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

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Query: EC:3.6.3.1 (Mg2+-ATPase)
1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Normal adult albino and Sprague-Dawley rats, under intraperitoneal Nembutal anesthesia, were used to demonstrate enzymatic activity in the choroid plexus and ventricular ependyma. The brain tissues were perfused or immersed with cold 2% glutaraldehyde and 8% sucrose in 0.1 M cacodylate buffer (pH 7.2-7.4) for 30 min and washed overnight in the same buffer solution., The choroid plexus (lateral and fourth ventricles) and ventricular ependyma (lateral ventricle) were trimmed from the fixed and washed brain tissues, which were frozen and sectioned. For histo- and cyto-chemical study, the sections were immersed in the following incubation media; for Na+, K+-ATPase (ouabain-sensitive, K+-dependent, p-nitrophenylphosphatase: p-NPPase) according to the one-step method of Mayahara et al. (1978): for Mg2+- ATPase, Wachstein-Meisel's incubation medium (1957); for adenylate cyclase (AC), following Araki and Saito's lead citrate method (1979). The cytochemical findings gave the following results. In the choroid plexus, the ouabain-sensitive electron-dense reaction products of NA+, K+-ATPase (p-NPPase) were strongly positive in the microvilli and along the inner surface of microvilli, without showing any Mg2+-ATPase and AC activities, and all three enzymatic activities were positive along the basal plasmalemmas and negative along the lateral and apical (not including microvilli) plasmalemmas. In the ventricular ependyma, Na+,K+-ATPase (P-NPPase) activity was not found, and the reaction product of AC was observed on the apical plasmalemmas and those of Mg2+-ATPase along the basal plasmalemmas. These cytochemical findings are helpful in understanding the regulation of cerebrospinal fluid production through Na+, K+-ATPase (p-NPPase) and cyclic AMP (AC).
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PMID:Cytochemical study on enzyme activity associated with cerebrospinal fluid secretion in the choroid plexus and ventricular ependyma. 611 20

The blood platelet has three morphologically distinct membrane systems. In addition to the plasma membrane the platelet has an 'open canalicular system' (surface-connected intracytoplasmic membrane system) and a microsome-like 'dense tubular system'. The open canalicular and dense tubular systems have been implicated in Ca2+ transport, cyclic nucleotide (cAMP) synthesis and prostaglandin and thromboxane synthesis. Precise definition of the function of the different membrane systems requires analysis of their unique chemical activities. Broken cell preparations are used to advantage for such studies. However, clean separation and definition of the origin and composition of the membrane fractions has been difficult because well-defined marker enzymes for the various membrane systems have not been conclusively established. Platelets were fixed for 5 min in 1% paraformaldehyde-0.2% glutaraldehyde and assayed for K+-dependent p-nitrophenyl phosphatase, Ca2+-, Mg2+-ATPase and adenylate cyclase K+-dependent p-nitrophenyl phosphatase was localized only at the plasma membrane while Ca2+-, Mg2+-ATPase and adenylate cyclase were found relatively segregated to the open canalicular and dense tubular systems. The segregation of these enzymes to separate membrane compartments may have significant implications with regard to understanding platelet function.
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PMID:Cytochemical evidence for the segregation of adenylate cyclase, Ca2+-, Mg2+-ATPase, K+-dependent p-nitrophenyl phosphatase in separate membrane compartments in human platelets. 611 48

K+-dependent, ouabain-sensitive nitrophenyl phosphatase (K+-NPPase) activity, which reflects the terminal dephosphorylation step of (Na+ + K+)-ATPase action, was studied histochemically in human thyroid normal follicular cells and in human thyroid carcinoma cells, using a newly developed one-step lead citrate method. In normal thyroid follicular cells, reaction product for K+-NPPase activity was found on the lateral plasma membrane and not on either the apical or basal plasma membrane. In thyroid carcinoma cells, a large amount of reaction product was observed on the lateral plasma membrane and also on the apical and basal plasma membrane. Appropriate control experiments indicated that the deposition of reaction product was K+ dependent and ouabain sensitive. Although there was some overlap in the distribution of reaction products for K+-NPPase and Mg2+-ATPase, significant differences were consistently observed. The biochemical findings indicated that the K+-NPPase activity per milligram of DNA in thyroid carcinoma cells was approximately 10 times higher than that in normal thyroid cells, and that a significant positive correlation exists between K+-NPPase and (Na+ + K+)-ATPase activity. The physiologic and pathologic implications of this localization for tracing the route of active Na+ transport, which might participate in the transport of iodide ion in both human thyroid normal follicular cells and human thyroid carcinoma cells, are discussed.
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PMID:Changes in localization of ouabain-sensitive, potassium-dependent p-nitrophenylphosphatase activity in human thyroid carcinoma cells. 613 23

