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)

Phospholipase A1, A2 and lysophospholipase activities in microsomes of Novikoff hepatoma host rat liver and regenerating rat liver were compared using 1-[9', 10'-3H2]palmitoyl-2-[1'-14C] linoleoyl-sn-glycero-3-phosphoethanolamine, 1-[1' -3H-]hexadecyl-2-acyl-sn-glycero-3-phosphoethanolamine, and 1-[9', 10'-3H2]palmitoyl-sn-glycero-3-phosphoethanolamine as substrates. 1. Microsomes of all three tissues showed two pH dependent peaks of hydrolytic activity, one at pH 7.5 and another at pH 9.5. 2. Phospholipid hydrolytic activity in microsomes from host liver and regenerating liver require Ca2+ for hydrolysis at pH 9.5, but not at pH 7.5. Hepatoma microsomes require Ca2+ for activity at both pH values. 3. Phospholipase A1 activity, stimulated by addition of Triton X-100 to the incubation mixtures, was detected in both host liver and regenerating liver microsomes. There was no evidence of phospholipase A1 activity in hepatoma microsomes. 4. Phospholipase A2 was detected in microsomes of all three tissues using 1-[1'-3H] hexadecyl-2-acyl-sn-glycero-3-phosphoethanolamine as a substrate. The activity required calcium and was inhibited by Triton X-100. 5. Lysophospholipase activity was evident in the microsomes from all three tissues. The activity was inhibited by both Ca2+ and Triton X-100. 6. Differences were also detected between host liver and hepatoma microsomal phospholipid hydrolase activities with respect to the effect of increasing protein concentration, apparent Michaelis-Menten constants, and time course of the reaction.
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PMID:Properties of microsomal phospholipases in rat liver and hepatoma. 1 Sep 88

Phospholipase and lysophospholipase activities are present in bovine thyroid (De Wolf et al., 1976). However, using exogenous [14C] phosphatidylcholine as substrate and subcellular fractions as enzyme source no activity could be detected at neutral and alkaline pH. Phospholipase A2 activity was found at neutral pH when [14C] phosphatidylethanolamine was substituted for [14C] phosphatidylcholine (De Wolf et al., 1976). In the present paper the occurrence of neutral and alkaline phospholipase A activities is clearly established. In addition their subcellular localization was investigated.
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PMID:Lipolytic enzymes in bovine thyroid tissue. II. Hydrolysis of [3H, 14C] phosphatidylethanolamine by neutral and alkaline phospholipase A activities. 8 60

1. A comparison of 2-hexadecanoylthio-ethane-1-phosphocholine and 3-hexadecanoylthio-propane-1-phosphocholine and their oxyester counterparts as substrates for some lipolytic enzymes was made. 2. The critical micelle concentration and the transition temperature of the synthetic substrates were compared with the values for 1-hexadecanoyl-sn-glycero-3-phosphocholine. 3. All above-mentioned compounds were deacylated by lysophospholipases. Phospholipase A2 hydrolyzed only the acyl- sulfur- and oxygenester bond in 2-hexadecanoyl-ethane-1-phosphocholine. 4. Kinetic parameters, Km and V, for hydrolysis of these substrates were determined. Km values for thioester substrates were 5--10 fold lower than for the corresponding oxyesters. Maximal hydrolysis rates were 2--5 times higher for the thioesters. 5. Hydrolysis of thioesters by phospholipase A2, lipase and lysophospholipase was shown to proceed by an S-acyl cleavage mechanism. 6. Beef liver lysophospholipase II was rapidly and stoichiometrically inactivated by diisopropylfluorophosphate and bis(p-nitrophenyl) phosphate. Inactivation by the latter inhibitor showed burst-like kinetics. 7. Attempts to show burst-kinetics during the pre-steady state hydrolysis of 2-hexadecanoylthio-ethane-1-phosphocholine by lysophospholipase II were negative. These results are interpreted to indicated that a step prior to deacylation of the enzyme is rate-determining.
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PMID:A comparison of acyl-oxyester and acyl-thioester substrates for some lipolytic enzymes. 43 7

