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

The possibility that augmentation of cardiac Na+-K+-dependent adenosine triphosphatase (Na-K-ATPase) by L-3,5,3'-triiodothyronine (T3) was mediated by early changes in intracellular ion concentrations ([Na+]1, [K+]1) was explored by time-course analysis after a single injection of T3 in thyroid-ablated (131I) rats. At 6 and 16 h after injection, T3 had no significant effect on cardiac [Na+]1, [K+]1, or microsomal Na-K-ATPase activity. At 24 and 48 h, however, T3 elicited proportionate increases in [K+]1 and Na-K-ATPase activity. Thus, no evidence was adduced that the T3-dependent increase in ventricular Na-K-ATPase activity is an adaptive response to prior changes in intracellular ion concentrations. The increase in [K+]1 is attributable to an increase in Na+ pump activity. Administration of T3 to hypothyroid rats had no effect on the transition temperature or the activation energy of ventricular microsomal Na-K-ATPase, as analyzed by an Arrhenius plot. Thus, the lipid microenvironment and the properties of the enzyme may be independent of thyroid status. The latter inference was supported by kinetic analysis, in that T3 had no effect on the Km for ATP or the K1/2's for Na+ and K+. Injection of T3 of the hypothyroid rat, however, significantly increased the Vmax's for ATP, Na+, and K+ of ventricular microsomal Na-K-ATPase. These results are in accord with the inference of thyroidal induction of Na-K-ATPase indistinguishable from those present in the athyroid state.
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PMID:Characteristics of thyroid-stimulated Na+-K+-ATPase of rat heart. 14 Jun 7

1. The influence of various Na+ concentrations on [3H]-ouabain binding was studied in experiments on a microsomal Na+-K+-adenosine triphosphatase (ATPase) from guinea-pig hearts. 2. The ATP-independent cardiac glycoside binding was not influenced by increasing Na+ concentrations. However, a good correlation was found between the ATP-dependent [3H]-ouabain binding and Na+ concentration. 3. A more detailed analysis of these results according to Hofstee (1952) revealed two distinct processes involved in this interaction: one ouabain binding process was activated at rather low Na+ concentrations, (K0.5 = 4.5 mM); this type of [3H]-ouabain binding was strongly correlated to the Na+ concentration necessary for half maximum phosphorylation (K0.5 = 1 mM). The other ouabain binding process was predominant at high Na+ concentrations (K0.5 = 69 mM). 4. On the basis of the commonly accepted ATPase reaction cycle a model for the interaction of cardiac glycosides with the Na+-K+-ATPase is proposed, assuming two different binding sites for cardiac glycosides (E2-P and E1-P) and involving a translocation of these drugs from an outer to an inner compartment of the cell membrane.
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PMID:Evidence for two different Na+-dependent [3H]-ouabain binding sites of a Na+-K+-ATPase of guinea-pig hearts. 14 57

Adult mallard ducks were fed a diet containing 50 ppm DDT for 6 months. Eggs laid during this period were collected and eggshell weight, thickness, and calcium were determined. Chronic ingestion of DDT resulted in production of eggshells that were significantly thinner and lighter than those of controls. Total calcium of thinned eggshells was also reduced; however, calcium per gram of eggshell was not altered, indicating that other eggshell constituents were not incorporated as well. Calcium adenosine triphosphatase activity in the microsomal fraction of eggshell gland epithelium was assayed in control and DDT-fed ducks. Enzyme activity in DDT-fed ducks was reduced to 65% of control values. Since Ca-ATPase has been shown to be associated with calcium transport, enzyme inhibition may be responsible for decreased eggshell weight and thickness. Electron microscopic evaluation of microsomal fractions showed elements of the plasma membrane, including cilia and microvilli, as well as rough and smooth endoplasmic reticulum. Inhibition of calcium transport at the plasma membrane of mucosal epithelium is proposed as a possible mechanism of DDT-induced eggshell thinning.
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PMID:Effects of DDT on eggshell quality and calcium adenosine triphosphatase. 14 96

