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)

In order to examine the role of phospholipids in the activation of membrane bound Ca2+/Mg2+ ATPase, the activities of Ca2+ ATPase and Mg2+ ATPase were studied in heart sarcolemma after treatments with phospholipases A, C and D. The Mg2+ ATPase activity was decreased upon treating the sarcolemmal membranes with phospholipases, A, C and D; phospholipase A produced the most dramatic effect. The reduction in Mg2+ ATPase activity by each phospholipase treatment was associated with a decrease in the Vmax value without any changes in the Ka value. The depression of Mg2+ ATPase in the phospholipase treated preparations was not found to be due to release of fatty acids in the medium and was not restored upon reconstitution of these membranes by the addition of synthetic phospholipids such as lecithin, lysolecithin or phosphatidic acid. In contrast to the Mg2+ ATPase, the sarcolemmal Ca2+ ATPase was affected only slightly by phospholipase treatments. The greater sensitivity of Mg2+ ATPase to phospholipase treatments was also apparent when deoxycholate-treated preparations were employed. These results indicate that glycerophospholipids are required for the sarcolemmal Mg2+ ATPase activity to a greater extent in comparison to that for the Ca2+ ATPase activity and the phospholipids associated with Mg2+ ATPase are predominantly exposed at the outer surface of the membrane.
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PMID:Alterations in Ca2+/Mg2+ ATPase activity upon treatment of heart sarcolemma with phospholipases. 296 79

Previous results have demonstrated that two inhibitors of Na-and-K-activated adenosine triphosphatase (ouabain, vanadate) lead to stimulated prostaglandin E2 release and to inhibited renin secretion in the rat renal cortical slice preparation. It was speculated that stimulation of phospholipase A2 activity accounted for the effect on prostaglandin E2 release. We used the same preparation in the present experiments, and showed that another inhibitor of Na-and-K-activated adenosine triphosphatase (K-free incubation medium) stimulates prostaglandin E2 release and inhibits renin secretion. Quinacrine antagonized the stimulatory effects of ouabain, vanadate, and K-free medium on prostaglandin E2 release (consistent with phospholipase A2 involvement), but did not antagonize their inhibitory effects on renin secretion. Collectively, these observations lend further weight to the argument against a mediatory role of prostaglandin synthesis in the renin secretory process.
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PMID:Quinacrine antagonizes the effects of Na,K-ATPase inhibitors on renal prostaglandin E2 release but not their effects on renin secretion. 298 87

The present study was designed to determine the subcellular distribution of the platelet (Ca2+ + Mg2+)-ATPase. Human platelets were surface labeled by the periodate-boro[3H]hydride method. Plasma membrane vesicles were then isolated to a purity of approx. 90% by a procedure utilizing wheat germ agglutinin affinity chromatography. These membranes were found to be 2.6-fold enriched in surface glycoproteins compared to an unfractionated vesicle fraction and almost 7-fold enriched compared to intact platelets. In contrast, the isolated plasma membranes showed a decreased specific activity of the (Ca2+ + Mg2+)-ATPase compared to the unfractionated vesicle fraction. This decrease in specific activity was found to be similar to that of an endoplasmic reticulum marker, glucose-6-phosphatase, and to that of a platelet inner membrane marker, phospholipase A2. We conclude, therefore, that the (Ca2+ + Mg2+)-ATPase is not located in the platelet plasma membrane but is restricted to membranes of intracellular origin.
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PMID:Evidence that the platelet plasma membrane does not contain a (Ca2+ + Mg2+)-dependent ATPase. 299 27

The effects of 15-hydroperoxyarachidonic acid (15-HPAA) on Na+, K+- and Mg+-ATPase activities in the blood-brain barrier (BBB) were examined using rat brain microvessels (MV). 15-HPAA markedly stimulated these ATPase activities in MV at low concentrations whereas the synaptosomal Na+, K+-ATPase activity was inhibited in a dose-dependent manner. Further neurochemical analysis revealed that this stimulatory effect of 15-HPAA in MV was not due to a simple detergent-like action of the compound on the membranes but rather to stimulation of the phospholipase A2 and lipoxygenase activity within MV. In addition, it was shown that free radical reactions were involved in the mechanism. Since such anti-edema drugs as 1,2-bis(nicotinamido)propane were proved to be potent suppressors of the enhanced ATPase activity, further speculations on the role of this effect for ischemic brain edema are offered.
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PMID:Enhancement of ATPase activity by a lipid peroxide of arachidonic acid in rat brain microvessels. 299 34

The bee and cobra venom phospholipases A2 as well as partially acetylated cobra venom phospholipase A2 are studied for their effect on phospholipid composition of synaptosomes and their Mg2+- and Na+,K+-ATPase activity. It is established that these phospholipases induce the splitting of phosphatidylethanolamine, phosphatidylcholine and phosphatidylserine, inhibition of the Na+,K+-ATPase activity and activation of Mg2+-ATPase. Bee venom phospholipase A2 is more effective than cobra venom phospholipase A2, the both phospholipases splitting phosphatidylethanolamine most intensively. The ATPase activity may be partially or completely restored by exogenic phosphatidylcholine and phosphatidylserine; exogenic phosphatidylethanolamine is not efficient in this respect.
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PMID:[Effect of phospholipases A2 from bee and cobra venom on the phospholipid composition and Na+-,K+-ATPase activity of synaptosomes]. 300 36