1. Rat stomach mucosa exhibited three distinguishable phospholipid-deacylating enzyme activities: lysophospholipase, phospholipase A1 and phospholipase A2. 2. The lysophospholipase hydrolyzed 1-palmitoyl lysophosphatidylcholine to free fatty acid and glycerophosphorylcholine. This enzyme had an optimum pH of 8.0, was heat labile, did not require Ca2+ for maximum activity and was not inhibited by bile salts or buffers of high ionic strength. 3. Phospholipase A2 and phospholipase A1 deacylated dipalmitoyl phophatidylcholine to the corresponding lyso compound and free fatty acid. The specific activity of phospholipase A2 was 2--4-fold higher than that of phospholipase A1 under all the conditions tested. Both activities were enhanced 4--7.5-fold in the presence of bile salts at alkaline pH and 11-18-fold at acidic pH. 4. In the absence of bile salts, phospholipase A1 exhibited pH optima at 6.5 and 9.5 and phospholipase A2 at pH 6.5, 8.0 and 9.5. The pH optima for phospholipase A1 were shifted to pH 3.0, 6.0 and 9.0 in presence of sodium taurocholate; the activity was detected only at a single pH of 9.5 in the presence of sodium deoxycholate and at pH 10.0 in the presence of sodium glycocholate. Phospholipase A2 optimum activity was displayed at pH 3.0, 6.0 and 8.0 in presence of taurocholage, pH 7.5 and 9.0, in presence of glycocholate and only at pH 9.0 in presence of deoxycholate. 5. Ca2+ was essential for optimum activity of phospholipases A1 and A2. But phospholipase A1 lost complete activity in presence of 0.5 mM ethyleneglycolbis-(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA) at pH 6.0, whereas phospholipase A2 lost only 50%. 6. Phospholipases A1 and A2 retained about 50% of their activities by heating at 75 degrees for 10 min. At 100 degrees, phospholipase A1 retained 22% of its activity, whereas phospholipase A2 retained only 7%.
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PMID:Phospholipid-deacylating enzymes of rat stomach mucosa. 63 60

1. The effects of six local anaesthetics have been studied on the activities of soluble phospholipases A2 (EC 3.1.1.4) and lysophospholipase (EC 3.1.1.5). 2. Phospholipase A2 activity in human seminal plasma towards sonicated radioactively-labelled phosphatidylethanolamine was slightly stimulated a low and inhibited at high concentrations of all anaesthetic compounds employed. The order of decreasing potency was chlorpromazine, dibucaine, tetracaine, lidocaine, cocaine and procaine. In line with previous findings, the mode of inhibition was seen to be competitive with respect to Ca2+. 3. Phospholipase A2 activity in crude venom of Crotalus adamanteus was not affected or slightly stimulated by local anaesthetics up to 10(-2) M concentrations, when egg yolk was used as substrate. However, with sonicated radioactively-labelled phosphatidylcholine or phosphatidylethanolamine as substrate, stimulation of phospholipase activity was seen with all local anaesthetics up to 10(-2) M, the order of decreasing potency again being chlorpromazine, dibucaine, tetracaine, lidocaine, cocaine and procaine. The mode of stimulation was seen to be un-competitive with respect to substrate and probably independent of any involvement of Ca2+. 4. As in seminal plasma phospholipase A2, the activity in crude Naja naja venom towards sonicated radioactively labelled phosphatidylcholine was stimulated at low and inhibited at high concentrations of dibucaine and chloropromazine, for example. The mode of inhibition was seen to be competitive with respect to Ca2+, whereas stimulation by the anaesthetic drugs was independent of Ca2+. Binding between drug and enzyme was demonstrated by equilibration filtration of purified phospholipase A2 of Naja naja venom through a Sephadex G 25-fine column, previously equilibrated with 0.5 mM radioactively labelled chlorpromazine. 5. Lysophospholipase activity in rat liver cytosol towards radioactively labelled lysophosphatidylcholine was inhibited by all local anaesthetics used; the order of decreasing potency was chlorpromazine, dibucaine, tetracaine, cocaine, lidocaine and procaine. The inhibition was un-competitive with respect to substrate. 6. The inhibitory and stimulatory potencies of the local anaesthetics employed closely parallel their lipid solubilities and anaesthetic potencies.
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PMID:Effects of local anaesthetics on phospholipases. 95 85

