Coenzyme A-mediated transacylation of sn-2 fatty acids from phosphatidylcholine in rat lung microsomes.
Evidence was obtained for a CoA-dependent transfer of linoleate from rat lung microsomal phosphatidylcholine to lysophosphatidylethanolamine without the intervention of a Ca2+-requiring phospholipase A2 activity and ATP. To study this CoA-mediated transacylation process, microsomes were prepared in which the endogenous phosphatidylcholine was labeled by protein-catalyzed exchange with phosphatidylcholines containing labeled fatty acids in the sn-2-position. The apparent Km for CoA in the transfer of arachidonate from phosphatidylcholine to 1-acyllysophosphatidylethanolamine was 1.5 microM. At saturating lysophosphatidylethanolamine concentrations, the transacylation was linear with the amount of microsomal protein, i.e., a fixed percentage of the labeled fatty acid was transferred independent of the amount of microsomal protein. A maximal transfer of 12.2% for arachidonate and 2.0% for linoleate from the respective phosphatidylcholines to lysophosphatidylethanolamine was observed in 30 min. With 1-acyl-2-[1-14C]arachidonoylphosphatidylcholine as acyl donor, lysophosphatidylethanolamine was the best acceptor followed by lysophosphatidylglycerol and lysophosphatidylserine. Lysophosphatidate barely functioned as acceptor. These data provide further evidence for the widespread occurrence of CoA-mediated transacylation reactions. The arachidonate transacylation from phosphatidylcholine to other phospholipids in lung tissue may contribute to the low level of arachidonate in pulmonary phosphatidylcholine.
Nijssen
J G
JG
van den Bosch
H
H
D000215:Acylation; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D003065:Coenzyme A / Q000502:physiology*; D005227:Fatty Acids / Q000378:metabolism*; D066298:In Vitro Techniques; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000378:metabolism; D008168:Lung / Q000378:metabolism*; D008246:Lysophospholipids; D008297:Male; D008861:Microsomes / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D001095:Arachidonic Acids; D005227:Fatty Acids; D008041:Linoleic Acids; D008246:Lysophospholipids; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; C008301:lysophosphatidylethanolamine; D016718:Arachidonic Acid; D019787:Linoleic Acid; D003065:Coenzyme A