Phospholipid synthesis in differentiating cells of rat intestine

Abstract

The activities of 11 of the enzymes involved in the synthesis of phospholipids have been determined in differentiating cells of rat intestine separated as a villus to crypt gradient. The undifferentiated crypt cells possessed activity for all the enzymes investigated. Cholinephosphotransferase and ethanolaminephosphotransferase showed no gradient of activity during differentiation. The lysophosphatide acyltransferases of choline and ethanolamine on the other hand did show a villus to crypt gradient in activity with the specific activity of the villus cell acyltransferases four times that of the crypt cell enzymes. There also was a villus to crypt gradient in the activities of the enzymes involved in the synthesis of CDP-diacylglycerol, phosphatidylinositol, phosphatidylserine, and sphingomyelin. The synthesis of phosphatidylethanolamine by the decarboxylation of phosphatidylserine showed no gradient in activity during differentiation. The increases in the activities of several of the enzymes during differentiation may be related to the synthesis of specific membranes, e.g., the microvillus membrane. This system appears to therefore lend itself well to further studies on the biogenesis of specific membranes.