Partial purification of pulmonary cytochrome P-448 from 3-methylcholanthrene-treated rats

Pulmonary cytochrome P-448 from 3-methylcholanthrene-pretreated rats was partially purified approximately 20-fold. The purified preparations containing 1.74 nmol per mg protein were essentially free of NADH-cytochrome b5 reductase and NADPH-cytochrome c reductase, and included a small amount of cytochrome b5 spectrophotometrically. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the partially purified cytochrome P-448 gave one major band and several minor bands when stained with Coomassie blue. The major band on which the presence of peroxidase activity could be determined had the apparent molecular weight of 57,000. In the presence of NADPH-cytochrome c reductase, lipid and NADPH, the pulmonary cytochrome P-448 was active in hydroxylation of benzo-[a]pyrene, but catalyzed N-demethylation of benzphetamine in a slow rate.