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

---

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

The mechanism of action of the cytotoxic protein P6 isolated from cobra venom (Naja naja) which shows preferential cytotoxicity particularly to Yoshida sarcoma cells has been studied by its effects on the membrane-bound enzyme (Na-++K-+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) of a variety of cell systems. Evidence obtained with Yoshida sarcoma cells, dog and human erythrocytes and three tissue culture cell lines KB (human oral carcinoma), Hela (human cervix carcinoma) and L-132 (human lung embryonic) shows that inhibition of (Na-++K-+)-ATPase by the P6 protein can be correlated with its lytic activity. (Na-++k-+)-ATPase of Yoshida sarcoma membrane fragments inactivated by P6 protein could be reconstituted by the addition of phosphatidylserine and phosphatidic acid. It is conceivable that lysis of cells by the P6 protein may be due to an imbalance of K-+ and Na-+ in the cell which leads to swelling and disintegration of the membrane structure. Observations indicate that the P6 protein combines with membrane constituents of susceptible cells. The overall evidence suggests that both the specificity of its protein structure and the highly basic nature of the P6 protein are factors which enable it to compete with the lipid moiety maintaining the (Na-++k-+)-ATPase of the susceptible cells in proper conformation for activity.
...
PMID:Inactivation of (Na-++K-+)-stimulated ATPase by a cytotoxic protein from cobra venom in relation to its lytic effects on cells. 12 1

Dephosphorylation of [32P]phosphoenzyme of bovine brain Na+,K+-stimulated ATP phosphohydrolase (EC 3.6.1.3), labelled by [gamma-32P]ATP, was investigated at 21 degrees C by means of a rapid-mixing technique. On addition of a high concentration of KCl (10 mM) to [32P]phosphoenzyme at steady state in the presence of Mg2+ and Na+, very rapid dephosphorylation was obtained. Simultaneously, the amount of [32P]orthophosphate increased at about the same rate. It was concluded that this K+-stimulated dephosphorylation and liberation of [32P]orthophosphate from the [32P]phosphoenzyme was rapid enough to participate in the Na+,K+-stimulated hydrolysis of ATP. In order to study the dephosphorylation in absence of continuing 32P-labelling, excess unlabelled ATP or a chelator of Mg2+ was added. Simultaneous addition of a high concentration of KCl to the [32P]phosphoenzyme formed in the presence of Mg2+ and Na+ but in the absence of K+, resulted in an initial very rapid phase and a subsequent slower phase of dephosphorylation. With KCl also initially present in the incubation medium, only the slow phase was observed. The slow phase of dephosphorylation also seemed to be sufficiently rapid to participate in the Na+, K+-stimulated ATPase reaction. On addition of a high concentration of ADP (5 mM) to [32P]phosphoenzyme formed in the presence of Mg2+ and Na+, an initial comparatively rapid, and later slow phase of dephosphorylation were detected. This gave further support for different forms of phosphoenzyme. Approximate concentrations of these forms, in the absence and presence of KCl, were estimated by extrapolation and the turnover of these forms was calculated. The nature of the kinetically different components of phosphoenzyme and their role in the Na+, K+-stimulated ATPase reaction is discussed.
...
PMID:Bovine brain Na+,K+-stimulated ATP phosphohydrolase studied by a rapid-mixing technique. K+-stimulated liberation of [32P] orthophosphate from [32P] phosphoenzyme and resolution of the dephosphorylation into two phases. 12 3

Digoxigenin-3,12-dibromoacetate (DDB), an alkylating derivation of digoxigenin, was synthesized and tested as a cardiotonic steroid (CS) site directed affinity label for Na+ +K+ -ATPase (ATP phosphohydrolase EC 3.6.1.3). DDB inhibited rat brain Na+ +K+ -ATPase with an I50 of 5 times 10(-6)M and readily displaced specifically bound 3H-ouabain from its binding sites on Na+ +K+ -ATPase. If the enzyme was exposed to DDB prior to the addition of 3H-ouabain its ability to bind 3H-ouabain was decreased, consistent with the concept that DDB interacted irreversibly with the cardiotonic steroid binding sites of Na+ +K+ -ATPase. However, DDB proved to be an even more effective inhibitor of 3H-ouabain binding under conditions where it was unlikely that it could interact with the CS binding sites of this enzyme, suggesting that DDB inhibited 3H-ouabain binding by non-cardiotonic site directed actions. Similarly, the presence of excess strophanthidin did not protect this enzyme against irreversible inhibition by DDB. The data suggest that the presence of a bromoacetate group at the 12 position on cardiotonic steroids does not confer CS binding site directed alkylating properties on these drugs.
...
PMID:Irreversible inhibition of 3H-ouabain binding to Na+ +K+ -ATPase by digoxigenin-3,12-dibromoacetate, an alkylating derivative of digoxigenin. 12 5

