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)

The effect of calf blood extract (Solcoseryl, SS) on mitochondrial oxidative function in various states was studied polarographically in vitro. 1) Mitochondrial respiration in all 4 conventional study states (Estabrook, 1967) was enhanced by the addition of SS, including states 1 and 2 (endogenous substrates only). 2) The effect of SS on mitochondrial oxygen consumption was concentration dependent, while ADP/O ratio remained constant. The effect of added respiratory substrates varied with the particular substrate at optimally active concentrations. With suboptimal substrate levels, ADP/O ratios were concentration dependent, in contrast to the SS effect. Under oligomycin ATPase inhibition, SS was no longer active, in contrast to DNP, which remained active. 3) In states 3 (added ADP) and 4 (ADP exhausted), oxygen consumption and oxidative phosphorylation were enhanced by SS in the presence or absence of citrate, glutamate, pyruvate, lactate, or ascorbate. However, in the presence of succinate, SS had no effect. 4) ADP/O ratio was decreased by SS in the presence of added substrate, suggesting that SS activation of H(+)-ATPase enhances ATP hydrolysis as well as oxidative phosphorylation and ATP synthesis. 5) The enhancing effect of SS on mitochondrial function is due to hydrophilic components of SS. The lipidic components obtained by Folch fraction of SS have no effect. It is concluded that the effects of SS respiratory substrates and uncouplers on mitochondrial function are essentially different. SS enhances both ATP synthesis and oxygen consumption by mitochondria.
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PMID:Nature of enhanced mitochondrial oxidative metabolism by a calf blood extract. 199 15

The ATP-dependent uptake of glutamate into synaptic vesicles isolated form mammalian brains is well characterized. Glutamate uptake requires an electrochemical proton gradient, is specific for glutamate over other amino acids, and is stimulated by chloride. To determine whether these characteristics are fundamental to the vesicular uptake system, vesicles were isolated from the brain and central nervous ganglia of several vertebrate and invertebrate species, which included goldfish, frogs, turtles, pigeons, rats, Drosophila, and crayfish, and these vesicles were assayed for glutamate uptake activity. ATP-dependent glutamate was found in all of the vertebrate species tested, but was not detected in Drosophila or crayfish vesicles. The nature of the vesicular uptake of glutamate was similar among all the vertebrates: the specificity for glutamate remained high, transport was energized by a vacuolar (V)-type ATPase, 2-4 mM chloride stimulated uptake three- to sixfold, and Km for glutamate was between 0.5 and 2 mM. While these major characteristics of the uptake system remained conserved among the vertebrates tested, minor differences were seen in glutamate specificity, the steady-state level of glutamate obtained in the vesicles, and Vmax of the glutamate uptake systems. These results indicate that the synaptic vesicle glutamate uptake system is present throughout the vertebrate class, and that while minor changes in the transport system have occurred, its major functional characteristics, such as stimulation by chloride and strict substrate specificity, have been conserved for over 350-400 million years.
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PMID:Phylogenetic studies on the synaptic vesicle glutamate transport system. 204 87

Energy coupling of L-glutamate transport in brain synaptic vesicles has been studied. ATP-dependent acidification of the bovine brain synaptic vesicles was shown to require CI-, to be accelerated by valinomycin and to be abolished by ammonium sulfate, nigericin or CCCP plus valinomycin, and K+. On the other hand, ATP-driven formation of a membrane potential (positive inside) was found to be stimulated by ammonium sulfate, not to be affected by nigericin and to be abolished by CCCP plus valinomycin and K+. Like formation of a membrane potential, ATP-dependent L-[3H]glutamate uptake into vesicles was stimulated by ammonium sulfate, not affected by nigericin and abolished by CCCP plus valinomycin and K+. The L-[3H]glutamate uptake differed in specificity from the transport system in synaptic plasma membranes. Both ATP-dependent H+ pump activity and L-glutamate uptake were inhibited by bafilomycin and cold treatment (common properties of vacuolar H(+)-ATPase). ATP-dependent acidification in the presence of L-glutamate was also observed, suggesting that L-glutamate uptake lowered the membrane potential to drive further entry of H+. These results were consistent with the notion that the vacuolar H(+)-ATPase of synpatic vesicles formed a membrane potential to drive L-glutamate uptake. ATPase activity of the vesicles was not affected by the addition of Cl-, glutamate or nigericin, indicating that an electrochemical H+ gradient had no effect on the ATPase activity.
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PMID:Energy coupling of L-glutamate transport and vacuolar H(+)-ATPase in brain synaptic vesicles. 214 57

