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)

Vesicles were reconstituted from a purified dicyclohexyl-carbodiimide-sensitive ATPase complex (TF0-F1) and phospholipids of a thermophilic bacterium PS3. These vesicles synthesized ATP from ADP and Pi with energy from an electrochemical proton gradient (delta-micronH+) formed by a pH gradient and an electrical potential across their membranes. Maximal ATP synthesis was achieved by incubating the vesicles in malonate at pH 5.5 with valinomycin, and then rapidly transferring them to a solution of pH 8.4 and 150 mM K+. Under these conditons ATP synthesis continued at a decreasing rate for 30 s at 40 degrees. Appreciable formation of ATP (40 to 150 nmol/mg of TF0-F1) occurred at an initial delta-micronH+ above 205 mV and moderate formation at an initial value above 180 mV. ATP hydrolysis by the vesicles produced a delta-micronH+, and the additions of 32Pi and hexokinase to them resulted in 32Pi esterification. Analysis of the time courses of 32Pi esterification and decays of the pH difference and membrane potential, followed using 9-aminoacridine and 8-anilinonaphthalene-1-sulfonate, respectively, as probes, showed a relationship between delta-micronH+ and the rate of ATP synthesis. These results demonstrate that purified TF0-F1 is itself a reversible H+-translocating ATPase of oxidative phosphorylation.
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PMID:Adenosine triphosphate synthesis by electrochemical proton gradient in vesicles reconstituted from purified adenosine triphosphatase and phospholipids of thermophilic bacterium. 1 11

Methylxanthines (MX) inhibit cell division in sea urchin and clam eggs. This inhibitory effect is not mediated via cAMP. MX also inhibit respiration in marine eggs, at concentrations which inhibit cleavage. Studies showed that no changes occurred in ATP and ADP levels in the presence of inhibitory concentrations of MX, indicating an extra-mitochondrial site of action for the drug. Subsequent studies revealed decreased levels of NADP+ and NADPH, when eggs were incubated with inhibitory concentrations of MX, but no change in levels of NAD+ and NADH. MX did not affect the pentose phosphate shunt pathway and did not have any effect on the enzyme NAD+ -kinase. Further studies showed a marked inhibitory effect on the glutathione reductase activity of MX-treated eggs. Reduced glutathione (GSH) could reverse the cleavage inhibitory effect of MX. Moreover, diamide, a thiol-oxidizing agent specific for GSH in living cells, caused inhibition of cell division in sea urchin eggs. Diamide added to eggs containing mitotic apparatus (MA) could prevent cleavage by causing a dissolution of the formed MA. Both MX and diamide inhibit a Ca2+-activated ATPase in whole eggs. The enzyme can be reactivated by sulfhydryl reducing agents added in the assay mixture. In addition, diamide causes an inhibition of microtubule polymerization, reversible with dithioerythritol. All experimental evidence so far suggests that inhibition of mitosis in sea urchin eggs by MX is mediated by perturbations of the in vivo thiol-disulfide status of target systems, with a primary effect on glutathione levels.
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PMID:Effects of caffeine and other methylxanthines on the development and metabolism of sea urchin eggs. Involvement of NADP and glutathione. 1 15

The stoichiometry of H+ ejection by mitochondria during hydrolysis of a small pulse of ATP (the H+/ATP ratio) has been reexamined in the light of our recent observation that the stoichiometry of H+ ejection during mitochondrial electron transport (the H+/site ratio) was previously underestimated. We show that earlier estimates of the H+/ATP ratio in intact mitochondria were based upon an invalid correction for scaler H+ production and describe a modified method for determination of this ratio which utilizes mersalyl or N-ethylmaleimide to prevent complicating transmembrane movements of phosphate and H+. This method gives a value for the H+/ATP ratio of 2.0 without the need for questionable corrections, compared with a value of 3.0 for the H+/site ratio also obtained by pulse methods. A modified version of the chemiosmotic theory is presented, in which 3 H+ are ejected per pair of electrons traversing each energy-conserving site of the respiratory chain. Of these, 2 H+ return to the matrix through the ATPase to form ATP from ADP and phosphate, and 1 H+ returns through the combined action of the phosphate and adenine nucleotide exchange carriers of the inner membrane to allow the energy-requiring influx of Pi and ADP3- and efflux of ATP4-. Thus, up to one-third of the energy input into synthesis of extramitochondrial ATP may be required for transport work. Since other methods suggest that the H+/site significantly exceeds 3.0, an alternative possibility is that 4 h+ are ejected per site, followed by return of 3 H+ through the ATPase and 1 H+ through the operation of the proton-coupled membrane transport systems.
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PMID:H+/ATP ratio during ATP hydrolysis by mitochondria: modification of the chemiosmotic theory. 1 16

