Reductive activation of oxygen by dihydroflavins

Reduced flavins may be reoxidised by molecular oxygen with concomitant production of hydrogen peroxide and transfer of one or two oxygen atoms to a substrate (Eqn. 27). 

The two classes of flavoenzymes which reduce oxygen are the oxidases and the monooxygenases. Because of the deleterious nature of hydrogen peroxide these enzymes are often in proximity to catalase which converts peroxide into oxygen and water. 

---