Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adenosine triphosphate (ATP) hydrolysis catalyzed by the plasma membrane (Na+,K+)ATPase isolated from several sources was inhibited by Mg+, provided that K+ and ATP were also present. Phosphorylation of the adenosine triphosphatase (ATPase) by ATP and by inorganic phosphate was also inhibited, as was p-nitrophenyl phosphatase activity. (Ethylenedinitrilo)tetraacetic acid (EDTA) and catecholamines protected from and reversed the inhibition of ATP hydrolysis by Mg2+, K+ and ATP. EDTA was protected by chelation of Mg2+ but catecholamines acted by some other mechanism. The specificities of various nucleotides as inhibitors (in conjunction with Mg2+ and K+) and as substrates for the (Na+, K+) ATPase were strikingly different. ATP, ADP, beta,gamma-CH2-ATP and alpha,beta-CH2-ADP were active as inhibitors, whereas inosine, cytidine, uridine, and guanosine triphosphates (ITP, CTP, UTP, and GTP) and adenosine monophosphate (AMP) were not. On the other hand, ATP and CTP were substrates and beta,gamma-NH-ATP was a competitive inhibitor of ATP hydrolysis, but not an inhibitor in conjunction with Mg2+ and K+. The Ca2+-ATPase from sarcoplasmic reticulum and F1, the Mg2+-ATPase from the inner mitochondrial membrane, were also inhibited by Mg2+. Catecholamines reversed inhibition of the Ca2+-ATPase, but not that of F1.
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PMID:Reversible inhibition of (Na+, K+) ATPase by Mg2+, adenosine triphosphate, and K+. 13 42

The preparation of cytoplasmic membranes from suspensions of Staphylococcus aureus lysed by an enzyme recently isolated in these laboratories is described. These membranes contained: protein, 34.4%; ribonucleic acid, 6.6%; lipids, 34.5%; and total phosphorus, 1.4%. Such membranes exhibited adenosine 5'-triphosphatase (E.C. 3.6.1.3) activity, liberating orthophosphate at an initial rate of 0.53 mumole per min per mg of protein under optimal conditions. The enzyme was Mg(++)-dependent and K(+)- or Na(+)-stimulated. Maximal activity was observed with a molar adenosine 5'-triphosphate (ATP) to Mg(++) ratio of 1. One mole of orthophosphate was liberated per mole of ATP; the other product of digestion was adenosine 5'-diphosphate. Inorganic pyrophosphate and the 5'-triphosphates of guanosine, uridine, and cytidine were also attacked by membrane preparations, but more slowly than ATP. Ouabain, p-chloromercuribenzoate, and 2,4-dinitrophenol did not alter adenosine triphosphatase activity, whereas both Atebrine and chlorpromazine were inhibitory.
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PMID:Adenosine triphosphatase in isolated membranes of Staphylococcus aureus. 423 Aug 57

When samples of pea tendril tissue were incubated in the Wachstein-Meisel medium for the demonstration of adenosine triphosphatases, deposits of lead reaction product were localized between the membranes of the chloroplast envelope. The presence of Mg(2+) was necessary for adenosine triphosphatase activity, and Ca(2+) could not substitute for this requirement. Varying the pH of incubation to 5.5 or 9.4 inhibited enzyme activity, as did the addition of p-chloromercuribenzoic acid or N-ethylmaleimide. The adenosine triphosphatase was apparently inactivated or degraded when the plants were grown in the dark for 24 hours prior to incubation. The enzyme was substrate-specific for adenosine triphosphate; no reaction was obtained with adenosine diphosphate, uridine triphosphate, inosine triphosphate, p-nitrophenyl phosphate, and sodium beta-glycerophosphate. Sites of nonspecific depositions of lead are described. The adenosine triphosphatase on the chloroplast envelope may be involved in the light-induced contraction of this organelle.
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PMID:Localization of adenosine triphosphatase activity on the chloroplast envelope in tendrils of Pisum sativum. 424 3

The presence of adenosine triphosphate, guanosine triphosphate, cytosine triphosphate, or uridine triphosphate reduced the rate of inactivation of vaccinia when heated at 50 C. The virus-associated nucleoside triphosphate phosphohydrolases (adenosine triphosphatase, guanosine triphosphatase, cytosine triphosphatase, and uridine triphosphatase) and ribonucleic acid polymerase were also protected from heat inactivation by these compounds. These obervations are best explained by postulating that ribonucleoside triphosphates bind to enzymes in the virus particle, and that these enzyme-substrate complexes are more resistant to thermal denaturation than are the enzymes without their substrates. The kinetics of heat inactivation of the vaccinia ATP phosphohydrolase activity is biphasic, suggesting that there are two proteins in the vaccinia particle that have this enzyme activity but they have different kinetics of heat inactivation. Any of the vaccinia-associated nucleotide phosphohydrolase activities are protected from heat inactivation by the presence of any one of the respective nucleoside triphosphates. This observation suggests that there is a single enzymatic site in vaccinia that is able to react with any ribonucleoside triphosphate.
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PMID:Protection of vaccinia from heat inactivation by nucleotide triphosphates. 431 59