(H+ + K+)-ATPase-enriched membranes were prepared from hog gastric mucosa by sucrose gradient centrifugation. These membranes contained Mg2+-ATPase and p-nitrophenylphosphatase activities (68 +/- 9 mumol Pi and 2.9 +/- 0.6 mumol p-nitrophenol/mg protein per h) which were insensitive to ouabain and markedly stimulated by 20 mM KCl (respectively, 2.2- and 14.8-fold). Furthermore, the membranes autophosphorylated in the absence of K+ (up to 0.69 +/- 0.09 nmol Pi incorporated/mg protein) and dephosphorylated by 85% in the presence of this ion. Membrane proteins were extracted by 1-2% (w/v) n-octylglucoside into a soluble form, i.e., which did not sediment in a 100 000 X g X 1 h centrifugation. This soluble form precipitated upon further dilution in detergent-free buffer. Extracted ATPase represented 32% (soluble form) and 68% (precipitated) of native enzyme and it displayed the same characteristic properties in terms of K+-stimulated ATPase and p-nitrophenylphosphatase activities and K+-sensitive phosphorylation: Mg2+-ATPase (mumol Pi/mg protein per h) 32 +/- 9 (basal) and 86 +/- 20 (K+-stimulated); Mg2+-p-nitrophenylphosphatase (mumol p-nitrophenol/mg protein per h) 2.6 +/- 0.5 (basal) and 22.2 +/- 3.2 (K+-stimulated); Mg2+-phosphorylation (nmol Pi/mg protein) 0.214 +/- 0.041 (basal) and 0.057 +/- 0.004 (in the presence of K+). In glycerol gradient centrifugation, extracted enzyme equilibrated as a single peak corresponding to an apparent 390 000 molecular weight. These findings provide the first evidence for the solubilization of (H+ + K+)-ATPase in a still active structure.
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PMID:Solubilization of active (H+ + K+)-ATPase from gastric membrane. 613 48

The purpose of this study was to examine muscle plasmalemma which is implicated as the site responsible for the appearance of malignant hyperthermia in human and susceptible strains of animals. In pigs with malignant hyperthermia (MH) the activity of Na+/K+, Mg2+-ATPase, p-nitrophenylphosphatase and Mg2+-ATPase fell significantly during anaesthesia. In the control group the contrary occurred. In both the groups tested there was a marginal rise in the levels of sialic acid. The levels of cholesterol and lysoderivatives were abnormal before the provoking agents were administered but they changed significantly after onset of the MH syndrome. Anaesthesia reduced the phospholipids level in both tested animal groups. Before and after the provoking agents an impoverishment in the polypeptide pattern in the range between 80,000 and 30,000 daltons of mol. wt. in MH susceptible animals occurred. It is postulated that in MH the macromolecular disorganization of the muscle plasma membranes means that defence mechanisms maintaining cell gradients do not work in the presence of provoking agents.
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PMID:Experimental porcine malignant hyperthermia: macromolecular characterization of muscle plasma membranes. 615 Oct 35

The state of assembly of the (H+ + K+)-ATPase in purified hog gastric mucosa membranes was studied by target size analysis applied to radiation-induced enzyme inactivation and polypeptide degradation data. Radiation inactivated the Mg2+-ATPase, K+-stimulated ATPase, and p-nitrophenyl phosphatase activities of the membrane preparation with a dose dependence characteristic of a target size of 270,000-daltons. Radiation also bleached the major 100,000-dalton sodium dodecyl sulfate-gel electrophoresis band of this preparation, indicating a radiation-induced degradation. This apparent polypeptide degradation exhibited a dose dependency corresponding to a target size of 250,000 daltons in situ. It is suggested that the gastric ATPase is a trimeric assembly of the 100,000-dalton polypeptides.
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PMID:Target molecular weight of the gastric (H+ + K+)-ATPase functional and structural molecular size. 626 22

The effects of mild periodate exposure on the kinetics of (Na+ + K+)-ATPase and K+-p-nitrophenylphosphatase were studied using rat cerebral microsome preparations. Fifty percent inhibition of both enzyme activities was attained near 3 microM periodate concentrations. This inhibition was biphasic with time. Mg2+-ATPase and Mg2+-p-nitrophenylphosphatase activities were much less inhibited by periodate. Periodate inhibition was partially reversed by dimercaprol and dithiothreitol but not by diffusion. The possible reaction products formic acid, formaldehyde, glyceraldehyde, and acetaldehyde had no inhibitory effects in similar concentrations. Periodate exposure produced no detectable changes in the activation of (Na+ + K+)-ATPase by Na+, K+, Mg2+, or ATP. Residues shared by both (Na+ + K+)-ATPase and K+-p-nitrophenylphosphatase are both critical to hydrolytic function and sensitive to mild oxidation by periodate.
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PMID:Inhibition of rat brain microsomal (Na+ + K+)-ATPase and K+-p-nitrophenylphosphatase by periodic acid. 628 25

