Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ADENOSINE TRIPHOSPHATASE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,135 records · Page 63Linked to original sources
PubMed1976

Evidence for a new intermediate state in the mechanism of (Na+ + K+)-adenosine triphosphatase.

A rapid mixing technique was used to follow the intermediate formation of phosphorylated enzyme and liberation of inorganic phosphate by a microsomal preparation of (Na+ + K+)-ATPase. In the presence of 100 mM Na+,but without added K+, phosphorylation reaches a constant level at a rate which is dependent on ATP concentration. Inorganic phosphate production lags during the inital phase of phosphorylation and then accumulates at a constant rate. These observations favor a scheme in which Pi is liberated as the result of turnover of the phosphorylated enzyme. In the presence of 100 mM Na+ and 2.5 mM K+ phosphate production was resolved into two phases consisting of an initial 'burst' and late steady state phase...

Adenosine Triphosphatases↗
PubMed1986

Effects of ethidium bromide on the mitochondrial adenosine triphosphatase from Trypanosoma cruzi.

Culturing of Trypanosoma cruzi in the presence of ethidium bromide (EB; 1.0-2.5 microM), for 5 days, affected the biogenesis of the Fo/F1-ATPase complex, presumably by EB interference with the expression of the putative Fo-sector subunits encoded by maxicircle DNA. In vitro, EB inhibited ATP hydrolysis by the Fo/F1-ATPase complex and also by soluble F1, the former preparation being the most strongly affected (EB I50, 250 microM). Analysis of EB effect at increasing MgATP concentrations, as well as combination of EB and p-chloromercuribenzoate inhibitions, indicated that the dye interacts with ATPase at sites other than the catalytic ones. No correlation was found between the in vitro inhibition of ATPase and EB effect on parasite growth.

Adenosine Triphosphatases↗
PubMed1990

[Adenosine triphosphatase from plasma membranes of cattle intestinal epithelium].

The activities of Na,K-, Ca,Mg- and Mg-ATPases in the membrane fractions of plasma membranes of intestinal enterocytes of cattle, brush border and basolateral membranes, were studied. The activities were estimated under conditions of alkaline phosphatase activity inhibition by theophylline to exclude the nonspecific hydrolysis of ATP as well as to establish the orientation of vesicles with the use of alamethicine. 98% of the Na,K-ATPase activity (0.99 +/- 0.031 mumol/mg protein/min) was found to be localized in basolateral membranes. Both the brush border and basolateral membranes were found to possess the Ca,Mg-ATPase (0.193 +/- 0.018 and 0.795 +/- 0.025 mumol/mg protein/min) and Mg-ATPase (0.22 +/- 0.013 and 0.403 +/- 0.022 mumol.mg protein/min) activities.

Adenosine Triphosphatases↗
PubMed2006

Role of the plasma membrane calcium adenosine triphosphatase on domoate-induced intracellular acidification in primary cultures of cerebelar granule cells.

Changes in intracellular pH (pH(i)) and cytosolic calcium concentration ([Ca(2+)](c)) caused by the glutamate agonist domoate (DOM) were studied in single cultured mouse cerebellar granule cells (CGC) by using the fluorescent probes 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester (BCECF-AM) and simultaneous evaluation of cytosolic calcium concentration with the fluorescent dye Fura-2 acetoxymethyl ester (Fura-2 AM). DOM caused a concentration-dependent increase in [Ca(2+)](c) and a concentration-dependent intracellular acidification of CGC. DOM-induced intracellular acidification was completely abolished by the use of Ca(2+)-free medium, suggesting that it was due mostly to an influx of extracellular calcium. The pH(i) decrease caused by DOM was also completely blocked in the presence of the AMPA/kainate receptor antagonist CNQX, indicating that the DOM-induced intracellular acidification was caused by DOM activation of the AMPA/kainate subtype of glutamate receptors. Different mechanisms that could be involved in DOM-induced pH(i) decrease, such as displacement of H(+) by Ca(2+) from a common intracellular binding site, DOM-induced alteration of pH(i) regulation mechanisms, and a possible acidification caused by DOM-induced increase of mitochondrial Ca(2+) uptake, were excluded. DOM-induced intracellular acidification was completely prevented by inhibitors of the plasma membrane calcium adenosine triphosphatase (ATPase) (PMCA), including orthovanadate, lanthanum extracellular pH of 8.5, and the specific PMCA inhibitor caloxin 2A1. Our results therefore indicate that PMCA is involved in DOM-induced intracellular acidification in primary cultures of CGC. Simultaneous recording of [Ca(2+)](c) and pH(i) indicates that the increase in intracellular calcium evoked by DOM will activate the calcium extrusion mechanisms through the calcium pump, which, in turn, will decrease intracellular pH by countertransport of H(+) ions.

Acid-Base Equilibrium↗
PubMed1986

Deficiency of uncoupler-stimulated adenosine triphosphatase activity in yeast mitochondria.

