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:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of the presynaptic neurotoxin beta-bungarotoxin (beta-BuTx) on the acetylcholine (ACh) storage system of synaptic vesicles isolated from the electric organ of Torpedo californica was studied. The toxin can totally inhibit active transport of [3H]ACh by the vesicles in a Ca2+-, time-, and concentration-dependent manner. Correlated with these effects is a 50-60% stimulation of the vesicle proton-pumping ATPase activity. The beta-BuTx-mediated transport inhibition and ATPase stimulation are antagonized by delipidated bovine serum albumin, not reversed by excess EGTA, and not mimicked by other cationic proteins or soybean or pancreatic trypsin inhibitors. The behavior is consistent with phospholipase A2 (PLA2)-dependent damage to the vesicle membrane caused by beta-BuTx, which results in uncoupling of the ATPase and ACh transporter systems. The nonneurotoxic Naja naja venom PLA2 causes similar effects, except that it is slightly more potent on a molar basis. About 100-fold more beta-BuTx is required to effect lysis of synaptic vesicles than to uncouple them. ATP is a strong inhibitor of beta-BuTx- but not of N. naja PLA2-mediated uncoupling. The observations suggest that a component of beta-BuTx toxicity in the cholinergic terminal might involve attack on synaptic vesicles or vesicle-like structures and that a nucleotide-like factor might modulate the toxicity.
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PMID:Uncoupling of cholinergic synaptic vesicles by the presynaptic toxin beta-bungarotoxin. 294 72

The in vivo effect of dimethoate and deltamethrin on body and organ weights, serum proteins and on plasma acetylcholinesterase (AChE), aromatic esterase and ATPase were examined in growing male rabbits throughout five months period. Both compounds had no significant effect on body weight; however, adrenal, testis & pituitary weights decreased (P less than 0.01); the liver and spleen weights increased (P less than 0.01) in a dose dependent manner. Serum total proteins and globulin decreased (P less than 0.01) in a dose dependent trend, while serum albumin was not greatly affected. AChE activity was increased (P less than 0.01) after 1 month of treatment with the two doses of dimethoate and deltamethrin; thereafter, AChE activity showed 40% inhibition of the control level. The activity of aromatic esterase increased markedly after the first month, then declined gradually until the fifth month. High dose of dimethoate markedly inhibited this enzyme particularly after the 5th month of treatment. Both doses of deltamethrin increased ATPase activity after the first month of treatment, then the ATPase activity was normal. Dimethoate inhibited ATPase particularly at the end of treatment in a dose dependent manner.
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PMID:In vivo chronic effect of dimethoate and deltamethrin on rabbits. 297 91

Red blood cell lysis is a common symptom following severe or prolonged oxidative stress. Oxidative processes occur commonly in sickle cells, probably mediated through denatured hemoglobin and the accumulation of ferric hemes in the membranes. Calmodulin-stimulated (Ca2+ + Mg2+)-ATPase from sickle red cell membranes is partially inactivated (Leclerc et al. (1987) Biochim. Biophys. Acta 897, 33-40). In this study (Ca2+ + Mg2+)-ATPase activity from normal adult erythrocyte membranes was measured in the presence of hemin. We report a time- and concentration-dependent inhibition of the activity of the enzyme by hemin due to a decrease in the maximum velocity. Only a mild inhibitory effect was observed in the presence of iron-free protoporphyrin IX, indicating the catalytic influence of the iron. Experiments carried out with hemin (ferric iron) liganded with imidazole or with reduced protoheme (ferrous iron) liganded with carbon monoxide, demonstrated that the inhibition requires that hemin be capable of binding additional ligands. The inhibition was not influenced by the absence of oxygen but was prevented by addition of bovine serum albumin. Addition of butylated hydroxytoluene, a protective agent of lipid peroxidation, failed to prevent the inhibition of calmodulin-stimulated (Ca2+ + Mg2+)-ATPase. As dithiothreitol partially restores the enzyme activity, we postulated that hemin interacts with the thiol groups of the enzyme.
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PMID:Inhibition of membrane erythrocyte (Ca2+ + Mg2+)-ATPase by hemin. 297 27

