[Oxidative modification of cytochrome P450 and other macromolecules during its turnover]

Possible mechanisms of cytochrome P4502B4 modification by H2O2 formed during catalytic turnover have been studied. Oxidative self-inactivation of cytochrome P4502B4 in monooxygenase system, reconstituted from highly purified membrane proteins: cytochrome P4502B4, NADDPH-cytochrome P450 reductase and cytochrome b5 in the presence of detergent Emulgen 913, involves the heme destruction and apoenzyme modification. The cytochrome P450 self-inactivation is accompanied by protein aggregation, oxidation of SH-groups and changes of the surface charge. H2O2 and non-specific radical reactions may be responsible for the intermolecular cross-linking. Oxidative modification of cytochrome P4502B4 may be initial stage of the protein decay in the cell.