Peroxide shunt pathway

Fig. 10.2. Catalytic cycle of P450 including the peroxide shunt pathway. RH is substrate, and ROH is product. The porphyrin molecule is represented as a parallelogram. The overall charge on the structures is shown to the left of each bracket. Intermediates 1, 2, 7, and 8 are neutral. Refer to text for a full description.

P450s are capable of utilizing an oxygen atom from peroxide to catalyze oxygen insertion without electron transport proteins or the NAD(P)H cofactor, through the peroxide shunt pathway ... 

Cyt P450 ,ani Increased activity in peroxide shunt pathway, towards napthalene 5-20-fold 1-2 [512]... 

Figure 32 (a) Catalytic reactions performed by calix[6]-tris(pyridine)Cu(II) via the peroxide shunt pathway. (b) Catecholase... 

Peroxides that directly convert the heme iron of P450s to a ferric hydroperoxy complex by the peroxide shunf (e.g., hydrogen peroxide, cumene peroxide, or tert-butyl oxide) could be useful for oxidation of various substrates. The essential problem in utilizing the peroxide shunf for P450 biocatalysis seems to lie in the time-dependent degradation of the heme and in oxidation of the protein [169, 170]. Methods of directed evolution, tike random and site-specific mutagenesis, were applied to evolve P450s to enhance the efficiency of the peroxide shunt pathway [171]. 

This observation confirmed that peroxide shunt pathway was not utilized in the NNK catalysis by LbL films of cyt P450 2E1 with microsomal CPR (Scheme 1) which would have otherwise caused less peroxide level to remain in the electrolyte solution compared to that produced with just polyion or microsomal CPR electrodes. Therefore, the electrochemically driven biocatalysis should have followed the natural CPR-mediated cyt P450 catalytic pathway in the designed electrostatically... 

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