Native sarcolemma (SL) from adult canine cardiac myocytes (Na+-K+-ATPase activity 74.2 +/- 3.0 mumol X mg-1 X h-1) was preincubated (10 min, 37 degrees C, pH 7.2) with 1) 20-600 microM palmitoyl carnitine, 2) 250 nM-2.5 mM propranolol, or 3) 20-600 microM palmitoyl carnitine plus propranolol at various concentrations (0.0, 0.025, 0.25, 0.5, 1.0, and 2.5 mM); after preincubation, Na+-K+-ATPase activity was assayed. Palmitoyl carnitine alone (series 1) had no effect on ATPase activity over the range of 20-400 microM but was inhibitory (30%) at 600 microM. Propranolol alone (series 2) did not alter ATPase activity at any concentration. When SL membranes were exposed to both palmitoyl carnitine and propranolol (series 3), a dose-dependent inhibition of ATPase activity was observed. The inhibitory effect was not reversed by 3.0% bovine serum albumin. Propranolol concentrations greater than 0.025 mM significantly inhibited the activity of SL exposed to palmitoyl carnitine (above 150 microM). Palmitoyl carnitine and propranolol do not have to be added simultaneously to produce combined inhibition. Activity was inhibited 50% when SL were pretreated with 100 microM palmitoyl carnitine followed by addition of 2.5 mM propranolol no inhibition occurred if preincubation conditions were reversed. Thus exposure of SL to propranolol and reported physiological levels of palmitoyl carnitine leads to irreversible inhibition of the Na+-K+-ATPase, which may be due to the combined membrane-perturbant actions of these amphipathic agents.
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PMID:Inhibition of sarcolemmal Na+-K+-ATPase by palmitoyl carnitine: potentiation by propranolol. 298 78

Highly purified membrane-bound Na,K-ATPase from pig kidney outer medulla was dissolved in the non-ionic detergent C12E8. Chromatography of the dissolved material on a DEAE matrix yielded enzymatical material having a ouabain-binding capacity of 6.9 nmoles per mg protein (measured according to Lowry et al., with bovine serum albumin as standard). This material, which after addition of lipids had the same K+-phosphatase turnover as the membrane-bound enzyme, could consist entirely of live molecules with a molecular weight of 145 kDa, a value close to that expected for alpha beta-promoters of Na,K-ATPase.
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PMID:Solubilization and further chromatographic purification of highly purified, membrane-bound Na,K-ATPase. 300 35

After 2 h of exogenous phospholipase A2 (PLA2) exposure, membrane phospholipid decreased from 3.22 +/- 0.31 to 1.06 +/- 0.13 mumol/mg (33% of control). All classes of phospholipid, except sphingomyelin, were hydrolyzed, whereas total cholesterol content was unaffected. Increases in nonesterified fatty acids (NEFA) were reflected primarily in oleic (18:1), linoleic (18:2), and arachidonic (20:4). Na+-K+-adenosinetriphosphatase (ATPase) activity was inhibited to 29% of control by 2 h of PLA2 treatment, and this inhibition was reversed (albeit, not completely after 5 min of PLA2 treatment) by removal of the hydrolysis products with 0.1% bovine serum albumin (BSA). In contrast, the apparent binding capacity for [3H]ouabain was not affected by PLA2 treatment. Unmasking of latent [3H]ouabain binding by alamethicin was utilized to estimate changes in the proportion of sealed vesicles present before and after PLA2 treatment. PLA2 treatment resulted in a time-dependent loss of sealed vesicles that paralleled the time course of phospholipid hydrolysis and was not reversed by washing with BSA. These studies demonstrate that cardiac Na+-K+-ATPase activity is inhibited by accumulation of endogenously produced lysophospholipids and NEFA. In contrast, loss of vesicle integrity may result from both accumulation of endogenously produced hydrolysis products and membrane phospholipid depletion.
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PMID:Deinhibition of cardiac Na+-K+-ATPase after exposure to exogenous phospholipase A2. 302 63

Fatal immune complex glomerulonephritis can be induced in rats by chronic intravenous administration of bovine serum albumin. There are three distinct stages, mild, moderate, and severe, in the development of renal immunopathology and pathophysiology in this model of chronic serum sickness. The work described here was undertaken to evaluate aspects of proximal tubule function in those different stages. Tissue water distribution, oxidative metabolism, and transport of representative organic anions and cations were measured in renal cortical slices. In mild chronic serum sickness all functions were normal except the transport of p-aminohippurate (PAH, organic anion), which was significantly decreased. This decrease appeared to be attributable to immunization with Freund's adjuvant. In the moderate stage of chronic serum sickness, proximal tubule functions and morphology appeared essentially normal. Only Na-K-ATPase activity was somewhat lower than in controls. However, proximal tubule dysfunction was a feature of severe chronic serum sickness. A significant inhibition of anion and cation transport was observed. Reduction in transport functions occurred together with impaired oxidative metabolism and severe reduction in Na-K-ATPase activity. Abnormalities of mitochondrial structure, a decrease in number of mitochondria, and a significant increase in intracellular H2O content provided additional evidence of degenerative changes in proximal tubule cells during the severe stage of chronic serum sickness. It was concluded that decreased transport of organic ions by the basolateral membrane in proximal tubules of rats with severe chronic serum sickness resulted from a breakdown in the metabolic machinery of the tubule epithelium rather than a specific injury to organic ion transport systems.
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PMID:Proximal tubule function in chronic serum sickness glomerulonephritis of rats. 315 65

