Superoxide complexes catalytic oxygen reduction

MoO(TPP)Br] can be chemically reduced by superoxide to give [MoO(TPP)], via Mov and Mo superoxide complexes, which are stable at low temperatures.114 In the presence of superoxide, the substitution reaction of [MoO(TPP)Br] with MeOH to give [MoO(TPP)(OMe)] proceeds via an Mo species rather than via [MoO(TPP)(MeOH)]+, which is the pathway in the absence of superoxide.277 Photochemical reduction of [MoO(TPP)(OMe)] yields [MoO(TPP)], which reacts with 02 in MeOH to re-form [MoO(TPP)(OMe)j and produce H202, thus giving a catalytic route for the photoassisted reduction of molecular oxygen to hydrogen peroxide.278... 

Five different steps have been distinguished in the hydroxylation reaction (1) combination of the substrate (RH) with the oxidized form of cytochrome P450, (2) reduction of the ferric state of the cytochrome s iron atom to the ferrous state by the transfer of one electron from NADPH through the catalytic action of the reductase (the reaction requires phosphatidylcholine), (3) formation of a ternary complex through the binding of oxygen, (4) formation of a superoxide anion bound to the oxidized cytochrome P450 after an intramolecular electron transfer, and (5) finally in the molecular complex (oxidized cytochrome, superoxide, and substrate), the superoxide attacks the substrate which becomes hydroxylated, and at the same time the reductase provides another electron and a molecule of water is formed as one of the products of the reaction. 

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