Treatment of HL-60 cells with 0.5 mM-butyric acid resulted in morphological changes, including the formation of cytoplasmic granules, nuclear condensation and segmentation. These differentiated cells had an elevated phospholipase A2 activity and an increased capacity to synthesize a variety of eicosanoids, including both lipoxygenase and cyclooxygenase products. Phospholipase A2-mediated release of arachidonic acid is accompanied by an equimolar production of potentially cytotoxic lysophospholipid. In association with the differentiation process, there was a 2-3-fold increase in lysophospholipase activity. Subsequent studies were undertaken to identify and characterize the lysophospholipases in this cell system, with 1-[1-14C]palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine as substrate. Hydrophobic chromatography of both undifferentiated and differentiated cell extracts revealed three peaks of enzyme activity. Extracts of differentiated cells contained a dramatic increase in activity contained in peak 2. The increase in enzymic activity of peak 2 appeared to account for the increase in total lysophospholipase activity found in the differentiated cell homogenates. The lysophospholipases contained in peaks 2 and 3 were purified to homogeneity and were 20 and 22 kDa respectively, as determined by denaturing polyacrylamide-gel electrophoresis. Peaks 2 and 3 were similar on the basis of amino acid composition, but had distinctive C-terminal peptide amino acid sequences. Enzymic characterization of these proteins demonstrated that there was no detectable level of non-specific esterase, acyltransferase or transacylase activity associated with these proteins. We concluded that peak 2 lysophospholipase is regulated by differentiation in HL-60 cells and may play an important role in protecting these cells from the cytolytic effects of the lysophospholipids produced by the activation of phospholipase A2.
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PMID:Butyric acid-induced differentiation of HL-60 cells increases the expression of a single lysophospholipase. 147 98

Phospholipase A2 (PLA2) treatment has been shown previously to stimulate the sodium-dependent high-affinity choline uptake system as assessed by both the specific binding of [3H]hemicholinium-3 ([ 3H]HCh-3) and the uptake of [3H]choline. In the present study, the specificity of PLA2-induced stimulation upon [3H]HCh-3 binding has been examined. PLA2, as well as phospholipase C (PLC), treatment of synaptic membranes produced a dose-dependent increase in the specific binding of [3H]HCh-3 whereas neither phospholipase B nor phospholipase D had any effect. PLC-induced stimulation of [3H]HCh-3 binding resulted from a significant decrease in the Kd without a change in the maximum binding of [3H]HCh-3 binding. PLC treatment of synaptosomes resulted in an inhibition of [3H]choline uptake accompanied by an inhibition of Na+, K+-adenosine triphosphatase activity. In contrast to the increase of [3H]HCh-3 binding, the specific binding of both [3H]desipramine and [3H]mazindol was decreased by PLA2 treatment. After PLA2 treatment, [3H]HCh-3 binding was increased about 2.5-fold over basal levels in different regions of the brain. Electrolytic lesions of the medial septal nucleus and kainic acid-induced lesions of the striatum resulted in a marked reduction of [3H]HCh-3 binding in the hippocampus and the striatum, respectively. Residual [3H]HCh-3 binding in the denervated hippocampus and lesioned striatum was increased by PLA2 treatment but remained lower than that in PLA2-treated controls. Finally, atropine-induced up-regulation of [3H]HCh-3 binding in vivo was not additive with PLA2-induced stimulation. These results support the hypothesis that PLA2 might be involved in the regulation of the sodium-dependent high-affinity choline uptake.
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PMID:Specificity of the activation of [3H]hemicholinium-3 binding by phospholipase A2. 273 47

