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)

On five-day-old and adult Wistar rats (of both sexes) experiments were made where the influence of the pH of the medium was assessed as well as that of a lower ATP supply on the activity of (Na(+)-K+) and Mg++ dependent ATPases (E.C.3.6.1.3.) isolated from tissue of the cerebral cortex and possibly the medulla oblongata. The enzyme activity is expressed in mumol.l-1 of released Pi (minute/mg protein). It was found that the drop of pH of the incubation medium (adjusted with HCl) to 7.0 and 6.4 (as compared with pH 7.4 in control measurements) did not cause in 5-day-old rats a significant change in the activity of ouabain sensitive ATPase of the cerebral cortex or medulla oblongata, while in adult rats a marked reduction was observed. At pH 6.4 in adult rats a greater drop of the activity in the cerebral cortex than in tissue of the medulla oblongata was demonstrated. Equally resistant was also ouabain sensitive ATPase in 5-day old rats against the ATP concentration of the medium; even a drop by 50% (as compared with control values) did not cause a significant reduction of activity, while in adult rats a significant drop was observed. In ouabain sensitive ATPase the position is different. In 5-day-old rats a lower pH reduces its activity to an equal extent for pH 7.0 and pH 6.4. In adult rats the activity is also reduced, the reduction being the more marked the more acid the pH of the medium (cerebral cortex).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[The effect of the pH environment and reduced ATP supply on ATPase activity in the brain of young and adult rats]. 214 Sep 8

An inhibition reactivation technique was used for histochemical staining of human skeletal muscle sections. Myofibrillar ATPase activity was inhibited by sodium hydroxymercuribenzoate (2.5 mM in 0.1 M Tris-HCl buffer, pH 7.2-7.5, 30 min) and successively reactivated by cysteine which was added to incubation solution (10 mM cysteine-HCl, 2.5 mM ATP-disodium salt, 50 mM potassium chloride and 27 mM calcium chloride in barbital buffer, pH 9.4, 35 min at 37 C). This technique allows the distinction of three fiber categories with different staining intensities in single cross-section. Dark, intermediate and light fibers correspond to IIB, I, and IIA types, respectively. Storage of air dried sections in the freezer at -20 C for one month had no influence on staining characteristics.
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PMID:Inhibition reactivation myofibrillar ATPase technique for demonstration of three fiber types in a single cryostat muscle section. 214 35

This report describes the first isolation and molecular characterization of the mitochondrial F1-ATPase from Trypanosoma brucei. The isolation procedure utilized is a modified chloroform extraction procedure. In contrast to earlier reports on the F1-ATPase from other trypanosomatids, the F1-ATPase we have isolated from the procyclic form of T. brucei a complex composed of five distinct subunits. Apparent molecular weights of these subunits are 55,000 [alpha], 42,000 [beta], 32,000 [gamma], 22,000 [delta], and 17,000 [epsilon]. The F1 moiety which possesses the active site of the H(+)-ATPase has an ATPase activity in the standard Tris-HCl coupled enzyme assay with a Vmax of 22.96 mumol min-1 (mg protein)-1 and a Km value of 0.60 mM. This ATPase activity is cold labile and is not susceptible to oligomycin inhibition as is the membrane bound enzyme. Upon reconstitution with F1-ATPase depleted membranes (urea particles) the ATPase regains oligomycin sensitivity to the same extent as that found in the intact inner membrane vesicles. ATP synthesis is also restored to these particles upon reconstitution with F1. These results indicate that this F1-ATPase as isolated is intact with respect to all the critical H(+)-ATPase functions.
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PMID:The mitochondrial ATP synthase of Trypanosoma brucei: isolation and characterization of the intact F1 moiety. 214 43

The half maximal inhibitory concentrations (IC50) of substituted benzimidazoles for the H+, K(+)-ATPase in hog gastric vesicles were measured by using the pyruvate kinase-lactate dehydrogenase-linked system in which hydrolysis of ATP was coupled with the oxidation of NADH. The vesicles were incubated in a solution containing a high concentration of KCl, valinomycin and Mg-ATP, and the intravesicular medium was acidified. The inhibitor was activated in the acidic medium and reacted with SH groups on the luminal (intravesicular) side of the ATPase. The active compound formed in the extravesicular medium (pH 6.11) was quenched by GSH. Under these conditions, IC50 of new compound E3810, 2[(4-(3-methoxypropoxy)-3-methylpyridine-2-yl)methyl-sulfinyl]-1H- benzimidazole sodium salt, was 0.072 microM and that of omeprazole was 0.47 microM at 25 degrees. On the other hand, the rates of formation of active compounds, tetracyclic sulfenamide derivatives, from original substituted benzimidazoles in 0.1 N HCl (k) were determined by measuring optical density at the characteristic wavelengths of the active compounds. There was a good correlation between IC50 and k for various substituted benzimidazoles including E3810, methoxy derivative of E3810, omeprazole, Ro 18-5364, H compound, picoprazole and timoprazole. This fact suggest that the rate of the formation of the acid-activated compound is a main factor determining the potency of the inhibitor.
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PMID:The potency of substituted benzimidazoles such as E3810, omeprazole, Ro 18-5364 to inhibit gastric H+, K(+)-ATPase is correlatedwith the rate of acid-activation of the inhibitor. 215 89

