of AroQ, represented by the Baker's yeast allosteric CM [ 4 ]. These enzymes show only partial sequence similarity to the prokaryotic CMs due to insertions of regulatory domains, but the helix-bundle topology and catalytic residues are conserved and the 3D structure of the E. coli CM dimer resembles a yeast CM monomer [ 5 , 5 , 6 ]. The E. coli P-protein CM domain consists of 3 helices and lacks allosteric regulation. The yeast CM has evolved by gene duplication and dimerization and each monomer has 12 helices. Yeast CM is allosterically activated by Trp and inhibited by Tyr [ 7 ].

This entry represents chorismate mutase from eukaryotes.

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. Crystal structures of the monofunctional chorismate mutase from Bacillus subtilis and its complex with a transition state analog. Proc. Natl. Acad. Sci. U.S.A. 90, 8600-3
3. The aroQ-encoded monofunctional chorismate mutase (CM-F) protein is a periplasmic enzyme in Erwinia herbicola. J. Bacteriol. 175, 4729-37
4. Energy and Enzyme Activity Landscapes of Yeast Chorismate Mutase at Cellular Concentrations of Allosteric Effectors. Biochemistry 58, 4058-4069
5. Mechanisms of catalysis and allosteric regulation of yeast chorismate mutase from crystal structures. Structure 5, 1437-52
6. A small, thermostable, and monofunctional chorismate mutase from the archaeon Methanococcus jannaschii. Biochemistry 37, 10062-73