Catalyzes the Claisen rearrangement of chorismate to prephenate. Probably involved in the aromatic amino acid biosynthesis. chorismate = prephenate Metabolic intermediate biosynthesis; prephenate biosynthesis; prephenate from chorismate: step 1/1. Homotrimer. This enzyme is monofunctional, and its activity is unaffected by the end-product aromatic amino acids.