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Query: HUMANGGP:009336 (ATPase)
 59,826 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The specific activity of mitochondrial ATPase (adenosine triphosphatase) in extracts of Schizosaccharomyces pombe decreased 2.5-fold as the glucose concentration in the growth medium decreased from 50mM to 15mM. 2. During the late exponential phase of growth, ATPase activity doubled. 3. Sensitivity to oligomycin and Dio-9 as measured by values for I50(mug of inhibitor/mg of protein giving 50% inhibition) at pH 6.8 increased sixfold and ninefold respectively during the initial decrease in ATPase activity, and this degree of sensitivity was maintained for the remainder of the growth cycle. 4. Increased sensitivity to NN'-dicyclohexylcarbodi-imide, triethyltin and venturicidin was also observed during the early stage of glucose de-repression. 5. Smaller increases in sensitivity to efrapeptin, aurovertin, 7-chloro-4-nitrobenzo-2-oxa-1,3-diaz-le, quercetin and spegazzinine also occurred. 6. The ATPase of glycerol-grown cells was less sensitive to inhibitors than that of glucose-repressed cells; change in values for I50 were not so marked during the growth cycle of cells growing with glycerol. 7. When submitochondrial particles from glycerol-grown cells were tested by passage through Sephadex G-50, a fourfold increase in activity was accompanied by increased inhibitor resistance. 8. Gel filtration of submitochondrial particles from glucose-de-repressed cells gave similar results, whereas loss of ATPase occurred in submitochondrial particles from glucose-repressed cells. 9. It is proposed that alterations in sensitivity to inhibitors at different stages of glucose derepression may be partly controlled by a naturally occuring inhibitor of ATPase. 10. The inhibitors tested may be classififed into two groups on the basis of alterations of sensitivity of the ATPase during physiological modification: (a) oligomycin, Dio-9, NN'-dicyclohexylcarbodi-imide, venturicidin and triethyltin, and (b) efrapeptin, aurovertin, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, quercetin and spegazzinine.
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PMID:Mitochondrial adenosine triphosphatase of the fission yeast, Schizosaccharomyces pombe 972h-. Changes in activity and inhibitor-sensitivity in response to catabolite repression. 1 53

This review has attempted to cover some of the findings that have been made in the mechanism of gastric secretion in recent years. It is hard to offer any firm conclusions, whether at the level of stimulus, metabolism, or the terminal process of secretion. However, some generalizations may be possible. At least amphibian gastric secretion is stimulated by cAMP as a second messenger, with histamine presumably acting as the primary messenger. The resultant metabolic change is due largely to a direct stimulation of catabolism, which in dog appears to be the metabolism of hexose, through the glycolytic process, the hexose monophosphate shunt, and the Krebs' cycle with cytoplasmic reduction and mitochondrial oxidation of pyridine nucleotides. No evidence could be obtained for changes in high energy phosphate or for lipolysis. One would expect gastric mucosal membranes during secretion to contain an anion-restricted electrogenic H+ pump, but they in fact contain an ATPase stimulated by monovalent cations and are insensitive to ouabain. In addition, hog or dog gastric membranes have the vectorial properties of H+ absorption, Rb+ extrusion, and ANS fluorescence enhancement with the addition of ATP, as well as protein phosphorylation by 32P dependent on a K+ gradient.
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PMID:Gastric secretion. 1 82

31P nuclear magnetic resonance spectra at 145.7 MHZ were obtained of concentrated suspensions of E. coli cells. The position of the Pi resonance was used to determine the pH, and in most experiments it was possible to distinguish the intracellular (pHin) and extracellular (pHex) values. During respiration pHin approached 7.55, while pHex varied from 6.0 to 8.0. With succinate as a carbon source and in a N2 environment, pHin - pHex. Upon addition of glucose, pHin greater than pHex. In the presence of an ATPase (adenosinetriphosphatase; ATP phosphohydrolase; EC 3.6.1.3) inhibitor dicyclohexylcarbodiimide, pHin remained equal to pHex even in the presence of glucose. In other experiments, oxygenation brought pHin above pHex even in the presence of dicyclohexylcarbodiimide. These experiments are consistent with Mitchell's hypothesis that, first, delta pH can be created by the reversal of the ATPase reaction and, second, that protons are pumped outward during respiration. In addition to Pi, about 10 more resonances were resolved, several of which were assigned to different phosphate metabolites.
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PMID:High-resolution 31P nuclear magnetic resonance studies of metabolism in aerobic Escherichia coli cells. 1 57

