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)

The Ca2+-sensitive ATPase (adenosine triphosphatase) of human erythrocyte membranes is activated, not only by Ca2+ ions, but also by a series of other bivalent metal ions including Sr2+, Ba2+, Mn2+, Ni2+, Co2+, Cd2+, Cu2+, Zn2+ and Pb2+. The degree of activation is dependent on the radius of the ion rather than on its nature, in contrast with the dissociation constant of the enzyme--metal ion complex.
 ...
PMID:Activation of membrane-bound high-affinity calcium ion-sensitive adenosine triphosphatase of human erythrocytes by bivalent metal ions. 12 84

Elementary spherical particles similar to those described in the mitochondria are found in isolated rat liver and spleen nuclear membranes. The particles are characterized by electron microscopy of sections and preparations negatively stained with phosphotungstic acid or with the ATPase histochemical reaction product. The particles exhibit adenosine triphosphatase activity and have a mushroom-like shape with a sphere about 85-90 angstrom in diameter attached to inner face of the inner nuclear membrane by a stalk about 50 angstrom in length and 35 angstrom in diameter. It is supposed that these particles, just as analogous particles localized at the inner mitochondrial membrane, are involved in the coupling of oxidation and phosphorylation in the nuclear envelope.
 ...
PMID:Elementary particles in isolated rat liver and spleen nuclear membranes. 12 76

Basal and trypsin-stimulated adenosine triphosphatase activities of Escherichia coli K 12 have been characterized at pH 7.5 in the membrane-bound state and in a soluble form of the enzyme. The saturation curve for Mg2+/ATP = 1/2 was hyperbolic with the membrane-bound enzyme and sigmoidal with the soluble enzyme. Trypsin did not modify the shape of the curves. The kinetic parameters were for the membrane-bound ATPase: apparent Km = 2.5 mM, Vmax (minus trypsin) = 1.6 mumol-min-1-mg protein-1, Vmax (plus trypsin) = 2.44 mumol-min-1-mg protein-1; for the soluble ATPase: [S0.5] = 1.2 mM, Vmax (-trypsin) = 4 mumol-min-1-mg protein-1; Vmax (+ trypsin) = 6.6 mumol-min-1-mg protein-1. Hill plot analysis showed a single slope for the membrane-bound ATPase (n = 0.92) but two slopes were obtained for the soluble enzyme (n = 0.98 and 1.87). It may suggest the existence of an initial positive cooperativity at low substrate concentrations followed by a lack of cooperativity at high ATP concentrations. Excess of free ATP and Mg2+ inhibited the ATPase but excess of Mg/ATP (1/2) did not. Saturation for ATP at constant Mg2+ concentration (4 mM) showed two sites (groups) with different Kms: at low ATP the values were 0.38 and 1.4 mM for the membrane-bound and soluble enzyme; at high ATP concentrations they were 17 and 20 mM, respectively. Mg2+ saturation at constant ATP (8 mM) revealed michealian kinetics for the membrane-bound ATPase and sigmoid one for the protein in soluble state. When the ATPase was assayed in presence of trypsin we obtained higher Km values for Mg2+. These results might suggest that trypsin stimulates E. coli ATPase by acting on some site(s) involved in Mg2+ binding. Adenosine diphosphate and inorganic phosphate (Pi) act as competitive inhibitors of Escherichia coli ATPase. The Ki values for Pi were 1.6 +/- 0.1 mM for the membrane-bound ATPase and 1.3 +/- 0.1 mM for the enzyme in soluble form, the Ki values for ADP being 1.7 mM and 0.75 mM for the membrane-bound and soluble ATPase, respectively. Hill plots of the activity of the soluble enzyme in presence of ADP showed that ADP decreased the interaction coefficient at ATP concentrations below its Km value. Trypsin did not modify the mechanism of inhibition or the inhibition constants. Dicyclohexylcarbodiimide (0.4 mM) inhibited the membrane-bound enzyme by 60-70% but concentrations 100 times higher did not affect the residual activity nor the soluble ATPase. This inhibition was independent of trypsin. Sodium azide (20 muM) inhibited both states of E. coli ATPase by 50%. Concentrations 25-fold higher were required for complete inhibition. Ouabain, atebrin and oligomycin did not affect the bacterial ATPase.
 ...
PMID:Membrane bound and soluble adenosine triphosphatase of Escherichia coli K 12. Kinetic properties of the basal and trypsin-stimulated activities. 12 30

