Catalyzes the Claisen rearrangement of chorismate to prephenate (PubMed:10894726). Acts at the first branch point in the aromatic amino acid pathway where it steers biosynthesis towards phenylalanine and tyrosine, and away from tryptophan (PubMed:10894726). chorismate = prephenate Each dimer has two allosteric binding sites that can bind the regulatory effectors tryptophan or tyrosine (PubMed:10894726). Can bind either one tryptophan or one tyrosine, two tryptophan or two tyrosine or one tryptophan and one tyrosine, which differentially affect the catalytic activity (By similarity). Activated by tryptophan and subject to feedback inhibition by tyrosine (PubMed:10894726). In the presence of both tryptophan and tyrosine, the enzyme is in the activated state (By similarity). kcat is 303.8 sec(-1) with chorismate as substrate (in the presence of 10 uM tryptophan and at 37 degrees Celsius). kcat is 89.3 sec(-1) with chorismate as substrate (in the presence of 100 uM tyrosine and at 37 degrees Celsius). Optimum temperature is 48 degrees Celsius. Metabolic intermediate biosynthesis; prephenate biosynthesis; prephenate from chorismate: step 1/1. Homodimer. Induced by growth on methanol carbon source (PubMed:10894726). Slightly induced by growth on the non-fermentable carbon source glycerol (PubMed:10894726). Not induced by histidine starvation (PubMed:10894726).