Selective Inactivation of Microsomal Drug Metabolizing Proteins by Visible Light

Rat liver microsomes treated with heterochromatic visible light (λ > 400 nm) and O2 showed a preferential inactivation of NADPH‐cytochrome P450 reductase and cytochrome P450, proteins involved in drug metabolism. Cytochrome P450 destruction correlates with lipid peroxidation; both are oxygen dependent and affected to the same extent by antioxidants and radical scavengers. Under anaerobic conditions. NADPH‐cytochrome P450 reductase is the only component which is inactivated; this is accompanied by FMN loss and activity can be restored by reconstitution.