Immunochemical Study on the Pathway of Electron Flow in Reduced Nicotinamide Adenine Dinucleotide-Dependent Microsomal Lipid Peroxidation1

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Abstract
NADH could support the lipid peroxidation of rat liver microsomes in the presence of ferric ions chelated by ADP(ADP-Fe). The reaction had a broad pH optimum (pH 5.8–7.4) and was more active in the acideic pH range. Antibodies to NADH-cytochrome b5 reductase (EC 1.6.2.2) and cytochrome b5 inhibited NADH-dependent lipid peroxidation in the presence of ADP-Fe, whereas the antibody against NADPH-cytochrome c reductase (EC 1.6.2.4) showed no inhibition. These observations suggest that the electron from NADH was supplied to the lipid peroxidation reaction via NADH-cytochrome b5. On the other hand NADPH-supported lipid peroxidation was strongly inhibited by the antibody against NADPH-cytochrome c reductase, confirming the participation of this flavoprotein in the NADPH -dependent reaction. In the presence of both ADP-Fe and ferric ions chelated by EDTA(EDTA-Fe), NADH-dependent lipid peroxidation was highly stimolated up to the level of the NADPH-dependent reaction. In this case, the antibody against cytochrome b5could not inhibit the reaction, while the antibody against NADH-cytochrome b5 reducase did not inhibit the reaction, while antibody aganist NADH-cytochrome b5reducase did inhibit it, suggesting the direct transfer of electrons from NADH-cytochrome b5reductase to EDTA-Fe complex.