Lipid peroxidation activity mediated by NADPH-cytochrome C reductase purified from rabbit liver microsomes.

Purified NADPH-cytochrome c reductase of rabbit liver microsomes was examined to determine whether or not the reported low lipid peroxidation activity of rabbit liver microsomes is due to the enzyme, NADPH-cytochrome c reductase. NADPH-cytochrome c reductase was purified from phenobarbital-treated rabbit liver microsomes to a specific activity of 14.9 to 21.4 unit per mg of protein with a yield of 15.2 to 16.4%. The purified sample (21.4 unit/mg of protein) was almost homogenous as determined by sodium dodecylsulfate gel electrophoresis. This sample was used for determining lipid peroxidation activity. EDTA and ferrous ion but not ADP were essential requirements for the activity. FMN enhanced the activity when low concentrations of the NADPH-cytochrome c reductase were used for the assay. NADP and 2'-AMP, which are inhibitors of NADPH-cytochrome c reductase, inhibited the lipid peroxidation activity. a-Tocopherol and p-chloromercuribenzoate (PCMB) also inhibited the activity. From these results, we confirmed the rabbit liver microsomal enzyme NADPH-cytochrome c reductase plays a role in lipid peroxidation activity. The reported low lipid peroxidation activity in rabbit liver microsomes does not appear to be caused by the NADPH-cytochrome c reductase.