Catalyzes the Claisen rearrangement of chorismate to prephenate. The joint presence of this enzyme together with cyclohexadienyl dehydratase and aromatic aminotransferase in the periplasmic compartment comprises a complete three-step chorismate to phenylalanine pathway and accounts for the so called hidden overflow pathway to phenylalanine in P.aeruginosa, in which two possible routes for it exists, namely either via phenylpyruvate or L-arogenate. chorismate = prephenate kcat is 6.4 sec(-1) for chorismate. Metabolic intermediate biosynthesis; prephenate biosynthesis; prephenate from chorismate: step 1/1. Homodimer.