The phospholipase activity of rat jejunal brush-border membranes was examined in the presence of several solubilizing agents, by measuring the hydrolysis of endogenous membrane phospholipids, as well as the hydrolysis of exogenous, radiolabelled substrates. Enzyme activity was highly stimulated by dispersion in 1% solutions of bile salts, or in a synthetic, bile-salt derivative, 3-[(3-cholamidopropyl)dimethylammonio]propanesulphonate (CHAPS). Under these conditions the endogenous membrane phospholipids were largely degraded to free fatty acids and water-soluble phosphate. In the presence of 1% CHAPS, hydrolysis of exogenous phosphatidylcholine was shown to be due to an initial phospholipase A2-type attack followed by a subsequent lysophospholipase-type attack. These activities co-purified with the brush-border membrane. Maximal phospholipase A2 hydrolysis occurred at an alkaline pH of 8-11, with bile-salt detergents present at greater than their critical micellar concentrations. Hydrolysis was completely divalent-ion independent. Phospholipase A2 activity was not stimulated by 50% diethyl ether or ethanol, or in the presence of 1% solutions of Triton X-100, Zwittergent 3-12, sodium dodecyl sulphate, or n-octylglucoside. Stimulation of phospholipase activity by detergents was not related to their effectiveness at solubilizing the membrane proteins. When assayed individually phosphatidylcholine and lysophosphatidylcholine were each hydrolyzed (at the sn-2 and sn-1 positions, respectively) at a rate of approximately 125 nmol/mg protein per min. When assayed together, the two substrates appeared to compete for the same active site over a wide range of concentrations. It was concluded that the brush-border membrane contains an integral membrane protein with phospholipase A2 and lysophospholipase activities, which is specifically stimulated by bile salts and bile salt-like detergents.
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PMID:Solubilization and assay of phospholipase A2 activity from rat jejunal brush-border membranes. 334 32

Rat platelets released phospholipase A2 and lysophospholipase upon activation with thrombin or ADP. The release of phospholipases was energy-dependent and was not in parallel with that of a known lysosomal marker enzyme, N-acetyl-beta-D-glucosaminidase. The phospholipases are derived from other granules (dense granules or alpha-granules) rather than lysosomal granules of the cells. All of the activities of both phospholipases in the cell free fraction obtained from the activated platelet reaction mixture was recovered in the supernatant after centrifugation at 105,000 X g. The degree of hydrolysis of phospholipids by the phospholipase A2 followed the order: phosphatidylethanolamine (PE) greater than phosphatidylserine (PS) greater than phosphatidylcholine (PC). Phospholipase A2 shows a broad pH optimum (greater than pH 7.0) and absolutely requires Ca2+. Lysophospholipase was specific to lysophosphatidylserine (lysoPS), and neither lysophosphatidylethanolamine (lysoPE) nor lysophosphatidylcholine (lysoPC) was hydrolyzed appreciably. Both 1-acyl- and 2-acyl-lysophosphatidylserine were equally hydrolyzed. Lysophospholipase activity shows similar pH optimum to phospholipase A2. The lysophospholipase activity was lost easily at 60 degrees C. The activity was reduced by the presence of EDTA, though low but distinct activity was observed even in the presence of EDTA. Addition of Ca2+ to the mixtures restores the full activity.
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PMID:Selective release of phospholipase A2 and lysophosphatidylserine-specific lysophospholipase from rat platelets. 357 Dec 10

It was found that phospholipase A2 and lysophospholipase, both of which were released from thrombin-stimulated rat platelets, had high affinity to insolubilized heparin. Phospholipase A2 released from rat platelets was purified by the sequential use of column chromatography on heparin-Sepharose and TSK gel G2000SW (high-performance liquid chromatography, HPLC). The enzyme was near homogeneous on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and HPLC, and its Mr was estimated to be 13,500. The purified enzyme was labile and lost its activity within 1 h when incubated at 37 degrees C. Phospholipids or detergent in the solution protected the enzyme against inactivation. Phospholipase activity was inhibited by p-bromophenacylbromide, but not by diisopropylfluorophosphate or iodoacetamide. Lysophospholipase, which was also released from rat platelets, was separated from phospholipase A2 by chromatography on heparin-Sepharose.
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PMID:Purification and characterization of phospholipase A2 released from rat platelets. 359 43


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