Partial purification and characterization of phenobarbital‐induced house fly cytochrome P‐450

Two forms of phenobarbital‐induced cytochrome P‐450 were partially purified from the Rutgers diazinon‐resistant strain of house fly using cholate solubilization, polyethylene glycol 6000 precipitation, and chromatography on DEAE cellulose. The preparation of highest purity had an absorbance maximum of 452 nm, a specific content of 10.0 nmol/mg protein, and an apparent molecular weight of 60,000 when examined by sodium dodecyl sulfate polyacrylamide electrophoresis. The yield of the highly purified cytochrome P‐450 was 2–3%. This form contained proportionately less cytochrome P‐420 than the original cholate solubilized microsomes, and is thus apparently more stable. A second form of cytochrome P‐450 having a specific content of 0.50–0.89 nmol/mg protein was eluted from DEAE cellulose with a 0‐0.25 M salt gradient. This is consistent with a previously reported elution pattern for Emulgen 913‐solubilized house fly microsomes. Several methods of solubilizing house fly microsomes were examined. High salt, 2M KCI, in the absence of detergents effectively solubilized cytochrome P‐450 (50–70% recovery) with little or no conversion to cytochrome P‐(420).