Lysophospholipid acyltransferases

Fig. 10. Involvement of a CoA-dependent transacylase in the production of lyso-platelet-activating factor (lyso-PAF) for the synthesis of PAF and the remodeling of the sn-2 acyl group of membrane phospholipids. The enzymes catalyzing these reactions are (I) CoA-dependent transacylase (with CoA as the acyl acceptor), (II) acetyl CoA lyso-PAF acetyltransferase, and (III) acyl-CoA Iysophospholipid acyltransferase. The reaction depicted for the CoA-dependent transacylase represents the reversal of the reaction catalyzed by acyl-CoA lysophospholipid acyltransferase. GPE, sn-glycero-3-phosphoethanolamine.

Chambers, K., and Brown, W. J. (2004). Characterization of a novel CI-976-sensitive lysophospholipid acyltransferase that is associated with the Golgi complex. Biochem. Biophys. Res. Commun. 313, 681-686. 

Fig. 2. Targeted lipidomics of 2-AG metabolism. Postulated pathways for 2-AG metabolism. Abbreviations PLC, phospholipase C DAG, diacylglycerol DGL, diacylglycerol lipase MGL, monoacylglycerol lipase PLA, phospholipase A AT, acyltransferase TAGL, triacylglycerol lipase PIP2, phosphatidylinositol bisphosphate ABHD-6/12 hydrolase lyso-PL, lysophospholipid lyso-PA, lysophosphatidic acid PA, phosphatidic add P, phosphatase COX, cydooxygen-ase LOX, lipoxygenase CYP450, cytochrome P450 CDP, cytidine diphosphate.

The chemistry of complex lipids is dominated by regioselective hydrolysis reactions of (1) the glyceryl fatty acid esters and (2) phosphate diesters. Both types of reactions are routinely performed with the corresponding esterases. A large variety of lipid active transferase enzymes is also commercially available. Phospholipases Aj, A, C, and D, for example, split any of the four ester bonds of a phospholipid regioselectively. The product without a fatty acid side chain at C2 of glycerol is called a lysophospholipid. Lecithin-cholesterol-acyltransferase transfers the fatty acid at C2, often linoleic acid, to the OH group at C3 of cho-... 

Microsomal fractions of oilseed rape readily incorporated (1- C) oleoyl CoA into PC, PA and TG, indicating the presence of active Kennedy pathway and PC-acyltransferase activities. Acyl transfer to PC was hugely stimulated in the presence of exogenous LPC but, in the presence of exogenous LPA the vast majority of the acyl transfer was to PA (Table 1). In each case the acylation of the added lysophospholipid was virtually the only route for oleate metabol-isation, resulting in the accumulation of labelled PC or PA over the short term. By means of pulse-chase studies, it was possible to observe some flow of label from PA towards TG and PC, which is consistent with the proposed operation of an equilibrium between DG and PC (1-4). It was more difficult to... 

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