Sequential Solubilization of Microsomal Mixed Function Oxidases

Addition of increasing levels of sodium deoxycholate to fixed quantities of liver microsomes from noninduced mice reveals a sequential release, in three discrete steps, of certain elements of the mixed function oxidase system. Only one of these stages influences aniline and naphthalene oxidase activity, suggesting the possibility that sequential release is related to differentiation of function. The cytochrome P-450 and the NADPH2-dependent cytochrome c reductase (EC 1.6.2.3) components can be separated by ammonium sulfate precipitation and reconstituted to form a system active against naphthalene. The partial removal of sodium deoxycholate from solubilized cytochrome P-450 by the addition of Dowex 1X 2-400 results in a decrease of contaminant cytochrome P-420 with a concomitant increase in the amount of cytochrome P-450, a phenomenon which suggests renaturation of cytochrome P-420 into cytochrome P-450.