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. BoxA acts as a reductase that uses NADPH to reduce the oxygenase component BoxB. BoxAB does not act on NADH or benzoate. benzoyl-CoA + H(+) + NADPH + O2 = 2,3-epoxy-2,3-dihydrobenzoyl-CoA + H2O + NADP(+) Binds 1 FAD per subunit. Binds 2 [4Fe-4S] clusters per subunit. Homodimer. The subunit composition of the active BoxA/BoxB protein complex is not known. By benzoate.