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)

Membrane vesicles from Azotobacter vinelandii O prepared by osmotic lysis of spheroplasts in tris (hydroxymethyl) aminomethane/acetate buffer (pH 7.8) contain a latent adenosine triphosphatase (ATPase). The ATPase can be activated when the vesicles are incubated in the presence of an electron donor (D-lactate) and a mixture of adenosine diphosphate and inorganic phosphate or by controlled treatment with trypsin. After the ATPase is activated, the membrane vesicles in the presence of adenosine triphosphate accumulate calcium but not glucose or rubidium (in the presence of valinomycin). ATP-dependent calcium uptake follows Michaelis-Menten kinetics with a Km of 48 muM and a Vmax of 20 nmol/min/mg of membrane protein and is highly specific for calcium over cations magnesium, barium, lanthanum, sodium, potassium, and lithium. The calcium accumulated in the presence of ATP is freely exchangeable with external calcium and is rapidly released in the presenceof uncouplers or ATPase inhibitors. Calcium uptake in the presenceof ATP is blocked by dicyclohexylcarbodiimide, ADP, p-chloromercuriphenylsulfonate, by the proton-conducting ionophores m-chlorophenylcarbonylcyanide hydrazone, nigericin, monensin, and gramicidin D, but not by potassium cyanide, anoxia, or valinomycin (in the presence of potassium). Measurements of the external pH of vesicle suspensions reveal that protons are actively taken up by the membranes during hydrolysis of ATP. These results suggest that vesicles prepared under these conditions have a topology which is inverted with respect to the intact cell and that calcium is accumulated by means of proton antiport.
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PMID:ATP-dependent calcium transport in isolated membrane vesicles from Azotobacter vinelandii. 0 92

Native solium and potassium adenosine triphosphatase from guinea pig kidney accepted a phosphate group from radioactive inorganic phosphate to form an acyl phosphate bond at the active site in the presence or absence of sodium ion. Magnesium ion was always required. In the presence of sodium ion and absence of adenosine triphosphate, there was no phosphorylation by inorganic phosphate. Addition of unlabeled adenosine triphosphate produced a potassium-sensitive phosphoenzyme which exchanged its phosphate-group with radioactive inorganic phosphate. The dephosphoenzyme was an intermediate in this exchange. The rate constant for dephosphorylation was about 0.05 per second. Addition of rubidium ion, a congener of potassium ion, to the potassium-sensitive phosphoenzyme produced a phosphoenzyme labeled from inorganic phosphate with a corresponding rate constant of 0.26 per s. This was a rubidium-complexed phosphoenzyme. Addition of magnesium ion to potassium-sensitive phosphoenzyme converted it into insensitive phosphoenzyme, the splitting of which was not accelerated by potassium ion or by adenosine diphosphate. Its rate constant was 0.07 per s. In the absence of sodium ion and adenosine triphosphate, inorganic phosphate was incorporated directly into a similar insensitive phosphoenzyme. In the presence of potassium ion or rubidium ion, inorganic phosphate was incorporated into a potassium-complexed or rubidium-complexed phosphoenzyme which exchanged 32-P with inorganic phosphate completely in less than 3 s. Incorporation of inorganic phosphate into a complex of the enzyme with the inhibitor, ouabain, is already described in the literature. Its rate constant was about 0.02 per s. Thus there appear to be at least four reactive states of the phosphoenzyme which equilibrate measurably with inorganic phosphate, namely, potassium-sensitive phosphoenzyme, potassium-complexed phosphoenzyme, insensitive phosphoenzyme, and ouabain phosphoenzyme. Two of these reactive states are functional intermediates in native sodium and potassium ion transport adenosine triphosphatase. The results are compatible with control of the reactivity of the active site by conformational changes in the surrounding active center and with regulation of the energy level of the phosphate group according to the kind of monovalent cation bound to the enzyme.
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PMID:Phosphorylation by inorganic phosphate of sodium plus potassium ion transport adenosine triphosphatase. Four reactive states. 12 73