1. Preincubation with N-ethylmaleimide inhibits the overall activity of highly purified (Na+ +K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) preparations of rabbit kidney outer medulla. 2. This inhibition is decreased by addition of ATP or 4-nitrophenylphosphate under non-phosphorylating conditions, and also by addition of ADP or adenylylimidodiphosphate. 3. N-ethylmaleimide treatment leads to inhibition of K+-stimulated 4-nitrophenylphosphatase activity, Na+-stimulated ATPase activity, and phosphorylation by ATP as well as by inorganic phosphate. These inhibitions strictly parallel that of the overal (Na+ +K+)-ATPase reaction. 4. N-ethylmaleimide lowers the number of sites which are phosphorylated by inorganic phosphate, without affecting the dissociation constant of the enzyme-phosphate complex. 5. N-ethylmaleimide does not affect the relative stimulation by ATP of the K+-stimulated 4-nitrophenylphosphatase activity. 6. These effects of N-ethylmaleimide can be explained as a complete loss of active enzyme, either by reaction of N-ethylmaleimide inside the active center, or by alterations in the quaternary structure through reactions outside the active center.
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PMID:Studies on (Na+ +K+) activated ATPase. XLI. Effects of N-ethylmaleimide on overall and partial reactions. 1 94

Ciliary 30S dynein of Tetrahymena was investigated with regard to modification of the ATPase activity with N-ethylmaleimide (NEM) in the presence of ATP. The elevation of enzyme activity due to the modification was largely repressed by addition of ATP at a concentration of 1 mM or more during preincubation of 20 h at 0 degrees C. The repression was highly specific for ATP, though ADP and AMPPNP showed slight repressive effects. After complete hydrolysis of ATP added to the preincubation mixture, however, elevation of 30S dynein ATPase activity occurred. It is suggested that the repression by ATP of NEM-induced elevation of 30S dynein ATPase activity is simply due to a protecting effect of ATP on certain SH group(s) (probably SH1-type group(s)) around the active center of 30S dynein. When 30S dynein was maximally activated by modification with NEM, ATP or ADP did not significantly promote the inactivation of the modified enzyme upon further treatment with NEM, indicating that 30S dynein lacks the characteristics of SH2-type groups. On the other hand, ATP also showed a protective effect against inhibition of native 30S dynein by high concentrations of NEM. High concentrations of ADP and AMPPNP were inhibitory to 30S dynein ATPase activity but inorganic phosphate did not inhibit 14S or 30S dynein ATPase activities at all.
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PMID:Effects of adenosine triphosphate on N-ethylmaleimide-induced modification of 30S dynein from Tetrahymena cilia. 1 51

Cytochemical localization of ATPase activities in cilia and basal bodies of Tetrahymena pyriformis revealed a number of possible sites of ATPases. In basal bodies, reaction product was localized on the periphery of basal body microtubules, in the core of the B-microtubules, on the dense basal body core, and on the basal plate; some reaction product was associated with the postciliary and basal microtubules. In the cilium, reaction product was associated with the ciliary membrane, the basal granule, the periphery of the outer doublet microtubules, in the core of the B-microtubules, and on the arms and either the central microtubules or the radial spoke heads. Reaction product deposition required ATP and either Ca2+ or Mg2+ or ADP and Mg2+. When incubated in the presence of ATP and Na+, reaction product was only found at the base of the cilium in the region of the ciliary necklace. Implications of the various sites of activity are discussed with respect to possible mechanisms of ciliary motility.
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PMID:Fine structural localization of phosphatases in cilia and basal bodies of Tetrahymena pyriformis. 2 Jun 78

An enzyme capable to split adenosine triphosphate (ATP) was shown to be firmly associated with mature herpes simplex virus particles purified from infected rabbit lung (ZP) cells. The enzyme localized in the viral envelope was markedly activated by bivalent cations, to the largest degree by Mg2+ at a pH optimum of 7.8--8.0. Na+ and K+ ions neither separately nor together showed any activating effect. Enzyme activity was not sensitive to the action of ouabain. No adenosine diphosphatase (ADPase) and adenosine monophosphatase (AMPase) activities were observed. ATPase activity was competitively inhibited by ADP. AMP and inorganic phosphate were without effect. The ATPase of nuclear membranes isolated from ZP cells exhibited similar properties but behaved differently to the action of sodium dithionite, dinitrophenol, oligomycin and gramicidin, as well as on heat inactivation. The origin of the virus enzyme is discussed.
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PMID:Some properties of the adenosine triphosphatase associated with herpes simplex virus and nuclear membrane of host cells. 2 4

