Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Patulin (4-hydroxy-4H-furo[3,2-c]pyran-2(6H)-one), a carcinogenic lactone produced as a major metabolite by several fungi, inhibited the Mg++-dependent Na+-K+ activated adenosine triphosphatase (ATPase) activity of mouse brain microsomal fractions with an estimated IC50 of 3.0 X 10(-4) M. Inhibition was concentration dependent. Hydrolysis of ATP was linear with both time and enzyme concentration either with or without patulin in reaction mixtures. Altered pH and activity curves for Na+-K+ ATPase demonstrated comparable inhibition by patulin in buffered acidic ranges through an optimum of 7.5, followed by a reduction of toxicity to this system at higher alkaline pH. Kinetic studies of cationic-substrate activation of Na+-K+ ATPase indicated noncompetitive inhibition with respect to ATP (at low affinity nucleotide-directed sites) and Na+ (in the presence of low, noninterfering concentrations of K+). Competitive inhibition with respect to activation of the Na+-k+-stimulated activity and K+-stimulated p-nitrophenyl phosphatase activity of the enzyme system was indicated by altered binding site parameters without change in apparent Vmax in the presence of patulin. Activity was partially restored by washing. Preincubation of patulin with dithiothreitol or glutathione protected the enzyme from inhibition. Results suggest that patulin exerted its effect on Na+-K+ ATPase either directly by interfering with K+ binding or indirectly by inducing a conformational change in the enzyme.
 ...
PMID:Effects of patulin on the kinetics of substrate and cationic ligand activation of adenosine triphosphatase in mouse brain. 2 94

The membrane-bound adenosine triphosphatase (ATPase) activity of Acholeplasma laidlawii B differs in many respects from the common (Mg2+, Ca2+)-ATPase activity of higher bacteria, most notably in that it is specifically activated by Mg2+ and strongly and specifically stimulated by Na+ (or Li+). Various inhibitors diminish the ATPase activity with a concentration dependence which suggests that a single enzyme species is responsible for all of the observed ATP hydrolytic activity (both basal and Na+ stimulated). The Km for ATP is influenced by temperature but not by membrane lipid fatty acid composition. Vmax is influenced by both of these factors, showing a break in Arrhenius plots which falls below the lipid phase transition midpoint but well above the lower boundary when a phase transition occurs within the temperature range studied. The apparent energy of activation for Vmax is strongly influenced by lipid fatty acid composition both above and below the break. When whole cells of A. laidlawii B are incubated in KCl or NaCl buffers, they rapidly swell and lyse if deprived of an energy source or treated with ATPase inhibitors at concentrations which significantly inhibit enzyme activity in isolated membranes, whereas in sucrose or MgSO4 buffers of equal osmolarity, the cells are stable under these conditions. These results suggest that the membrane ATPase of A. laidlawii B is intimately associated with the membrane lipids and that it functions as a monovalent cation pump which regulates intracellular osmolarity as the (Na+, K+)-ATPase does in eucaryotes.
 ...
PMID:Physiological role and membrane lipid modulation of the membrane-bound (Mg2+, na+)-adenosine triphosphatase activity in Acholeplasma laidlawii. 3 51

Mechanisms of Li+ stimulation of proline transport were studied in cells of Escherichia coli 7 and NR70, a mutant of strain 7 lacking adenosine triphosphatase (EC 3.6.1.3). An electrochemical potential difference of Li+ induced in an inward direction of energy-depleted cells caused a transient uptake of proline depending on the driving force provided. When proline was added to unbuffered cell suspensions under anaerobic conditions, the medium was found to be acidified only in the presence of Li+ but not in the presence of Na+ or K+. This acidification was abolished by the addition of a permeant anion, SCN-, to the medium containing Li+, but this was not demonstrated with cells of a mutant strain deficient in a carrier protein specific for proline. These results support the assumption that proline is taken up by a mechanism of Li+-proline cotransport in E. coli.
 ...
PMID:Role of lithium ions in proline transport in Escherichia coli. 3 40

This study examined the effects of vanadate on the potassium dependent phosphatase activity present in purified human kidney microsomal (Na+ + K+)-adenosine triphosphatase. Vanadate anion inhibited the K+-dependent phosphatase at a K1 of 35 nM. This inhibition was noncompetitive with the substrate, p-nitrophenylphosphate. The inhibition by vanadate at 1 mM K+ was only 45% of the inhibition that was observed at 10 mM K+. Neither preincubation of the enzyme with vanadate, nor changing the pH of the assay from 8.2 to 7.2 had any effect on the K1 for vanadate. The inclusion of 2.5 mM isoproterenol, to complex the yanadate, reversed the inhibition, as did diluting the enzymatic reaction. Vanadate also inhibited the overall (Na+ + K+)-ATPase reaction at a K1 of 1.91 microM. This inhibition was also reversible upon inclusion of isoproterenol in the assay. Increasing the level of magnesium from 6 mM to 30 mM lowered the K1 of vanadate to 0.25 microM. The possible role of vanadate as a physiological mediator of (Na+ + k+)-atpase activity is discussed.
 ...
PMID:The effect of vanadate on human kidney potassium dependent phosphatase. 3 61

