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)

Ouabain-sensitive ATP hydrolysis (Na,K-ATPase activity) was measured in digitonin-permeabilized monolayers of cultured cells derived from rabbit non-pigmented ciliary epithelium. Diminished Na,K-ATPase activity was observed in cells that had been pre-treated 10 min with the protein kinase C activator, PDBu, as well as in cells that had been cooled to 4 degrees C for 4 h then rewarmed to 37 degrees C for 30 min (cool-rewarm manoeuvre). In the intact cells, ouabain binding was not decreased either by PDBu treatment or the cool-rewarm manoeuvre. However, both PDBu and the cool-rewarm manoeuvre increased the rate of ouabain-sensitive potassium (86Rb) uptake measured in intact cells. Cell ATP content was diminished in PDBu-treated cells and cells subjected to the cool-rewarm manoeuvre. We suggest that an episode of ATP depletion might initiate a mechanism which causes lasting, partial inhibition of Na,K-ATPase activity. In keeping with this suggestion, diminished Na,K-ATPase activity was observed in cells that had been pre-treated 20 min with the metabolic inhibitors CCCP or rotenone and in cells pre-treated 2.5 h in dextrose-free medium. This study illustrates that Na,K-ATPase activity measured in the permeabilized cell is a complex parameter which is not necessarily a reliable indicator of sodium pump responses in the intact cell.
...
PMID:Partial inhibition of Na,K-ATPase activity in cultured rabbit non-pigmented ciliary epithelium following an episode of cytoplasmic ATP depletion. 977 20

Fermenting Escherichia coli wild type cells, grown anaerobically at alkaline pH (pH 8.3-8.6), upon transfer into the medium at pH 7.5-7.8 were shown to maintain intracellular pH at 7.5, acidify medium, take in K+, generate membrane potential of -160 mV and produce molecular hydrogen. Proton-potassium exchange proceeded in one step, was inhibited by the N,N'-dicyclohexylcarbodiimide (DCCD) and protonophore CCCP. H+ secretion was sensitive to osmotic shock, and K+ uptake up to the potassium gradient between the cytoplasm and the medium of more than 2 x 10(3) occurred at Km 3.0 mM and was carried out upon upshock or downshock. The stoichiometry of DCCD-inhibited cation fluxes was unstable upon change of experimental conditions. This H+,K+ exchange was not observed in E. coli mutants with the defect in the alpha-subunit of H(+)-ATPase F0F1 complex (uncA) or in the TrkA system of K+ uptake (trkA trkD). The DCCD-inhibited ATPase activity of membrane vesicles did not show any significant dependence on K+ activity in the medium. We suggest that proton and potassium transport systems are involved in the regulation of intracellular pH in E. coli. K+ uptake in the bacteria grown anaerobically at alkaline pH is carried out by the TrkA system, which functions as uniporter, interacts with the F0F1 proton pump by means of transmembrane electrochemical gradient for H+ which is used as the driving force. Growth medium pH, probably, determines the character of interaction of the TrkA with the F0F1.
...
PMID:Regulation of intracellular pH and proton-potassium exchange in fermenting Escherichia coli grown anaerobically in alkaline medium. 982 60

The study of the effect of KCN, DCCD and CCCP as inhibitors of the energy yielding processes showed that the efficacy of phage infection depended on respiration, proton ATPase, and proton electrochemical potential of hydrogen ions. There was a 49.5-68.0% decrease of the efficacy of phage infection after addition of the above mentioned inhibitors at the period of the contact of cells with bacteriophages at the stage of the phage nucleic acid transfer. The Embden-Meyerhof-Parnas route inhibitors NaF and CH2ICOOH less affected the efficacy of phage infection. The same effect was observed during addition of Na3AsO4 as the ATP synthesis inhibitor. This efficacy decrease was probably due the inhibition of the processes of the substrate level phosphorylation and the deplete of the intracellular ATP content.
...
PMID:[A comparative analysis of energy process inhibitors on the efficiency of phage infection in staphylococci]. 985 41

