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)

A microsomal fraction rich in Na+, K+-ATPase (sodium-plus-potassium ion-dependent adenosine triphosphatase) and the corresponding K+-dependent p-nitrophenyl phosphatase from the rectal salt gland of the spiny dogfish was solubilized by treatment with deoxycholate at high ionic strength. On gel filtration through Sepharose 6B, the ATPase apoenzyme could be separated, in apparently soluble form, from the tissue-fraction phospholipids and was almost free of enzymic activity (2% of the p-nitrophenyl phosphatase activity and 0.2% of the ATPase activity being recovered). On mixing the apoenzyme with an activator consisting of cooked ox brain, a large proportion of the original enzymic activity was obtained. Specific activities of the re-activated enzyme were somewhat higher than in the material before gel filtration: values of 1300-1450 mumol and 250-290 mumol/h per mg of protein were obtained for the hydrolysis of ATP and of p-nitrophenyl phosphate respectively. The activity was inhibitible by ouabain.
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PMID:The reversible delipidation of a solubilized sodium-plus-potassium ion-dependent adenosine triphosphatase from the salt gland of the spiny dogfish. 17 57

Adenosine triphosphatase (ATPase) activity in erythrocyte membranes from patients with Duchenne dystrophy was inhibited by ouabain less than in normal individuals in assay systems containing high or low contents of salt. Epinephrine and cyclic adenosine monophosphate increased total ATPase activity in all samples, and epinephrine restored ouabain sensitivity to the Duchenne membranes. Basal adenyl cyclase activity in about twice that of controls. Epinephrine stimulated adenyl cyclase activity of normal membranes two to three times, but did not stimulate the enzyme in Duchenne membranes. These differences may reflect a genetic abnormality of the membrane.
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PMID:Biochemical abnormalities of erythrocyte membranes in Duchenne dystrophy. Adenosine triphosphatase and adenyl cyclase. 18 Sep 37

Membrane vesicles isolated from untransformed Balb/c and Swiss mouse fibroblasts and from those transformed by simian virus 40 catalyzed carrier-mediated uptake of L-alpha-aminoisobutyric acid. Concentrative uptake required the presence of a Na+ gradient (external Na+ greater than internal Na+) and occurred independently of endogenous (Na+ + K+) ATPase activity. This process is electrogenic, since uptake was stimulated by a K+ diffusion gradient (internal greater external) in the presence of valinomycin or by the addition of the Na+ salt of a permeant ion, conditions expected to create an interior-negative membrane potential. Both the initial rate of concentrative uptake of L-alpha-aminoisobutyric acid and its maximal accumulation, driven by a standard Na+ gradient, were decreased in vesicles from density-inhibited, untransformed cells and increased in those from cells transformed by simian virus 40 compared with vesicles from proliferating untransformed cells. An increased maximal velocity (Vmax) of uptake stimulated by Na+ gradient was observed in vesicles from transformed cells compared with those from untransformed cells, suggesting an increase in the number of carriers or in their mobility. Since the relative extent of accumulation of this model amino acid driven by a standard Na+ gradient also differed with growth or transformed status, an additional possibility for cellular regulation of this process could be alteration of membrane Na+ permeability or carrier response to Na+.
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PMID:Regulation of active alpha-aminoisobutyric acid transport expressed in membrane vesicles from mouse fibroblasts. 18 3

Membrane vesicles isolated from untransformed Balb/c and Swiss mouse fibroblasts and their SV 40-transformed derivatives were shown to catalyze carrier-mediated, intravesicular uptake of alpha-aminoisobutyric acid and D-glucose. Concentrative uptake of alpha-aminoisobutyric acid required the presence of a Na+-gradient (external greater than internal) and could occur independently of endogenous (Na+ + K+)ATPase activity. A K+ diffusion gradient (internal greater than external) in the presence of valinomycin, or the addition of the Na+ salt of a highly permeant anion, conditions expected to create an interior-negative membrane potential stimulated Na+-gradient-dependent uptake, suggesting this process is electrogenic. D-Glucose uptake was nonconcentrative and did not require ion gradients or metabolic conversion. Na+ gradient-dependent transport of alpha-aminoisobutyric acid was reduced both in initial rate and extent of uptake in vesicles from confluent untransformed cells and increased in those from SV 40-transformed cells, compared with activities observed in vesicles from proliferating untransformed cells. No changes in D-glucose carrier activity were observed when assayed at low glucose concentrations.
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PMID:Regulation of amino acid and glucose transport activity expressed in isolated membranes from untransformed and SV 40-transformed mouse fibroblasts. 18 48

