Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The disruption of a kidney cortex microsomal membrane preparation by a binary, nonionic detergent, was followed by using as markers, the changes in total protein content, and (Na+, K+)-ATPase in a supernatant fraction. Both markers responded similarly to changes in pH, microsome concentration and detergent concentration, but responded differently for time-dependent studies. The (Na+, K+)-ATPase activity was increased 2.2-fold (76.1 mumoles Pi/mg protein/h, 95% ouabain-sensitive) by a single detergent treatment and 3.5-fold (92% ouabain-sensitive) by a sequential detergent treatment. Changes in the critical micelle concentration (cmc) were observed for varying detergent and protein concentrations, which suggest interactions of monomeric detergent with the membrane. The peak of (Na+, K+)-ATPase activity occurred above the cmc which suggests the participation of micelles in releasing the enzyme from the membranes. Hill plots of the protein released as the detergent concentration was varied showed a change in the slope near the cmc indicating a four-fold increase in the binding of detergent to membranes as the detergent concentration is increased above the cmc. These results suggest that the disruption of membranes by detergent involves the binding of detergent monomers to the membrane followed by the formation of co-micelles of the detergent with segments of the membrane to complete the separation process.
...
PMID:The action of a binary nonionic detergent on a kidney membrane fraction. 0 17

A density gradient-purified microsomal membrane preparation from rabbit fundic gastric mucosa was used for a detailed study of the K+-stimulated ATPase and associated intermediate reactions. Membranes incubated with gamma-[32P]ATP show the rapid incorporation of 32P into phosphoprotein. Phosphoprotein levels were markedly reduced (1) when ATP hydrolysis went to completion or (2) upon addition of unlabeled ATP, thus suggesting the participation of a rapid turnover phosphorylated intermediate in the gastric microsomal ATPase. Addition of K+, Rb+ or Tl+ greatly reduced the level of the intermediate while stimulating ATPase activity; the observed affinities of these cations were similar for the effects on both ATPase and intermediate levels, with Tl+ greater than K+ greater than Rb+. Neither ATPase nor intermediate were stimulated by Na+, and ouabain was without effect on the reactions, thus differentiating this system from the (Na+ + K+)-ATPase. Addition of various inhibitors showed differential effects on the partial reactions of the gastric ATPase system. N-ethylmaleimide and Zn2+ showed characteristics of completely abolishing the K+-stimulated component of ATPase as well as the effects of K+ in reducing the level of intermediate, thus suggesting that these agents exert their inhibitory effect on a phosphoprotein phosphatase partial reaction. F- abolished the K+-stimulated ATPase, but its more complex effects on the intermediate suggested an additional reaction step within the domain of the phosphorylated intermediate. Results are consistent with a model system for the gastric microsomal ATPase involving a Mg2+-dependent protein kinase, a phosphorylated intermediate(s), and a K+-stimulated phosphoprotein phosphatase.
...
PMID:Studies on the phosphorylated intermediates of a K+-stimulated ATPase from rabbit gastric mucosa. 0 43

The effects of monovalent cations on calcium uptake by fragmented sarcoplasmic reticulum have been clarified. Homogenization of muscle tissue in salt-containing solutions leads to contamination of this subcellular fraction with actomyosin and mitochondrial membranes. When, in addition, inorganic cations are contributed by the microsomal suspension and in association with nucleotide triphosphate substrates there is an apparent inhibition of the calcium transport system by potassium and other cations. However, when purified preparations were obtained after homogenization in sucrose medium followed by centrifugation on a sucrose density gradient in a zonal rotor, calcium uptake and the associated adenosine triphosphatase activity were considerably activated by potassium and other univalent cations. When plotted against the log of the free calcium concentration there was only a slight increase in calcium uptake and ATPase activity in the absence of potassium ions but sigmoid-shaped curves were obtained in 100 mM K+ with half-maximal stimulation occurring at 2 muM Ca2+ for both calcium uptake and ATPase activity. The augmentation in calcium uptake was not due to an ionic strength effect as Tris cation at pH 6.6 was shown to be inactive in this respect. Other monovalent cations were effective in the order K+ greater than Na+ greater than NH4+=Rb+=Cs+ greater than Li+ with half-maximal stimulation in 11 mM K+, 16 mM Na+, 25 mM NH4+, Rb+, and Cs+ and in 50 mM Li+. There was nos synergistic action between K+ AND Na+ ions and both calcium uptak and associated ATPase were insensitive to ouabain. Thallous ions stimulate many K+-requiring enzymes and at one-tenth the concentration were nearly as effective as K+ ions in promoting calcium uptake. The ratio of Ca2+ ions transported to P1 released remained unchanged at 2 after addition of K+ ions indicating an effect on the rate of calcium uptake rather than an increased efficiency of uptake. In support of this it was found that during the stimulation of calcium uptake by Na+ ions there was a reduction in the steady state concentration of phosphorylated intermediate formed from [gamma-32P]ATP. It is considered that there is a physiological requirement for potassium ions in the relaxation process.
...
PMID:Caclium uptake and associated adenosine triphosphatase activity in fragmented sarcoplasmic reticulum. Requirement for potassium ions. 1 56

