Regulation of the gastric microsomal (H+ + K+)-transporting ATPase system by the endogenous activator. Effect of phospholipase A2 treatment.

Pig gastric microsomal (H+ + K+)-stimulated ATPase activity was nearly abolished within 10 min of digestion with phospholipase A2 at room temperature. The enzyme activity could be largely restored by a cytosolic activator protein partially purified from the gastric cells. The K+ sensitivity and turnover of 32P-labelled intermediates produced by the control and the activator-reconstituted microsomal (H+ + K+)-stimulated ATPase were closely similar but were widely different to those from treated membranes without activator reconstitution. The data suggest an essential requirement for the endogenous activator for gastric (H+ + K+)-stimulated ATPase function.