Plasma membranes were prepared from cultured Chinese hamster ovary cells utilizing a two-phase polymer system and were characterized by enzymatic and chemical assay, and by electron microscopy. The usual degree of purification of presumptive membrane markers such as Na+-K+ ATPase (ATP phosphohydrolase, EC 3.6.1.3) ranged from three-to eightfold. Gel electrophoresis in SDS revealed several polypeptides and two glycopeptides which were enriched in the plasma membrane fraction.
...
PMID:The isolation and characterization of the plasma membrane of cultured chinese hamster ovary cells. 12 93

1. Insulin stimulates the activity of membrane-bound ATPase isolated from frog skeletal muscle and from rat brain. The increase in activity of the membrane-bound ATPase system isolated from frog ranged from 9-8 to 53% at concentrations of Na+ (25 mM), K+ (10 mM), and ATP (2 mM) similar to those in in vivo experiments conducted previously (Moore, 1973). The increased activity of the membrane-bound ATPase is, therefore, at least as great as the insulin-induced increase in Na efflux (10-38%) from intact cells (Moore, 1973). If the concentration of Na+ is lowered to 4 mM and that of ATP lowered to 0-5 mM albumin, and 10(6) M, the increase in ouabain-inhibitable ATPase activity can reach as high as 400%. 2. Ouabain, at a concentration (10(-3) M) sufficient to inhibit stimulation of the frog ATPase by increasing Na from 4 to 25 mM, completely blocked the stimulation of ATPase activity due to insulin. 3. At 2 mM-ATP, 100 mM-Na+, and 20 mM-K+, conditions which maximally activate the (Na+ + K+)-ATPase, insulin did not increase the ATPase, activity. Stimulation was consistently seen at 10 mM-K+, 0-5 mM-ATP, and either 4 mM or 25 mM-Na+. 4. The finding that insulin does not stimulate the ATPase activity in conditions in which the (Na+ + K+)-ATPase component is maximally activated and especially the fact that ouabain can reproducibly inhibit insulin stimulation of the membrane-bound ATPase activity strongly suggest that interaction of insulin with its receptor upon the plasma membrane somehow stimulates the (Na+ + K+)-ATPase system (ouabain sensitive; ATP phosphohydrolase, EC (3.6.1.3). These results are consistent with previous studies of the effect of insulin upon Na efflux from intact cells (Moore, 1973) and support the previous conclusion that the component of Na efflux stimulated by insulin is active. The evidence suggests that insulin probably does not affect Vmax of the (Na+ + K+)-ATPase system, but may increase the affinity of the enzyme system to one or more effectors, most likely Na+, ATP, and perhaps K+. 5. Oxidized glutathione (2-7 X 10(-6) M), 10(-6) M, 10(-7) M, and 10(-8) M cyclic AMP did not affect the ATPase activity 10(-6)Malbumin, and . 6. The results are consistent with the view that the Na pump, (Na+ + K+)-ATPase, is intimately involved with the physiological action of insulin and may be transducer between the binding of insulin to its receptor on the plasma membrane and the cellular actions of insulin.
...
PMID:Effect of insulin upon membrane-bound (Na+ + K+)-ATPase extracted from frog skeletal muscle. 12 36

Exposure of rat brain Na+ + K+-ATPase (ATP phosphohydrolase E.C. 3.6.1.3) to concentrations of cassaine greater than 1 x 10(-4) M resulted in a poorly reversible inhibition of this enzyme. Inhibition did not require the presence of ATP and developed rapidly, but the final amount of inhibition observed was independent of time. The amount of inhibition observed at a given concentration of cassaine was reduced by increasing the concentration of membranes in the system. The inhibition of Na+ + K+-ATPase activity was associated with equivalent inhibition of the phosphorylation and (3H)-ouabain binding reactions of this enzyme, while the uninhibited enzyme was apparently kinetically normal. Concentrations of cassaine which produced this stable inhibition of Na+ + K+-ATPase had no effect on the Mg2+-activated ATPase or the NADH cytochrome-c-reductase activities of crude rat brain microsomal preparations. Cassaine inhibited the cholinesterase activity of rat brain microsomes with a Ki of about 5 x 10(-5) M, but his inhibition was fully reversible. The poorly reversible inhibitory actions of cassaine, thus, appeared specific for Na+ + K+-ATPase. Because this stable pattern of inhibition of the Na+ + K+-ATPase by cassaine required drug concentrations at least one hundred-fold greater than those which produce positive inotropic effects, it appears unlikely that this pattern of Na+ + K+-ATPase inhibition is involved in the cardiotonic actions of this drug.
...
PMID:Studies on the stable inhibition of Na+ + K+-ATPase by cassaine. 13 Feb 44

