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)

Elevation of cAMP changes the morphology of C6 rat glioma cells from a fibroblast to an astrocyte type of appearance. This change is prevented by the presence of serum from different species (chicken, mouse, rat, horse, adult bovine, fetal bovine, and human) in the cell culture medium. In this communication the component in serum responsible for this effect is identified as lysophosphatidic acid for the following reasons: First, lysophosphatidic acid alone at concentrations which are present in serum reverts the morphological response. Second, both lysophosphatidic acid and the component in serum no longer revert the morphological response after treatment with phospholipase B (E.C.3.1.1.5). Third, lysophosphatidic acid and serum produce an analogous intracellular Cai2+ signal in rat glioma C6 cells as measured by fluorescence spectrophotometry with the Ca2+ ion indicator Fura 2. Fourth, both the morphological response and the Cai2+ increase are prevented by pretreatment of the cells with 100 ng/ml phorbol 12-myristate 13-acetate. Finally, a maximal Cai2+ increase induced by FCS prevents the subsequent Cai2+ signal by lysophosphatidic acid. Interestingly, the morphological response is also reverted by Al3+ together with F- ions and also by lower n-alkanols such as ethanol and n-propanol suggesting that a regulatory GTP-binding protein is involved in the reversion. It is further shown that activation of the phosphatidylinositol 4,5-bisphosphate cleavage signal system is not responsible for the reversion of the morphological response.
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PMID:Lysophosphatidic acid reverts the beta-adrenergic agonist-induced morphological response in C6 rat glioma cells. 809 26

Retinol esterified with long-chain fatty acids is a common dietary source of vitamin A, that is hydrolyzed prior to absorption. An intrinsic brush border membrane retinyl ester hydrolase activity had previously been demonstrated for rat small intestine [Rigtrup, K. M., & Ong, D. E. (1992) Biochemistry 31, 2920-2926]. This activity has now been purified to apparent homogeneity by a three-column procedure to obtain a protein of apparent molecular weight of 130,000. The purified protein retained the pattern of bile salt stimulation, specificity for the acyl moiety of the retinyl ester, and the Km values previously observed for the activity present in the isolated brush border membrane. This protein also had a potent phospholipase activity, while having little measurable ability to hydrolyze triacylglyceride and cholesteryl ester substrates. The retinyl ester hydrolase enzyme was localized to the distal two-thirds of the small intestine. A polyclonal antiserum against rat brush border phospholipase B reacted with the purified retinyl ester hydrolase, strongly suggesting that this enzyme was the same as that previously purified and characterized as a calcium-independent brush border phospholipase B [Pind, S., & Kuksis, A. (1991) Biochem. Cell Biol. 69, 346-357]. Detailed kinetic studies revealed lower Km values for retinyl palmitate substrate compared to phosphatidylcholine substrate, with all tested bile salts. The Km values for each substrate were bile salt dependent and differently altered when bile salts were changed. Vmax values were also bile salt dependent. Retinyl palmitate was hydrolyzed most rapidly in the presence of deoxycholate and least rapidly in taurocholate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Purification and partial characterization of a retinyl ester hydrolase from the brush border of rat small intestine mucosa: probable identity with brush border phospholipase B. 811 29

Leaves of higher plant Vicia faba contains two Phospholipase A2 (PLA2) activities which are detected in cytosolic fractions. Based on a gel filtration column chromatography, two cytosolic PLA2 activities migrated with molecular masses of 70 kDa and 14 kDa. The first (70 kDa peak) was optimally active at pH 4.5 and was not dependent on [Ca2+] for its activity. In the presence of 5 mM CaCl2, 'phospholipase B' activity was shown in the 70 kDa peak. The second (14 kDa peak) was optimally active in the pH range 9-10 and required millimolar concentrations of calcium for optimal activity. The two activities were not inhibited by dithiothreitol. Neither anti-pancreatic PLA2 antiserum nor anti-(pig spleen 100 kDa cytosolic PLA2) antiserum immunoprecipitated any activity of the two plant PLA2's. The present results indicate that at least the 14 kDa form of the two PLA2 enzymes detected in leaves of higher plants is biochemically and immunochemically different from the well characterized Ca(2+)-dependent mammalian PLA2's.
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PMID:Detection of two phospholipase A2(PLA2) activities in leaves of higher plant Vicia faba and comparison with mammalian PLA2's. 817 4

