Polar head-group and acyl side-chain requirements for phospholipid-dependent (Na-+ plus K-+)-ATPase.

The abilities of different phospholipids to reactivate a lipid-depleted (Na-+ plus K-+)-ATPase (EC 3.6.1.3) have been compared. The phospholipids contained either the same group of hydrocarbon chains withhh different polar groups, or different hydrocarbon groups wit the same polar group; they were prepared by enzymic modification of the polar group of phosphatidylserine isolated from bovine brain and of phosphatidylcholine extracted from egg. Only the acidic phospholipids reactivated the ATPase but the amount of reactivation depended on the nature of the hydrocarbon chains as well as the polar group. These findings are discussed in relations to the compositions of the two different groups of fatty acyl chains constituting the hydrocarbon portions of the phospholipids.