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)

Previous research by the authors had suggested that uridine-diphosphate-glucuronyl-transferase (UDP-GT) is a useful preneoplastic marker in chemical carcinogenesis. Recently the authors report that they found typical clear cell foci in a macroscopically normal liver surrounding focal nodular hyperplasia with a 6 cm diameter in a 27-year old woman who had been using oral contraceptives (OCs) containing ethinyl-estradiol and lynestrenol for 9 years. These foci were further characterized by a reduction of canalicular and cytoplasmic ATPase activity, an increased glycogen content, and a positive immunohistochemical reaction for UDP-GT. OC users develop 2 basic types of benign liver tumors: hepatic adenoma and focal nodular hyperplasia. Hepatic adenoma appears to be caused by OCs, whereas the relationship between OC use and focal nodular hyperplasia is less clear. The tumorigenic action of OCs has been ascribed to a promotor action on liver cells; however, there is no evidence that OCs are initiators of liver tumors. The case reported shows 2 manifestations of toxic lesions promoted by OC use: the development of focal nodular hyperplasia and enzyme-altered foci comparable to those seen in experimental liver carcinogenesis. Further studies are needed to get more information about the preneoplastic potential of these foci in humans. Since enzyme-altered foci could not be identified in the liver tissue of healthy women, these foci may be of prognostic significance in longterm OC users.
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PMID:Increased UDP-glucuronyltransferase in putative preneoplastic foci of human liver after long-term use of oral contraceptives. 392 52

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

T3 and T4 at 10(-6)M caused a significant inhibition on [3H]uridine incorporation into RNA in calf-thyroid slices. This effect was not altered by addition of 10(-3) M PTU or MMI. The metabolism of 125I-T3 was studied under the same conditions. There was a very slight dehalogenation after 60 min (less than 5%) which was inhibited by PTU. The time course of the uptake of labeled T3 showed a temperature dependence, and this uptake was not altered by 10(-6)M KI, 1-T4, DIT or MIT, thus indicating specificity. The early phase of labeled T3 entrance into the cell was inhibited by the addition of colt T3 in a dose- dependent manner from 10(-9) to 10(-5)M. Slices previously stimulated by cAMP or CGMP showed a significant increase in the uptake of labeled T3. ATPase activity or ATP, protein or RNA synthesis does not seem to play a role in this process. The relationship between substitutions in the thyronine molecule and its biological action on RNA synthesis was also studied, and some preliminary conclusions were drawn. These studies demonstrate that T3 has a direct action on the thyroid.
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PMID:Uptake, metabolism and action of triiodothyronine in calf-thyroid slices. 616 33

Activation of lymphocytes by antigens and mitogens can effectively be prevented by ouabain, a known inhibitor of (Na+ + K+)-ATPase. Recently it was shown that lowering of intracellular levels of monovalent cations is not involved in the inhibitory effect of ouabain. (Na+ + K+)-ATPase was found to be closely associated with acyl-CoA : lysophosphatidylcholine acyltransferase in the plasma membrane of lymphocytes. Both enzymes are activated as an immediate consequence of mitogen binding. Human peripheral lymphocytes were stimulated with concanavalin A. Ouabain suppressed the induction of RNA and DNA synthesis in a concentration-dependent way. Increase of RNA synthesis was suppressed only if the glycoside were added within the first hours of activation. If ouabain was added later, incorporation of uridine remained at the rate that was reached at the time of glycoside administration, pointing to an early event where ouabain may be operative. Ouabain, in a dose-dependent manner similar to that affecting RNA and DNA synthesis, inhibited the increase in the incorporation of oleate into phospholipids in stimulated lymphocytes, whereas the turnover of phospholipid fatty acids in resting lymphocytes was unaffected. Increasing extracellular K+ concentrations reversed the binding of ouabain to lymphocytes. Simultaneously, the inhibition of stimulated RNA synthesis was decreased and the inhibition of oleate incorporation was reversed. These results suggest that the suppression of lymphocyte activation by ouabain is due to the inhibition of membrane phospholipid metabolism mediated by (Na+ + K+)-ATPase.
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PMID:Inhibition of lymphocyte activation by ouabain. Interference with the early activation of membrane phospholipid metabolism. 617 Mar 33

The ultrastructural localization of Ca2+, Mg2+-activated ATPase was studied in phytohaemagglutinin activated lymphocytes and in normal unstimulated lymphocytes. Cells, fixed in paraformaldehyde--glutaraldehyde, were incubated in a medium containing 3 mM ATP, 5 mM CaCl2 and 2.4 mM Pb(NO3)2 in 0.1 M tris buffer at pH 8.5, the optimum pH for histochemical demonstration of this enzyme. Reaction product was localized in the endoplasmic reticulum, nuclear membrane, Golgi apparatus and mitochondria and on the membrane surrounding large electron-dense bodies. Cytoplasmic vesicles and the plasma membrane were negative. Activity in unstimulated lymphocytes showed a similar localization but the amount of endoplasmic reticulum was much less than in activated lymphocytes. The pH of the medium was critical for the localization of the enzyme. At pH 7.5, the cytoplasmic reaction was almost completely inhibited but a dense precipitate was present on the outer surface of the plasma membrane. The reaction was stimulated by either Ca2+ or Mg2+ and was greatly decreased in the absence of these cations or in the presence of p-chloromercuribenzoate or N-ethylmaleimide. Oligomycin inhibited selectively the reaction in mitochondria but not the reaction at other sites. While the reaction in mitochondria showed complete substrate specificity, a mild reaction was obtained at the other sites with uridine diphosphate or sodium beta-glycophosphate as substrate. ATP was, however, the preferential substrate.
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PMID:Ultrastructural localization of adenosine triphosphatase activity in lymphocytes activated in vitro by phytohaemagglutinin. 618 Oct 20

The paper is concerned with a study of the molecular mechanisms responsible for activation of B lymphocyte division by polyanions, polyacrylic acid (PAA) and dextran sulfate (DS). The mitogenic doses of PAA and DS were discovered to provoke an early increase in lymphocyte plasma membrane permeability. The cell membrane permeability for K+, Ca2+ and for labeled thymidine and uridine was measured in murine spleen cultures in vitro The K+ outflow from the cells was recorded according to variation in K+ concentration in the extracellular medium with the aid of a selective valinomycin electrode. The intensity of cell penetration by exogenous 45Ca, 3H-uridine or 3H-thymidine was determined by radioindicator analysis of the cytoplasma isotope pool. One to 2 min after adding the mitogenic doses of PAA or DS, the K+ outflow from lymphocytes markedly increased. It has been proved that this effect is not connected with inhibition of Na+, K+-ATPase of the plasma membrane. The increased membrane permeability for 45Ca and 3H-uridine was recorded 30-40 min after lymphocyte activation with the polyanion, that for 3H-thymidine was seen later (after 4-6 h). It is assumed that the differences between the time of recording high accumulation in the cytoplasm of 45Ca, 3H-uridine and 3H-thymidine and the time of recording high outflow of K+ from lymphocytes are determined by the differences in the sensitivity of the methods applied.
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PMID:[Increase in the permeability of the lymphocyte plasma membrane for uni- and bivalent cations and low-molecular metabolites following exposure to mitogenic polyanions]. 620 3

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


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