We have modeled the energy metabolism of the perfused rat heart in order to elucidate the interaction of physiological and biochemical control mechanisms. This model which includes glycolysis, the Krebs cycle, and related metabolism, contains 68 submodels of individual enzymes and transport mechanisms including both cytosolic and mitochondrial reactions. The method of model construction, which relies heavily on fitting observed in situ behavior to known algebraic rate laws for isolated enzymes, and its data requirements and necessary assumptions are described. Simulation of a CO-induced anoxic preparation is described in detail. Here glycolysis increases sharply, due to both increased glucose uptake and phosphorylase activation (there is rapid interconversion between a and b forms, both of which are active here); this causes a damped glycolytic oscillation originating with the glycogen-handling enzymes rather than phosphofructokinase. The behavior and physiological consequences of ATPase activity and of a lactate permease which exports lactate to the perfusate are discussed.
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PMID:Computer simulation of energy metabolism in anoxic perfused rat heart. 1 2

We have previously shown that acute coronary occlusion in the dog is often accompanied by increased adrenaline release into the blood. In the present study the consequences of this humoral reaction were studied in anaesthetised healthy mongrel dogs subjected to adrenaline infusion administered at a rate relevant to spontaneous release of this amine in coronary occlusion. Adrenaline was infused in a dose of 1.2 microgram.kg-1.min-1 for 4 h. Dogs receiving saline served as the control. Adrenaline administration led to the decrease in insulin/glucose ratio, to a significant fall in serum triiodothyronine and in blood pH. Free fatty acid levels doubled. Histochemically, a diminution in succinic dehydrogenase and ATPase activity in adrenaline-treated hearts was found. A significant fall in the activity of mitochondrial hexokinase in these hearts was detected spectrophotometrically. Electron microscopic study revealed alterations in the mitochondrial structure. These findings indicate that an excess of adrenaline in ammounts similar to that seen in experimental infarction leads to profound metabolic and hormonal disturbances and exerts a detrimental effect upon myocardium.
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PMID:Evidence for the detrimental effect of adrenaline infused to healthy dogs in doses imitating spontaneous secretion after coronary occlusion. 2 14

31P nuclear magnetic resonance spectra of glycolyzing, anaerobic Escherichia coli cells and their perchloric acid extracts were obtained at 145.7 MHz. Time-dependent intracellular concentrations of nucleoside di- and triphosphates, Pi, and sugar phosphates were measured during glycolysis with 2-min resolution, while intracellular and extra-cellular pH values were monitored simultaneously. Upon glucose addition, anaerobic E. coli cells rapidly produce acids and develop a transmembrane pH gradient (delta pH). Glycolysis rates were calculated from the changes in the external pH. It was found that glycolysis rates are strongly dependent on internal pH, sharply decreasing when the pH drops below approximately 7.2. The ATPase inhibitor, dicyclohexylcarbodiimide (DCCD), prevented NTP hydrolysis and inhibited delta pH formation. The uncoupler, carbonyl cyanide p-triflouromethoxyphenyl hydrazone (FCCP), drastically reduced both the delta pH and the NTP level. When the cells were previously treated with DCCD, FCCP collapsed the delta pH while the NTP levels remained high. It is concluded that ATP produced by glycolysis is hydrolyzed by the membrane ATPase to generate a delta pH and that FCCP stimulates ATP hydrolysis by ATPase and collapses the proton gradient.
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PMID:31P nuclear magnetic resonance studies of bioenergetics and glycolysis in anaerobic Escherichia coli cells. 2 85

1. 5-Methyltetrahydrofolic acid transport was studied across everted sacs of rat jejunal segments from control and whole body X-irradiated (700 rad) rats at 10(-5)M concentrations (at which optimum transport occurs) at various pHs.2. The folate transport from mucosal to serosal compartment was inhibited by about 55% in irradiated rat at the pH of the intestinal chyme (6.5). Extraneous ATP in the incubation system could restore the defective transport of the irradiated intestine.3. The maximum folate transport which occurred at pH 4.0 was not adversely affected by whole body irradiation. An acidic, pH dependent, passive uptake of 5-methyltetrahydrofolic acid was observed.4. The normal absorption barrier of the small bowel was not disrupted by the acidification process as practically no uptake was observed with irradiated segments pretreated at pH 4.0 except in the presence of ATP.5. Leucine and serine transport at a zero concentration gradient indicated active transport mechanisms which were not affected by acidification. Their uptake was additively increased in the presence of glucose and ATP, further indicating that the normal physiology of the intestines was not affected by the acidification process.6. An intestinal mucosal cell surface ATPase was observed which was Mg(2+) dependent. It could hydrolyse solution phase ATP and thus generate the protons necessary for the acidification of a microenvironment where passive uptake of the neutral folate species could occur.7. The ATPase activity was inhibited about 90% by 50 mM-Na azide at pH 6.5. Below this concentration folate transport was also inhibited.8. Na azide did not inhibit folate transport at pH 4.0, suggesting that its inhibition of folate uptake at pH 6.5 is related to its inhibitory effect on ATPase, rather than on folate transport per se. ATPase activity was therefore essential for folate transport at the pH of the intestinal chyme.
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PMID:An ATPase dependent, radiosensitive acidic microclimate essential for intestinal folate absorption. 2 19

