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)

Addition of hydrogen peroxide (greater than 10 mM) to aerated derepressed cells of S. cerevisiae in the absence of substrate caused a boost of endogenous respiration and both intra- and extracellular acidification, without any significant change in cellular ATP level. Furthermore, a hyperpolarization of the plasma membrane was indicated by an enhanced accumulation of tetraphenylphosphonium in the cells. The extracellular pH attained was as low as 3.5. The acidification could be suspended by the H(+)-ATPase inhibitors diethylstilbestrol and dicyclohexylcarbodiimide and was, in general, associated with an opposite flux of K+. K+ also stimulated the H(+)-ATPase activity in the purified plasma membrane fraction. These results are consistent with the plasma membrane H(+)-ATPase being involved in the H+ extrusion induced by H2O2 in the absence of substrate. Extended exposure of cells to H2O2 led eventually to an arrest of both respiration and ion fluxes that could be again lifted by depolarizing the plasma membrane. Along with differences in the cellular NADH/NAD+ ratio and in the participation of organic acids, this makes the H2O2-induced acidification distinct from that induced by glucose.
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PMID:Activation of the plasma membrane H(+)-ATPase of Saccharomyces cerevisiae by addition of hydrogen peroxide. 183 83

In some bacteria, an Na+ circuit is an important link between exergonic and endergonic membrane reactions. The physiological importance of Na+ ion cycling is described in detail for three different bacteria. Klebsiella pneumoniae fermenting citrate pumps Na+ outwards by oxaloacetate decarboxylase and uses the Na+ ion gradient thus established for citrate uptake. Another possible function of the Na+ gradient may be to drive the endergonic reduction of NAD+ with ubiquinol as electron donor. In Vibrio alginolyticus, an Na+ gradient is established by the NADH: ubiquinone oxidoreductase segment of the respiratory chain; the Na+ gradient drives solute uptake, flagellar motion and possibly ATP synthesis. In Propionigenium modestum, ATP biosynthesis is entirely dependent on the Na+ ion gradient established upon decarboxylation of methylmalonyl-CoA. The three Na(+)-translocating enzymes, oxaloacetate decarboxylase of Klebsiella pneumoniae, NADH: ubiquinone oxidoreductase of Vibrio alginolyticus and ATPase (F1F0) of Propionigenium modestum have been isolated and studied with respect to structure and function. Oxaloacetate decarboxylase consists of a peripheral subunit (alpha), that catalyses the carboxyltransfer from oxaloacetate to enzyme-bound biotin. The subunits beta and gamma are firmly embedded in the membrane and catalyse the decarboxylation of the carboxybiotin enzyme, coupled to Na+ transport. A two-step mechanism has also been demonstrated for the respiratory Na+ pump. Semiquinone radicals are first formed with the electrons from NADH; subsequently, these radicals dismutate in an Na(+)-dependent reaction to quinone and quinol. The ATPase of P. modestum is closely related in its structure to the F1F0 ATPase of E. coli, but uses Na+ as the coupling ion. A specific role of protons in the ATP synthesis mechanism is therefore excluded.
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PMID:Mechanisms of sodium transport in bacteria. 197 Jun 50

The effect of halothane, a potent and popular volatile anesthetic, on isolated rat liver mitochondria was examined. Halothane inhibited state 3 and dinitrophenol-induced uncoupled respiration with NAD(+)-linked substrates, but not with FAD-linked substrates, and did not affect the oxidation-reduction state of mitochondrial cytochromes. Moreover, halothane increased state 4 respiration and ATPase activity and decreased the extra-mitochrondrial pH change coupled to ATP synthesis. These results indicate that halothane impairs mitochondrial ATP production by interfering with both the electron transport from NAD+ to FAD and the coupling of oxidative phosphorylation. Halothane only slightly affected the membrane potential, which is commonly dissipated by typical classical uncouplers. Moreover, halothane inhibited both ATP-driven and respiration-driven Ca2+ accumulation in mitochondria and stimulated Ca2+ release from mitochondrial stores at concentrations higher than those at which it inhibited ATP production. These findings indicate that the uncoupling action of halothane is not classical. During halothane anesthesia, these mitochondrial abnormalities may contribute to hepatocyte dysfunctions.
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PMID:Halothane impairs the bioenergetic functions of isolated rat liver mitochondria. 216 74