A human, 85-kDa arachidonoyl-specific, cytosolic phospholipase A2 was expressed using the baculovirus-insect cell expression system. Expression resulted in the production of an active protein which consisted of approximately 3% of the total protein in the host Spodoptera frugiperda (Sf9) cells at 67 h after infection. The phospholipase A2 was purified to apparent homogeneity and exhibited calcium-dependent phospholipase A2 activity with a specific activity of 8 mumol/min/mg protein, as well as calcium-independent lysophospholipase activity with a specific activity of 17 mumol/min/mg protein. The phospholipase A2 was expressed as a phosphoprotein and was primarily phosphorylated on serine residues. Phosphatase treatment of the recombinant phospholipase A2 resulted in dephosphorylation of the enzyme and a 63% decrease in phospholipase A2 activity. This decrease in activity is similar in magnitude to the decrease in activity observed with phosphatase-treated phospholipase A2 from stimulated mammalian cells. These data demonstrate that the 85-kDa phospholipase A2 is expressed as an activated phosphoprotein in Sf9 cells.
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PMID:The 85-kDa, arachidonic acid-specific phospholipase A2 is expressed as an activated phosphoprotein in Sf9 cells. 821 60

The occurrence of a 14-kDa secretory phospholipase A2 (PLA2) in guinea pig alveolar macrophages (AM) and its relationship with the release of arachidonic acid (AA) were investigated. Freshly collected AM showed no detectable PLA2 activity as measured by the in vitro hydrolysis of phosphatidic acid. However, the PLA2 activity increased progressively when AM were maintained in culture to reach a level 60- to 100-fold greater than basal values within 20 h, with a parallel secretion into the incubation medium. By contrast, the activities of other phospholipid-hydrolyzing enzymes (platelet-activating factor acetylhydrolase and lysophospholipase) were modified only marginally. Both intra- and extracellular increases of PLA2 activity were abrogated with actinomycin D or cycloheximide. The enhanced PLA2 activity preferentially hydrolyzed negatively charged phospholipids in the order phosphatidic acid > phosphatidylglycerol > phosphatidylethanolamine > phosphatidylcholine, had an optimum pH of 7.5, and required a millimolar Ca2+ concentration for optimal activity and an apparent molecular mass of 14 kDa. Taken together, these results suggest that cultured AM elaborate an enzyme similar to the group II PLA2. On the other hand, our results show that AM hydrolyzed exogenous 2-arachidonoyl phosphatidylcholine and released AA and metabolites on FMLP stimulation. However, in contrast to the increase observed in the activity of the 14-kDa PLA2, the enzymatic activity involved in the hydrolysis of 2-arachidonoyl phosphatidylcholine and AA release remained constant with the culture duration of AM. Finally, dexamethasone markedly inhibited the increase of PLA2 activity, but only marginally inhibited the release of AA and metabolites from FMLP-stimulated AM. We conclude that guinea pig AM elaborate a 14-kDa PLA2 similar to the group II PLA2 through RNA- and protein synthesis-dependent processes. This elaboration appears to be induced by the adhesion of AM and is clearly dissociated from the liberation of AA.
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PMID:Increased synthesis and secretion of a 14-kDa phospholipase A2 by guinea pig alveolar macrophages. Dissociation from arachidonic acid liberation and modulation by dexamethasone. 822 50

Sera from pre-eclamptic women exhibit an increased lipolytic activity compared to sera of women with normal pregnancies. The null hypothesis of this study was that the increased release of free fatty acids (FFA) was due to hydrolysis of circulating triglycerides. The nature of the increased lipolytic activity was investigated by incubating sera from pre-eclamptic (PE) and normal pregnant women (C) with various lipid substrates radiolabeled in the FFA position. The release of FFA in PE-sera was not due to hydrolysis of triglycerides or diglycerides. Lysophosphatidylcholine, however, served as substrate for the enhanced lipolytic activity. By using lysophosphatidylcholine with radiolabeled FFA in the sn-1-position we found that 32 +/- 10 nmol FFA ml-1 h-1 was released in PE-sera, compared to 10 +/- 4 nmol FFA ml-1 h-1 in C-sera. This lysophospholipase activity appears independent of Ca2+ and other divalent cations. The increased release of FFA in sera of pre-eclamptic women can be explained by the presence of a lysophospholipase which releases the remaining fatty acid of lysophosphatidylcholine.
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PMID:Increased lipolytic activity of sera from pre-eclamptic women due to the presence of a lysophospholipase. 827 60

