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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)

A comparative study was carried out of some properties of "soluble" Na+, K+-ATPase obtained from different subcellular membrane brain structures by means of non-ionic detergents of triton X-100 and digitonin. It is established that temperature and pH-optima of "soluble" Na+, K+-ATPase are close to these optima of the initial membrane preparations. A certain difference is observed in the dynamics of temperature and pH-dependence of Na+, K+-ATPase activity in the extracts from different subcellular structures. The stability of the preparations in storage was investigated. A conclusion is made that more stable enzyme extracts may be obtained by means of digitonin.
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PMID:[Some properties of "soluble" Na+ and K+-ATPase obtained from various subcellular membrane structures of the brain by use of non-ionic detergents]. 0 Aug 31

The optimal conditions are selected for electron-cytochemical detection of the ATPase activity in nuclei of the skeletal muscles of rabbits and nuclei of Vicia faba L. meristem. It is shown that the previous fixation of nuclei in the rabbit skeletal muscle for 10 min in a mixture of the buffer solutions of 4% glutaric dialdehyde and 4% neutral formalin (1:1) causes a decrease in their ATPase activity by 78% in the medium containing Mg2+ and by 34% - in the medium containing Ca2+; in nuclei of horse bean seedlings meristem it lowers respectively by 28 and 16%. Ions of lead in a concentration of 0.4 mM evoke a decrease in the ATPase activity in the medium containing Mg2+, in nuclei of the rabbit skeletal muscles by 35% and in nuclei of horse bean meristem by 15% in the medium containing Ca2+. The vaule of the residual activity is sufficient for detection of the product of ATP enzymic hydrolysis reaction by activity is sufficient for detection of the product of ATP enzymic hydrolysis reaction by the method of electronic cytochemistry. An increase in the Pb2+ concentration higher than 2.8 mM evokes nonenzymic hydrolysis of ATP. The ATPase activity under the electron-cytochemical study is found within the range of pH 6.3-8.5. The product of reaction forms most intensively at pH 7.2-7.5 in the medium with both Mg2+ and Ca2+.
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PMID:[Determination of optimal conditions for the electron-cytochemical detection of ATPase activity in isolated nuclei]. 0 Aug 36

The etioplasts of dark-grown bean leaves showed ATPase (adenosine triphosphatase) activity which had a pH optimum of 8.5, was stimulated by dithiothreitol and unaffected by light-triggering. Bean chloroplasts showed a low activity of dark-induced ATPase with a pH optimum of 8.5 and a substantial amount of light-triggered activity with a pH optimum of 8.0. The light-triggered activity depended on dithiothreitol and Mg2+ and was promoted by phenazine methosulphate. Light-triggered ATPase activity was completely inhibited by 20mum-dicyclohexylcarbodi-imide. Etioplasts developed light-triggered ATPase activity in response to 30 min illumination of the etiolated leaves. During the 48 h of light-induced greening of dark-grown leaves there was a 70% increase of the chloroplast ATPase activity found after light-triggering and a 30% fall in the dark-induced activity, both expressed on a per leaf basis. As the larger part of these changes occurred during the first 30 min of illumination, it is concluded that most or all of the chloroplast ATPase was present in the etioplast, a conclusion identical with that of Lockshin et al. (1971) for maize. During 48 h of greening there was a tenfold increase in the amount of thylakoid membrane in the leaf together with an 83% fall in the ATPase activity per m2 of thylakoid membrane, measured after light-triggering.
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PMID:Plastid development in primary leaves of Phaseolus vulgaris. Development of plastid adenosine triphosphatase activity during greening. 0 Sep 90

