Identification of (N-acyl)ethanolamine phosphoglycerides and acylphosphatidylglycerol as the phospholipids which disappear as Dictyostelium discoideum cells aggregate

The cellular slime mold Dictyostelium discoideum contains a phospholipid fraction which comprises 10% of the phospholipids in the early developing amoebae and disappears during the aggregation stage of development. As a first step in studying its metabolism, the composition of the fraction has been determined. It was easily isolated by preparative silicic acid thin-layer chromatography because its Rf was considerably higher than most commonly encountered phospholipids. Its Rf was the same as synthetic phosphatidyl-N-acylethanolamine and synthetic acylphosphatidylglycerol (also called semilysobisphosphatidic acid). Strong absorption peaks characteristic of amide bonds in the infrared spectrum of the isolated D. discoideum phospholipid showed that N-acylethanolamine phosphoglycerides were present. The presence of acylphosphatidylglycerol was revealed when mild alkaline hydrolysis of the lipid fraction produced glycerophosphorylglycerol as the only water-soluble, phosphate-containing product. The composition of the fraction was determined by chemical analysis and thin-layer chromatography of the intact phospholipids and their partially or completely hydrolyzed products. The composition of the fraction was 30% diacylglycerophosphoryl-N-acylethanolamine, 50% alkenylacylglycerophosphoryl-N-acylethanolamine, and 20% acylphosphatidylglycerol. The stereoconfiguration of the glycerophosphorylglycerol moiety of the acylphosphatidylglycerol was found to be sn-3-glycerophosphoryl-sn-1'-glycerol.