Brush-border membranes were isolated from rabbit small intestine by procedures involving precipitation of undesired membranes with either 10 mM MgCl2 or 10 mM CaCl2. The membranes were compared on the basis of marker enzyme content and lipid composition. Ca2+-prepared membranes displayed a greater enrichment of alkaline phosphatase and sucrase activity compared to homogenate than did the Mg2+-prepared membranes. The former also displayed an impoverishment of (Na+ + K+)-ATPase activity, the specific activity of which increased several-fold in Mg2+-prepared membranes. Membranes prepared with Ca2+ were characterized by a lower phosphoacylglycerol-protein ratio and a higher phosphatidylethanolamine-phosphatidylcholine ratio. Although lysophosphoacylglycerols accounted for about 6% of the total phospholipids in these membranes compared to 2% in Mg2+-prepared membranes, the free fatty acid content was similar in both types of membranes. It was concluded that Ca2+ prepared membranes were less contaminated by basolateral membranes than were Mg2+-prepared membranes and the use of Ca2+ did not notably enhance degradation of endogenous lipids by brush-border membrane phospholipase A.
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PMID:A comparison of brush-border membranes prepared from rabbit small intestine by procedures involving Ca2+ and Mg2+ precipitation. 300 39

Treatment of purified preparations of Na,K-ATPase by phospholipase A2 has led to the formation of two-dimensional crystals of the protein. Control tests with another phospholipase and two detergents have shown that crystallization occurs as the result of hydrolysis and/or solubilization of the phospholipids in the enzyme vesicles. Experimentation with various buffer systems has indicated that reduction in the amount of phospholipids alone is sufficient for inducing the formation of crystalline sheets. Inclusion of crystal inducing ions in the buffer facilitates the crystallization process, resulting in more extensive arrays. The new crystalline sheets are exclusively dimeric with average unit cell dimensions: a = 15.8 +/- 0.4 nm, b = 4.9 +/- 0.2 nm, and gamma = 64 +/- 3 degrees. Examination of the micrographs shows that the initial intermolecular interaction leading to the formation of sheets is between the alpha subunits. Results from this study suggest that removal and/or modification of phospholipids by phospholipases could prove successful in crystallizing those membrane proteins in which excess lipid is the main barrier to the formation of two-dimensional arrays.
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PMID:Novel crystalline sheets of Na,K-ATPase induced by phospholipase A2. 301 9

Effects of purified Mojave toxin on rat synaptic membrane (Ca+2 + Mg+2)-ATPase and dihydropyridine receptor were determined. The toxin was observed to stimulate specifically (Ca+2 + Mg+2)-ATPase approximately two-fold with no effect on Mg+2 dependent ATPase activity. Examination of the effects of increasing amounts of purified Mojave toxin on binding of the calcium channel blocker, nitrendipine, indicated that the addition of 10 micrograms (4.5 X 10(-10) moles) of toxin resulted in greater than 90% inhibition of nitrendipine binding. Furthermore, binding studies revealed the toxin to have little affinity for the ligand indicating its interaction with calcium channel components. Since Mojave toxin has associated with it a phospholipase A2 activity, we investigated the effects of 4-bromophenacylbromide, a known inhibitor of phospholipase A2 activity in order to discern the possible effects of the purified toxin on synaptic membranes. At concentrations previously shown to be inhibitory of purified phospholipase A2 from cobra venom, both ATPase activity and nitrendipine binding of synaptic membranes were significantly inhibited. Thus we cannot rule out the possibility that the endogenous phospholipase activity of the purified toxin is responsible for its effects on the rat brain synaptic functions studied here. Binding studies conducted in the presence of verapamil and diltiazem indicated that the toxin interacts with allosteric sites responsible for regulation of the binding of nitrendipine. Although we have not tested the effects of Mojave toxin on other ion channels and/or receptors, results presented here suggest the potential usefulness of this toxin as a molecular probe of the calcium channel complex.
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PMID:The effects of purified Mojave toxin on rat synaptic membrane (Ca+2 + Mg+2)-ATPase and the dihydropyridine receptor. 301 16

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

Mammalian cells treated with low concentrations of phospholipase C become permeable to the protein toxin alpha-sarcin. A similar permeabilization is not induced upon treatment with other lipases such as phospholipase A2, sphingomyelinase, or cholesterol esterase. Concentrations of 10 micrograms/ml alpha-sarcin almost completely blocked translation in HeLa cells treated with 0.3 U/ml phospholipase C (PL-C) for 1 h. In contrast, 200 micrograms/ml of alpha-sarcin had no effect at all on protein synthesis in untreated cells. Other macromolecules such as horseradish peroxidase and luciferase also enter into cells if they are treated with phospholipase C. This permeabilization method is fully reversible. As soon as 5 min after PL-C removal, the cells become impermeable to alpha-sarcin. Other metabolites such as uridine nucleotides are partially released after PL-C incubation, whereas the content of 86Rb+ remains at control levels, probably because the Na+/K+ ATPase activity increases.
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PMID:Exogenous phospholipase C permeabilizes mammalian cells to proteins. 313 47


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