 From energetic adenosine triphosphate (ATP) generation to xenobiotic degradation, the use of dioxygen as a biological oxidant is widespread and varied in the exact mechanism of its use.Enzymes employ many different schemes to use dioxygen, and this largely depends on the substrate and reaction at hand.In the monooxygenases, only a single atom of dioxygen is incorporated into a substrate with the other being reduced to a water molecule.