The oxygenase reductase FAD/NADH binding domain acts as part of the multi-component bacterial oxygenases which oxidize hydrocarbons. These flavoprotein monooxygenases use molecular oxygen as a substrate and require reduced FAD. One atom of oxygen is incorportated into the aromatic compond, while the other is used to form a molecule of water. In contrast dioxygenases add both atoms of oxygen to the substrate.