To examine the potential effect of the cellular ATP concentration and of the phosphate potential on the function of the sodium pump in intact renal cells, the ATP content of dog cortical tubules was first modified by a 30-min preincubation with one of the following effectors: 5 or 10 mM fructose, 2.5 mM adenosine 5'-monophosphate (AMP), or 2.5 mM adenosine in the presence of substrates (10 mM glutamine + 1 mM glutamate with either 10 mM lactate (low ATP) or 10 mM pyruvate (high ATP)). The tubules were then incubated in Krebs-Henseleit saline using two different phosphate concentrations and the same substrate mixture. The ATP content in tubular cells was modified by these treatments, ranging from 2.2 to 5.7 mM. The oxygen uptake by the tubules was measured before and after application of a small amount of nystatin (0.05 mM, 6 mumol/g wet wt.), added to impose an identical and submaximal increment of work to the Na(+)-K+ ATPase in tubules, irrespective of their ATP condition. This manoeuvre was followed by the addition of 1 mM ouabain to inhibit the sodium pump and quantify the respiration related to the activity of the Na+ pump. No significant effect of the ATP content on the respiratory cost of the Na(+)-K+ ATPase activity was noted when the [ATP] was above the normal concentration of approximately 3.0 mM before or after introduction of nystatin. In a second group of experiments, tubules were treated with 0.1 mM digitonin (13 mumol/g wet wt.) and resuspended in intracellular-like and sodium-free medium. The respiration was measured before and after the addition of increasing Mg-ATP concentrations (0-12 mM). A fixed quantity of Na+ (20 mM) was then introduced before ouabain was applied. The oxygen uptake was measured in these three conditions. We observed a fixed increment of ouabain-sensitive respiration upon stimulation of the pump activity by sodium at ATP concentrations ranging from 2 to 7 mM. The same observation applied when the free energy released from ATP hydrolysis ranged from -50 to -56 kJ.mol-1 and when the [ATP]/[ADP].[Pi] ratio ranged from 1.5 to 7.5 mM-1. These results suggest that the Na+:ATP stoichiometry of the Na(+)-K+ ATPase is not modified by [ATP] in dog cortical tubules when the ATP content is at or above the physiological value. Furthermore, the stoichiometry of the pump does not appear to change when the phosphate potential and (or) the free energy released from ATP hydrolysis are altered.
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PMID:Relationship between intracellular ATP and the sodium pump activity in dog renal tubules. 215 85

((+-)-1,-2,3-bis-[(4-Methoxyphenyl)-methoxy]propyl)-1H-imidazole (SC 38249) and its 4-methoxyphenetyl analogue (SKF 96365) have been recently reported to block not only voltage-operated Ca2+ channels, but also the channels (second messenger-operated) that open after receptor activation of polyphosphoinositide hydrolysis in smooth muscle fibers and platelets. Fura-2 fluorescence studies in cerebellar neurons, glial and PC12 cells confirmed these effects of SC38249 and in addition demonstrated that the drug causes an inhibition of Ca2+ extrusion, presumably via the Ca2+ ATPase. This effect was particularly evident when [Ca2+]i was increased, regardless of treatment (glutamate or ionomycin). In contrast, the NMDA receptor channel activated by glutamate was not affected by SC 38249.
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PMID:Multiple actions of SC 38249: the blocker of both voltage-operated and second messenger-operated Ca2+ channels also inhibits Ca2+ extrusion. 216 44

Glycine was taken up by a synaptic vesicle fraction from spinal cord in a Mg-ATP-dependent manner. The accumulation of glycine was inhibited by carbonyl cyanide-m-chlorophenylhydrazone (CCCP) and nigericin, agents known to destroy the proton gradient across the vesicle membrane. Vesicular uptake of glycine was clearly different from synaptosomal uptake, with respect to both the affinity constant and the effect of Na+, ATP, CCCP, and temperature. Oligomycin and strychnine did not inhibit the vesicular uptake, showing that neither mitochondrial H(+)-ATPase nor binding to strychnine-sensitive glycine receptors was involved. It is suggested that the vesicular uptake of glycine is driven by a proton gradient generated by a Mg2(+)-ATPase. A low concentration of Cl- had little effect on the uptake of glycine, whereas the uptake of glutamate in the same experiment was highly stimulated. High concentrations of gamma-amino-n-butyric acid and beta-alanine inhibited vesicular glycine uptake, but glutamate did not. Accumulation of glycine was found to be fourfold higher in a spinal cord synaptic vesicle fraction than in a vesicle fraction from cerebral cortex.
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PMID:Uptake of glycine into synaptic vesicles isolated from rat spinal cord. 231 84

Intracellular recordings were obtained from guinea pig hippocampal CA1 pyramidal neurons maintained in vitro. Focal applications of glutamate produced depolarizations followed by prolonged hyperpolarizations. The mechanisms underlying this postglutamate hyperpolarization (PGH) were investigated. PGH did not reverse polarity with hyperpolarization to potentials at or near the presumed K+ equilibrium potential. A transient increase in conductance was associated with the PGH; control values returned well before the termination of PGH. Application of Mn2+, an antagonist of voltage-dependent calcium conductance, blocked synaptic transmission and the afterhyperpolarization (AHP) that follows a directly evoked train of action potentials but did not diminish the PGH or the transient conductance increase. Intracellular application of the calcium chelator ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid blocked AHP but did not affect PGH. Reductions in temperature from 37 to 27-32 degrees C reduced the amplitude of PGH and prolonged its duration but increased the amplitude and duration of AHP. The transient conductance increase associated with PGH was unaffected. Application of strophanthidin, a specific antagonist of Na+-K+-ATPase, reversibly blocked PGH and led to large increases in the amplitude and duration of the AHP. It is concluded that PGH is produced by activation of the electrogenic sodium pump by glutamate-induced excitation. As such, PGH is a useful physiological assay of electrogenic sodium transport. In addition, maintenance of the Na+ gradient by the sodium pump is important for the buffering of Ca2+ influx.
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PMID:Activation of electrogenic sodium pump in hippocampal CA1 neurons following glutamate-induced depolarization. 242 52

