Metabolism of platelet-activating factor in human platelets. Transacylase-mediated synthesis of 1-O-alkyl-2-arachidonoyl-sn-glycero-3-phosphocholine.
The present study demonstrates that inactivation of exogenous 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (alkylacetyl-GPC; platelet-activating factor) by human platelets is mediated by the sequential action of two enzymes, 1) a Ca2+-independent acetylhydrolase recovered in the cytosolic fraction of platelets that deacylates alkylacetyl-GPC forming alkyllyso-GPC and 2) a CoA-independent, N-ethylmaleimide-sensitive transacylase associated with platelet membranes that incorporates a long-chain fatty acid into alkyllyso-GPC to produce alkylacyl-GPC. Separation of platelet phospholipids and subsequent resolution into individual molecular species by high-performance liquid chromatography revealed that the newly formed alkylacyl-GPC was exclusively alkylarachidonoyl-GPC and that the arachidonoyl group for acylation of alkyllyso-GPC was provided by phosphatidylcholine. We conclude that the previously described platelet arachidonoyl transacylase (Kramer, R.M., and Deykin, D. (1983) J. Biol. Chem. 258, 13806-13811) may play an important role in the metabolism of platelet-activating factor.
D000217:Acyltransferases / Q000097:blood*; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000097:blood; D001792:Blood Platelets / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D010972:Platelet Activating Factor / Q000502:physiology*; D014316:Tritium
D001095:Arachidonic Acids; D002250:Carbon Radioisotopes; D010972:Platelet Activating Factor; D014316:Tritium; D016718:Arachidonic Acid; D000217:Acyltransferases; C039766:arachidonyl transacylase