H(+) + prephenate = 3-phenylpyruvate + CO2 + H2O Inhibited by L-phenylalanine but not by L-tyrosine or L-tryptophan. Optimum pH is 5-10. Thermostable. Amino-acid biosynthesis; L-phenylalanine biosynthesis; phenylpyruvate from prephenate: step 1/1. Homodimer.