1. ATPase isolated from Rhodospirillum rubrum by chloroform extraction and purified by gel filtration or affinity chromatography shows three bands (alpha, beta and gamma) upon electrophoresis in sodium dodecyl sulphate. 2. Ca2+-ATPase activity of the preparation is inhibited by aurovertin and efrapeptin but not by oligomycin. Activity may be inhibited by treatment with 4-chloro-7-nitrobenzofurazan and subsequently restored by dithiothreitol. 3. The enzyme fails to reconstitute photophosphorylation in chromatophores depleted of ATPase by sonic irradiation. 4. Most of the active protein from the crude chloroform extract binds to an affinity chromatography column bearing an immobilised ADP analogue but not to a column bearing immobilised pyrophosphate. 5. In the absence of divalent cations, a component with a very high specific activity for Ca2+-ATPase is eluted from the column by 1.6 mM ATP. This protein migrates asa single band on 5% polyacrylamide gel electrophoresis and only possesses three subunits. At 12 mM ATP an inactive protein is eluted which does not run on acid or alkali polyacrylamide gels and shows a complex subunit structure. 6. ATPase preparations prepared by acetone extraction or by sonic irradiation of chromatophores may also be purified 10-fold by affinity chromatography. 7. The inclusion of 5 mM MgCl2 or CaCl2 during affinity chromatography of chloroform ATPase increases the capacity of the column for the enzyme and demands a higher eluting concentration of ATP. 8. When the enzyme is more than 90% inhibited by efrapeptin or 4-chloro-7-nitrobenzofurazan, the binding characteristics of the enzyme are not affected. 9. 10 mM Na2SO3, which greatly stimulates the Ca2+- and Mg2+-dependent ATPase activity of the enzyme and increases Ki (ADP) for Ca2+-ATPase from 50 to 850 micron, prevents binding to the affinity column. Binding may be restored by the addition of divalent cations. 10. Na2SO3 increases the rate of ATP hydrolysis, ATP-driven H+ translocation and ATP-driven transhydrogenase in chromatophores. 11. It is proposed that anions such as sulphite convert the chromatophore ATPase into a form which is a more efficient energy transducer.
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PMID:Affinity chromatography of H+-translocating adenosine triphosphatase isolated by chloroform extraction of Rhodospirillum rubrum chromatophores. Modification of binding affinity by divalent cations and activating anions. 2 12

Chromaffin granules isolated from bovine adrenal gland were incubated with (3)H-labelled nucleotides and [(14)C]noradrenaline to study the uptake of these substances. [(3)H]ATP, [(3)H]ADP and [(3)H]AMP are taken up by these organelles by the same temperature-dependent mechanism. The apparent K(m) for ATP and ADP is 1.4mm, and for AMP it is 2.9mm. The uptake of ATP has a flat pH optimum, whereas the catecholamine uptake increases with more alkaline pH. Atractyloside and carboxyatractyloside are competitive and specific inhibitors of nucleotide uptake, whereas reserpine inhibits only that for catecholamines. Mg(2+) ions activate uptake of both catecholamine and nucleotides, whereas EDTA and N-ethylmaleimide inhibit these processes. Nucleotide and catecholamine uptakes are inhibited by uncouplers of oxidative phosphorylation and by two ATP analogues. NH(4) (+) ions and nigericin in the presence of KCl inhibit only catecholamine uptake. It is concluded that nucleotide uptake, as proposed previously for catecholamine uptake, depends on an electrochemical proton gradient produced by a proton-translocating adenosine triphosphatase localized in the membrane of chromaffin granules. Furthermore, as suggested by the effect of NH(4) (+) and nigericin, catecholamine uptake apparently depends on the chemical part of this gradient, whereas the results for nucleotide uptake are consistent with its dependence on the electrical component.
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PMID:A characterization of the nucleotide uptake of chromaffin granules of bovine adrenal medulla. 2 25

Exogenous and endogenously generated reduced pyridine nucleotides caused marked stimulation of O(2) uptake when added to treponemal cell-free extracts, which indicated that terminal electron transport was coupled to the consumption of O(2). Oxidation of reduced nicotinamide adenine dinucleotide (NADH) was shown to correlate stoichiometrically with O(2) reduction, suggesting that NADH was being oxidized through a mainstream respiratory chain dehydrogenase. Oxygen evolution in treponemal extracts was observed after the completion of O(2) uptake which was stimulated by exogenous NADH and endogenously generated reduced NAD phosphate. Oxygen evolution was inhibited by both cyanide and pyruvate, which was consistent with O(2) release from H(2)O(2) by catalase. The addition of exogenous H(2)O(2) to treponemal extracts caused rapid O(2) evolution characteristic of a catalase reaction. A spectrophotometric assay was used to measure ATP formation in T. pallidum cell-free extracts that were stimulated with NADH. P/O ratios from 0.5 to 1.1 were calculated from the amounts of ATP formed versus NADH oxidized. Phosphorylating activity was dependent on P(i) concentration and was sensitive to cyanide, N, N'-dicyclohexylcarbodiimide, and carbonyl cyanide m-chlorophenyl hydrazone. Adenine nucleotide pools of T. pallidum were measured by the firefly luciferin-luciferase assay. Shifts in adenine nucleotide levels upon the addition of NADH to cell-free extracts were impossible to evaluate due to the presence of NAD(+) nucleosidase. However, when whole cells, previously incubated under an atmosphere of 95% N(2)-5% CO(2), were sparged with air, ATP and ADP levels increased, while AMP levels decreased. The shift was attributed to both oxidative phosphorylation and to the presence of an adenylate kinase activity. T. pallidum was also found to possess an Mg(2+) - and Ca(2+) -stimulated ATPase activity which was sensitive to N, N' -dicyclohexylcarbodiimide. These data indicated a capability for oxidative phosphorylation by T. pallidum.
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PMID:Respiration and oxidative phosphorylation in Treponema pallidum. 2 9


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