The effect of phospholipase C on the activity of adenosine triphosphatase and acetylcholinesterase in synaptic membranes isolated from the cerebral cortex of squirrel monkey

A synaptic-membrane fraction rich in junctional components and Na-K ATPase and AChE activity was isolated from the cerebral cortex of the squirrel monkey. Incubation of membrane preparations with phospholipase C decreased the activity of Na-K ATPase by 50 per cent but had no effect on the activity of AChE. Analysis of the membrane fraction showed that phospholipase C cleaved both choline phosphoglyceride and the diacyl type of ethanolamine phosphoglyceride from membrane lipids. Addition of egg lecithin at low concentrations partially restored the activity of Na-K ATPase. Kinetic studies revealed that treatment with phospholipase C may produce a non-competitive type of inhibition as a result of the cleavage of a charged phosphorylated nitrogen base from membrane lipids.