The effect of rhein on the oxygen consumption, oxidative phosphorylation, ATPase activity and redox state of electron carriers of rat liver mitochondria has been studied. Rhein inhibits ADP- and uncoupler-stimulated respiration on various NAD-linked substrates and succinate, but stimulates state 4 respiration of mitochondria respiring on succinate. Experiments on specific segments of the respiratory chain showed that rhein does not inhibit electron flow through cytochrome oxidase. Electron flow through site 2, the ubiquinone-cytochrome b-cytochrome c1 complex, was also unaffected by rhein, which failed to inhibit the oxidation of duroquinol. Rhein affects oxidative phosphorylation by inhibiting both electron transfer and ADP-driven H+ uptake. The inhibition of succinate oxidation by rhein was found to take place at a point between succinate and ubiquinone, perhaps at the level of succinic dehydrogenase. Spectroscopic evidence demonstrated that rhein induces a NAD(P)H oxidation in mitochondria respiring either on endogenous substrates or on glutamate + malate, and an inhibition of the cytochrome b reduction by succinate. These observations, together with other evidence, suggest that rhein inhibits electron transport in rat liver mitochondria at the dehydrogenase-coenzyme level, particularly when the electron carriers are in a relatively oxidized state and/or when the inner membrane-matrix compartment is in the condensed state.
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PMID:Sites of inhibition of mitochondrial electron transport by rhein. 252 79

The uncE114 mutation (Gln42----Glu) in subunit c of the Escherichia coli H+ ATP synthetase causes uncoupling of proton translocation from ATP hydrolysis (Mosher, M. E., White, L. K., Hermolin, J., and Fillingame, R. H. (1985) J. Biol. Chem. 260, 4807-4814). In the background of strain ER, the mutation led to dissociation of F1 from the membrane. Ten revertants to the uncE114 mutation were isolated, and the uncE gene was cloned and sequenced. Six of the revertants were intragenic and had substitutions of glycine, alanine, or valine for the mutant glutamate residue at position 42. The intragenic, revertant uncE genes were incorporated into an otherwise wild type chromosome of strain ER. Membrane vesicles prepared from each of the revertants showed a restoration of F1 binding to F0. The Val42 revertant differed from the other two revertants in that the ATPase activity of F1 was inhibited when membrane bound. This was shown by the stimulation of ATPase activity when F1 was released from the membrane. The Gly42 and Ala42 revertants demonstrated membrane ATPase activity that was resistant to dicyclohexylcarbodiimide treatment. Resistance was shown to be due to the increased dissociation of F1 from the membrane under ATPase assay conditions. The Ala42 revertant showed a significant reduction in ATP-dependent quenching of quinacrine fluorescence that was attributed to less efficient coupling of ATP hydrolysis to H+ translocation, whereas the other revertants showed responses very near to that of wild type. Minor changes in the F1-F0 interaction in all three revertants were indicated by an increase in H+ leakiness, as judged by reduced NADH-dependent quenching of quinacrine fluorescence. The minor defects in the revertants support the idea that residue 42 is involved in the binding and coupling of F1 to F0 but also show that the conserved glutamine (or asparagine) is not absolutely necessary in this function.
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PMID:Conserved polar loop region of Escherichia coli subunit c of the F1F0 H+-ATPase. Glutamine 42 is not absolutely essential, but substitutions alter binding and coupling of F1 to F0. 252 84

We have previously provided evidence for ATP-dependent glutamate uptake into synaptic vesicles, and, based upon the unique properties of the vesicular uptake system, we have proposed that the vesicular glutamate translocator plays a crucial role in selecting glutamate for neurotransmission. In this study, we have solubilized the vesicular glutamate uptake system, proposed to consist of at least a glutamate translocator and a proton pump Mg-ATPase, from rat brain synaptic vesicles, and reconstituted the functional ATP-dependent glutamate uptake system into liposomes. The glutamate uptake in the reconstituted system is dependent upon ATP, markedly potentiated by low millimolar concentrations of chloride and inhibited by agents known to dissipate electrochemical proton gradients. Moreover, it exhibited low affinity for glutamate (Km = 2 mM), yet high specificity for glutamate; thus, it did not recognize aspartate and other agents known to interact with glutamate receptors. These properties are indistinguishable from those observed in intact synaptic vesicles. The solubilized functional components of the glutamate uptake system, alone or as a complex, have been estimated to have a Stokes radius in the range of 69 to 84 A. The reconstitution experiments described here provide a functional assay for the solubilized vesicular glutamate uptake system and represent an initial step towards the purification of the glutamate translocator.
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PMID:Characterization of the solubilized and reconstituted ATP-dependent vesicular glutamate uptake system. 252 94


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