No methods are currently available for fully reliable monitoring of membrane potential changes in suspensions of walled cells such as yeast. Our method using the Nernstian cyanine probe diS-C3(3) monitors even relatively fast changes in membrane potential delta psi by recording the shifts of probe fluorescence maximum lambda max consequent on delta psi-dependent probe uptake into, or exit from, the cells. Both increased [K+]out and decreased pHout, but not external NaCl or choline chloride depolarise the membrane. The major ion species contributing to the diS-C3(3)-reported membrane potential in S. cerevisiae are thus K+ and H+, whereas Na+ and Cl- do not perceptibly contribute to measured delta psi. The strongly pHout-dependent depolarisation caused by the protonophores CCCP and FCCP, lack of effect of the respiratory chain inhibitors rotenone and HQNO on the delta psi, as well as results obtained with a respiration-deficient rho- mutant show that the major component of the diS-C3(3)-reported membrane potential is the delta psi formed on the plasma membrane while mitochondrial potential forms a minor part of the delta psi. Its role may be reflected in the slight depolarisation caused by the F1F0-ATPase inhibitor azide in both rho- mutant and wildtype cells. Blocking the plasma membrane H(+)-ATPase with the DMM-11 inhibitor showed that the enzyme participates in delta psi build-up both in the absence and in the presence of added glucose. Pore-forming agents such as nystatin cause a fast probe entry into the cells signifying membrane damage and extensive binding of the probe to cell constituents reflecting obviously disruption of ionic balance in permeabilised cells. In damaged cells the probe therefore no longer reports on membrane potential but on loss of membrane integrity. The delta psi-independent probe entry signalling membrane damage can be distinguished from the potential-dependent diS-C3(3) uptake into intact cells by being insensitive to the depolarising action of CCCP.
...
PMID:Factors and processes involved in membrane potential build-up in yeast: diS-C3(3) assay. 1039 18

When human sperm was incubated in medium deprived of glucose, glucose restoration caused a transient hyperpolarization of the plasma membrane. This hyperpolarization was also induced by fructose but not by 2-deoxyglucose, a substrate that cannot be metabolized. The hyperpolarization was inhibited by NaF, a glycolysis inhibitor, but not by mitochondrial inhibitors (cyanide, rotenone and antimycin), suggesting that it depended on glycolysis. Furthermore, the hyperpolarization was still induced in medium containing a high concentration of KCl and was insensitive to the K(+) channel blocker TEA and the Cl(-) channel blocker niflumic acid, but it was blocked by ouabain. This suggested that upon glucose addition, there was an increase in the concentration of ATP, that in turns increased the Na(+),K(+)-ATPase activity. Since this pump is electrogenic (2K(+)/3Na(+)) the plasma membrane hyperpolarized. On the other hand, CCCP, a proton ionophore, inhibited the hyperpolarization induced by glucose. When CCCP was added to glucose-treated hyperpolarized sperm, it caused a depolarization that triggered a Ca(2+) influx sensitive to nickel, an inhibitor of voltage-dependent calcium channels. Moreover, CCCP caused hyperpolarization in sperm incubated in medium without calcium, a known condition that depolarizes sperm. This indicated that CCCP induced proton permeability in the plasma membrane that was able to change the membrane potential to a value corresponding to the E(H) and that was also able to clamp it, so that it prevented the hyperpolarization induced by glucose.
...
PMID:Glucose induces a Na(+),K(+)-ATPase-dependent transient hyperpolarization in human sperm. I. Induction of changes in plasma membrane potential by the proton ionophore CCCP. 1072 6

