Incorporation of arachidonic acid into 1-acyl-2-lyso-sn-glycero-3-phosphocholine of the human neutrophil.
In this study, the initial incorporation of arachidonic acid into human neutrophils has been examined. Neutrophils pulse labeled for 5 min with [3H]arachidonic acid rapidly incorporated this fatty acid into 1,2-diacylglycerophosphocholine. However, when neutrophils were pulse labeled with [3H]arachidonic acid for 5 min, washed, and allowed to incubate for an additional 120 min, the relative amount of [3H]arachidonic acid increased in alkylacylglycerophosphocholine molecular species. Similar, when neutrophils were pulse labeled, washed, and allowed to incubate in the presence of 30 microM unlabeled arachidonic acid for 120 min, [3H]arachidonic acid was also remodeled into alkylacylglycerophosphocholine. These results implied that the initial incorporation of [3H]arachidonic acid proceeded via a free fatty acid intermediate into 1,2-diacyl-GPC, while the subsequent remodeling of arachidonate-containing glycerophospholipids did not. This initial incorporation was further investigated in a number of cell-free systems. Disrupted neutrophils incubated with [14C]arachidonoyl-CoA incorporated [14C]arachidonic acid into 1,2-diacyl-GPC containing 16:0, 18:0, and 18:1 at their sn-1 position in a pattern similar to that seen when whole neutrophils were incubated with arachidonic acid for 5 min. A small percentage of [14C]arachidonate from [14C]arachidonoyl-CoA was incorporated into 1-alkyl-2-acyl-GPC. The enzymatic activity responsible was found predominately in the membrane fraction of the broken cell preparation. This selectivity of the CoA-dependent acyltransferase for 1-acyl-linked glycerophosphocholine was further examined by adding [14C]arachidonoyl-CoA and various 1-radyl-2-lyso-GPC to neutrophil membrane preparations. These studies provide evidence that the initial incorporation of arachidonic acid into sn-glycero-3-phosphocholine takes place by an arachidonoyl-CoA: lysophosphatidylcholine acyltransferase(s) which is selective for the 1-acyl-2-lyso-GPC.
D000214:Acyl Coenzyme A / Q000097:blood; D000217:Acyltransferases / Q000097:blood; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000097:blood*; D002474:Cell-Free System; D006801:Humans; D007700:Kinetics; D008244:Lysophosphatidylcholines / Q000097:blood*; D009504:Neutrophils / Q000378:metabolism*; D014316:Tritium
D000214:Acyl Coenzyme A; D001095:Arachidonic Acids; D008244:Lysophosphatidylcholines; D014316:Tritium; C026563:arachidonyl-coenzyme A; D016718:Arachidonic Acid; D000217:Acyltransferases