Cyclic voltammetry performed at rapid scan rates on cytochrome P450 from Pseudomonas putida (P450CAM) in didodecyldimethylammonium bromide (DDAB) films on graphite electrodes revealed a couple (E) at 830mV (vs Ag/AgCl). E was not significantly observed at scan rates less than 30V/s at room temperature, suggesting that the oxidized species is unstable. The lifetime of E could be prolonged at 4 degrees C, which allowed reversible access to E at scan rates as low as 1V/s. E was found to be sensitive to imidazole in solution and to variations in pH, suggesting that the redox reaction is occurring at the metal center (i.e., Fe(IV/III)). Electrolysis reactions with different P450 substrates revealed that the electrochemically generated high-valent species is able to convert thioanisole to methyl phenyl sulfoxide.