UTILIZATION OF 2-MONOACYLGLYCEROLS FOR PHOSPHATIDYLCHOLINE BIOSYNTHESIS IN THE INTESTINE

Conventional preparations of intestinal microsomes were observed to incorporate acetone-solubilized 2-oleoyl-[2-H-3]glycerol into dioleoylglycerophosphocholine in the presence of oleoyl CoA and CDP-choline. The apparent K(m) values for CDP-choline utilization were 77 +/- 10-mu-M in rat and 72 +/- 5-mu-M in hamster. The incorporation ratio of glycerol into triacylglycerols and phosphatidylcholines was 4.5:1 and 25:1 in the rat and hamster, respectively. Endogenous diacylglycerols generated by phospholipase C treatment of microsomes readily equilibrated with the diacylglycerols arising via the monoacylglycerol pathway as indicated by a dilution of the radioactivity in the triacylglycerol and phosphatidylcholine synthesized from radioactive 2-monooleoylglycerol. These results suggest an alternative pathway for glycerophospholipid formation in the intestinal mucosa during possible inhibition of the phosphatidic acid pathway by dietary 2-monoacylglycerols. It is concluded that exogenously added monoacylglycerol can serve as a precursor for microsomal diacyl- and triacylglycerol as well as phosphatidylcholine. The inability to demonstrate comparable monoacylglycerol utilization in earlier experiments is attributed to the inhibition of choline phosphotransferase by the detergents used to solubilize the acylglycerols.