The BoxA/BoxB complex catalyzes the aerobic reduction/oxygenation of the aromatic ring of benzoyl-CoA to form 2,3-epoxy-2,3-dihydrobenzoyl-CoA. BoxB acts as the benzoyl-CoA oxygenase, after being reduced by the reductase component BoxA. BoxAB does not act on NADH or benzoate. benzoyl-CoA + H(+) + NADPH + O2 = 2,3-epoxy-2,3-dihydrobenzoyl-CoA + H2O + NADP(+) Monomer. The subunit composition of the active BoxA/BoxB protein complex is not known. By benzoate. Belongs to the benzoyl-CoA oxygenase component B family.