Effects of lysophospholipids and diacylglycerols on the transfer of arachidonic acid to phospholipids and triacylglycerols in rat brain membranes.
Brain membranes catalyze the acylation of lysophospholipids and diacylglycerols (DAG) to form the respective phospholipids and triacylglycerols (TAG). These acylation reactions were examined using brain plasma membrane-enriched fractions by measuring the incorporation of [14C]arachidonic acid into TAG and individual phospholipids under a variety of conditions. In the absence of added lipid substrates, the amount of [14C]arachidonic acid incorporated into TAG in the presence of ATP, Mg2+, and CoA was approx twice the amount incorporated into phosphatidylositol (PtdIns), and more than 10 times the amount incorporated into phosphatidylcholine (PtdCho), phosphatidylethanolamine (PtdEtn) and phosphatidylserine (PtdSer). These results suggest the presence of endogenous DAG, lysoPtdIns, and the required enzymes in the membrane preparations for acylation reactions. The addition of DAG, lysoPtdCho or lysoPtdIns to the incubation system resulted in a 2-20-fold increase in the rate of incorporation of labeled arachidonic acid into TAG, PtdCho or PtdIns, respectively. LysoPtdEtn and lysoPtdSer were poor substrates for the synthesis of PtdEtn and PtdSer. On the other hand, the addition of lysoPtdSer stimulated the incorporation of [14C]arachidonic acid into TAG and into most phospholipids, especially phosphatidic acid, the synthesis of which was enhanced more than 10-fold. Exogenous lysoPtdCho and lysoPtdIns inhibited the incorporation of [14C]arachidonate into TAG in the presence of DAG, and DAG inhibited the incorporation of [14C]arachidonic acid into phospholipids in the presence of lysophospholipids. In general, [14C]palmitic acid was less effectively incorporated into lipids than arachidonic acid. These results suggest reciprocal regulatory effects of DAG and lysophospholipids on acyltransfer to phospholipids and triacylglycerol in brain membranes.
MacQuarrie
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Division of Molecular Biology and Biochemistry, School of Basic Life Sciences, University of Missouri-Kansas City 64110.
Yao
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Sun
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D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003065:Coenzyme A / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology*; D008244:Lysophosphatidylcholines / Q000494:pharmacology; D008246:Lysophospholipids / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology; D008563:Membrane Lipids / Q000378:metabolism*; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014280:Triglycerides / Q000378:metabolism
D004075:Diglycerides; D008244:Lysophosphatidylcholines; D008246:Lysophospholipids; D008563:Membrane Lipids; D010169:Palmitic Acids; D010743:Phospholipids; D014280:Triglycerides; C025449:lysophosphatidylinositol; D016718:Arachidonic Acid; D019308:Palmitic Acid; D000255:Adenosine Triphosphate; D008274:Magnesium; D003065:Coenzyme A