Discrete sites of adenosine triphosphatase (ATPase) activity were demonstrated within the nucleoli of unfixed cultured human fibroblasts (IMR90, VA13, and AG2804 cells) by an adaptation, for electron microscopic cyto-chemistry, of Wachstein and Meisel's lead nitrate method. The majority of nucleoli contained more than one ATPase-positive region, but the total ATPase-positive material appeared to occupy only a minor portion of the nucleolar volume. These regions were roughly spherical with an irregular contour, and at times appeared to be components of perinucleolar chromatin or to be located adjacent to nucleolar interstices. The distribution of these regions within the nucleolus and their segregation by actinomycin D suggested that the ATPase-positive regions correspond to the fibrillar centers, which represent nucleolar organizer regions. The cytochemically demonstrable nucleolar ATPase was strictly dependent on the presence of divalent cations. Optimal reactions was seen at 5 mM Mg2+, but near optimal activity was obtained with lower concentrations of Mg2+ in the presence of Ca2+. Calcium alone and Mn2+ alone produced suboptimal reaction. Studies with different nucleoside phosphates as reaction substrates showed that the enzyme is specific for adenosine derivatives, ATP and dATP being equally good substrates. Guanosine triphosphate, cytidine triphosphate, uridine triphosphate, and d-thymidine triphosphate were ineffective as substrates, as were nucleoside mono- and diphosphates and other phosphate esters tested. It is suggested that the cytochemical ATPase reaction visualized the regions of the nucleolus in which ribosomal DNA of intranucleolar chromatin is undergoing conformational alterations.
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PMID:Visualization of nucleolar substructure in cultured human fibroblasts by magnesium-activated adenosine triphosphatase reaction. 611 91

In order to elucidate the biochemical basis for the selective cytotoxicity of D-glucosamine to neoplastic cells, the effect of glucosamine on the growth and several functions of mastocytoma P-815 cells were examined. Incubation of mastocytoma cells with 5 mM glucosamine resulted in a marked inhibition of growth and a significant reduction of cellular uptake and oxidation of glucose and of cellular levels of adenosine triphosphatase (ATP). Glucosamine also reduced the uridine nucleotide pool sizes, and accumulated uridine diphosphate (UDP)-N-acetylglucosamine. However, growth inhibition by glucosamine, which was reversed by glucose, was not prevented by exogenous uridine. In addition, glucosamine suppressed the phosphorylation of thymidine and its incorporation into deoxyribonucleic acid (DNA). The suppression of cell division by glucosamine was accompanied by the elevation of several functions of mastocytoma cells, including the accumulation of adenosine-3', 5'-monophosphate (cAMP), histamine, and serotonin. The incorporation of [(35)S]SO(4)(2-) into acidic glycosaminoglycan was also increased. Of these functional alterations, the elevation of cAMP levels was the earliest detectable change, indicating that growth and functions of mastocytoma cells are also regulated by cAMP. However, glucosamine did not affect the adenylate cyclase activity of plasma membrane in vitro, suggesting the necessity of intact membrane structure for the action of glucosamine.
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PMID:Effect of D-glucosamine on growth and several functions of cultured mastocytoma P-815 cells. 626 62

Cystic fibrosis (CF) airway epithelia are characterized by enhanced Na(+) absorption probably due to a lack of downregulation of epithelial Na(+) channels by mutant CF transmembrane conductance regulator. Extracellular nucleotides adenosine 5'-triphosphate (ATP) and uridine 5'-triphosphate (UTP) have been shown to activate alternative Ca(2+)-dependent Cl(-) channels in normal and CF respiratory epithelia. Recent studies suggest additional modulation of Na(+) absorption by extracellular nucleotides. In this study we examined the role of mucosal ATP and UTP in regulating Na(+) transport in native human upper airway tissues from patients with 16 patients with CF and 32 non-CF control subjects. To that end, transepithelial voltage and equivalent short-circuit current (I(SC)) were assessed by means of a perfused micro-Ussing chamber. Mucosal ATP and UTP caused an initial increase in lumen-negative I(SC) that was followed by a sustained decrease of I(sc) in both non-CF and CF tissues. The amiloride-sensitive portion of I(SC) was inhibited significantly in normal and CF tissues in the presence of either ATP or UTP. Both basal Na(+) transport and nucleotide-dependent inhibition of amiloride-sensitive I(SC) were significantly enhanced in CF airways compared with non-CF. Nucleotide-mediated inhibition of Na(+) absorption was attenuated by pretreatment with the Ca(2+)-adenosine triphosphatase inhibitor cyclopiazonic acid but not by inhibition of protein kinase C with bisindolylmaleimide. These data demonstrate sustained inhibition of Na(+) transport in non-CF and CF airways by mucosal ATP and UTP and suggest that this effect is mediated by an increase of intracellular Ca(2+). Because ATP and UTP inhibit Na(+) absorption and stimulate Cl(-) secretion simultaneously, extracellular nucleotides could have a dual therapeutic effect, counteracting the ion transport defect in CF lung disease.
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PMID:Inhibition of amiloride-sensitive epithelial Na(+) absorption by extracellular nucleotides in human normal and cystic fibrosis airways. 1110 28