The catecholamine transporter from bovine chromaffin granules has been solubilized by using low concentrations of sodium cholate in the presence of phospholipids. The functional solubilized protein has been incorporated into liposomes after removal of the detergent either by gel filtration or by dialysis. Reserpine-sensitive accumulation against a concentration gradient is achieved by artifically imposing a pH gradient across the membrane. In the reconstituted system adenosine 5'-triphosphate (ATP) serves as an energy source only at higher detergent concentrations. The proton-translocating adenosine triphosphatase (ATPase) is solubilized in parallel with the increasing efficiency of ATP as an energy source. Several criteria are proposed to distinguish between carrier-mediated (reserpine sensitive) and unmediated transport in the reconstituted system. The reserpine-sensitive process shows affinity and ss presented in this communication provide further support for the contention that concentrative uptake in biogenic amine storage vesicles is driven by a transmembrane pH gradient, which, in the native system, is generated by a proton-translocating ATPase. Moreover, the assays described provide a tool for the isolation and purification of the transport protein.
 ...
PMID:Solubilization and reconstitution of the catecholamine transporter from bovine chromaffin granules. 4 69

Homogenates of Tritrichomonas foetus exhibited a Mg2+-dependent adenosine triphosphatase (ATPase) activity, with a pH optimum in Tris buffers of 8.2 to 8.3. The activity was not sensitive to oxygen. At high concentrations, quercetin and 4-chloro-7-nitrobenzofurazan inhibited ATPase activity in the cytoplasmic extract by 20 and 70%, respectively, whereas oligomycin, venturicidin, triethyltin, leucinostatin, dibutylchloromethyltin chloride, spegazzinine, efrapeptin, citreoviridin and sodium azide had no effect and N,N'-dicyclohexylcarbodi-imide stimulated the activity somewhat. The activity was localized in a population of small cytoplasmic particles which also contained an acid phosphatase. There was no indication of an association of ATPase with hydrogenosomes. The ATPase activity (or activities) in this aerotolerant anaerobe is different from the ATPases characteristic of mitochondria or of anaerobic bacteria.
 ...
PMID:Adenosine triphosphatase activity of Tritrichomonas foetus. 4 53

The effect of ouabain, a specific sodium-potassium dependent adenosine triphosphatase (Na+-K+-ATPase) inhibitor, on antigen-induced histamine release was studied using guinea pig lung fragments sensitized in vitro with rabbit antibodies against bovine serum albumin. Histamine was assayed spectrofluorometrically. When sensitized tissue had been preincubated with ouabain (less than or equal to 1.0 x 10(-4) M) for 10 min prior to antigenic challenge, release of histamine was significantly inhibited (maximum 54%, p less than 0.001, N=9, paired t test). The most significant inhibition was obtained near the optimal concentration of antigen. The inhibition was dependent on the length of preincubation (less than or equal to 20 min), and was partially reversible upon washing the tissue removing the ouabain. Ouabain did not seem to prolong the duration of the histamine release process. Increase in potassium ion (less than or equal to 1.1 x 10(-2)M) inhibited the histamine release and had additive effects to ouabain action. Dibutyryl cyclic AMP (less than or equal to 5 x 10(-3) M), which could enhance the release, strongly antagonized the inhibition. Glucose removal from the medium did not abolish the ouabain effect. The results seem to indicate that immunologic release of histamine is under the influence of the membrane Na+-K+-ATPase activity.
 ...
PMID:Inhibition of antigen-induced histamine release by ouabain. 5 30

The sodium-potassium activated adenosine triphosphatase (NaKATPase) activity of the rat cornea was investigated histochemically using a Pb2+-precipitation technique in which adenosine triphosphate (ATP) is used as substrate and two methods for potassium-dependent para-nitrophenyl-phosphatase (K-NPPase) activity. With all the three techniques used it was demonstrated that the sodium-potassium-activated adenosine triphosphatase (NaK-ATPase) activity is localized in the cell membranes of the endothelium whereas a much weaker activity was observed in the epithelium. When the Pb2+-technique was used, the epithelial cell membranes showed a weaker reaction in the presence of ouabain. This activity was only Mg2+-dependent and was presumably due to an Mg2+-dependent ATPase. The validity of the histochemical techniques for NaK-ATPase activity is discussed. The results emphasize the importance of the endothelium as the main site of Na+ transport in the cornea. Small amounts of the enzyme are also present in the epithelium, which seems to be rich in Mg2+-ATPase. Provided that careful controls are performed, all the methods give consistent results in the cornea.
 ...
PMID:Transport adenosine triphosphatase activity in the rat cornea. 6 3

Three new techniques are described for staining the Langerhans cell in whole mounts of fresh human and guinea pig epidermis. These employ paraphenylenediamine, gold sodium thiomalate and cobalt chloride, respectively, and require appropriate epidermal separation with EDTA, ammonium thiocyanate or sodium bromide. Used in conjunction with a modified adenosine triphosphatase stain, these techniques provide greater capability for observing the Langerhans cell in disease states than can be achieved by any single stain. A combined stain with adenosine triphosphate and gold is also described.
 ...
PMID:New staining techniques for the Langerhans cell. 7 Sep 19

Sodium glycocholate was shown to remove a Ca2+-activated adenosine triphosphatase from the external surface of the rat mast cell without causing lysis. Sensitized mast cells pretreated with sodium glycocholate showed a decrease in histamine-releasing capacity when triggered with antigen, Synacthen and ATP. Release induced by calcium ionophore A23187 was unaffected.
 ...
PMID:Effect of removal of calcium-activated adenosine triphosphatase from rat mast cells by treatment with sodium glycocholate. 7 27


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>