Administration of beta- and gamma-isomers of hexachlorocyclohexane (HCH) at 800 ppm dietary level for 2 weeks to albino rats produced noticeable hepatocellular damage as indicated by elevations in serum aminotransferases and decreases in hepatic soluble enzymes. Although serum total LDH activity was not altered, the LD5 isoenzyme was proportionately higher in the HCH isomers treated animals. Treatment of rats with beta- and gamma-isomers of HCH increased the hepatic glucose-6-phosphate dehydrogenase and aldolase activities suggesting a higher rate of glucose oxidation. Liver glucose-6-phosphatase activity was decreased in these animals indicating inactivation of gluconeogenesis in liver. Dietary beta- and gamma-HCH decreased the liver mitochondrial DNP/Mg++/Ca++-activated ATPases thus affecting the energy metabolism. An unaltered ratio of DNP/Mg++-ATPase, a study of swelling pattern of hepatic mitochondria, and NAD+ permeability test suggested the maintenance of structural integrity of mitochondrial membrane in these pesticide fed animals. Liver microsomal Na+,K+-ATPases were lower in these animals.
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PMID:Biochemical changes produced by beta- and gamma-hexachlorocyclohexane isomers in albino rats. 246 8

An addition of the inhibitor protein (IF1) to submitochondrial particles (SMP) essentially free of endogenous IF1 (AS-SMP) results in a synchroneous inhibition of ATP hydrolysis and ATP-dependent reduction of NAD+ by succinate without any effect on the oxidative phosphorylation rate. The binding of IF1 to the membrane-bound ATPase leads to the loss of the inhibitor protein sensitivity to trypsin despite the delta mu H+ generation. The data obtained are consistent with a model according to which there exist the hydrolase and synthetase forms of F1 and contradict the generally accepted concepts on the delta mu H+-dependent dissociation of the F1-IF1 complex.
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PMID:[Interaction of ATPase from submitochondrial fragments and a natural inhibitor protein during delta-mu-H+ generation on a membrane]. 253 16

We examined the energy requirement for maltose transport in right-side-out membrane vesicles derived from Escherichia coli. When membrane vesicles were made from strains producing tethered maltose-binding proteins by dilution of spheroplasts into phosphate buffer, those from an F0F1 ATPase-containing (unc+) strain transported maltose in the presence of an exogenous electron donor, such as ascorbate/phenazine methosulfate, at a rate of 1-5 nmol/min per mg of protein, whereas those from an isogenic unc- strain failed to transport maltose. Transport in vesicles obtained from the latter strain could be restored in the presence of electron donors if the vesicles were made to contain NAD+ and either ATP or an ATP-regenerating system. ATP hydrolysis was apparently required for transport, since nonhydrolyzable ATP analogues did not sustain transport. Maltose transport significantly increased ATP hydrolysis in ATP-containing vesicles from unc- cells. Finally, ATP-containing vesicles from unc- strains producing normal maltose-binding proteins could accumulate maltose in the absence of electron donors. These results provide convincing evidence that it is the hydrolysis of ATP that drives maltose transport, and probably also other periplasmic-binding-protein-dependent transport systems.
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PMID:Maltose transport in membrane vesicles of Escherichia coli is linked to ATP hydrolysis. 253 94

The specific activity of the Mg2+-ATPase and the (Ca2+ + Mg2+)-ATPase has been measured in a microsomal fraction from pig antral smooth muscle with the phosphate-release assay and the NADH-coupled enzyme assay, and the release of inorganic phosphate as a function of time is compared with the concomitant production of ADP. Both assays are found to overestimate the true Mg2+-ATPase activity. The adenylate kinase inhibitor P1,P5-di(adenosine-5'-)pentaphosphate (Ap5A) reduces the specific activity of the Mg2+-ATPase measured in the NADH-coupled enzyme assay to about half of its original value; however, it does not affect the specific activity of the Mg2+-ATPase in the Pi-release assay. The considerable overestimation of the Mg2+-ATPase activity in the NADH-coupled enzyme assay results from a combined action of an ATP pyrophosphatase (ATP in equilibrium AMP + PPi) and adenylate kinase activity contaminating the microsomes. The adenylate kinase activity in the microsomes catalyses the conversion of AMP formed by the ATP pyrophosphatase together with ATP into two ADP's. Also the phosphate-release assay is prone to an overestimation artefact because an inorganic pyrophosphatase will degrade the pyrophosphate and thus lead to additional Pi-production. Measurements of AMP and NAD+ production by HPLC confirmed our proposed reaction scheme. The same (Ca2+ + Mg2+)-ATPase activity is found in both assays, because the (Ca2+ + Mg2+)-ATPase activity is calculated from the difference in ATPase activity in the presence and absence of Ca2+, so that as a consequence the interfering activities are automatically subtracted.
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PMID:Measurement of microsomal ATPase activities: a comparison between the inorganic phosphate-release assay and the NADH-coupled enzyme assay. 253 60

