Flavin monooxygenase catalytic cycle

Figure 10.6. Catalytic cycle of the flavin-containing monooxygenase.

The catalytic cycle of each flavoenzyme consists of two distinct processes, the acceptance of redox equivalents from a substrate and the transfer of these equivalents to an acceptor. Accordingly, the catalyzed reactions consist of two half-reactions a reductive half-reaction in which the flavin is reduced and an oxidative half-reaction, in which the reduced flavin is reoxidized. This review summarizes the chemistry of simple flavoprotein reductases, dehydrogenases, (di)thiol oxidoreductases, oxidases, and monooxygenases (Table 1) (5 0) This grouping provides a good appreciation about what type of common mechanisms can be distinguished and what type of substrates can be converted. Information on the chemistry of complex flavoenzymes can be found in the Further Reading section. 

Scheme 24 Catalytic cycle of flavin-containing monooxygenases.

Scheme 2.147 Catalytic cycle of flavin-dependent monooxygenases...

Flavin-dependent monooxygenases function through a reaction cycle that is schematically presented in Fig. 4.79. These enzymes perform their catalytic reaction through the generation of a reactive form of the flavin cofactor, formed by 2-electron reduction of the flavin followed by its reaction with molecular oxygen. As a result, the so-called C(4a)-peroxyflavin intermediate is formed, whose electrophilic reactivity is further increased by protonation of the distal oxygen of the peroxide to yield the C(4a)-hydroperoxyflavin form of the cofactor (Fig. 4.80). 

---