Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.1.5 (neuropathy target esterase)
1,070 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Structural requirements of inorganic phosphorus compounds as specific activators or inhibitors for phospholipase A2 and phospholipase B were investigated using orthophosphate, pyrophosphate and polyphosphate. It was observed that orthophosphate and pyrophosphate stimulated the activities of phospholipase A2 from bee venom, snake (Naja naja) venom and pig pancreas, and also phospholipase B from the yeast Torulaspora delbrueckii. However, polyphosphate was found to act as an inhibitor for phospholipase A2 in the above species and also for phospholipase B from T. delbrueckii. Orthophosphate and pyrophosphate induced gradual aggregation of liposome, but polyphosphate prolonged the lifetime of the liposome, suggesting that orthophosphate and pyrophosphate destabilize the bilayer structure of phosphatidylcholine and polyphosphate stabilizes it.
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PMID:Effects of inorganic phosphorus compounds on the hydrolysis of phosphatidylcholine liposomes by phospholipid-deacylating enzymes. 771 Jul 2

Venoms from two related Australian ants, a jumper ant (Myrmecia pilosula) and a bulldog ant (Myrmecia pyriformis), were quantitatively analysed for the following enzymic activities: phospholipase A2, phospholipase B, phospholipase C, hyaluronidase, esterase, acid phosphatase, alkaline phosphatase and phosphodiesterase. Both venoms contained phospholipase A2, phospholipase B, hyaluronidase, acid phosphatase and alkaline phosphatase activities. Myrmecia pyriformis venom had significantly greater phospholipase B, acid phosphatase and alkaline phosphatase activities than Myrmecia pilosula venom. No detectable quantities of phospholipase C, esterase or phosphodiesterase activities were found in either venom.
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PMID:Some enzymic activities of two Australian ant venoms: a jumper ant Myrmecia pilosula and a bulldog ant Myrmecia pyriformis. 772 23

Ether lipids were obtained from a wide range of archaeobacteria grown at extremes of pH, temperature, and salt concentration. With the exception of Sulfolobus acidocaldarius, unilamellar and/or multilamellar liposomes could be prepared from emulsions of total polar lipid extracts by pressure extrusion through filters of various pore sizes. Dynamic light scattering, and electron microscopy revealed homogeneous liposome populations with sizes varying from 40 to 230 nm, depending on both the lipid source and the pore size of the filters. Leakage rates of entrapped fluorescent or radioactive compounds established that those archaeobacterial liposomes that contained tetraether lipids were the most stable to high temperatures, alkaline pH, and serum proteins. Most ether liposomes were stable to phospholipase A2, phospholipase B and pancreatic lipase. These properties of archaeobacterial liposomes make them attractive for applications in biotechnology.
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PMID:Stability of pressure-extruded liposomes made from archaeobacterial ether lipids. 776 79

A sensitive method for continuously monitoring the activity of the human cytosolic phospholipase A2 (cPLA2) is described. Recombinant cPLA2 efficiently hydrolyzes fatty acid esters of 7-hydroxycoumarin, producing the free fatty acid and the highly fluorescent 7-hydroxycoumarin. All of the observed 7-hydroxycoumarinyl ester hydrolase activity (7-HCEase) in a preparation of the purified recombinant cPLA2 was due to this enzyme since: (1) all of the ester hydrolase activity comigrated on nondenaturing polyacrylamide gel with a protein characterized as the cPLA2 by Western analysis; (2) the immunoreactive protein also possessed both phospholipase A2 and lysophospholipase activities; and (3) arachidonyl trifluoromethyl ketone, a potent inhibitor of the phospholipase A2 activity of cPLA2, also inhibited the 7-HCEase activity. A study of the 7-HCEase activity demonstrated that when 7-hydroxycoumarinyl gamma-linolenate was dispersed in a phospholipid matrix it was hydrolyzed by cPLA2 at a rate comparable to that of an arachidonyl-containing phospholipid substrate and with an identical reaction progress curve. In the presence of phospholipid vesicles, the cPLA2-catalyzed hydrolysis of hydrophobic 7-hydroxycoumarinyl esters was stimulated by submicromolar concentration of free calcium and showed a preference for polyunsaturated substrates. The cPLA2-catalyzed hydrolysis of the water-soluble substrate 7-hydroxycoumarinyl 6-heptenoate was catalyzed by cPLA2 in the absence of calcium and other lipids.
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PMID:A continuous fluorescence-based assay for the human high-molecular-weight cytosolic phospholipase A2. 785 35