Subcellular fractions were isolated from homogenates of human and rat gastric mucosal membranes by means of differential centrifugation; the highest Na+, K(+)-ATPase activity was detected in microsomal fraction. The enzymatic activity was higher in human gastric mucosal membrane as compared with the rat tissue. Na+, K(+)-ATPase activity was inhibited by 0.1% SDS added into the homogenization mixture. Ouabain 1.5 x 10(-3) M did not affect the enzymatic activity. The enzyme had a pH optimum in both these tissues at pH 7.2 = 7.4 in 30 mM imidazol-HCl buffer and at pH 7.1-7.2 in 40 mM Tris-HCl buffer. K+ exhibited maximal activating effect at 20 mM concentration in human gastric mucosal membrane and at 5 mM concentration in rat tissue. The ratio ATP/Mg2+ as 1:1 proved to be optimal at 2 mM concentration.
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PMID:[Comparative characteristics of the distribution and various properties of Na,K-ATPase from human and rat gastric mucosa]. 216 65

Stimulation of the gastric parietal cell requires massive membrane transformations as H(+)-pumps from the domain of cytoplasmic tubulovesicles are recruited into the apical plasma membrane domain. The recycling of membrane pools, through fusion and fission processes that accompany stimulation and inhibition of HCl secretion, also involves highly selective events of protein incorporation and segregation. This manuscript describes several proteins that have been identified with the apical plasma membrane from maximally stimulated parietal cells, and broadly characterizes them either as permanent resident proteins of the apical membrane, or transient proteins that move into and out of the apical membrane as the cell progresses through the secretory cycle. A typical example of transient association with the apical membrane concerns the pump proteins, including the 94 kDa catalytic alpha-subunit of the H+K(+)-ATPase and its newly discovered beta-subunit glycoprotein, which move between tubulovesicles. Proteins that remain associated with the apical plasma membrane during rest and secretion include actin, and an 80-kDa phosphoprotein, which has been variously called 80 K, ezrin, p81 and cytovillin, and whose phosphorylation is increased by the histamine/cAMP pathway of parietal cell stimulation. An example of a cytosolic protein that becomes associated with the apical plasma membrane after stimulation is a 120-kDa protein, which appears to have protein kinase activity. Note that the identification, localization and characterization of the K+ and Cl- transport proteins, which participate in net HCl secretion, are of immediate importance.
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PMID:Membrane and protein recycling associated with gastric HCl secretion. 216 24

The effects of the anti-inflammatory seleno-organic compound ebselen on gastric H+/K(+)-ATPase, H+/K(+)-ATPase-mediated proton transport and on parietal cell HCl production was studied. Ebselen inhibited K(+)-stimulated ATPase activity in leaky gastric membranes (IC50:0.15 microM) and H+/K(+)-ATPase-mediated proton transport in intact gastric membrane vesicles (IC50:0.7 microM). Histamine- and dibutyryl-cAMP-stimulated HCl production in isolated and enriched guinea-pig parietal cells was inhibited with an IC50 value of 12 microM. The mercaptan dithioerythritol and the nucleotide ATP prevents the H+/K(+)-ATPase against inactivation and dithioerythritol was found to restore already inhibited enzyme activity and ATPase mediated H+ transport. Furthermore, dithioerythritol could prevent ebselen-induced inhibition of HCl production in the parietal cell preparation. It is concluded that ebselen inhibits acid secretion in the parietal cell by interference with SH groups of the gastric proton pump, the H+/K(+)-ATPase. Therefore ebselen can be regarded as an anti-inflammatory drug for which in vitro anti-secretory properties can be demonstrated.
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PMID:Interaction of the anti-inflammatory seleno-organic compound ebselen with acid secretion in isolated parietal cells and gastric H+/K(+)-ATPase. 217 97