Exposure of isolated arteries to oxidatively modified low density lipoprotein (LDL) has been reported to suppress endothelium-dependent relaxation (EDR). To determine whether lipid degradation products in oxidized LDL contribute to impaired relaxation, we have tested the responsiveness of isolated rabbit aortas to endothelium-dependent relaxants (acetylcholine, ATP, and calcium ionophore A23187) and nitroglycerin before and after 2-hour incubations with selected lipids and LDL preparations. Concentrations (10 microM) of lecithin, phosphatidylserine, lysophosphatidylserine, sphingomyelin, phosphatidic acid, palmitate, arachidonate, and auto-oxidized arachidonate had no effect on EDR. Concentrations (10 microM) of lysolecithin, lyso-platelet activating factor, and sphingosine significantly suppressed endothelium-dependent relaxation. Native LDL (100 micrograms/ml incubation buffer) containing only small amounts of lysophosphatidylcholine exerted no effect on EDR. In contrast, LDL preparations oxidatively modified by exposure to cultured endothelial cells or copper inhibited EDR. When modified LDL was depleted of its lysolecithin by treatment with a selective phospholipase B (lysolecithinase), the inhibitory effects were attenuated. In contrast, native LDL accumulating lysolecithin under the influence of a phospholipase A2 (lecithinase) exerted inhibitory effects mimicking those of oxidized LDL. Lipids and lipoproteins had no effect on the responsiveness to nitroglycerin, an endothelium-independent vasodilator. We conclude that lysolecithin in oxidatively modified LDL contributes importantly to its vasomotor effects.
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PMID:Effects of lysolipids and oxidatively modified low density lipoprotein on endothelium-dependent relaxation of rabbit aorta. 841 38

Human cytosolic phospholipase A2 (cPLA2) is an arachidonic acid specific enzyme which may play a role in arachidonic acid release, eicosanoid production, and signal transduction. The PLA2 activity of this enzyme is stimulated by microM levels of Ca2+. Using a pure recombinant enzyme, we have confirmed that cPLA2 is not absolutely dependent on Ca2+, since Sr2+, Ba2+ and Mn2+ also gave full enzyme activity. Heavy metals, in contrast, inhibited enzyme catalysis suggesting the involvement of an essential cysteine residue. In the absence of Ca2+, high salt concentrations overcame the requirement for divalent metals, indicating that Ca2+ is not required for PLA2 catalytic activity. cPLA2 also displays a lysophospholipase (lyso PLA) activity with lysophosphatidylcholine micelles as a substrate. Unlike the PLA2 activity, the lyso PLA activity toward these micelles is not stimulated by Ca2+. However, upon the addition of glycerol or Triton X-100 to the assay, Ca2+ activation is observed, indicating that substrate presentation can affect the apparent Ca2+ dependence. Glycerol was found to be a potent stimulator of lyso PLA activity and specific activities up to 50 mumol min-1 mg-1 were observed. In addition to the PLA2 and lyso PLA activities, we report that cPLA2 displays a relatively low, CoA-independent transacylase activity which produces phosphatidylcholine from lysophosphatidylcholine substrate. The observation of this novel transacylase activity is consistent with the formation of an acyl-enzyme intermediate.
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PMID:Metal ion and salt effects on the phospholipase A2, lysophospholipase, and transacylase activities of human cytosolic phospholipase A2. 848 88

