Abstract
We measured phospholipase activities in both the microsomal and the cytosolic enriched fractions of rat alveolar macrophages by using exogenous arachidinic acid-labeled phospholipids. The microsomal fractions contain a neutral calcium-independent phospholipase A 2 (PLA 2) which acts on substrates phosphatidylcholine (PC) and phosphatidylinositol (PI), a calcium-independent PLA 2 acting on phosphatidylethanolamine (PE), and a neutral calcium-dependent PI-specific PLC. The cytosolic fractions contain calcium-dependent phospholipases: PLA 2 that hydrolyses PC at alkaline pH, and a neutral PI-specific phospholipase C (PLC). The largest release of arachidonic acid from PI occurred with the cytosolic fractions at pH 6 in the presence of calcium. That hydrolysis involved a PLA 2, and a PLC followed by the action of a diacyglycerol and 2-monoacylglycerol lipases. The cytosol also contains a calcium-independent PLA 2 acting on PE. Our investigation shows that rat alveolar macrophages possess a number of phospholipases, as well as diacylglycerol and 2-monoacylglycerol lipases. The above enzymes could play an essential role in the remodeling of membrane phospholipids in resting cevls, and the generation of physiologically active lipids in activated cells.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism
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