DIFFERENTIAL ROLE IN LIPID-PEROXIDATION BETWEEN RAT P450 1A1 AND P450 1A2

The role of cytochrome P450 (P450) in lipid peroxidation induced by NADPH or peroxide was investigated in a reconstituted system. When cumene hydroperoxide, t-butyl hydroperoxide and hydrogen peroxide were used as initiators, the rates of malondialdehyde (MDA) formation were much higher in a reconstituted system containing P450 1A1 than those observed in a reconstituted system containing P450 1A2. In contrast to peroxide-induced lipid peroxidation, P450 1A2 catalysed NADPH-induced lipid peroxidation more effectively than did P450 1A1 regardless of the presence of ADP-Fe(NO3)3. Carbon monoxide inhibited NADPH-induced formation of MDA in a reconstituted system containing P450 1A2, but not P450 1A1. In addition, superoxide dismutase (SOD) was an effective inhibitor in a NADPH-induced lipid peroxidation system catalysed by P450 1A2 but not by P450 1A1. These results suggest that a peroxide-induced reaction might proceed readily with P450 1A1, whereas P450 1A2 mainly functions in NADPH-induced lipid peroxidation via generation of an active oxygen species. It is furthermore indicated that the difference in the effect of SOD in NADPH-induced lipid peroxidation depends on the P450 used.