Electroenzyme-catalyzed oxidation of styrene and cis-beta-methylstyrene using thin films of cytochrome P450cam and myoglobin

Protein-polyion films grown layer-by-layer and cast protein-surfactant film s were employed on electrodes for catalytic oxidation of styrene derivative s to epoxides. Cytochrome P450cam and myoglobin in these films mediated the electrochemical reduction of oxygen to hydrogen peroxide, which activates these heme proteins to catalyze olefin oxidation. Compared to bare electrod es with the proteins dissolved in solution, ultrathin protein-polyion films on Au electrodes coated with mercaptopropane sulfonate gave the best catal ytic activities for the oxidations. Improved performance of protein-polyion films is related to efficient, reversible heme Fe-III/Fe-II electron trans fer and better mechanical stability than the surfactant films. Furthermore, dependence of product stereochemistry on oxygen availability in the reacti on medium for the oxidation of cis-beta-methylstyrene suggested two pathway s for olefin oxidation, which had not been reported previously for cyt P450 enzymes. The stereoselective pathway depends on an active, high-valent iro n-oxygen intermediate as in the natural enzyme system, while the nonstereos elective pathway may involve a peroxyl radical near the protein surface.