Publications

• Multiple enzymatic activities of the human cytosolic 85-kDa phospholipase A2: hydrolytic reactions and acyl transfer to glycerol.

  Hanel A.M., Gelb M.H.

  The recombinant human 85-kDa cytosolic phospholipase A2 (cPLA2), when assayed in the presence of glycerol, catalyzes the transfer of acyl chains of radiolabeled phosphatidylcholine and para-substituted phenyl esters of fatty acids to glycerol, in addition to hydrolyzing these substrates. The produ ... >> More

  The recombinant human 85-kDa cytosolic phospholipase A2 (cPLA2), when assayed in the presence of glycerol, catalyzes the transfer of acyl chains of radiolabeled phosphatidylcholine and para-substituted phenyl esters of fatty acids to glycerol, in addition to hydrolyzing these substrates. The product of the transacylation reaction is monoacylglycerol (MAG), and the acyl chain is predominantly esterified (> or = 95%) to a primary hydroxyl group of glycerol (sn-1/3); the stereochemistry is not known. Increasing concentrations of glycerol accelerate enzyme turnover both by providing an additional mechanistic pathway for the enzyme-substrate complex to form products and by increasing the intrinsic hydrolytic and transacylation activities of the enzyme. Significant enzymatic hydrolysis of sn-1/3-arachidonylmonoacylglycerol was measured, while sn-1/3-alpha-linolenoyl- and sn-2-arachidonylmonoacylglycerols were not detectably hydrolyzed. 1,3-Propanediol also serves as an acyl acceptor for the enzyme. cPLA2 hydrolyzes analog of lysophosphatidylcholine that lacks the sn-2 hydroxyl group. The enzyme will hydrolyze sn-1-acyl chains of rac-1-(arachidonyl, alpha-linolenoyl, palmitoyl)-2-O-hexadecyl-glycero-3-phosphocholine lipids and transfer the acyl chain to glycerol. Thus, cPLA2 has phospholipase A1 activity but only if an ether linkage rather than an ester linkage is present at the sn-2 position, and it is shown that the sn-1 acyl chains of both enantiomers of phosphatidylcholine are hydrolyzed. Phenyl [14C]-alpha-linolenate and five para-substituted phenyl esters of [3H]-alpha-linolenic acid with pKa values ranging from 7.2 to 10.2 for the phenol leaving groups were incorporated into 1,2-ditetradecyl-sn-glycero-3-phosphomethanol/Triton X-100 mixed micelles as substrates for the transacylation/hydrolysis reactions of the enzyme. Average product ratios, which are defined as the amount of monoacylglycerol formed to phenyl ester hydrolyzed, were 2.1 +/- 0.1 (n = 5) for the para-substituted phenyl esters and 2.0 +/-0.3 (n = 7) for phenyl alpha-linolenate. The similarity of the ratios, despite the range of pKa values for the leaving groups, is consistent with the formation of a common enzyme intermediate that partitions to give either fatty acid or MAG. That intermediate may be a covalent acyl enzyme. Finally, the acyl chain specificity of cPLA2 was investigated to better understand the preference of the enzyme for phospholipids with sn-2-arachidonyl chains. << Less

  Biochemistry 34:7807-7818(1995) [PubMed] [EuropePMC]

  This publication is cited by 6 other entries.

• Function, activity, and membrane targeting of cytosolic phospholipase A(2)zeta in mouse lung fibroblasts.

  Ghosh M., Loper R., Ghomashchi F., Tucker D.E., Bonventre J.V., Gelb M.H., Leslie C.C.

  Group IVA cytosolic phospholipase A(2) (cPLA(2)alpha) initiates eicosanoid production; however, this pathway is not completely ablated in cPLA(2)alpha(-/-) lung fibroblasts stimulated with A23187 or serum. cPLA(2)alpha(+/+) fibroblasts preferentially released arachidonic acid, but A23187-stimulate ... >> More

  Group IVA cytosolic phospholipase A(2) (cPLA(2)alpha) initiates eicosanoid production; however, this pathway is not completely ablated in cPLA(2)alpha(-/-) lung fibroblasts stimulated with A23187 or serum. cPLA(2)alpha(+/+) fibroblasts preferentially released arachidonic acid, but A23187-stimulated cPLA(2)alpha(-/-) fibroblasts nonspecifically released multiple fatty acids. Arachidonic acid release from cPLA(2) alpha(-/-) fibroblasts was inhibited by the cPLA(2)alpha inhibitors pyrrolidine-2 (IC(50), 0.03 microM) and Wyeth-1 (IC(50), 0.1 microM), implicating another C2 domain-containing group IV PLA(2). cPLA(2) alpha(-/-) fibroblasts contain cPLA(2)beta and cPLA(2)zeta but not cPLA(2)epsilon or cPLA(2)delta. Purified cPLA(2)zeta exhibited much higher lysophospholipase and PLA(2) activity than cPLA(2)beta and was potently inhibited by pyrrolidine-2 and Wyeth-1, which did not inhibit cPLA(2)beta. In contrast to cPLA(2)beta, cPLA(2)zeta expressed in Sf9 cells mediated A23187-induced arachidonic acid release, which was inhibited by pyrrolidine-2 and Wyeth-1. cPLA(2)zeta exhibits specific activity, inhibitor sensitivity, and low micromolar calcium dependence similar to cPLA(2)alpha and has been identified as the PLA(2) responsible for calcium-induced fatty acid release and prostaglandin E(2) production from cPLA(2) alpha(-/-) lung fibroblasts. In response to ionomycin, EGFP-cPLA(2)zeta translocated to ruffles and dynamic vesicular structures, whereas EGFP-cPLA(2)alpha translocated to the Golgi and endoplasmic reticulum, suggesting distinct mechanisms of regulation for the two enzymes. << Less

  J. Biol. Chem. 282:11676-11686(2007) [PubMed] [EuropePMC]

  This publication is cited by 6 other entries.