Catalyzes the Claisen rearrangement of chorismate to prephenate. Probably involved in the aromatic amino acid biosynthesis. chorismate = prephenate The formation of the complex with AroG activates the chorismate mutase activity by more than two orders of magnitude to a catalytic efficiency (kcat/Km) typical for chorismate mutase. This activation is primarily caused by a more than 30-fold-decreased Km value, but also by a four-fold increase in kcat. The activity of the complex is inhibited by phenylalanine and tyrosine by about 70 and 40%, respectively. Metabolic intermediate biosynthesis; prephenate biosynthesis; prephenate from chorismate: step 1/1. Homodimer. Interacts with AroG.