[Use of lipid exchange proteins for investigation of lipid dependence of rat liver cytochrome P-450].

The ability of lipid exchange proteins to introduce foreign phospholipids into intact microsomes was used for a study of the lipid dependence of rat liver cytochrome P-450. Cytochrome P-450 was converted into inactive cytochrome P-420 by treatment of rat liver microsomes with lysophosphatidylcholine. When such microsomes were incubated with phosphatidylcholine in the presence of lipid exchange proteins the lysophosphatidylcholine was partly replaced by phosphatidylcholine and the inactive cytochrome P-450 was reactivated. Similar incubation of the inactivated microsomes with phosphatidylethanolamine did not lead to reactivation of the enzyme.