Role of lipid in the electron transfer between NADPH-cytochrome P-450 reductase and cytochrome P-450 from mammalian liver cells

1. The anaerobic NADPH-reduction of the isozymes cytochrome P-450 LM2 and LM4 was used as a functional tool to study the component interaction in reconstituted monooxygenase systems in dependence on different phospholipids.2. The isozymes were shown to exhibit similar lipid interaction. The lipids generally favour a catalytically active 1 :1 complex formation between reductase and cytochrome P-450 as the rate-determining unit in electron transfer.3. The cytochrome P-450 reduction proceeds in a biphasic reaction. In dilauroyl phosphatidylcholine (DLPC)-reconstituted systems the amount of the fast reduction ψ1, is stoichiometrically limited by the reductase in deficit: ψ1, corresponds to the 1:1 complex formation capability of the reductase.4. In vesicle-reconstituted systems an ‘overstoichiometric’ reductase cycling is observed which gives rise to a significantly increased amount of fast reduction ψ1, Reductase cycling is proposed to occur in protein clusters of cytochrome P-450 and reductase in deficit.5....