The mechanism of cytochrome P450 2B4 self-inactivation during catalytic turnover has been studied in monooxygenase reconstituted system containing from monomers of the membrane proteins: NADPH-cytochrome P450 reductase, cytochrome P450 2B4 and cytochrome b5 in presence of detergent emulgen 913. It was shown that P450 is inactivated at a high rate during benzphetamine oxidation. Hydrogen peroxide formed at the cytochrome P450 active center plays the key role in hemoprotein inactivation during uncoupling of monooxygenase reactions. The mechanism oxidative heme modification has been studied in monooxygenase reconstituted system also. It was demonstrated that formed at the active center is responsible for the loss of P450 heme and localized outside of active hemoprotein center is responsible for the heme destruction.