Characterization of NADPH-cytochrome P-450 reductase in a mouse hepatoma cell line

NADPH-cytochrome c reductase in Hepa-1 cells was induced 2-fold by phenobarbital, but was not induced by benz[a]anthracene or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The apparent Km of the enzyme for NADPH was 0.57 microM; the activity was inhibitable by NADP; and segregated primarily to the microsomal fraction. Cytoplasm of Hepa-1 cells bound antibody to rabbit cytochrome P-450 reductase. 3T3 cells, which possessed one sixth of the cytochrome c reductase activity of Hepa-1 cells, bound correspondingly less cytochrome P-450 reductase antibody. This supports the notion that cytochrome P-450 reductase was responsible for the cytochrome c reductase activity that was measured.