A photochemical analogue of strophanthidin, 3-azidoacetylstrophanthidin (AAS) was synthesized and tested as a cardiotonic steroid (CS) site directed photoaffinity label for Na+ + K+-ATPase (ATP phosphohydrolase, E.C. 3.6.1.3). AAS-inhibited rat brain ATPase with an I50 of about 1 x 10(-6) M readily displaced 3H-ouabain from its specific binding sites on this enzyme and produced a positive inotropic effect in guinea pig atrial strips. In the absence of UV light its interaction with the CS binding sites of Na+ + K+-ATPase appeared reversible. In the presence of UV light and acetylphosphate, AAS produced about 15% irreversible inhibition of Na+ + K+-ATPase, compared with about 5% irreversible inhibition in the absence of either UV light or acetyl phosphate. Since acetylphosphate supports specific glucoside binding at the CS binding sites of Na+ + K+-ATPase these data are consistent with the concept that AAS is a cardiotonic steroid site directed photoactivatable inhibitor of Na+ + K+-ATPase.
...
PMID:Cardiotonic site directed irreversible inhibition of Na+ + K+-ATPase by 3-azidoacetylstrophanthidin, a photochemical analogue of strophanthidin. 13 Feb 45

The effects of several alkali metal cations on the relationship between steady state phospho-enzyme levels and initial velocity and equilibrium levels of [3H]-ouabain binding to (Na+ + K+)-ATPase (ATP phosphohydrolase EC 3.6.1.3.) were examined. Only Na+ increased both phospho-enzyme and [3H] ouabain binding levels above those observed in the presence of Mg2+ alone. While Na+ stimulated phosphorylation with an apparent Km of about 1 mM, its stimulation of [3H] ouabain binding was biphasic, the lower Km for stimulation corresponding to the Km for formation of phospho-enzyme. Among the other alkali metal cations, potassium, rubidium and lithium were at least eight times more effect in reducing phospho-enzyme levels than in reducing [3H] ouabain binding. This discrepancy is not due to the stability of the enzyme-ouabain complex, nor to any action on the rates of formation or dissociation of the enzyme-ouabain complex. The data thus suggest that [3H] ouabain interacts with the K+, Rb+ or Li+ -enzyme complexes. For Li+, this hypothesis is further supported by the observation that Li+ can cirectly increase the equilibrium level of [3H] ouabain binding to this enzyme under certain conditions.
...
PMID:Effects of alkali metal cations on phospho-enzyme levels and [3H] ouabain binding to (Na+ + K+)-ATPase. 13 82

Biochemicalical evidence is presented which demonstrates that the Neurospora crassa plasma membrane ATPase (ATP phosphohydrolase, EC 3.6.1.3) is an electrogenic pump. The electrical potential across the Neurospora plasma membrane, as monitored by [14C]SCN- uptake by isolated Neurospora plasma membrane vesicles, is markedly increased interior positive under conditions of ATP hydrolysis catalyzed by plasma membrane ATPase. [14C]SCN- uptake by the vesicles is minimal in the presence of Tris phosphate, Tris phosphate plus Mg+2, Tris ADP plus Mg+2, and Tris ATP, but is markedly stimulated in the presence of Tris ATP plus Mg+2.
...
PMID:The neurospora plasma membrane ATPase is an electrogenic pump. 13 43

Membrane vesicles were prepared by osmotic lysis of spheroplasts from M13-infected Escherichia coli. Reduced nicotinamide adenine dinucleotide (NADH) oxidase (reduced NAD: oxidoreductase, EC 1.6.99.3) and Mg2+-Ca2+-activated adenosine triphosphatase (ATP phosphohydrolase, EC 3.6.1.3), which are normally localized to the inner surface of the cytoplasmic membrane, were 50% acceesible to their polar substrates in these vesicles. The major coat protein of coliphage M13 is also bound to the cytoplasmic membrane (prior to phage assembly) but with its antigenic sites exposed to the exterior of the cell. Antibody to M13 coat protein was used to fractionate membrane vesicles. Neither agglutinated nor unagglutinated vesicles had altered NADH oxidase and adenosine triphosphatase specific activities. This is inconsistent with such vesicles being a mixture of correctly oriented and completely inverted membrane sacs and suggests that NADH oxidase, adenosine triphosphatase, M13 coat protein, or all three proteins rearrange during vesicle preparation.
...
PMID:Fractionation of membrane vesicles from coliphage M13-infected Escherichia coli. 13 27


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---