The direct oxidation of ethanol by a catalase- and alcohol dehydrogenase-free reconstituted system containing cytochrome P-450☆

Abstract Ethanol oxidation activity has been reconstituted in a system composed of NADPH-cytochrome c reductase, synthetic dilauroylglycerol-3-phosphorylcholine and cytochrome P -450 purified from liver microsomes of phenobarbital-treated rats. This system is free of alcohol dehydrogenase and catalase activities. Furthermore, sodium azide (1 m m ), a catalase inhibitor, is without effect on ethanol metabolism. There is a requirement for both NADPH-cytochrome c reductase and cytochrome P -450 and a partial requirement for phospholipid for ethanol oxidation by the reconstituted system. In addition, both NADPH and O 2 are required for catalysis. Under optimal reaction conditions, the rate of acetaldehyde formation if 25 to 50 nmol/min/nmol of cytochrome P -450. Cytochrome P -450 from other sources, including the homogeneous P -450LM 2 from phenobarbital-treated rabbits, have also been found to catalyze ethanol oxidation in reconstituted systems. Antibody prepared against cytochrome P -450 inhibits ethanol metabolism in the reconstituted system consistent with a cytochrome P -450-mediated reaction. Furthermore, cumene hydroperoxide can replace both NADPH and NADPH-cytochrome c reductase in ethanol oxidation and catalysis can be demonstrated in a system composed of only cytochrome P -450, lipid, ethanol, and cumene hydroperoxide. These data implicate cytochrome P -450 in the direct oxidation of ethanol by this system.