Catalyzes the Claisen rearrangement of chorismate to prephenate (PubMed:2646272, PubMed:2187528, PubMed:10894726, PubMed:31498992, PubMed:9642265, PubMed:10428795). Acts at the first branch point in the aromatic amino acid pathway where it steers biosynthesis towards phenylalanine and tyrosine, and away from tryptophan (Probable). chorismate = prephenate Each dimer has two allosteric binding sites that can bind the regulatory effectors tryptophan or tyrosine (PubMed:31498992, PubMed:2187528, PubMed:10428795, PubMed:9642265). 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 (PubMed:31498992). Activated by tryptophan and subject to feedback inhibition by tyrosine (PubMed:10428795, PubMed:31498992, PubMed:2646272, PubMed:2187528). In the presence of both tryptophan and tyrosine, the enzyme is in the activated state (PubMed:2646272, PubMed:31498992). kcat is 176 sec(-1) for chorismate (PubMed:2187528). kcat is 176 sec(-1) for chorismate (in the presence of 10 uM of tryptophan) (PubMed:2187528). kcat is 348 sec(-1) for chorismate (in the presence of 10 uM of tryptophan and at 30 degrees Celsius) (PubMed:9642265). kcat is 129 sec(-1) for chorismate (in the presence of 300 uM of tyrosine) (PubMed:2187528). kcat is 387 sec(-1) for chorismate (in the presence of 100 uM of tyrosine and at 30 degrees Celsius) (PubMed:9642265). kcat is 320 sec(-1) for chorismate (in the presence of 100 uM of phenylalanine and at 30 degrees Celsius) (PubMed:9642265). Optimum pH isin the absence of effectors. Optimum pH is 7 in the presence of tryptophan. Optimum pH is 5 in the presence of tyrosine. Optimum temperature is <38 degrees Celsius. Metabolic intermediate biosynthesis; prephenate biosynthesis; prephenate from chorismate: step 1/1. Homodimer. Not affected by altering tryptophan or tyrosine levels.