Regulation of the fatty acid composition of alkyl ether phospholipid in Ehrlich ascites tumor cells. The substrate specificities of 1-O-alkylglycerol 3-phosphate and 1-O-alkylglycero-3-phosphocholine acyltransferases.

Activity for the acylation of 1-O-alkyl-GP was found in the microsomes of Ehrlich ascites tumor cells. The reaction product was shown to be 1-O-alkyl-2-acyl-GP by identifying the acetolysis product as 1-O-alkyl-2-acyl-3-acetylglycerol. The acyl transfer activity to 1-O-alkyl-GP was significantly lower than that to 1-acyl-GP. The substrate specificity of 1-O-alkyl-GP acyltransferase was rather broad as regards thiol esters. Similar specificity was observed with 1-acyl-GP acyltransferase. In contrast to these acyltransferase systems, the 1-acyl- and 1-O-alkyl-GPC acyltransferases were specific for polyunsaturated fatty acyl-CoA's. Since a high percentage of polyunsaturated fatty acid and a little palmitic acid were located at the 2-position of 1-O-alkyl-2-acyl-GPC(E), the observed specificities for acyl-COA's of these acyltransferase systems can be considered in relation to the fatty acid composition at the 2-position of 1-O-alkyl-2-acyl-GPC(E) in the cells.