Activation of Molecular Oxygen in Cytochromes P450

Abstract

The complex multistep mechanism of oxygen activation in P450 is reviewed as a sequence of the following reactions: Substrate binding, reduction of the heme iron from ferric to the ferrous state, binding of dioxygen, second electron transfer and formation of peroxo-ferric intermediate, two sequential protonation events to give hydroperoxo-ferric intermediate, and finally, after O–O bond scission, the ferryl-oxo intermediate, termed compound I. Details of these processes and the role of interactions with redox partners, as well as substrate variability in the overall efficiency of P450 catalysis, are discussed. In addition, common points and variations between the soluble prokaryotic and membrane-bound eukaryotic cytochromes P450 with respect to the oxygen activation mechanisms are briefly compared.