1. An activator of the (Ca2+ plus Mg2+)-stimulated ATPase present in the human erythrocytes (membrane) has been isolated in soluble form from hemolysates of these cells. Partial purification has been achieved through use of carboxymethyl-Sephadex chromatography. The resulting activator fraction contained no hemoglobin and only 0.3% of the total adenylate kinase activity of the cell. 2. Whereas the activator was released from erythrocytes subjected to hemolysis in 20 miosM buffer at pH 7.6 or at pH 5.8, only the membranes prepared at pH 7.6 were affected by it. 2. Whereas the activator was released from erythrocytes subjected to hemolysis in 20 miosM buffer at pH 7.6 or at pH 5.8, only the membranes prepared at pH 7.6 were affected by it. 3. When (Ca2+ plus Mg2+)-ATPase activity was measured by 32Pi release from (gamma-32P)ATP, freeze-thawed erythrocytes, as well as membranes prepared at pH 5.8 and at pH 7.6, expressed lower values than noted by assay for total Pi release. When ADP instead of ATP was used as substrate, significant amount of Pi were released by these erythrocyte preparations. Further study revealed (a) production of ATP and AMP from ADP with membranes and hemolysate alone, and (b) exchange of the gamma-and B-position phosphate on (gama-32P)ATP in the presence of membranes plus hemolysates. These observations established the presence of adenylate kinase activity in the (membrane-free) hemolysates and in membranes. It further supports the conclusion that Pi release from ADP by human erythrocytes (freeze-thawed) and by their isolated membranes is due to formation of ATP by adenylate kinase and hydrolysis of this generated ATP by (Ca2+ plus Mg2+)-ATPase. 4. The following points were also established: (a) absence of an ADPase in human erythrocytes; (b) the (Ca2+ plus Mg2+)-ATPase activator enhanced cleavage only of the gama-position of ATP and (c) the (Ca2+ plus Mg2+)-ATPase activator is neither adenylate kinase nor hemoglobin.
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PMID:Studies on an activator of the (Ca2+ plus Mg2+)-ATPase of human erythrocyte membranes. 0 Oct 98

The protein and proteolipid complexes and oligomycin insensitive soluble ATPase were prepared from rat liver mitochondria. The incubation of soluble ATPase with protein and proteolipid complexes resulted in restoration of ATPase sensitivity to oligomycin at room temperature. The process of reconstruction depended on pH, incubation time, temperature and other conditions.
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PMID:[The fragmentation and reconstruction of the oligomycin-sensitive ATPase system of liver mitochondria]. 0 Nov 3

In energy transducing systems the direction of energy transfer is proposed to be maintained by the synchronized turnovers of the conformational change of one protein coupling up to affect another. Catalysis by those systems implies, therefore, that under new space restrictions the groups of the transducing enzyme increase and decrease reactivity between themselves, with activatory and/or inhibitory ligands (H+, H2O, metals, etc.) and with the electron shells of the reactant molecules. The exergonic reaction-dependent turnover of the forms of the enzyme within the transition complexes would be maintained, therefore, under asymmetric phase angles of conformational-dependent reactivity that would effectively restrict the microscopic reversibility of transducing systems. Some well known reactions, such as hemoglobins Bohr effect, can be used to illustrate that microscopic (molecular) interactions subject to thermodynamic equilibria laws may similarly paricipate as driving forces in energy transducing sytems. This would allow the thermodynamic description of the role of proton translocation as that of a modificatory force of the structural parameters of proteins. Similarly, the relationship between the liganded states of hemoglobin and its change in conformation has been used to develop an illustrative model relating changes in oxido-reduction of electron carriers to induced-fit effects leading to a sequence of ATPase forms in transition complexes which become stabilized as high energy intermediates under the constraints imposed by the membrane of energy transducing organelles.
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PMID:Hypothesis on the role of liganded states of proteins in energy transducing systems. 0 Nov 21

TTP accelerated ATP-induced superprecipitation of actomyosin in as low a concentration as 30 muM and decreased light scattering by actomyosin. These effects could also be observed in the same way, but to a lesser degree, by addition to TDP. Myosin was able to hydrolyze TTP to TDP, but some important differences were confirmed between myosin TTPase and ATPase. Myosin TTPase was inhibited by actin and showed a much larger Km than that of ATPase. TTP significantly inhibited myosin B ATPase and ATP greatly inhibited myosin B TTPase. These findings suggest that the accelerating effect of TDP and TTP may be due to the binding of thiamine phosphate to the regulatory site of myosin followed by a change in its physical chemical property, rather than due to the competitive binding of thiamine phosphate to the catalytically activity site of myosin.
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PMID:Thiamine triphosphatase activity of myosin and accelerating effect of thiamine di- and tri-phosphates on superprecipitation of actomyosin. 0 81