Ultrasonic treatment of microsome fraction or the preparation of partially purified Na+, K+-ATPase from cattle brain resulted in the formation of closed structures which immobilized rubidium and sodium ions and were easily discovered in electron microscope. Gradual release of bound rubidium ions was observed under the incubation of ultrasonic-treated membrane preparation in salt solutions. This process was activated by ATP. ATP-activated release of rubidium was observed only in the presence of sodium and was inhibited by ouabain. A hypothesis on the participation of sodium pump in the ion transport through membranes of artificial vesicles is discussed.
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PMID:[Properties of artificial vesicles from biological membranes]. 12 87

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.
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PMID:Effects of alkali metal cations on phospho-enzyme levels and [3H] ouabain binding to (Na+ + K+)-ATPase. 13 82

Vasodilator responses to acute intra-arterial infusions of K+ are attenuated in dogs with chronic one-kidney perinephritic hypertension in rats with chronic two-kidney Goldblatt hypertension, and in men with essential hypertension. There is evidence that K+ evokes vasodilation by stimulating vascular smooth muscle membrane Na+-K+-activated adenosine triphosphatase, thereby increasing activity of the cellular Na+-K+ electrogenic pump. We therefore proposed that there may be an underlying decrease in the operation of this pump in vascular smooth muscle of hypertensives. The operation of the cellular Na+-K+ pump may be estimated by measurement of rubidium uptake. Thus, so further investigate our hypothesis, we measured 86Rb uptake in small mesenteric arteries and splanchnic veins from 12 dogs with chronic uncomplicated one-kidney perinephritic hypertension and from 12 normotensive control dogs. Vessels were excised under thiamylal anesthesia and incubated in cold medium (plasma or Krebs-Henseleit solution) for sodium loading and then the velocity of 86Rb uptake was estimated in the absence of or in the presence of ouabain, a specific inhibitor of the Na+-K+ pump. In neither arteries nor veins was there evidence for differences between hypertensives and normotensives in the ouabain-insensitive uptake of 86Rb. In contrast, the ouabain-sensitive 86Rb uptake was depressed by 42% in arteries (P less than 0.05) and by 49% in veins (P less than 0.01) from hypertensive dogs, if incubated in the dog's own plasma. These results indicate that the activity of a ouabain-sensitive Na+-K+ pump may be depressed in vascular tissue from dogs with chronic one-kidney perinephritic hypertension. Because the Na+-K+ pump in vascular smooth muscle is probably electrogenic, such an abnormality, by partially depolarizing the muscle cell membrane, would help to account for the elevated vascular resistance found in these dogs.
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PMID:Depressed function of a ouabain-sensitive sodium-potassium pump in blood vessels from renal hypertensive dogs. 13 55

Membrane vesicles were prepared from Azotobacter vinelandii spheroplasts by lysis in either potassium phosphate (pH 7.0) or Tris1-acetate (pH 7.8) buffers. These 2 types of preparations differ considerably in their properties: 1) Examination by scanning electron microscopy reveals that the Pi vesicles consist primarily of closed structures 0.6-0.8 micrometer in diameter with a rough or particulate surface similar to that of spheroplasts. The Tris vesicles are significantly smaller, 0.1-0.3 micrometer in diameter, and have a much smoother surface structure. 2) Antisera from rabbits immunized with A. vinelandii lipopolysaccharide antigen will agglutinate Pi vesicles but not Tris vesicles. 3) Tris vesicles have a fourfold higher specific activity of latent H+-ATPase than Pi vesicles. After exposure to Triton X-100 similar ATPase activities are observed for both types of vesicles. 4) Pi vesicles transport calcium in the presence of ATP or lactate at less than 30% of the rats observed for Tris vesicles. 5) Tris vesicles have less than 22% of the transport capacity of Pi vesicles for accumulation of labeled sucrose and less than 3% of the capacity for valinomycin-induced uptake of rubidium observed during respiration. 6) Quinacrine fluorescence intensity is reduced by 30% during lactate oxidation and 20% during ATP hydrolysis by Tris vesicles. Under similar conditions, fluorescence in Pi vesicles is quenched by only 7% and less than 2%, respectively. These findings suggest that Pi vesicles have the normal orientation of the intact cell whereas Tris vesicles have an inverted topology.
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PMID:Isolation of membrane vesicles with inverted topology by osmotic lysis of Azotobacter vinelandii spheroplasts. 14 14

