Effects of deoxycholate and phospholipase A2 on choline and ethanolamine phosphotransferases of chicken brain microsomes.

Ethanolamine phosphotransferase (EC 2.7.8.1) and choline phosphotransferase (EC 2.7.8.2) activities were assayed in fresh microsomes from adult chicken brains with either diacylglycerols or alkylacylglycerols. Pretreatment of microsomes with 1.25 mM sodium deoxycholate, a concentration less than the critical micelle concentration, produced a slight inhibition of choline phosphotransferase activity. A deoxycholate concentration (5.0 mM) greater than the critical micelle concentration (3.0 mM) decreased the choline phosphotransferase activity by more than 70% but had no effect on ethanolamine phosphotransferase activity. Inclusion of 1.25 mM deoxycholate in the assay medium decreased choline phosphotransferase activity 35% but increased ethanolamine phosphotransferase activity 50%. The deoxycholate appeared to inactive the choline phosphotransferase. Phospholipase A2 (Vipera russelli) treatments of microsomes removed phosphoglycerides and decreased both phosphotransferase activities to a similar extent. Decreased activities are probably due to disruption of the membrane structure. Choline and ethanolamine phosphotransferase activities are apparently in different enzymes which lack specificity for the type of diglyceride. Thus, the systematic names should include 1,2-diradyl-sn-glycerol instead of 1,2-diacyl-sn-glycerol.