An ATPase stimulated by HCO - ions and other oxybases and inhibited by SCN- has been found in main excretory duct of rat submaxillary gland, a tissue, capable of actively secreting HCO - 3 ions. No such ATPase was found in the rabbit duct, which normally does not secrete HCO - 3. The HCO - 3 ATPase was localized in the plasma membrane fraction of the homogenate, as evidenced by the marker 5'-nucleotidase. The activities of the HCO - 3 ATPase increased in metabolic alkalosis and decreased in metabolic acidosis in parallel to secretion of HCO - 3 and K+ ions by the duct epithelium. These findings provide further evidence that the membrane-bound HCO - 3 ATPase is involved in active H+/HCO - 3 transport.
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PMID:H+ transport and membrane-bound HCO - 3 ATPase in salivary duct epithelium. 0 8

A simple procedure for the purification of Mg2+-stimulated ATPase of Escherichia coli by fractionation with poly(ethylene glycols) and gel filtration is described. The enzyme restores ATPase-linked reactions to membrane preparations lacking these activities. Five different polypeptides (alpha, beta, gamma, delta, epsilon) are observed in sodium dodecyl sulfate electrophoresis. Freezing in salt solutions splits the enzyme complex into subunits which do not possess any catalytic activity. The presence of different subunits is confirmed by electrophoretic and immunological methods. The active enzyme complex can be reconstituted by decreasing the ionic strength in the dissociated sample. Temperature, pH, protein concentration, and the presence of substrate are each important determinants of the rate and extent of reconstitution. The dissociated enzyme has been separated by ion-exchange chromatography into two major fragments. Fragment IA has a molecular weight of about 100000 and contains the alpha, gamma, and epsilon polypeptides. The minor fragment, IB, has about the same molecular weight but contains, besides alpha, gamma, and epsilon, the delta polypeptide. Fragment II, with a molecular weight of about 52000, appears to be identical with the beta polypeptide. ATPase activity can be reconstituted from fragments IA and II, whereas the capacity of the ATPase to drive energy-dependent processes in depleted membrane vesicles is only restored after incubation of these two fractions with fraction IB, which contains the delta subunit.
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PMID:ATPase of Escherichia coli: purification, dissociation, and reconstitution of the active complex from the isolated subunits. 0 81

The transmembrane electrical potential (deltaphi), the proton flux (H+), the rate of electron transport (e), the pH gradient (deltapH) and the rate of phosphorylation (ATP) were measured in chloroplasts of spinach. Photosynthesis was excited periodically with flashes of variable frequencies and intensities. A new method is described for determining the rate of electron transport and proton flux. Under conditions where the rate of electron transport and proton flux are not pH controlled the following correlations were found in the range 50 mV less than or equal to deltaphi less than or equal to 125 mV and 1.8 less than or equal to deltapH less than or equal to 2.7: (1) The pH gradient, deltapH, increases with H+ independently of Phout between 7-9. (2) The rate of phosphorylation, ATP, depends exponentially on deltapH (at constant deltaphi) and is independent of pHout between 7-9. (3) The rate of phosphorylation, ATP, depends also on deltaphi (at constant deltapH and at constant proton flux H+). (4) The proton flux via the ATPase pathway, Hp+, depends non-linearly on the ratio of the proton concentrations: Hp+ approximately (Hin+/Hout+)b, (b=2.3--2.6). The proton flux via the basal pathway, Hb+, depends linearly on the ratio of the proton concentrations: Hb+ approximately (Hin/Hout). (5) The ratio deltaH+/ATP (e/ATP, i.e. the ratio of the total proton flux, Hp+ + Hb+, and the rate of ATP formation, ATP, depends strongly on deltaphi and on deltapH. The ratio is deltaH+/ATP approximately 3 (e/ATP approximately 1.5) at deltapH 2.7 and deltaphi = 125 mV. (6) It is supposed that the reason for the dependence of deltaH+/ATP on deltaphi anddeltapH is the different functional dependence of the basal proton flux Hb+ and the phosphorylating proton flux Hp+ on deltapH and deltaphi. The calculation of deltaH+/ATP on the basis of this assumption is in fair agreement with the experimental values. Also the "threshold" effects can be explained in this way. (7) The ratio of deltaHp+/ATP, i.e. the ratio of the phosphorylating proton flux Hp+ and ATP, is deltaHp+/ATP APPROXIMATELY 2.4.
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PMID:Relations between the electrical potential, pH gradient, proton flux and phosphorylation in the photosynthetic membrane. 0 16


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