Cytochrome P450-like substrate oxidation catalyzed by cytochrome c and immobilized cytochrome c

Cytochrome c (cyt.c) was shown to catalyze cytochrome P450 (P450)-like oxidative reactions, such as N-, and 0-demethylation, S-oxidation, and epoxidation of olefins. A more detailed examination showed that (i) N-methylcarbazole and thioanisole oxidation with H₂ ¹⁸O₂ catalyzed by cyt.c resulted in introduction of ¹⁸O into the product, and (ii) during the epoxidation of cis-stilbene catalyzed by cyt.c, the stereochemistry of the substrate was retained and ¹⁸O was introduced when H₂ ¹⁸O₂ was used as an oxidant. These results show that cyt.c catalyzed N-demethylation, S-oxidation, and epoxidation in the same manner as P450. To utilize these P450-like reactivities effectively, cyt.c was immobilized on poly-γ-methyl-L-glutamate. Up to 99% of the cyt.c used was immobilized. This immobilized cyt.c catalyzed N-demethylation, S-oxidation, and epoxidation in the same manner as both P450 and free cyt.c, and the activities of these reactions were increased by the immobilization. In N-demethylation of N, N-dimethylaniline with cumene hydroperoxide (CHP) catalyzed by cyt.c, the V_max for CHP was increased by 4.4-fold by the immobilization of the enzyme, while the K_m remained unchanged. Since P450 is involved in the metabolism of many xenobiotics, the above results suggest that immobilized cyt.c may be useful in drug metabolism research.