We describe the purification and first biochemical characterization of an enzymatic activity in venom from the marine snail Conus magus. This enzyme, named conodipine-M, is a novel phospholipase A2 with a molecular mass of 13.6 kDa and is comprised of two polypeptide chains linked by one or more disulfide bonds. The amino acid sequence of conodipine-M shows little if any homology to other previously sequenced phospholipase A2 enzymes (PLA2s). Conodipine-M thus represents a new group of PLA2s. This is remarkable, since conodipine-M displays a number of properties that are similar to those of previously characterized 14-kDa PLA2s. The enzyme shows little, if any, phospholipase A1, diacyglycerol lipase, triacylglycerol lipase, or lysophospholipase activities. Conodipine-M hydrolyzes the sn-2 ester of various preparations of phospholipid only in the presence of calcium and with specific activities that are comparable to those of well known 14-kDa snake venom and pancreatic PLA2s. The Conus enzyme binds tightly to vesicles of the negatively charged phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphomethanol and catalyzes the hydrolysis of this substrate in a processive fashion. Conodipine-M does not significantly discriminate against phospholipids with unsaturated versus saturated fatty acids at the sn-2 position or with different polar head groups. Linoleoyl amide and a phospholipid analog containing an alkylphosphono group at the sn-2 position are potent inhibitors of conodipine-M. We suggest that the functional resemblance of conodipine-M to other PLA2s might be explained by the utilization of similar catalytic residues.
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PMID:Conodipine-M, a novel phospholipase A2 isolated from the venom of the marine snail Conus magus. 787 86

Membrane-bound neuropathy target esterase (NTE) and associated phenyl valerate carboxylesterases were solubilized from chicken embryo brain by phospholipase A2. Phospholipase A2 from bee or cobra (Naja) venoms were the most effective preparations in solubilizing brain NTE and other phenyl valerate carboxylesterases. Phospholipase C and several proteinases (endoproteinase, pronase E, proteinase K, thermolysin, trypsin) did not solubilize brain membrane-bound carboxylesterases but reduced their activity. NTE solubilization by phospholipase A2 did not affect its apparent Km and Vmax for the substrate phenyl valerate or the susceptibility of phenyl valerate carboxylesterases to inhibition by paraoxon and mipafox. NTE thermal stability diminished after the treatment of brain membrane fragments with phospholipase A2.
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PMID:Solubilization of neuropathy target esterase and other phenyl valerate carboxylesterases from chicken embryonic brain by phospholipase A2. 788 4

Mouse plasma platelet-activating factor acetylhydrolase (PAF-AH) has an apparent Km of 7.4 microM and a Vmax of 21.6 nmol/min per mg protein. Comparison with values reported for the human and the rat enzymes shows at least a 5-fold higher Vmax and similar enzyme-substrate affinity. Although lecithin:cholesterol acyltransferase (LCAT) and one component of the PAF-AH share similar masses and lipoprotein association, they are distinct enzymes. Similarly, PAF-AH is distinct from the phospholipase A2 (PLA2) and the lysophospholipase of mouse plasma. A series of PAF structural analogs showed either competitive inhibition or a mixed type of inhibition of PAF-AH. Mouse plasma PAF-AH is highly sensitive to 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) and is activated by deoxycholate. SDS-PAGE showed that two distinct proteins with molecular masses of 46 and 63 kDa contribute to the PAF-AH activity. The HDL-VHDL lipoprotein associated PAF-AH is precipitated to an extent of about 60% by phosphotungstate-MgCl2 and Tween 20 only partially solubilises the precipitated enzyme under conditions which can precipitate and solubilise the human enzyme.
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PMID:The mouse plasma PAF acetylhydrolase: I. Characterization and properties. 792 89