The addition of 5 . 10(-5) M or less of dicyclohexylcarbodiimide to Mycoplasma mycoides var. Capri preferentially influences K+ influx rather than efflux and reduces by 30--40% the activity of the membrane-bound Mg2+- ATPase. Adding valinomycin to metabolizing cells does not markedly affect K+ distribution but induces a rapid and complete loss of intracellular K+ in non-metabolizing cells. Uncoupling agents such as dinitrophenol, carbonylcyanide p-trifluoromethoxyphenylhydrazone, dissipate the K+ concentration gradient only when combined with valinomycin. Variations in the merocyanine fluorescence intensity indicate that a transmembrane electrical potential (delta psi) is generated on cell energization. This delta psi, not affected by valinomycin or uncouplers when used alone, is collapsed by a mixture of both. No change in fluorescence intensity can be detected when glucose is added to dicyclohexylcarbodiimide treated organisms. These experiments suggest that the membrane-bound Mg-ATPase activity control K+ distribution in these organisms through the generation of a transmembrane electrical potential difference.
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PMID:Active K+ transport in Mycoplasms mycoides var. Capri. Relationships between K+ distribution, electrical potential and ATPase activity. 3 12

1) The rate of 2,3-bisphosphoglycerate breakdown is independent of pH value. 2) The adenine nucleotide pattern at alkaline pH values with its characteristic lowering of ATP and the accompanying accumulation of fructose-1,6-bisphosphate is caused by a relative excess of the activity of the hexokinase-phosphofructokinase system as compared wity pyruvate kinase. 3) The breakdown of adenine nucleotides proceeds via AMP mainly through phosphatase and not via AMP deaminase. 4) The constancy of the sum of nucleotides as long as glucose is present is postulated to be due to resynthesis via adenosine kinase which competes successfully with adenosine deaminase. 5) A procedure is given to calculate ATPase activity of glucose-depleted red cells. The results indicate that the ATPase activity is less at lower pH values and declines with time. An ATPase with a high Km for ATP is postulated. 6) During glucose depletion ATP production is mostly derived from the breakdown of 2,3-bisphosphoglycerate and the supply from the pentose phosphate pool both of which proceed at a constant rate. The contribution of pentose phosphate from the breakdown of adenine nucleotides amounts to 40% of the lactate formed at pH 6.8 and is about twice the lactate at pH 8.1.
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PMID:The breakdown of adenine nucleotides in glucose-depleted human red cells. 4 52

Chick embryo cells transformed by the Bryan "high titer" strain of Rous sarcoma virus (RSV-BH) are heavily vacuolated. A variety of microscopic techniques have been used demonstrating that the vacuoles are cytoplasmic, bounded by membrane, and are composed largely of water. Proteins, lipids, glycoproteins, glycolipids, glycosaminoglycans, glycogen, and nucleic acids were undetectable in the vacuoles. Physiological requirements for development of the vacuoles, and reversal of vacuolization, were examined in cells infected with a virus mutant, RSV-BH-Ta, which induces reversible temperature-dependent transformation. Na+ was the only component of the cell culture medium found essential for both the development and reversal of vacuoles. Glucose depletion or dinitrophenol treatment inhibited vacuolization, suggesting a possible energy requirement in the vacuolization process. Ouabain, an inhibitor of Na+-K+ ATPase, enhanced vacuolization, but a variety of other substances affecting cell surface components were in active. Two sugars, glucosamine and mannosamine, prevented the disappearance of vacuoles. The observations suggest that cellular vacuolization may be a normal physiological response to an increase in water and Na+, and, in the specific case of transformation by RSV-BH, may be relevant to the physiological basis for malignancy.
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PMID:Transformation of cells by rous sarcoma virus: cytoplasmic vacuolization. 5 59


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