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 983 and cholate by three consecuti ve 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 activitie s. 3. The influences of increasing concentrations of lung cytochrome b 5 on benzphetamine N-demethylation reactions were examined in four di fferent reconstitution systems containing Lung cytochrome P450LgM2, lu ng cytochrome P450 reductase and lipid. In each system concentration o f reductase was doubled with respect to former system. 4. In all syste ms cytochrome b 5 stimulated benzphetamine N-demethylase activity espe cially when cytochrome b 5 was present at 0.5:1 molar ratio with respe ct to cytochrome P450LgM2. 5. Besides, the greatest fold of increase i n benzphetamine N-demethylation activity due to addition of cytochrome b 5 was observed in System 1 with the lowest concentration of reducta se.