Lysophospholipids are generated during the turnover and breakdown of membrane phospholipids. We have identified and partially characterized three enzymes involved in the metabolism of lysophospholipids in human brain, namely, lysophospholipase, lysophospholipid:acyl-CoA acyltransferase (acyltransferase), and lysophospholipid:lysophospholipid transacylase (transacylase). Each enzyme displayed comparable levels of activity in biopsied and autopsied human brain, although in all cases the activity was somewhat lower in human than that in rat brain. All three enzymes were localized predominantly in the particulate fraction, with lysophospholipase possessing the greatest activity followed by acyltransferase and transacylase. Lysophosphatidylcholine possessed a Km in the micromolar range for lysophospholipase and transacylase, and in the millimolar range for acyltransferase, whereas arachidonyl-CoA displayed a Km in the micromolar range for acyltransferase. The three enzymes differed in their pH optima, with lysophospholipase being most active at pH 8.0, transacylase at pH 7.5, and acyltransferase at pH 6.0. Both bromophenacyl bromide and N-ethylmaleimide inhibited lysophospholipase activity and, to a lesser extent, that of acyltransferase and transacylase. None of the enzyme activities were affected by the presence of dithiothreitol or EDTA, although particulate lysophospholipase was activated approximately two-fold by the addition of 5 mM MgCl2 or CaCl2 but not KCl. Transacylating activity was stimulated by CoA, the EC50 of activation being 6.8 microM. Acyltransferase displayed an approximately threefold preference for arachidonyl-CoA over palmitoyl-CoA, whereas the acylation rate of different lysophospholipids was in the order lysophosphatidylinositol > 1-palmitoyl lysophosphatidylcholine > 1-oleoyl lysophosphatidylcholine >> lysophosphatidylserine > lysophosphatidylethanolamine. This, and the preference of human brain phospholipase A2 for phosphatidylinositol, suggests that this phospholipid may possess a higher turnover rate than the other phospholipid classes examined. Human brain homogenates also possessed the ability to transfer fatty acid from lysophosphatidylcholine to lysophosphatidylethanolamine. In addition, we also present evidence that diacylglycerophospholipids can act as acyl donors for the transacylation of lysophospholipids. We have therefore demonstrated the presence of, and partially characterized, three enzymes that are involved in the metabolism of lysophospholipids in human brain. Our results suggest that lysophospholipase may be the major route by which lysophospholipids are removed from the cell membrane in human brain. However, all three enzymes likely play an important role in the remodeling of membrane composition and thereby contribute to the overall functioning of membrane-associated processes.
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PMID:Characterization of lysophospholipid metabolizing enzymes in human brain. 793 40

The Ca(2+)-sensitive cytosolic phospholipase A2 (cPLA2) displays both a phospholipase A2 and a lysophospholipase activity. Numerous hydrolases, including lipases, catalyze the hydrolysis of ester bonds by means of an active site triad of amino acids that includes a serine or a cysteine residue. We have examined whether human cPLA2 belongs to this class of enzymes by using site-directed mutagenesis. Although chemical inactivation of cPLA2 by the sulfhydryl reagent N-ethylmaleimide made it appear that cysteine(s) may be essential for catalysis, all 9 cysteine residues of cPLA2 proved dispensable, allowing near-normal enzyme activity when substituted by alanine. We noted that cPLA2 contains a 110-amino-acid region with sequence homology to phospholipase B (PLB) from Penicillium notatum. Interestingly, one of the conserved serines of cPLA2, Ser-228, within this domain aligns with the lipase consensus sequence Gly-X(Leu)-Ser(137)-X(Gly)-Gly of PLB. Replacement of Ser-228 by alanine (or threonine or cysteine) yielded catalytically inactive cPLA2, even though the native conformation was maintained as determined by CD spectroscopy. Likewise, the lysophospholipase activity was completely abolished by the Ser-228 mutations. In contrast, substitution by alanine of three different serines of cPLA2 (Ser-195, Ser-215, or Ser-577) that also aligned with the PLB sequence allowed for substantial enzymatic activity of cPLA2. Our findings provide evidence that 1) Ser-228 participates in the catalytic mechanism of cPLA2 and that 2) both the phospholipase A2 and the lysophospholipase activities of cPLA2 are catalyzed by the same active site residue(s).
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PMID:Serine 228 is essential for catalytic activities of 85-kDa cytosolic phospholipase A2. 808 30

A novel fluorescence assay for quantifying lysophospholipase activity is described which utilizes a commercially available acrylodated intestinal fatty-acid-binding protein (ADIFAB) and non-radiolabelled substrate. Quantification of enzyme activity is based on the decrease in ADIFAB fluorescence at 432 nm in the presence of nanomolar concentrations of non-esterified ('free') fatty acids. Lysophospholipase activity measured by the ADIFAB assay and a conventional radiometric assay yield comparable results and have comparable levels of sensitivity (approximately 10 pmol/min per ml). The ADIFAB assay has the advantageous features of continuous monitoring of enzyme activity and the availability of a broad range of potential substrates, because non-radiolabelled lysophospholipids can be employed in the assay. The hydrolytic activities of four lysophospholipases were determined, including a bacterial secreted phospholipase A2/lysophospholipase, the human-eosinophil-secreted lysophospholipase, a human intracellular lysophospholipase (peak 3) isolated from HL-60 cells and a high-molecular-mass cytosolic phospholipase A2/lysophospholipase from a mouse mammary carcinoma. Each of these enzymes was found to have a distinctive hydrolytic profile as determined by an array of lysophospholipids differing in their polar headgroups and sn-1 fatty-acyl substituents.
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PMID:The substrate specificities of four different lysophospholipases as determined by a novel fluorescence assay. 812 24


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