Oligomycin-sensitive ATPase activity was studied in isolated yeast mitochondria. The protonophore CCCP, at a concentration which completely inhibited ATP synthesis, induced only a low rate of hydrolysis of externally added ATP, and the extent of hydrolysis was dependent upon phosphate (Pi) concentration. CCCP promoted hydrolysis of intramitochondrial ATP. However, hydrolysis of externally added ATP was total in a medium containing potassium phosphate plus valinomycin. Without ionophores, ATPase activity was only observed at high external pH or with detergent-treated mitochondria. Under state 4 conditions, external ATP had access to the catalytic nucleotide site of ATPase as shown by 32Pi-ATP exchange experiments. These results are discussed in terms of a limitation of the translocase-mediated ATP/ADP exchange in uncoupled mitochondria.

Adenine Nucleotides↗
PubMed1975

Formation of adenosine triphosphate from Pi and adenosine diphosphate by purified Ca-2+-adenosine triphosphatase.

Ca-2+-ATPase purified from sarcoplasmic reticulum of rabbit muscle forms a phsophoeznyme when exposed to inorganic phosphate in the presence of Mg-2+. On addition of ADP and Ca-2+ virtually all of the phosphate bound to the enzyme is transferred to form ATP. It has been shown previously and confirmed by us that (a) the purified ATPase contains one major polypeptide and about 30% phospholipids; (b) on removal of residual detergent by passage through Sephadex the enzyme forms vesicular membranes; and (c) these vesicles are leaky and incapable of accumulating Ca-2+. Our findings therefore indicate that we have observed ATP generation from ADP and P-i without the formation of an ion gradient across a membrane. We propose that the energy derived from ion-protein interaction drives the formation of ATP.

Adenosine Diphosphate↗
PubMed1972

Demonstration of a phosphopeptide intermediate in the Mg ++ -dependent, Na + - and K + -stimulated adenosine triphosphatase reaction of the erythrocyte membrane.

Human erythrocyte membranes are phosphorylated by [gamma-(32)P]ATP in association with the Mg(++)-dependent, Na(+) and K(+)-stimulated ATPase (EC 3.1.6.3) reaction. To delineate the membrane species involved, phosphorylated membranes were analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate, under conditions that minimize hydrolysis of acyl phosphate linkages. Three radioactive components were detected, of which only one was a phosphopeptide, of apparent molecular weight 105,000. The phosphate bound to this peptide undergoes rapid turnover and is discharged by hydroxylamine. In the presence of Mg(++), the phosphorylation of this peptide is specifically stimulated by Na(+) and blocked by ethylene diamine tetraacetate; its dephosphorylation is stimulated by K(+) and blocked by ouabain. We conclude that this phosphopeptide is an intermediate in the Mg(++)-dependent, Na(+)- and K(+)-stimulated ATPase reaction of the erythrocyte membrane.

Adenosine Triphosphatases↗
PubMed1977

Formation of ATP by the adenosine triphosphatase complex from spinach chloroplasts reconstituted together with bacteriorhodopsin.

The energy-linked ATPase complex has been isolated from spinach chloroplasts. This protein complex contained all the subunits of the chloroplast coupling factor (CF1) as well as several hydrophobic compoenents. When the activated complex was reconstituted with added soybean phospholipids, it catalyzed the exchange of radioactive inorganic phosphate with ATP. Sonication of the complex into proteoliposomes together with bacteriorhodopsin yield vesicles that catalyzed light-dependent ATP formation. Both the 32Pi-ATP exchange reactions and ATP formation were sensitive to uncouplers such as 3-tert-butyl-5,2'-dichloro-4'-nitrosalicylanilide, bis-(hexafluoroacetonyl)acetone and carbonyl cyanide-p-trifluoromethoxyphenyl-hydrazone, that act to dissipate a proton gradient. The energy transfer inhibitors dicyclohexylcarbodiimide, triphenyltin chloride and 2-beta-D-glucopyranosyl-4,6'-dihydroxydihydrochalcone were also effective inhibitors of both reactions.

Adenosine Triphosphatases↗
PubMed1980

Functional arginine residues and carboxyl groups in the adenosine triphosphatase of the thermophilic bacterium PS-3.

Treatment of purified ATPase of the thermophilic bacterium PS-3 with the arginine reagent phenylglyoxal or with Woodward's reagent K, gave complete inactivation of the enzyme. The inactivation rates followed apparent first-order kinetics. The apparent order of reaction with respect to inhibitor concentrations gave values near to 1 with both reagents, suggesting that inactivation was a consequence of modifying one arginine or carboxyl group per active site. ADP and ATP strongly protected the thermophilic ATPase against both reagents. GDP and IDP protected less, whilst CTP did not protect. Experiments in which the incorporation of [14C]phenylglyoxal into the enzyme was measured show that extrapolation of incorporation to 100% inactivation of the enzyme gives 8-9 mol [14C]phenylglyoxal per mol ATPase, whilst ADP or ATP prevent modification of about one arginine per mol.

Adenosine Diphosphate↗
PubMed1977

Membrane-bound adenosine triphosphatase of Escherichia coli. III. Effects of sodium azide on the enzyme functions.

