Type III polyketide synthase involved in the biosynthesis of benzophenones and xanthones. The preferred substrate is benzoyl-CoA, but can also use 3-hydroxybenzoyl-CoA with a lower activity. benzoyl-CoA + 2 H(+) + 3 malonyl-CoA = 2,4,6-trihydroxybenzophenone + 3 CO2 + 4 CoA 3-hydroxybenzoyl-CoA + 2 H(+) + 3 malonyl-CoA = 2,3',4,6-tetrahydroxybenzophenone + 3 CO2 + 4 CoA kcat is 9.66 min(-1) with benzoyl-CoA as substrate. Optimum pH is 6.5-7.0. Optimum temperature is 35 degrees Celsius. Homodimer. The T135L mutagenesis transforms the trihydroxybenzophenone synthase into a phenylpyrone synthase. Belongs to the thiolase-like superfamily. Chalcone/stilbene synthases family.