The interaction of protein substrates with protease La from Escherichia coli enhances its ability to hydrolyze ATP and peptide bonds. These studies were undertaken to clarify how unfolded proteins allosterically stimulate this ATPase activity. The tetrameric protease can bind four molecules of ATP, which activates proteolysis, or four molecules of ADP, which inhibits enzymatic activity. Protein substrates stimulate binding of the nonhydrolyzable ATP analog [3H] adenyl-5'yl imidodiphosphate, although they do not increase the net binding of [3H]ATP or [3H]ADP. Once bound, ATP is quickly hydrolyzed to ADP, which remains noncovalently associated with protease La even through repeated gel filtrations. Exposure to protein substrates (e.g. denatured bovine serum albumin at 37 degrees C) induces the release of all the bound ADP from the enzyme. Nonhydrolyzable ATP analogs bound to the enzyme were not released by these substrates. Proteins that are not degraded (e.g. native bovine serum albumin) and oligopeptides that only bind to the catalytic site do not induce ADP release. Thus, polypeptide substrates have to interact with an allosteric site to induce this effect. The protein-induced ADP release is inhibited by high concentrations of Mg2+ and is highly temperature-dependent. Protein substrates promoted [3H]ATP binding in the presence of ADP and Mg2+ (i.e. ATP-ADP exchange) and reduced the ability of ADP to inhibit the enzyme's peptidase and ATPase activities. These results indicate that: 1) ADP release is a rate-limiting step in protease La function; 2) bound ADP molecules inhibit protein and ATP hydrolysis in vivo; 3) denatured proteins interact with the enzyme's regulatory site and promote ADP release, ATP binding, and their own hydrolysis.
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PMID:Protein substrates activate the ATP-dependent protease La by promoting nucleotide binding and release of bound ADP. 331 97

1. A mechanical tissue chopper was used to obtain 35-75 mg explants from 21- to 28-day-old chick liver to determine assay conditions (substrates, buffers, time), regulators (metals and hormones) and points of endogenous regulation of de novo lipogenesis (ATPase, reductive potential and protein phosphorylation). High- and low-bicarbonate-based buffers (Earl's balance salts, EBSS and Hanks' balanced salts, HBSS; respectively) were used in conjunction with sources and types of bovine serum albumin (BSA), divalent cations (Mg2+ or Ca2+), substrate (glucose or acetate) and hormones (insulin and catecholamines). 2. Neither EBSS nor HBSS changed in vitro lipogenesis, CO2 or glucose production when 20 mM HEPES was added to these salts. 3. Neither the presence nor the source of BSA (Sigma or Armour) affected metabolism. In contrast, reducing the vessel reaction surface area (5.1 vs 10.5 cm2) decreased metabolic rates. 4. Acetate was more readily utilized than glucose as an in vitro fatty acid precursor. Use of glucose was complicated by production of glucose from endogenous precursors and by label recycling. Divalent cations (Mg2+ or Ca2+) had little affect upon lipogenesis. 5. Chicken insulin (50 ng/ml) did not affect lipogenesis; however, incorporation of acetate into fatty acids was decreased by dibutyryl cyclic AMP. A catecholamine-induced decrease in vitro lipogenesis indicates that major points of regulation are under control of phosphorylation-dephosphorylation steps.
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PMID:Measurement of glucose and lipid metabolism in avian liver explants. 342 27

Corneal thickness is a reflection of endothelial barrier and pump functions. The corneal edema that occurs during intraocular inflammation is a consequence of the breakdown of one or both of these parameters. Results of this study demonstrate that, during intraocular inflammation induced by an intravitreal injection of bovine serum albumin (BSA), the permeability of rabbit corneal endothelia to inulin was increased. By comparison, treatment with oral aspirin and/or subconjunctival triamcinolone acetonide prevented the endothelial barrier breakdown induced by the BSA. Concomitant with the loss of the barrier function, endothelial ouabain binding decreased in the BSA injected eye, indicating a reduction in endothelial Na/K ATPase pump site density. A subconjunctival injection of triamcinolone prevented this decrease in pump sites. The increase in endothelial permeability and the decrease in pump site density correlated with an increase in corneal thickness. It can be concluded that the intraocular inflammation induced by BSA effects corneal edema by both an increase in endothelial permeability and a decrease in Na/K ATPase pump site density. Subconjunctival triamcinolone is effective in preventing this response.
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PMID:Effect of inflammation on the corneal endothelial pump and barrier. 349 91


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