Effect of lipid depletion on the kinetics of microsomal NADH-cytochrome C reductase.

Removal of lipids from the microsomes with 90% acetone resulted in 50% or more decrease of NADH-cytochrome c reductase activity. The decrease of the enzyme activity was a result of lowering of Vmax and increase in Km. When sufficient amounts of phosphatidylserine or phosphatidylinositol were added to the acetone-treated microsomes, the reductase activity was restored completely to the original level. On the other hang, when ferricyanide was used in place of cytochrome c as electron acceptor, the rate of reduction of ferricyanide was not affected by the lipid depletion and Vmax and Km for ferricyanide remained unchanged.