(1) A (K+ + H+)-ATPase containing membrane fraction, isolated from pig gastric mucosa, has been further purified by means of zonal electrophoresis, leading to a 20% increase in specific activity and an increase in ratio of (K+ + H+)-ATPase to basal Mg2+-ATPase activity from 9 to 20. (2) The target size of (Na+ + K+)-ATPase, determined by radiation inactivation analysis, is 332 kDa, in excellent agreement with the earlier value of 327 kDa obtained from the subunit composition and subunit molecular weights. This shows that the Kepner-Macey factor of 6.4 X 10(11) is valid for membrane-bound ATPases. (3) The target size of (K+ + H+)-ATPase is 444 kDa, which, in connection with a subunit molecular weight of 110000, suggests a tetrameric assembly of the native enzyme. The ouabain-insensitive K+-stimulated p-nitrophenylphosphatase activity has a target size of 295 kDa. (4) In the presence of added Mg2+ the target sizes of the (K+ + H+)-ATPase and its phosphatase activity are decreased by about 15%, while that for the (Na+ + K+)-ATPase is not significantly changed. This observation is discussed in terms of a Mg2+-induced tightening of the subunits composing the (K+ + H+)-ATPase molecule.
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PMID:Studies on (K+ + H+)-ATPase. VI. Determination on the molecular size by radiation inactivation analysis. 630 21

Vanadate inhibited K+-activated and K+-activated ouabain-sensitive p-nitrophenyl phosphatases of rat myometrium at nanomolar concentrations. The vanadate concentrations required for 50% inhibition were 220 +/- 30 nM for the K+-activated component of the enzyme and 200 +/- 30 nM for the K+-activated ouabain-sensitive component. Micromolar concentrations of vanadate inhibited acid and alkaline p-nitrophenyl phosphatases. ATP-dependent Ca uptake by the plasma membrane vesicles was not inhibited by 10nM - 1 mM vanadate. Mg2+-ATPase was also not affected. Thus K+-activated and K+-activated ouabain-sensitive p-nitrophenyl phosphatase activities of the plasma membrane were most sensitive to inhibition by vanadate. Preliminary experiments demonstrated that similar to ouabain, vanadate inhibited potassium-induced abolition of spontaneous contractile activity of isolated rat myometrium in K-free Krebs. This effect of vanadate is consistent with vanadate inhibition of K+-activated ouabain-sensitive p-nitrophenyl phosphatase.
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PMID:Effect of vanadate on rat myometrium plasma membrane enzyme activities. 690 27

Inhibition of Na+/K+-ATPase and Mg2+-ATPase activities by in vitro exposure to Cd2+, Pb2+ and Mn2+ was investigated in rat brain synaptic plasma membranes (SPMs). Cd2+ and Pb2+ produced a larger maximal inhibition of Na+/K+-ATPase than of Mg2+-ATPase activity. Metal concentrations causing 50% inhibition of Na+/K+-ATPase activity (IC50 values) were Cd2+ (0.6 microM) < Pb2+ (2.1 microM) < Mn2+ (approximately 3 mM), and the former two metals were substantially more potent in inhibiting SPM versus synaptosomal Na+/K+-ATPase. Dixon plots of SPM data indicated that equilibrium binding of metals occurs at sites causing enzyme inhibition. In addition, IC50 values for SPM K+-dependent p-nitrophenylphosphatase inhibition followed the same order and were Cd2+ (0.4 microM) < Pb2+ (1.2 microM) < Mn2+ (300 microM). Simultaneous exposure to the combinations Cd2+/Mn2+ or Pb2+/Mn2+ inhibited SPM Na+/K+-ATPase activity synergistically (i.e., greater than the sum of the metal-induced inhibitions assayed separately), while Cd2+/Pb2+ caused additive inhibition. Simultaneous exposure to Cd2+/Pb2+ antagonistically inhibited Mg2+-ATPase activity while Cd2+/Mn2+ or Pb2+/Mn2+ additively inhibited Mg2+-ATPase activity at low Mn2+ concentrations, but inhibited antagonistically at higher concentrations. The similar IC50 values for Cd2+ and Pb2+ versus Mn2+ inhibition of Na+/K+-ATPase and the pattern of inhibition/activation upon exposure to two metals simultaneously support similar modes of interaction of Cd2+ and Pb2+ with this enzyme, in agreement with their chemical reactivities.
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PMID:Inhibition of ATPase activity in rat synaptic plasma membranes by simultaneous exposure to metals. 859 55


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