Dietary polyethylene glycol (PEG) induces an increase in the specific activity of Na+-K+-activated adenosine triphosphatase (Na-K-ATPase) in the cecum mucosa of rats. Using cecum mucosa homogenates and cellular subfractions obtained by differential centrifugation, the induction process was studied with respect to time course, subcellular distribution and properties of the enzyme. In comparison with controls, Na-K-ATPase specific activity was stimulated in PEG treated rats in the total homogenate and the microsomal (105000 X g) but not in the mitochondrial (9000 X g) or nuclear (1000 X g) sediment. The specific activity of Mg-ATPase did not change in any of the fractions. Na-K-ATPase induction was statistically significant after 2 days and complete after 1-2 weeks, in parallel with the previously described stimulation in net sodium absorption. Kinetic analysis showed Vmax for ATP to be doubled while Km for ATP, Na and K as well as the optimal Mg/ATP ratio and Ki for ouabain remained unchanged. It is proposed that Na-K-ATPase and active sodium transport are closely associated in rat cecum and that dietary Na-K-ATPase stimulation is due to the induction of more enzyme molecules per unit basolateral cell membrane.
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PMID:Induction of Na-K-ATPase in plasma membranes to rat cecum mucosa by diet: time course and kinetics. 14 84

The composition and function of fragmented sarcoplasmic reticulum from pig skeletal muscle was examined in the period immediately post mortem. Muscle was defined as being either slowly glycolysing or rapidly glycolysing on the basis of colour, pH and concentrations of glycogen and lactate. The microsomal fraction was separated on a discontinuous gradient of 35, 40 and 45% (w/v) sucrose into heavy and intermediate fractions which sedimented to the interfaces, and a light fraction which remained on the surface of the 35%-sucrose layer. The sarcoplasmic reticulum from rapidly glycolysing muscle had a lower buoyant density than had that from slowly glycolysing muscle. This was reflected in the consistent lack of material in the heavy fraction and a greater proportion in the light fraction. The latter material had significantly lower ratios (w/w) of protein to phospholipid (2.3:1 versus 3.8:1) and of protein to cholesterol (10.4:1 versus 15.6:1). There were no gross differences in phospholipid content or in fatty acid composition of individual phospholipid classes in the membranes from the two types of muscle. Analysis of membrane proteins by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis showed that ATPase (adenosine triphosphatase) was a major component of each fraction and that its contribution to the total protein content of the membrane was greater in rapidly glycolysing muscle, suggesting a loss of non-ATPase proteins. The two fractions of sarcoplasmic reticulum prepared from rapidly glycolysing muscle had approximately one-third the normal activities of Ca(2+) binding and Ca(2+) uptake in the presence of ATP and one-half the passive Ca(2+)-binding capacity in the absence of ATP of the fractions from slowly glycolysing muscle. However, the (Ca(2+)+Mg(2+))-stimulated ATPase activities were similar. Efflux from actively loaded vesicles, after the addition of EDTA, consisted of a rapid and a slow phase. Vesicles from rapidly glycolysing muscle lost 60% of associated Ca(2+) (approx. 0.10mumol of Ca(2+)/mg of protein) during the rapid phase, compared with 30% (approx. 0.17mumol of Ca(2+)/mg of protein) in those from slowly glycolysing muscle. The efflux rate during the slower phase was comparable in both types of vesicles. Analysis of the temperature-dependence of (Ca(2+)+Mg(2+))-stimulated ATPase activity revealed that a high-activation-energy process operating in the temperature range 31-45 degrees C in the intermediate and light fractions from slowly glycolysing muscle was not apparent in vesicles from rapidly glycolysing muscle. Conditions that result in the prolonged activation of glycogenolysis in pig muscle post mortem primarily affect the protein components of the sarcoplasmic-reticular membrane, giving rise to a loss of loosely associated proteins. The function of the membranes observed under these conditions does not appear to be due to enhanced permeability of the membrane to Ca(2+) and may be the result of a defect in the transport of Ca(2+) into the vesicles.
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PMID:Characteristics of sarcoplasmic reticulum from slowly glycolysing and from rapidly glycolysing pig skeletal muscle post mortem. 14 57

A microsomal fraction from canine brain gray matter has been extracted with the detergent sodium dodecyl sulfate to partially purify the membrane-bound (Na+ + K+)-stimulated adenosine triphosphatase. Phospholipid, glycolipid, and a family of other glycoproteins are also enriched by the procedure; it is proposed that the product is an intrinsic membrane protein fraction. 6--8-fold purification of (Na+ + K+)-ATPase is obtained without solubilizing the enzyme and without irreversibly altering its turnover number. Final specific activities are 350--400 mumol of ATP hydrolyzed/h per mg protein. The stimulation and reversible inactivation of the (Na+ + K+)-ATPase by dodecyl sulfate were examined for information relevant to the mechanism of action of the detergent.
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PMID:Purification from brain of an intrinsic membrane protein fraction enriched in (Na+ + K+)-ATPase. 14 8