The calcium antagonists verapamil, nitrendipine, mibefradil, and amlodipine accumulate in chromaffin granule ghosts with apparent equilibrium partition coefficients [(mol/mg membrane lipid)/(mol/mg solvent water)] of 246 +/- 105 (N = 8), 2700 +/- 600 (N = 4), 7400 +/- 2200 (N = 4), and 8100 +/- 1100 (N = 5), respectively. In the presence of 1.2 mM MgATP, the partition coefficients were 854 +/- 206 (N = 10), 2300 +/- 600 (N = 4), 32,700 +/- 8,900 (N = 7), and 20,300 +/- 5,000 (N = 11) for verapamil, nitrendipine, mibefradil, and amlodipine, respectively. Except for nitrendipine, the apparent partition coefficients in the presence of MgATP were significantly different from the control (P < 0.001). For amlodipine and verapamil, the vacuolar H(+)-ATPase inhibitors bafilomycin A1 (30 nM) and N-ethylmaleimide (2 mM) and the protonophore (uncoupler) carbonyl cyanide m-chlorophenylhydrazone (CCCP, 10 microM) completely blocked the increase in partition coefficients in response to MgATP. The extra amlodipine, mibefradil, and verapamil that accumulated in response to MgATP were released into the medium by CCCP (10 microM) by 18% (N = 5), 30% (N = 5), and 88% (N = 5) for amlodipine, mibefradil, and verapamil, respectively. Thus, amlodipine, mibefradil, and verapamil, but not nitrendipine, accumulate in catecholamine storage vesicles in response to delta mu H+ generated by the endogenous V-type H(+)-ATPase, and are partially released by de-energetisation. Hence, these calcium antagonists can reach unexpectedly high concentrations in certain target cells, and give pharmacodynamic properties not shared by nitrendipine.
...
PMID:Energy-dependent accumulation of calcium antagonists in catecholamine storage vesicles. 1081 Apr 46

Synaptic vesicles, isolated from a sheep brain cortex, accumulate Ca(2+) in a manner that depends on the pH and pCa values. In the presence of 100 microM CaCl(2), most of the Ca(2+) taken up by the vesicles was vanadate-inhibited (86%) at pH 7.4, whereas at pH 8.5, part of the Ca(2+) accumulated (36%) was DeltapH-dependent (bafilomycin and CCCP inhibited) and part was insensitive to those drugs (31%). We also observed that both vanadate-sensitive and bafilomycin-sensitive Ca(2+) accumulations were completely released by the Ca(2+) ionophore, ionomycin, and that these processes work with high (K(0.5)=0.6 microM) and low (K(0.5)=217 microM) affinity for Ca(2+), respectively. The DeltapH-dependent Ca(2+) transport appears to be largely operative at Ca(2+) concentrations (>100 microM) which completely inhibited the vanadate-sensitive Ca(2+) uptake. These Ca(2+) effects on the Ca(2+) accumulation were well correlated with those observed on the vanadate-inhibited Ca(2+)-ATPase and bafilomycin-inhibited H(+)-ATPase, respectively. The Ca(2+)-ATPase activity reached a maximum at about 25 microM (pH 7.4) and sharply declined at higher Ca(2+) concentrations. In contrast, Ca(2+) had a significant stimulatory effect on the H(+)-ATPase between 250 and 500 microM Ca(2+) concentration. Furthermore, we found that DeltapH-sensitive Ca(2+) transport was associated with proton release from the vesicles. About 21% of the maximal proton gradient was dissipated by addition of 607.7 microM CaCl(2) to the reaction medium and, if CaCl(2) was present before the proton accumulation, lower pH gradients were reached. Both vanadate-inhibited and bafilomycin-inhibited systems transported Ca(2+) into the same vesicle pool of our preparation, suggesting that they belong to the same cellular compartment. These results indicate that synaptic vesicles of the sheep brain cortex contain two distinct mechanisms of Ca(2+) transport: a high Ca(2+) affinity, proton gradient-independent Ca(2+) pump that has an optimal activity at pH 7.4, and a low Ca(2+) affinity, proton gradient-dependent Ca(2+)/H(+) antiport that works maximally at pH 8.5.
...
PMID:Distinction between Ca(2+) pump and Ca(2+)/H(+) antiport activities in synaptic vesicles of sheep brain cortex. 1082 79

