Catalyzes the Claisen rearrangement of chorismate to prephenate. Probably involved in the aromatic amino acid biosynthesis. chorismate = prephenate Inhibited by 40% with 500 uM tyrosine, and a tyrosine concentration as high as 5 mM reduced activity to 5%. Optimum temperature is 70 degrees Celsius. Metabolic intermediate biosynthesis; prephenate biosynthesis; prephenate from chorismate: step 1/1. Homotrimer.