1 The specific [3H]-ouabain binding to microsomal fractions derived from cat heart, liver, spleen, and kidney increased significantly following chronic administration of ethanol. 2 Since ouabain binds exclusively to cell membrane (Na+ + K+)-adenosine triphosphatase ((Na+ + K+)-ATPase), these results provide evidence for an increase in number of (Na+ + K+)-ATPase macromolecules during chronic alcoholism. 3 The importance of the increase in number of (Na+ + K+)-ATPase molecules in the adaptive increase in ethanol metabolism and cardiac myopathy in chronic alcoholism is discussed.
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PMID:[3H]-Ouabain binding to peripheral organs of cats: effect of ethanol. 14 33

The subcellular distribution of calcium-stimulated adenosine triphosphatase in the albino rabbit dental pulp was studied. The purity of the microsomal fraction was examined by measuring the marker enzymes and by electron microscopic observation. Some properties of calcium-stimulated adenosine triphosphatase were investigated.
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PMID:Studies on calcium-stimulated adenosine triphosphatase in the albino rabbit dental pulp. Its subcellular distribution and properties. 15 Apr 33

The effect of lipid peroxidation on the Ca2+-accumulating and Ca2+-retaining abilities of the microsomal fraction from chicken breast muscle was investigated. At 25 degrees C, enzymic lipid peroxidation did not seriously affect either of these abilities unless ascorbic acid was present, when both were diminished. At 37 degrees C, Ca2+-concentrating ability was decreased further by the effects of heat damage to the membrane. Membrane lipid peroxidation did not affect microsomal adenosine triphosphatase activity unless the microsomal fraction was subsequently washed with albumin. This effect of albumin is possibly due to removal of lipid-breakdown products. Addition of soya-bean phospholipids to the peroxidized vesicles washed with albumin restored adenosine triphosphatase activity, demonstrating a non-specific phospholipid requirement.
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PMID:The effect of lipid peroxidation on the calcium-accumulating ability of the microsomal fraction isolated from chicken breast muscle. 15 35

Microsomal fraction was prepared by ultracentrifugation of homogenates of cortical tissue from bovine brains. The preparation displayed ATPase (adenosine triphosphatase) activity in the presence of Mg(2+) (6.4mumol of P(i)/h per mg of protein) and Ca(2+) (3.4mumol of P(i)/h per mg of protein). Kinetic analysis of the activation of the enzyme preparation by Ca(2+) resulted in the demonstration of two apparent K(m) values for Ca(2+) (6.0x10(-8)m and 1.2x10(-6)m). Treatment of the microsomal membranes with Triton X-100 resulted in solubilization of the ATPase, though with some loss of activity. The solubilized microsomal proteins were incorporated into liposomes. By incubation of the liposomes in media containing (45)Ca(2+) an ATP-dependent uptake of Ca(2+) was demonstrated. The solubilized preparation was subjected to preparative isoelectric focusing in granulated gel beds. Two distinct peaks of Mg(2+)- and Ca(2+)-dependent ATPase activity were observed at pH4.8 (peak 4.8) and at pH6.3 (peak 6.3). The material isolated in peaks 4.8 and 6.3 was focused in polyacrylamide gel with pH gradients. The material corresponding to peak 4.8 consisted of a single protein, whereas peak 6.3 contained one major and at least one minor protein. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis confirmed these results and indicated that the major component of peak 4.8 and the protein of peak 6.3 both had a molecular weight of 105000. The material in peaks 4.8 and 6.3 was assayed for ATPase activity in the presence of various concentrations of Ca(2+). Kinetic analysis of the results for peak 4.8 demonstrated an apparent K(m) value for Ca(2+) of 4.1x10(-8)m. The enzyme isolated at pH6.3 had an apparent K(m) value of 3.8x10(-6)m. However, when the material from peak 4.8 was incubated in the presence of 1mm-Mg(2+) the ATPase could not be activated by Ca(2+).
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PMID:Isolation and partial characterization of magnesium ion- and calcium ion-dependent adenosine triphosphatase activity from bovine brain microsomal fraction. 15 42


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