In contrast with wild-type Salmonella typhimurium LT2, strain HfrA did not have ATP-driven energy-dependent transhydrogenase activity, although ATP-dependent quenching of atebrin fluorescence was normal. Respiration-dependent and energy-independent transhydrogenase, and Ca2+-activated ATPase (adenosine triphosphatase) activities were similar in both strains. Purified ATPases from the two strains had similar specific activities, similar subunit polypeptides, and were equally effective in restoring energy-dependent transhydrogenase activities to membrane particles of strain LT2 from which the ATPase had been stripped. The purified ATPases from both strains could restore respiration-dependent but not ATP-dependent transhydrogenation to stripped particles of strain HfrA. Both strains grew aerobically equally well on salts media containing glucose, malate, succinate, citrate, acetate, pyruvate, fumarate, lactate or aspartate as substrates. Growth on glucose under anaerobic conditions was similar. Strains LT2 and HfrA were equally effective in the accumulation under both aerobic and anaerobic conditions of the amino acids proline, phenylalanine, histidine, lysine, isoleucine and aspartic acid. Inhibition of amino acid accumulation by KCN and dicyclohexylcarbodi-imide occurred to the same extent in both strains. The complete inhibition by dicyclohexylcarbodi-imide of amino acid uptake under anaerobic conditions suggested that ATP could drive amino acid uptake in both strains. The ability of strain HfrA to carry out ATP-dependent transport or quenching of atebrin fluorescence but not ATP-dependent transhydrogenation is different from the wild-type strain and from any previously described energy-coupling mutant. It is difficult to reconcile the properties of this mutant with the chemiosmotic hypothesis.
 ...
PMID:Salmonella typhimurium HfrA, a mutant in which adenosine triphosphate can drive amino acid transport but not energy-dependent nicotinamide nucleotide transhydrogenation. 12 57

The specific activity of sodium-potassium-activated adenosine triphosphatase in the mucosa of the colon rises when the dietary load of potassium is increased. The change in enzymatic activity depends on the presence of intact adrenal glands, since adrenalectomy abolishes the response of Na-K-ATPase to potassium loading. The increased secretory rate of aldosterone normally evoked by potassium loading appears to mediate at least in part of the effect of potassium loading, since aldosterone induces a discernible increase in the specific activity of Na-K-ATPase in the colon of adrenalectomized rats.
 ...
PMID:Potassium adaptation and Na-K-ATPase activity in mucosa of colon. 12 14

Lactoperoxidase-catalysed iodination was used to label intestinal epithelial cell sheets with 125I. The iodination was carried out under conditions that allowed little penetration of lactoperoxidase into the cells and membrane-bound 125I therefore provided an effective marker for following plasma-membrane fragments through subcellular-fractionation procedures. 2. After homogenization and isopycnic zonal centrifugation through sucrose gradients two peaks of membrane-bound 125I were detected. One coincided with brush border enzymes such as alkaline phosphatase, disaccharidases and L-leucine B-naphthylamidase, whereas the other was coincident with the major peak of (Na++K+)-stimulated ATPase (adenosine triphosphatase), which has been thought to be concentrated in the basolateral plasma membranes of these cells. Neither peak of 125I reflected the distribution of any marker for an intracellular organelle. 3. A larger proportion of the (Na++K+)-stimulated ATPase, and thus of the basolateral plasma-membrane material, was found in a crude 'mitochondrial' fraction. It was not readiily separated from mitochondria by conventional techniques of subcellular fractionation. 4. Treatment of the 'mitochondrial' fraction with digitonin increased the density of basolateral plasma membrane but had little effect on mitochondrial density. A purified preparation of digitonin-loaded basolateral plasma membranes was isolated at a density of 1.20-1.22 by isopycnic centrifugation. 5. The enzymic composition of this preparation of basolateral plasma membranes is compared with previous preparations isolated from intestinal mucosal 'scrape' materials and from isolated cells.
 ...
PMID:Basolateral plasma membranes of intestinal epithelial cells. Identification by lactoperoxidase-catalysed iodination and isolation after density perturbation with digitonin. 12 58

Mesonephroi of sheep embryos ranging from 12 to 100 mm C.R. length were examined for the occurrence and localization of transport-ATPase. Native cryostat sections were incubated according to the technique of Guth and Albers for demonstrating the nitrophenylphosphatase activity of Mg2+-Na+-K+-adenosine triphosphatase. The basal cytoplasm of the collecting tubule of the narrow segment of the distal tubule exhibit strong activity, the wide segment of the distal tubule is moderately active. Glomeruli, proximal tubule, and Wolffian duct remain unstained. The basal labyrinths of the reactive nephron segments are believed to be the sites of a Na+-K+ exchange pump. In mature and regressing mesonephroi, the findings fully agree with biochemical data; in maturating mesonephroi, whose basal labyrinth is not yet fully established, the biochemical assay proves to be more sensitive. The specifity of the reaction was ascertained by diverse inhibitors and activating ions. The localization of Mg2+-ATPase is different to the above mentioned reaction pattern, as it shows moderate activity in the proximal tubule, too (mature mesonephros). Mesonephroi of very young embryos exhibit strongest Mg2+-ATPase activity in the proximal tubule; here the distal and collecting tubule stain only moderately.
 ...
PMID:Histochemical localization of Mg2+-Na+-K+-adenosine triphosphatase in different stages of the sheep mesonephros. 12 45