Phosphodiesterase activator protein and troponin-C have been purified from rat testis and rabbit skeletal muscle, respectively. The two proteins appear to be structurally distinct since the activator protein migrates faster than troponin-C on sodium dodecyl sulfate-polyacrylamide gels. Each of the calcium-binding proteins will, however, substitute for the other in their respective biological systems. Testis activator protein forms a complex with rabbit muscle troponin subunits TnI and TnT soluble in low salt. This hybrid complex (AIT) can regulate rabbit skeletal muscle actomyosin ATPase activity. AIT regulation, although influenced by free Aa2+ levels, is distinct from that of native troponin. Likewise, muscle troponin-C can substitute for activator protein in the stimulation of cyclic nucleotide phosphodiesterase. Troponin-C will fully stimulate phosphodiesterase although its affinity is 600-fold lower than that of activator protein. Ca2+ regulation studies demonstrate that both proteins require micormolar levels of free Ca2+ to induce phosphodiesterase activation. Activator protein requires 1.2 x 10(6) M and troponin-C, 1.9 X 10(6) M free Ca2+ for half-maximal stimulation of phosphodiesterase. The biological cross-reactivity of these proteins supports the sequence homology recently reported by Watterson et al. (Watterson, D.M., Harrelson, W.G., Keller, P.M., Sharief, F., and Vanaman, T.C. (1976) J.Biol. Chem. 251, 4501-4513). In addition, this preliminary study suggests that this nonmuscle troponin-C-like protein potentially may function in other Ca2+-regulated cellular events in addition to its moculation of cyclic nucleotide levels.
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PMID:Biological cross-reactivity of rat testis phosphodiesterase activator protein and rabbit skeletal muscle troponin-C. 19 60

Since phenobarbital administration produces a profound increase in bile flow without changing bile acid secretion, we examined whether this drug increases the activity of hepatic sodium-potassium-activated ATPase [Na+-K+)-ATPase], the postulated regulating enzyme in the secretion of bile salt independent bile flow. After freeze-thawing to increase substrate accessibility, (Na+-K+) ATPase activity was determined by ouabain inhibition of total ATPase activity. Its activity was highest in isolated liver surface membrane fractions enriched in bile canalicult. Phenobarbital administration significatly increased (Na+-K+)-ATPase activity in both liver surface membrane fractions as well as liver homogenates. This enhanced activity is apparently selective for other membrane phosphatases and the enzyme activity in other tissues is either unaltered or decreased. Kinetic analysis of (Ka+-K+)-ATPase indicates that phenobarbital treatment increased maximum velocity and half-maximum activation constant was unchanged, consistent with activation of latent molecules or an increased number of enzyme molecules. The latter process seems more likely because cycloheximide prevented phenobarbital induction and activators were not demonstrated in vitro. Examination of the full time course of phenobarbital induction to determine whether phenobarbital increased synthesis or decreased degradation was consistent with increased synthesis since the apparent degradation rates were similar with or without phenobarbital treatment. The apparent half-life for (Na+-K+)-ATPase was estimated to be approximately 2.5 days, consistent with liver surface membrane protein turnover. The correlation of changes in bile flow with (Na+-K+)-ATPase was examined under several experimental situations. Phenobarbital caused a parallel increase in each during the 1st 2 days of greatment: thereafter other factors become rate limiting for flow, since enzyme activity doesn't reach a new steady state until 4-days. Consistent with increased sodium-potassium exchange, bile sodium was unchanged while potasium concentrations were significantly reduced. Changes in both bile flow and (Na+-K+)-ATPase induced by phenobarbital are independent of thyroid hormone. These studies support the postulate that (Na+-K+)-ATPase is an important factor in regulation of bile flow. In addition, phenobarbital enhancement of both bile flow and (Na+-K+)-ATPase is dependent upon de novo protein synthesis.
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PMID:Stimulation of hepatic sodium and potassium-activated adenosine triphosphatase activity by phenobarbital. Its possible role in regulation of bile flow. 19 64

Plasma membranes from heart (sarcolemma) were prepared by the method of Kidwai, A.M. (1975) Methods in Enzymology (Fleischer, S. and Packer, L., eds.), Vol XXXIA, pp. 134--144, Academic Press, New York). On many occasions the sarcolemmal fraction identified by the enzyme markers such as (Na+ + K+)-ATPase banded at heavier densities (d greater than 1.25 g/ml) than expected for plasma membrane (d less than 1.15 g/ml). Radio-iodination of the membrane was added as an independent marker and conditions for the reproducible preparation of the sarcolemma were studied. Cultured heart cells were enzymatically iodinated under conditions which did not affect viability and labeled primarily the sarcolemma. The distribution of radioactivity in homogenates of cultured cells on the density gradient corresponded to that of the enzymes' activity. The best sarcolemma preparation was obtained with 0.3 M KCl extraction of heart homogenates in the presence of 0.05 M pyrophosphate, especially if the salt was also present during the fractionation by density gradient centrifugation. Alterations in the density were also observed with erythrocytes and cultured liver cells' plasma membrane. The data suggests a meta-stable state of the plasma membranes due to handling or storage which could cause alterations of some of their physical properties (e.g. density).
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PMID:Plasma membranes from cardiac cells in culture. Enzymatic radio-iodination, evaluation of preparation and properties of the sarcolema. 19 65

