STIMULATORY EFFECTS OF LUNG CYTOCHROME B5 ON BENZPHETAMINE N-DEMETHYLATION IN A RECONSTITUTED SYSTEM CONTAINING LUNG CYTOCHROME P450LGM2

1. Cytochrome b 5 was partially purified from sheep lung microsomes in the presence of detergents Emulgen 913 and cholate by three consecutive DEAE-cellulose and Sephadex G-100 gel filtration chromatographies. 2. The specific content of cytochrome b 5 was 16.5 nmol/mg protein and purified cytochrome b 5 fractions were free of cytochrome P450, NADPH-cytochrome P450 reductase and NADH-cytochrome b 5 reductase activities. 3. The influences of increasing concentrations of lung cytochrome b 5 on benzphetamine N-demethylation reactions were examined in four different reconstitution systems containing Lung cytochrome P450LgM2, lung cytochrome P450 reductase and lipid. In each system concentration of reductase was doubled with respect to former system. 4. In all systems cytochrome b 5 stimulated benzphetamine N-demethylase activity especially when cytochrome b 5 was present at 0.5:1 molar ratio with respect to cytochrome P450LgM2. 5. Besides, the greatest fold of increase in benzphetamine N-demethylation activity due to addition of cytochrome b 5 was observed in System 1 with the lowest concentration of reductase.