1) Sodium azide and diphenyl phosphorazidate (DPPA) inhibited purified membrane-bound ATPase [coupling factor of oxidative phosphorylation; EC 3.6.1.3] of Escherichia coli non-competitively with Ki values of 39 and 51 micrometer, respectively. 2) Sodium azide and DPPA inhibited the activity of ATPase bound to the membrane as effectively as that of the purified enzyme. 3) The effects of sodium azide on succinate-dependent ATP synthesis, Pi-ATP exchange, and ATP hydrolysis reactions by the membrane vesicles were compared under the same conditions. At concentrations below 1.0 mM, sodium azide inhibited ATP hydrolysis, but Pi-ATP exchange and ATP synthesis were almost unaffected. At 10 mM sodium azide, both Pi-ATP exchange and ATP synthesis reactions were completely inhibited, probably because at this concentration, sodium azide acted as a proton-conducting uncoupler.

Adenosine Triphosphatases↗
PubMed1981

Adenosine triphosphatase in non-secreting and secreting mast cells.

A Ca++-Mg++ ATPase has been demonstrated in the plasma membrane of rat peritoneal mast cells. The enzyme is localized by electron microscopy on the outer surface of the membrane. This agrees with the biochemical findings. A Ca++-Mg++ activated ATPase has also been shown to be present in the granule membrane. The optimal pH of the plasma membrane enzyme is close to the optimal pH for the histamine release. All the 14 inhibitors of plasma membrane ATPase tested - which caused varying degrees of inhibition of the enzyme - also inhibited histamine release induced by antigen, compound 48/80 and the divalent ionophore A23187. The conclusion from the study with the inhibitors is that a mild inhibition of the enzyme is compatible with histamine release, but a pronounced inhibition of the enzyme is always associated with inhibition of histamine release. ATP in low concentrations potentiates the release.

Adenosine Triphosphatases↗
PubMed1975

Stimulation of rat liver mitochondrial adenosine triphosphatase by anions.

The hydrolysis of MgATP by isolated rat liver mitochondrial ATPase (EC 3.6.1.3) at pH 8.0 was stimulated by various anions. The rate of hydrolysis was increased from 18 to 170 mumol per min per mg, a 9.4-fold stimulation, by HSeO3 at 1 mM MgATP. In the absence of a stimulatory anion, reciprocal plots of initial velocity studies with MgATP as the variable substrate were curved (Hill coefficient approximately 0.5). With the addition of anion, the reciprocal plots became linear. When the substrate was MgITP or MgGTP with the isolated enzyme or MgATP with submitochondrial particles, no curvature of the reciprocal plots was observed. With purified ATPase, anions stimulated the hydrolysis of MgITP, MgGTP, MgUTP or MgCTP only slightly. With submitochondrial particles the stimulation by anions of MgATP hydrolysis was limited to approximately 2-fold. These data are interpreted to indicate the existence of two substrate sites for MgATP and an anion-binding site on the isolated enzyme.

Adenosine Triphosphatases↗
PubMed1975

Physical and enzymatic properties of nucleotide-depleted beef heart mitochondrial adenosine triphosphatase.

Tightly bound adenine nucleotides are removed from multiple binding sites on beef heart mitochondrial ATPase (F1) by chromatography on columns of Sephadex equilibrated with 50% glycerol. Release of nucleotides from the enzyme is associated with large decreases in sedimentation velocity (from 11.9 S to 8.4 S) which may be observed in concentrated solutions of polyols. Polyol-induced conformational changes are reversed when the enzyme is returned to dilute buffers. The nucleotide-depleted enzyme restores oxidative phosphorylation in F1-deficient submitochondrial particles. Reconstitution of nucleotide-depleted F1 with the ATP analog (adenylyl-imidodiphosphate (AMP-PNP), almost 5 moles of AMP-PNP per mole of enzyme, results in preparations with substantially inhibited ATPase activity which nevertheless restores oxidative phosphorylation and the 32Pi-ATP exchange reaction in F1-deficient submitochondrial particles. Incubation of the analog-labeled enzyme with ATP and Mg++ results in partial displacement of the analog and a time-dependent recovery of ATPase activity.

Adenine Nucleotides↗
PubMed1981

MgATP-induced inhibition of the adenosine triphosphatase activity of submitochondrial particles.

1. The ATP-hydrolytic activity of ox heart submitochondrial particles can be increased from 2-3 mumol/min per mg of protein to 10-12 mumol/min per mg of protein by incubation in media containing 50 mM-Na2B4O7. This process appears to be due to the partial release of inhibitor protein from the particles. 2. The ATPase activity of submitochondrial particles can be inhibited by incubation with the substrate, MgATP. This inhibition is not due to the accumulation of the hydrolysis products, MgADP and Pi, but could involve the process of ATP hydrolysis. 3. The mechanism of MgATP-induced inhibition of ATPase activity is proposed to involve a conformational change in one of the intermediate enzyme species of the ATP-hydrolytic sequence. 4. MgATP inhibits the ATPase activity of control submitochondrial particles at a higher rate and to a greater extent than it does that of inhibitor-protein-depleted submitochondrial particles, suggesting that the conformational change involves the endogenous inhibitor protein.

Adenosine Triphosphatases↗