Effects of phospholipases on Cl-ATPase in the rat brain

We investigated the effects of phospholipases on the activity of microsomal Cl-ATPase in the rat brain, in reference to those on the activities of Na,K-ATPase and anion-insensitive Mg-ATPase. In the presence of phospholipase A2 or phospholipase C, which almost completely hydrolyzed microsomal phosphoglycerides, the activities of Cl-ATPase and Na,K-ATPase were decreased to 8-50% of the control, but anion-insensitive Mg-ATPase activity was not altered. On the other hand, with sphingomyelinase treatment, only anion-insensitive Mg-ATPase was slightly inactivated. On the addition of phospholipids (phosphatidylserine (PS), phosphatidylinositol (PI) and microsomal phospholipid mixture), Cl-ATPase activity slightly recovered only with PI, while Na,K-ATPase activity partially recovered with either phospholipid. These data suggest that Cl-ATPase requires intact membrane lipid conformation and especially PI for its maximal activity.