Brush-border and basal-lateral membranes were prepared from rabbit intestinal epithelial cells by differential centrifugation and MgCl2 precipitation. The ADP-ribosylation of proteins in these fractions when incubated with [adenylate-32P]NAD+ and cholera toxin was investigated. Three proteins of molecular mass 45, 40 and 37 kDa were labelled in a toxin-dependent manner in each membrane fraction. The incorporation of 32P-labelled ADP-ribose was 18-fold greater in brush-border membranes than in basal-lateral membranes, comparable to the enrichment of sucrase (marker enzyme for the brush border) in these membranes. There was a 20% release of the 40 and 45 kDa proteins from the brush-border membrane following this ADP-ribosylation. Activation of adenylate cyclase by both cholera toxin and sodium fluoride was 2.7- and 2.3-fold greater, respectively, in basal-lateral membranes than in brush-border membranes, comparable to the enrichment of Na+/K+-ATPase (marker enzyme for the basal-lateral membrane) in these membranes. The effect of sodium fluoride on membranes pretreated with cholera toxin revealed no increase in adenylate cyclase activity above that due to the toxin. This presumably means that both toxin and fluoride activate adenylate cyclase by the same regulatory protein. The results show that cholera toxin catalyzes the ADP-ribosylation of regulatory proteins in the brush-border membrane, and these proteins then migrate to the basal-lateral membrane where they activate the catalytic component of adenylate cyclase.
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PMID:The activation of rabbit intestinal adenylate cyclase by cholera toxin. 260 57

A simple and fast ion pair reversed-phase high-performance liquid chromatographic method has been developed for the simultaneous determination of ATP, ADP, AMP, GTP, GDP, IMP, NADP+, NADPH+, NAD+, NADH, ADP-ribose, inosine, adenosine, hypoxanthine, and xanthine. This method allows us to have a complete picture of the most important nucleotides present in fresh human erythrocytes. Furthermore it is particularly useful in the study of the erythrocyte adenine nucleotide catabolism allowing the detection of degradation products such as IMP, inosine, adenosine, hypoxanthine, and xanthine. The separation of the compounds under investigation is achieved in less than 15 min using a reversed-phase 3-micron Supelcosil LC-18 column and adding tetrabutylammonium, as ion-pair agent, to the buffers. The short time of analysis, the high reproducibility of the system, and the accurate evaluation of the compounds of interest make this method particularly suitable for routine analysis. Finally it is possible to use this assay as an alternative method of measuring activities of enzymes which catalyze reactions involving some of these compounds, as in the case of Na+-K+ ATPase, AMP deaminase, and adenosine deaminase.
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PMID:A very fast ion-pair reversed-phase HPLC method for the separation of the most significant nucleotides and their degradation products in human red blood cells. 282 56

Effect of methotrexate (MTX) on mitochondrial oxygen uptake, oxidative phosphorylation and on the activity of several enzymes linked to respiratory chain was studied. MTX was able to inhibit state III respiration activated by ADP and to decrease the respiratory coefficient with the substrates alpha-ketoglutarate and glutamate; these effects became pronounced when mitochondria were pre-incubated with MTX for 10 min. No effect was observed on ATPase activity of undamaged or broken mitochondria; the same was true for NADH-oxidase, NADH-dehydrogenase, NADH-cytochrome c reductase, succinate oxidase, and cytochrome c oxidase activity. The effect on the steady-state of cytochrome b, as well as, the inhibitory effect on state III of respiration with NAD+-linked substrates, offers a reasonable possibility to suggesting that the inhibition site of MTX could be in a place anterior to cytochrome b region, and not linked to respiratory chain.
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PMID:Methotrexate: studies on the cellular metabolism. I. Effect on mitochondrial oxygen uptake and oxidative phosphorylation. 283 95


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