For organophosphates or phosphonates to initiate delayed neuropathy two steps are necessary: (1) progressive covalent reaction with neuropathy target esterase (NTE) to produce a form of inhibited NTE which can be reactivated by incubation with aqueous potassium fluoride (KF) and (2) progressive "aging" of inhibited NTE to a form which can no longer be reactivated by KF. However, it has been shown recently that certain N-unsubstituted organophosphoro-monoamidates (analogues of methamidophos) cause delayed neuropathy even though the inhibited NTE appeared not to have aged (Johnson et al. (1991). Arch. Toxicol., 65, 618-624). In order to study the generality of this phenomenon, we have examined some N-substituted compounds. We report in vitro studies of inhibition and reactivation and aging of both NTE and acetylcholinesterase (AChE) prior to toxicological tests. All the compounds studied were less inhibitory to both NTE and AChE in concentrated rather than in dilute suspensions of EDTA-washed brain particles without added cofactors. There was an apparent disposal of up to 100 mumoles of test compound by particles from 95 mg hen brain, which is far greater than can be explained by covalent binding. The activity is distinct from calcium-dependent "A" esterase. Several N-alkyl phosphoromonoamidates were found to be potent and selective inhibitors of NTE: second-order rate constant for O-n-pentyl N-benzylphosphoramido-fluoridate (Cmpd 6) = 5.6 x 10(7) M-1 min-1 at 37 degrees, which is about 100x higher than for acetylcholinesterase (AChE). Inhibited NTE and AChE from several chiral phosphoromono-amidates did not reactivate spontaneously (21 hours at 37 degrees). Virtually 100% reactivation by KF of AChE inhibited by phosphoromonoamidates was achieved at all times tested. Acetylcholinesterase inhibited by 2,5-dichlorophenyl N,N'-di-n-butylphosphorodiamidate was 42-56% reactivated by incubation with KF (192 mM in pH 5.2 buffer for 30 minutes at 37 degrees). We believe this is the first report of reactivation of any enzyme after inhibition by a phosphorodiamidate. For NTE inhibited by tabun (O-ethyl N-dimethylphosphoroamidocyanidate), virtually complete and rapid aging (t1/2 = 5.5-8.4 minutes) was observed. Consistent but only partial reactivation by KF was achieved 2 or more hours after inhibition of NTE by Cmpd 6 or by its 2,6-difluoro-analogue (Cmpd 7). However, a small but significant aging (approximately 15-20% loss of reactivatability) was measured soon after a 1 minute inhibition by Cmpd 7, but no further change occurred in 21 hours.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Interactions in vitro of some organophosphoramidates with neuropathy target esterase and acetylcholinesterase of hen brain. 849

Organophosphorus esters have been used in the plastics industry as antioxidants and plasticizers, in agriculture as insecticides, and in the military as nerve agents. Some of these compounds have organophosphorus ester-induced delayed neurotoxicity (OPIDN) different from the acute toxicity caused by the acetylcholine esterase inhibiting activity. this review describes recent progress in studies on OPIDN and, discusses the future direction of studies. OPIDN is characterized by a more than 7 day incubation period, lower limb paralysis accompanied by axonal degeneration, and age- and species-specificity. Younger animals and rodents are not very sensitive to OPIDN. As well as fast recovery of inhibited neurotoxic esterase or neuropathy target esterase (NTE) in the sciatic nerve, detoxicating mechanisms including carboxylesterases are contributing to age- and species-specificity for OPIDN. Although, anterograde axonal transport does not seem to be affected by OPIDN, slow down of retrograde axonal transport was observed. Inhibition of NTE, and aging of inhibited NTE has been thought to be responsible for OPIDN, but there are some arguments against the role of NTE in OPIDN. Phosphorylation of cytoskeletal proteins by kinases such as calcium dependent-calmodulin kinase II and/or high affinity neurotoxic compound binding site(s) are possible candidates for the initiation of OPIDN. Triphenyl phophite (TPP), a compound commonly used in the plastics industry, has delayed neurotoxicity that is somewhat different from OPIDN. The onset of TPP-induced neuropathy is earlier than that of OPIDN, and rodents are sensitive to TPP. In addition to the axonal damage, cell damage is observed in TPP-induced neuropathy. Mitochondrial energy metabolism-related enzymes could be the target of this neuropathy. Future studies should be focused on the relation of OPIDN to the phosphorylation of cytoskeletal proteins and high affinity binding site(s), and on the development of rodent models. These studies would answer the questions related to OPIDN, and further contribute toward elucidating the pathogenesis of degenerative neuronal diseases.
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PMID:[A review of studies of the delayed neurotoxicity induced by organophosphorus esters]. 852 48


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