(Na+K)-activated ATPase activity from gills of yearling spring chinook was examined using a new rapid assay method. Characterization of the enzyme activity was performed. Optimal activity was obtained at pH 7.2 in the presence of 240 mM NaCl, 120 mM KCl, 20 mM MgCl2 and 10 mM Na2ATP. Maximal inhibition of the enzyme was observed in the presence of 0.5 mM ouabain. Differential centrifugation indicated that 75% of the enzymatic activity was sedimented at 1000 x g. Only 8% of the activity was found in the microsomal pellet. Treatment with 0.1% sodium deoxycholate liberated activity from the 1000 x g pellet and elevated the activity. This treatment caused a loss of 20% of the original activity of the preparation. Statistical analysis of the sampling procedure for gill (Na+K)-activated ATPase activity indicated that there was small variation in the technique itself when compared to variation between the individual gill arches and between individual fish. Results indicate that for meaningful comparisons of groups of fish, the sampling of the gill arches must be standardized and a large number of individual fish must be sampled.
...
PMID:Characterization of gill (Na + K)-activated adenosine triphosphatase from chinook salmon, Oncorhynchus tshawytscha. 1 43

A vesicular microsomal fraction isolated from hog fundic mucosa demonstrates the capacity to take up equal amounts of RB+ and Cl-. The amount of the Rb+ uptake is sensitive to the extravesicular osmolarity, and rate of uptake is sensitive to temperature. 86Rb+ efflux is dependent upon the cation composition of the diluting solution. ATP, but not beta-gamma methylene ATP, induces a reversible efflux of 86Rb+ from loaded vesicles, and this is dependent upon a functional K+-ATPase. The ATP induced efflux is not affected by CCCP (carbonyl cyanide m-chlorophenylhydrazone) or TCS (tetrachlorosalicylanilide) nor by lipid soluble ions or valinomycin. Nigericin inhibits the efflux by 40%. Uptake of the lipid soluble ion 14C-SCN- has been demonstrated and is enhanced by ATP only in the presence of valinomycin. The results are consistent with a neutral or isopotential exchange of H+ for Rb+ mediated by K+-ATPase.
...
PMID:Cation transport by gastric H+:K+ ATPase. 1 7

An ATPase is demonstrated in plasma membrane fractions of goldfish gills. This enzyme is stimulated by Cl- and HCO-3, inhibited by SCN-. Biochemical characterization shows that HCO-3 stimulation (Km = 2.5 mequiv./l) is specifically inhibited in a competitive fashion by SCN- (Ki = 0.25 mequiv./l). This residual Mg2+-dependent activity is weakly affected by SCN-. In the microsomal fraction chloride stimulation of the enzyme occurs in the presence of HCO-3 (Km for chloride = 1 mequiv/l); no stimulation is observed in the absence of HCO-3. Thiocyanate exhibits a mixed type of inhibition (Ki = 0.06 mequiv./l) towards the Cl- stimulation of the enzyme. Bicarbonate-dependent ATPase from the mitochondrial fraction is stimulated by Cl-, but this enzyme has a relatively weak affinity for this substrate (Km = 14 mequiv./l).
...
PMID:A Cl-/HCO-3-ATPase in the gills of Carassius auratus. Its inhibition by thiocyanate. 1 77

