Electrochemical Activity of Cytochrome P450 1A2: The Relevance of O₂ Control and the Natural Electron Donor

The direct electrochemical response of membrane-bound human cytochrome P450 1A2 (CYP1A2) was studied on pyrolytic graphite electrodes, while encapsulated in a sol-gel matrix. The enzymatic reduction of O₂ was evaluated in the presence and absence of its electron donor partner, cytochrome P450 oxidoreductase (CPR). When used without CPR, CYP1A2 was shown to be highly sensitive to O₂ even in the presence of residual amounts. Under aerobic conditions (air-saturated solutions), the catalytic signal attributed to the reaction with O₂ was lost, suggesting the enzyme was inactivated. In contrast, the CYP1A2/CPR complex retained O₂ reductase activity with high O₂ concentration in solution. The results demonstrated a crucial role of CPR in stabilizing the immobilized CYP1A2 enzyme and in the preservation of O₂ electrocatalysis, when using this electrochemical set-up. Though the enzyme's monooxygenase activity towards caffeine was not detected, this study highlights the complexity of coupling CYP1A2 reduction currents with substrate turnover, owing to the simultaneous electrochemical measurement of the O₂ reduction reaction.