Using myosin, heavy meromyosin, and subfragment-1 the steady state rate of Mg-modified adenosine triphosphatase (Mg-ATPase) was determined over a range of substrate concentrations between 10(-8) M and 5 X 10(-3)M, at 0.5 M and 0.05 M KC1 (pH 7.4 at 20 degrees C). At the substrate concentrations below 10(-5) M, myosin Mg-ATPase was observed to show that two active sites interact, as suggested by the analysis of transient kinetic studies (Walz, F. G., Jr.: J. Theor. Biol. 41, 357-373 (1973)). The increase in the activity at Mg-ATP concentrations higher than 10(-4) M corresponds to the binding of Mg-ATP to myosin sites not responsible for the catalytic action. With heavy meromyosin and subfragment-1, the activity was best expressed by the Michaelis equation. With heavy meromyonsin, the activation at high ATP concentrations is detectable, though not as pronounced as with myosin, but not with subfragment-1.
 ...
PMID:The effects of substrate concentration on the Mg-adenosine triphosphatase activity of myosin. 13 Jan 98

Temporal patterns of biosynthesis of the Ca2+ + Mg2+-dependent adenosine triphosphatase of sarcomplasmic reticulum were obtained from studies with primary cultures of rat skeletal muscle cells. Rates of synthesis at various stages of differentiation were estimated from the incorporation of tritium-labeled leucine into the ATPase. Cells were solubilized with detergent, and newly synthesized ATPase was isolated from cells by antibody precipitation in the presence of carrier ATPase. Radioactivity incorporated into the ATPase was determined after gel electrophoresis of the precipitates and counting of gel slices containing the ATPase band. In Dulbecco's modified Eagle's medium containing 10% horse serum and 0.5% chick embryo extract, mononucleated myoblast cells began to form multinucleated myotubes after about 50 hours in culture. Prior to fusion little ATPase synthesis was detectable; during fusion the ATPase was synthesized at an accelerating rate for a period of about 30 hours. The rate of synthesis levelled off after about 90 hours coincident with termination of fusion. In Dulbecco's modified Eagle's medium containing 20% fetal calf serum and 8% embryo extract, the onset of fusion was delayed for 30 to 40 hours. In this medium biosynthesis of the ATPase was also delayed so that biosynthesis of the ATPase appeared to be correlated with fusion of muscle cells. Cells cultured in Culbecco's modified Eagle's medium containgin 10% horse serum, but only 60 muM Ca2+, proliferated but did not fuse. Under these conditions, synthesis of the ATPase was measurable at 50 to 60 hours, and the rate of synthesis accelerated until 120 hours when it declined. Under all conditions degradation of the ATPase occurred with a half-life of 20 hours whereas the half-life of total protein degradation was 40 hours. Synthesis of the sarcoplasmic reticulum ATPase, like that of a number of other muscle-specific proteins, is greatly accelerated as myoblasts fuse and differentiate into myotubes. Fusion is not essential for this phenomenon, however, although it is normally concomitant with it.
 ...
PMID:Assembly of the sarcoplasmic reticulum. Biosynthesis of the adenosine triphosphatase in rat skeletal muscle cell culture. 13 98

Mg-dependent and (Na+ + K+)-stimulated adenosine triphosphatase (ATP-ase) activities were assayed in butanol extracts of duodenal tissue from germ-free, specific-pathogen-free, and ex-germfree mice associated with an indigenous microflora from specific-pathogen-free mice. In the germfree mice the levels of both ATPase activities were significantly higher than the levels in specific-pathogen-free mice. By contrast, the ex-germfree animals colonized by an entire indigenous microflora, the values fell to levels close to those for specific-pathogen-free animals. (Na+ + K+)-stimulated ATPase was not inhibited by ouabain in extracts from any of the three kinds of mice. These findings show that the indigenous microbial flora influences the intestinal ATPase activity of mice and, because of the connection between (Na+ + K+-stimulate ATPase and active transpoort, undoubtedly affects the process of absorption in the intestinal tract.
 ...
PMID:Influence of the indigenous gastrointestinal microbial flora on duodenal Mg2+ -dependent and (Na+ + K+) -stimulated adenosine triphosphatase activities in mice. 13 8


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