To ascertain the coupling between Ca2+ and H+ fluxes during Ca2+ transport by the Ca2(+)-pumping ATPase of the sarcoplasmic reticulum, we used well characterized reconstituted proteoliposomes. The method for the functional reconstitution of the Ca2(+)-ATPase was an extension of our recently published procedure (Rigaud, J. L., Paternostre, M. T., and Bluzat, A. (1988) Biochemistry, 27, 2677-2688). The reconstituted vesicles which sustained high Ca2+ transport activities in the absence of Ca2+ precipitating anions exhibited low ionic passive permeability. Proton fluxes generated by external acid pulses have been monitored by using the fluorescence of the pH-sensitive probe pyranine trapped inside proteliposomes. When K+ was the only permeant ion, low proton-hydroxyl passive permeability was found (permeability coefficient congruent to 5 x 10(-5) cm s-1). In the presence of Cl-1 ions, a higher proton permeability was observed, presumably due to diffusion of HCl molecules. It was further demonstrated that systematic characterization of the passive permeability is essential for understanding and controlling the ATP-dependent Ca2+ accumulation in the reconstituted liposomes. The first line of evidence for Ca2(+)-H+ countertransport during operation of the Ca2(+)-ATPase came from Ca2+ uptake measurements. The ATP-dependent Ca2+ accumulation into proteoliposomes was shown to be critically dependent upon the ionic composition of the medium and the presence of ionophores. In K2SO4 medium a very low Ca2+ uptake was obtained which was only slightly affected by the presence of valinomycin. On the contrary, Ca2+ accumulation was increased 3-4-fold in the presence of the protonophore carbonyl-cyanide-p-trifluoromethoxy phenylhydrazone, indicating that a transmembrane pH gradient was built up during Ca2+ uptake that inhibited the transport activity of the pump. Accordingly, we found that Ca2+ loading capacity increased with internal buffer capacity. Finally in KCl medium, high Ca2+ accumulation was observed even in the absence of protonophore in agreement with a rapid dissipation of the pH gradient in the presence of chloride ions. Additional evidence that the Ca2+ pump of sarcoplasmic reticulum operated as a Ca2(+)-H+ countertransport was provided by measurements of ATP-dependent intraliposomal alkalinization using entrapped 8-hydroxyl-1,3,6-pyrene trisulfonate (pyranine) and accumulation of the weak acid acetate. In K2SO4 medium, transmembrane pH gradients of about 1 pH unit were generated with kinetics parallel to those of the Ca2+ uptake.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Evidence for proton countertransport by the sarcoplasmic reticulum Ca2(+)-ATPase during calcium transport in reconstituted proteoliposomes with low ionic permeability. 217 42

A summary of recent studies on relations between the properties of the membrane incorporating the H+-K+-ATPase, the H+ motive force in gastric acid secretion, and the secretory state of the parietal cell is presented. Depending on tissue secretory state, two distinct H+-K+-ATPase-rich membranes predominate in tissue homogenates, the gastric microsomes derived from the intracellular tubulovesicles of the resting cell and the stimulation-associated (SA) vesicle derived from the apical membrane of the acid-secreting cell. Structural and chemical differences between both vesicular types lend support to the notion that the formation of an expanded, elaborated apical membrane in the secreting parietal cell results from fusion of tubulovesicles containing the H+-K+-ATPase to an apical membrane of different chemical composition. Comparison of polypeptide composition of microsomes and SA membranes provides a way to identify and isolate membrane and cytoskeletal components putatively involved in the membrane interconversion process. Comparison of transport properties between gastric microsomes and SA vesicles demonstrates that stimulation triggers the appearance of rapid K+ and Cl- permeabilities in the H+-K+-ATPase membrane, allowing efficient acid accumulation in SA vesicles by the combination of rapid KCl influx followed by ATPase-driven H+ for K+ exchange, i.e., by K+ recycling. These stimulation-triggered conductances are functionally independent. Nevertheless, their concurrent inhibition by certain divalent cations (Mn2+,Zn2+) suggests their location within a single physical domain. The compatibility of the K+-recycling model for HCl accumulation in SA vesicles with gastric HCl secretion and selected electrophysiological observations and certain implications of the findings for cellular mechanisms of transport regulation in the context of a membrane fusion and recycling model are discussed.
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PMID:Ion transport studies with H+-K+-ATPase-rich vesicles: implications for HCl secretion and parietal cell physiology. 240 81

2-Azido-ATP, a photoaffinity ATP analogue, was incorporated into actin and the influence of the incorporation on the actin function was studied. The replacement of ADP with 2-azido-ADP in F-actin both before and after photocross-linking decreased appreciably the actin-activated S1-ATPase activity. Photocross-linked 2-azido-ADP-F-actin could be depolymerized by dialysis against a solution containing 0.1 mM CaCl2, 0.1 mM ATP and 1 mM Tris-HCl (pH 8.0). However, once it depolymerized, it lost very quickly the ability to polymerize even in the presence of a sufficient amount of ATP and Ca2+.
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PMID:The effect of the replacement of ADP with a photoaffinity ATP analogue, 2-azido-ADP, in F-actin on its function. 252 51


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