Fluorescent amines, 9-aminoacridine, acridine orange and quinacrine, were used as probes for a pH gradient (deltapH) across gastric microsomal vesicles. Analysis of probe uptake data indicates that 9-aminoacridine distributes across the membrane as a weak base in accordance with the deltapH. On the other hand, acridine orange and quinacrine show characteristics of binding to membrane sites in addition to the accumulation in response to deltapH. A discussion of the advantages and limitations of the probes is presented. Application of these probes to pig gastric microsomal vesicles indicates that that K+-stimulated ATPase is responsible for the transport of H+ into the vesicles and thus develops a deltapH across the membrane. The deltapH generated by the K+-ATPase has a definite requirement for internal K+. The proton gradient can be discharged slowly after ATP depletion or rapidly either by detergent disruption of the vesicles or by increasing their leakiness using both H+ and K+ ionophores. On the other hand, the sole use of the K+ ionophore, valinomycin, stimulates the ATP-induced formation of deltapH by increasing the availability of K+ to internal sites. This stimulation by valinomycin requires the presence of permeable anions like Cl-. Analysis of the Cl- requirement indicates that in the presence of valinomycin the net effect is the accumulation of HCl inside the gastric vesicles. With an external pH of 7.0, the ATP-generated deltapH was calculated to be from 4 to 4.5 pH units. The results are consistent with the hypothesis that the K+-stimulated ATPase drives a K+/H+ exchange across the gastric vesicles. Since other lines of evidence suggest that these gastric microsomes are derived from the tubulovesicular system of the oxyntic cell, the participation of the ATP-driven transport processes in gastric HCl secretion is of interest.
...
PMID:A study of H+ transport in gastric microsomal vesicles using fluorescent probes. 2 82

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 effects of acute and chronic administration of D-Galactosamine (GalN), Ethanol and Phenobarbital were investigated on the activities of lysosomal enzymes, i.e.; acid phosphatase, beta-glucuronidase and n-acetyl-beta-glucosaminidase, and others such as gamma-GTP and adenosine triphosphatase. The histochemical distribution of gamma-GTP in the liver was also studied on biopsy specimens from patients with chronic hepatitis, and gamma-GTP levels in the serum of patients receiving drugs inductable of hepatic microsomal enzymes. 1) After a single intraperitoneal injection of GalN, the lysosomal enzyme activities were lowered in the necrotic areas, but raised in the perinecrotic areas, the proliferative Kupffer cells and intra- and/or extra-cellular eosine bodies. 2) gamma-GTP activities in rat liver after chronic administration of GalN were markedly increased in bile canalicular membrane of periportal parenchymal cells, the epithelium of bile duct and ductules, and som inflammatory cells of portal fields. Levels of serum gamma-GTP were also elevated. On histochemical studies with biopsy specimens from patients with chronic active hepatitis showing elevated gamma-GTP activity, the activity was revealed a similar localization to GalN-treated rats. These data suggested that the increased activities might be reflected on the active stage in chronic hepatitis. 3) Chronic ethanol treatment in rats induced clearly-stained lysosomes varied in size, especially large-sized. The activities of hepatic gamma-GTP were slightly increased in the bile canalicular membrane of periportal parenchymal cells and the epithelium of proliferative bile ductules. 4) It has been shown by histochemical and biochemical techniques that hepatic gamma-GTP activity was increased after phenobarbital administration in rats. A significant rise in serum gamma-GTP was observed in patients on long-term treatment with anti-epileptic drugs. These data indicated that the increased activities of serum gamma-GTP might be accompanied with induction of hepatic microsomal drug-metabolizing enzymes.
...
PMID:[Clinical and experimental histochemical studies on the activities of liver lysosomal enzymes and gamma-glutamyl transpeptidase (gamma-GTP) (author's transl)]. 3 25

Male Sprague-Dawley rats were treated with mirex, po, at 0, 5, 10, and 50 mg/kg/day in 0.4 ml of corn oil for 3 days. Forty-eight hours after the last treatment, the biliary excretion of exogenously provided polar metabolites of 14C-imipramine was suppressed at all levels of mirex in a dose-dependent manner. Biliary excretion of phenolphthalein glucuronide was suppressed at high doses of mirex. These effects of impaired biliary excretion were accompanied by increased bile flow. Persistence of the mirex-induced biliary excretory dysfunction toward otherwise readily excretable, preformed metabolites suggests aberration of transport of these substances from the liver to bile. Whereas mitochondrial Mg++-ATPase and microsomal Na+-K+-ATPase activities were both inhibited by exposure to mirex in a dose-dependent manner, the latter activity was consistently inhibited to a higher degree. These results are suggestive of mirex-induced interference with energy production and utilization in the manifestation of hepatobiliary dysfunction.
...
PMID:Possible molecular mechanism of mirex-induced hepatobiliary dysfunction. 3 23


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

---