Ferrous dioxygen complex protonation

SCHEME 4.3 Cytochrome P450 and peroxidase pathways to hydroperoxo-ferric intermediate or Compound 0 (5). Ferric cytochrome P450 (1) is reduced to the ferrous state (2), which can hind dioxygen to form oxy-ferrous complex (3). Reduction of this complex results in the formation of peroxo-ferric complex (4), which is protonated to give hydroperoxo-ferric complex (5). The same hydroperoxo-ferric complex is formed in peroxidases and catalases via reaction with hydrogen peroxide. 

The dissociation of water produces a five-coordinate Fe(III) complex (B) that can be reduced to an Fe(II) analog. Ferrous P450cam (C) readily binds dioxygen to form the oxy form of the enzyme. Dioxygen binds in a bent end-on mode (t/ -Oz) with the iron center formally oxidized to Fe(III) and the O2 reduced by one electron to superoxide (D). Addition of a second electron from putidaredox-in follows to further reduce the complex to an Fe(III)-peroxo species (E). Proton transfer is required before the cleavage of the 0-0 bond an Fe(III)-hydroperoxo... 

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