Previous studies in chick embryo cardiac myocytes have shown that the inhibition of Na+/K+-ATPase with ouabain induces cell shrinkage in an isosmotic environment (290 mOsm). The same inhibition produces an enhanced RVD (regulatory volume decrease) in hyposmotic conditions (100 mOsm). It is also known that submitting chick embryo cardiomyocytes to a hyperosmotic solution induces shrinkage and a concurrent intracellular alkalization. The objective of this study was to evaluate the involvement of intracellular pH (pHi), intracellular Ca2+ ([Ca2+]i) and Na+/K+-ATPase inhibition during hyposmotic swelling. Changes in intracellular pH and Ca2+ were monitored using BCECF and fura-2, respectively. The addition of ouabain (100 microM) under both isosmotic and hyposmotic stimuli resulted in a large increase in [Ca2+]i (200%). A decrease in pHi (from 7.3 +/- 0.09 to 6.4 +/- 0.08, n = 6; p < 0.05) was only observed when ouabain was applied during hyposmotic swelling. This acidification was prevented by the removal of extracellular Ca2+. Inhibition of Na+/H+ exchange with amiloride (1 mM) had no effect on the ouabain-induced acidification. Preventing the mitochondrial accumulation of Ca2+ using CCCP (10 microM) resulted in a blockade of the progressive acidification normally induced by ouabain. The inhibition of mitochondrial membrane K+/H+ exchange with DCCD (1 mM) also completely prevented the acidification. Our results suggest that intracellular acidification upon cell swelling is mediated by an initial Ca2+ influx via Na+/Ca2+ exchange, which under hyposmotic conditions activates the K+ and Ca2+ mitochondrial exchange systems (K+/H+ and Ca2+/H+).
...
PMID:Na+/K+-ATPase inhibition during cardiac myocyte swelling: involvement of intracellular pH and Ca2+. 1097 71

Effects of phytohormones gibberellic acid (GA) and abscisic acid (ABA) on the ATP-dependent transmembrane transport of protons were studied in plasma membrane vesicles (PMVs) from non-dormant potato tubers. The uptake of H+ into PMVs was assessed by the fluorescence quenching of acridine orange (AO) after the addition of ATP to the incubation medium. Addition of ATP to the incubation medium led to the instantaneous rise of the AO fluorescence intensity followed by its decrease. The fluorescence quenching was not observed in the presence of either protonophore CCCP or inhibitors of the membrane-bound H+-ATPase. It is concluded that the ATP-induced quenching of the AO fluorescence resulted from the accumulation of protons in PMVs due to the function of the plasma membrane-bound H+-ATPase. Depending on their concentrations, GA and ABA either inhibited or stimulated the ATP-driven H+ translocation across the vesicle membrane. The growth-stimulating hormone GA at concentrations of 10(-9)-10(-5) M increased the initial rate of the fluorescence quenching, whereas 10(-4) M GA slightly inhibited the H+ translocation. The growth inhibitor ABA at a concentration of 10(-9) M slightly increased the rate of the proton accumulation in PMVs; at higher concentrations (10(-8)-10(-4) M), ABA inhibited the H+ translocation. Acetic acid, which has pK similar to pK of GA and ABA, did not influence the ATP-dependent H+ accumulation in PMVs, suggesting the hormone-specific action of GA and ABA on the H+-ATPase activity. In the presence of DCC, which completely inhibited the accumulation of H+, GA and ABA did not affect the passive proton efflux from PMVs. It is proposed that the mechanisms of the regulatory effects of phytohormones may involve modification of H+-ATPase activity leading to changes in the electrochemical gradient of H+ across the plasma membrane.
...
PMID:Effect of phytohormones on the transmembrane translocation of protons in plasma membrane vesicles from tubers of Solanum tuberosum L. 1098 85

Myocellular sodium homeostasis is commonly disrupted during critical illness for unknown reasons. Recent data suggest that changes in intracellular sodium content and the amount of ATP provided by glycolysis are closely related. The role of glycolysis and oxidative phosphorylation in providing fuel to the Na(+)-K(+) pump was investigated in resting rat extensor digitorum longus muscles incubated at 30 degrees C for 1 h. Oxidative inhibition with carbonyl cyanide m-chlorophenylhydrazone, known as CCCP (0.2 microM), or by hypooxygenation did not alter myocellular sodium or potassium content ([Na(+)](i), [K(+)](i), respectively), whereas treatment with iodoacetic acid (0.3 mM), which effectively blocked glycolysis, dramatically increased [Na(+)](i) and the [Na(+)](i)/[K(+)](i) ratio. Experiments using ouabain and measurements of myocellular high-energy phosphates indicate that Na(+)-K(+)-ATPase activity is only impaired when glycolysis is inhibited. The data suggest that normal glycolysis is required to regulate intracellular sodium in fast-twitch skeletal muscles, because it is the predominant source of the fuel for the Na(+)-K(+)-ATPase.
...
PMID:ATP from glycolysis is required for normal sodium homeostasis in resting fast-twitch rodent skeletal muscle. 1150 Mar 3


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

---