We have screened the bloodstream form of Trypanosoma brucei for the presence of enzymes that could serve as markers for the microbodies and the highly repressed mitochondrion of this organism. None of seven known microbody enzymes were detected at all, but glycerol-3-phosphate oxidase, ATPase, isocitrate dehydrogenase, acid phosphatase and part of the hyperoxide dismutase and malate dehydrogenase activities were found to be particle-bound after fractionation of homogenates by differential centrifugation. Part of the ATPase activity was sensitive to oligomycin, an inhibitor of oxidative phosphorylation. This oligomycin-sensitive activity can serve as a specific marker for the mitochondria. More than 80% of the NAD+-linked glycerol-3-phosphate dehydrogenase in T. brucei was found to be particulate and latent. The enzyme could be activated by Triton X-100, by the combined action of sonication and salt, but not by salt alone, and partially by freezing and thawing. We conclude that the NAD+-linked glycerol-3-phosphate dehydrogenase is located inside an organelle.
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PMID:Particle-bound enzymes in the bloodstream form of Trypanosoma brucei. 19 9

1. Both valinomycin and p-trifluoromethoxy carbonyl cyanide phenylhydrazone (FCCP) are required for full release of respiration by cytochrome c oxidase-containing proteoliposomes (prepared by sonicating beef heart cytochrome aa3 in salt solution with 4 parts phosphatidylcholine, 4 parts phosphatidylethanolamine and 2 parts cardiolipin) in the presence of external ascorbate and cytochrome c. In the absence of valinomycin the response to FCCP is rather sluggish, as reported by Wrigglesworth et al. (1976) (Abstracts, 10th Int. Congr. Biochem., No. 06-6-230). 2. The Km for cytochrome c in 67 mM, pH 7.4, phosphate buffer with ascorbate as substrate, was 9 micrometer in both absence and presence of valinomycin and FCCP. Energization thus acts non-competitively towards cytochrome c oxidation. 3. The apparent Km for oxygen is greater in the energized than in the deenergized state; double reciprocal plots of respiration rate versus oxygen concentration are concave downward in the absence of uncouplers, as found with intact mitochondria. Energization thus acts "competitively" towards oxygen. 4. Despite the lack of a functional ATPase system, all the kinetic features of energization found in intact mitochondria can be mimicked in the reconstituted liposomes. This supports the chemiosmotic idea that electrical and perhaps H+ gradients modify the oxidase activity in reconstituted vesicles.
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PMID:Control of respiration in proteoliposomes containing cytochrome aa3. I. Stimulation by valinomycin and uncoupler. 20 20

The effects of two lectins, wheat germ agglutinin and concanavalin A, were studied on a variety of parameters of two highly purified (Na+ + K+)-ATPases (ATP phosphohydrolase, EC 3.6.1.3), from the rectal salt gland of Squalus acanthias and from the electroplax of Electrophorus electricus. Both lectins agglutinated the rectal gland enzyme equally, but wheat germ agglutinin inhibited (Na+ + K+)-ATPase activity much more. The electroplax enzyme was only marginally agglutinated and inhibited by the lectins. Neuraminidase treatment of the rectal gland (Na+ + K+)-ATPase had no effect on germ agglutinin inhibition. The inhibition of the rectal gland (Na+ + K+)-ATPase by wheat germ agglutinin could be reversed by N,N'-diacetylchitobiose, which has a high affinity for wheat germ agglutinin. Neither ouabain inhibition nor ouabain binding to the rectal gland enzyme was affected by wheat germ agglutinin. The p-nitrophenylphosphatase activity of the rectal gland enzyme was not inhibited by wheat germ agglutinin. Na+-ATPase activity, which reflects ATP binding and phosphorylation at the substrate site was inhibited by wheat germ agglutinin and this inhibition was reversed by potassium. Evidence is cited (Pennington, J. and Hokin, L.E., in preparation) that the inhibition of the (Na+ + K+)-ATPase by wheat germ agglutinin is due to binding to the glycoprotein subunit.
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PMID:Effects of wheat germ agglutinin and concanavalin A on parameters of highly purified sodium-potassium adenosine triphosphatases from Squalus acanthias and Electrophorus electricus. 21 Aug 20


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