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DIFFERENT INFLUENCES OF 2 FRACTIONS OF LUNG CYTOCHROME-B5 ON RECONSTITUTED LUNG BENZPHETAMINE N-DEMETHYLASE SYSTEM

1995-10-01
ARINC, E
Adalı, Orhan
PASHA, RPK
BASARAN, N
Chromatography of lung microsomal cytochrome b5 obtained from DEAE-cellulose columns, yielded two distinct cytochrome b5 fractions, These cytochrome b5 fractions were further purified by Sephadex G-100 gel filtration chromatography. The specific cytochrome b5 content of fraction 1 and fraction 2 was found to be 16.5 and 16.4 nmol/mg protein respectively. Both fractions were free of cytochrome P-450, NADPH-cytochrome P-450 reductase and NADH-cytochrome b5 reductase activities. The effects of lung cytochrome b5 (fraction 1 and fraction 2) and liver cytochrome b5 on benzphetamine N-demethylase activity were examined, Four different reconstitution systems were used, Lung cytochrome b5 fraction 2 and liver cytochrome b5 stimulated N-demethylase activity in all four systems when b5:P-450 molar ratio was low, i.e. 0.25 or 0.5, Both cytochrome b5 samples inhibited N-demethylase activity when b5:P-450 ratio exceeded 1:1 molar ratio, In contrast lung cytochrome b5 fraction 1 stimulated N-demethylase activity in all four systems, Maximal enhancement of the activity was obtained when b5:P-450 ratio was 0.5. The greatest increase in N-demethylation activity was observed in the reconstitution system with the lowest concentration of cytochrome P-450 reductase, conditions which most closely resemble intact microsomes.