Benzoate dioxygenase reductase (BenDO) FAD/NAD binding domain. Oxygenases oxidize hydrocarbons using dioxygen as the oxidant. As a Class I bacterial dioxygenases, benzoate dioxygenase like proteins combine an [2Fe-2S] cluster containing N-terminal ferredoxin at the end fused to an FAD/NADP(P) domain. In dioxygenase FAD/NAD(P) binding domain, the reductase transfers 2 electrons from NAD(P)H to the oxygenase which insert into an aromatic substrate, an initial step in microbial aerobic degradation of aromatic rings. Flavin oxidoreductases use flavins as substrates, unlike flavoenzymes which have a flavin prosthetic group.