The addition of bacteriophage T5 to anaerobic, fermenting cells of Escherichia coli B or K-12 in the presence of 8-anilino-1-naphthalene sulfonate (ANS), N-phenylnaphthyl-1-amine (NPN), or dansyl ethylamine causes the fluorescence of these probes to rise in two steps, the first occurring immediately upon addition, the second delayed by 6 min. The conditions necessary for observing this phenomenon are defined (cell density, probe concentration, substrate, absence of an electron acceptor, multiplicity of infection, growth, and harvesting conditions). The magnitudes of the first and second steps in fluorescence are dependent upon the multiplicity of infection; the timing of the steps is not. The first step correlates with a breakdown in the potassium or rubidium permeability barrier of the cells, and it occurs either aerobically or anaerobically, with fermentable or nonfermentable substrates. The second step occurs only with cells that are without an available electron acceptor, are fermenting, and which have a functional membrane-bound, Ca2+-dependent adenosine triphosphatase (ATPase). The results are consistent with disturbance of energization of the cell membrane by the membrane-bound ATPase at the time of the second step in fluorescence. No changes in the intracellular level of adenosine 5'-triphosphate (ATP) was seen, whereas the extracellular level increased sharply, starting 3--6 min after phage addition. The quantity of ATP found in the medium by 30 min after infection amounted to about four times the amount present inside the cells at the time of infection. The quantity and rate of efflux of ATP was similar under aerobic and anaerobic conditions.
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PMID:Relationship between steps in 8-anilino-1-naphthalene sulfonate (ANS) fluorescence and changes in the energized membrane state and in intracellular and extracellular adenosine 5'-triphosphate (ATP) levels following bacteriophage T5 infection of Escherichia coli. 15 81

The authors studied the effect of rubidium, lithium and cesium on the ATPase system and c-AMP protein kinase in brain. They demonstrated that rubidium could replace potassium in the Na+K-ATPase system, whereas lithium and cesium had no effect on this enzyme activity in the absence of potassium. K+-dependent ATPase was activated by even low rubidium concentrations; lithium and cesium inhibited it. None of three (rubidium, lithium and cesium) affected c-AMP protein kinase.
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PMID:Effect of rubidium, lithium and cesium on brain ATPase and protein kinases. 19 47

The activity of Na+, K+-activated adenosinetriphosphatase and the uptake of a potassium analog, rubidium, were found to be similar in cerebral microvessels and choroid plexus when measured in vitro. This similarity suggests that sodium and potassium concentrations in the nascent brain extracellular fluid are determined by the same active process that regulates their concentration in nascent cerebrospinal fluid. The brain microvessels may thereby play on active role in brain potassium homeostasis and brain extracellular fluid formation.
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PMID:Cerebral vessels have the capacity to transport sodium and potassium. 22 60

Changes of coronary flow in the isolated perfused spontaneously beating guinea pig heart were induced by elevation of potassium concentration in the perfusion medium (4-16 meq/l). Potassium caused a dose-dependent transient increase of diastolic coronary inflow. The response was inhibited by ouabain (1.4 X 10(-7) M) or reduced temperature. Rubidium ions elicited almost identical vasodilator effects which were also inhibited by ouabain. Autoregulation of coronary flow, reactive hyperemia, and hypoxic coronary dilation were not significantly altered in the presence of ouabain. The results support the hypothesis that potassium as well as rubidium cause vasodilation by activating a Na+, K+-ATPase. On the other hand, they do not favour the view of an essential involvement of potassium ions in local regulation of coronary flow under the conditions studied.
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PMID:Studies on potassium induced coronary dilation in the isolated guinea pig heart. 94 8


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