Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.1 (Mg2+-ATPase)
 1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several inhibitors of energy metabolism decreased the ATP-stimulated uptake of catecholamines by isolated synaptic vesicles from rat brain and by chromaffin granules from bovine adrenal medulla. Catecholamine uptake was inhibited by dinitrophenol, S-13 and oleic acid, which are known to block active transport by dissipating trans-membrane proton gradients. Thus a proton gradient appears to be involved in catecholamine transport. Both catecholamine uptake and vesicle-associated Ca2+/Mg2+-ATPase were inhibited by dicyclohexylcarbodiimide and tributyltin, which had previously been shown to inhibit the Ca2+/Mg2+-ATPase of mitochondria. However, mitochondrial ATPase was not involved in catecholamine uptake as oligomycin and aurovertin, more specific inhibitors of mitochondrial ATPase, did not affect catecholamine uptake. It is suggested that ATP stimulates catecholamine uptake by serving as a substrate for the ATPase. Activity of this enzyme causes translocation of protons across the vesicle membrane establishing a trans-membrane proton gradient. The proton gradient drives the transport of catecholamines.
 ...
PMID:Energy utilization in the uptake of catecholamines by synaptic vesicles and adrenal chromaffin granules. 58 46

The cytochemical distribution of Ca2+-Mg2+-ATPase was studied ultrastructurally, using a lead capture method at pH 8.5 and compared in various tissues. In thymic, splenic and activated peripheral blood lymphocytes and in cultured HeLa cells activity was consistently localised on the nuclear envelope, endoplasmic reticulum, Golgi apparatus, mitochondria and weakly on centrioles, but not on the plasma membrane. Intracellular activity was similarly distributed in intestinal absorptive cells where activity was particularly strong in the Golgi apparatus, and in hepatocytes where, however, activity was generally weak. Intracellular activity was lacking in renal glomerular and tubular cells and in cerebellar neurons and neuroglia. Variable activity was present on the outer surface of the plasma membrane, particularly on the brush borders of intestinal and renal tubular absorptive cells, the basolateral invaginations of distal tubules and the bile canaliculi. Mitochondrial activity, when present, was inhibited by oligomycin. The localisation at different sites may represent biochemically different ATPases including endoplasmic reticular ATPase involved in intracellular calcium regulation, oligomycin-sensitive mitochondrial ATPase, dynein-like ATPase associated with centrioles and an ectoenzyme associated with cell surface specialisations.
 ...
PMID:Intracellular distribution of Ca2+-Mg2+ adenosine triphosphatase (ATPase) in various tissues. 253 Jan 99

On solubilization with Triton X-100 of sarcoplasmic reticulum vesicles isolated by differential centrifugation, the Ca2+-ATPase is selectively extracted while approximately half of the initial Mg2+-, or 'basal', ATPase remain in the Triton X-100 insoluble residue. The insoluble fraction, which does not contain the 100 000 dalton polypeptide of the Ca2+-ATPase, contains high levels of cytochrome c oxidase. Furthermore, its Mg2+-ATPase activity is inhibited by specific inhibitors of mitochondrial ATPase, indicating that the 'basal' ATPase separated from the Ca2+-ATPase by detergent extraction originates from mitochondrial contaminants. To minimize mitochondrial contamination, sarcoplasmic reticulum vesicles were fractionated by sedimentation in discontinuous sucrose density gradients into four fractions: heavy, intermediate and light, comprising among them 90-95% of the initial sarcoplasmic reticulum protein, and a very light fraction, which contains high levels of Mg2+-ATPase. Only the heavy, intermediate and light fractions originate from sarcoplasmic reticulum; the very light fraction is of surface membrane origin. Each fraction of sarcoplasmic reticulum origin was incubated with calcium phosphate in the presence of ATP and the loaded fractions were separated from the unloaded fractions by sedimentation in discontinuous sucrose density gradients. It was found that vesicles from the intermediate fraction had, after loading, minimal amounts of mitochondrial and surface membrane contamination, and displayed little or no Ca2+-independent basal ATPase activity. This shows conclusively that the basal ATPase is not an intrinsic enzymatic activity of the sarcoplasmic reticulum membrane, but probably originates from variable amounts of mitochondrial and surface membrane contamination in sarcoplasmic reticulum preparations isolated by conventional procedures.
 ...
PMID:Highly purified sarcoplasmic reticulum vesicles are devoid of Ca2+-independent ('basal') ATPase activity. 610 77

The principle organelle marker enzymes and various adenosine triphosphatase (ATPase) activities were studied in human skeletal muscle. The reproducibility of each assay was established under optimal and linear assay conditions. Whole homogenates of normal human quadriceps muscle were fractionated by centrifugation on a continuous sucrose density gradient. Gradient fractions were assayed for organelle marker enzymes and frequency-density histograms were constructed for each enzyme. Good resolution of the principal organelles was obtained. Adenosine triphosphatase (ATPase) was assayed under conditions of maximal stimulation by Ca2+, or Mg2+ or Na2+, K+ + Mg2+. The distribution of these activities was compared with those of the organelle marker enzymes. Both Ca2+-ATPase and Mg2+-ATPase were distributed to both the mitochondrial and myofibrillar fractions but could be distinguished by the inhibition of mitochondrial ATPase with sodium azide. The distribution of Na+, K+-activated, Mg2+-dependent ATPase (Na+, K+ ATPase) activity suggested a sarcolemmal localization. The results of electron microscopy of gradient fractions were consistent with the organelle content of the fractions as determined by enzymic analyses. These studies provide reference information for the subsequent investigation of organelle pathology of human muscle disorders.
 ...
PMID:Analytical subcellular fractionation of normal human skeletal muscle by sucrose density gradient centrifugation. 613 12

The limiting membranes of pituitary growth hormone and prolactin secretory granules contain a Mg2+-ATPase sensitive to anions. This enzyme is in many ways similar to mitochondrial ATPase. The enzyme was potently inhibited by oligomycin (Ki 6.5 X 10(-9) M), and was much more sensitive to the inhibitor than pituitary mitochondrial ATPase (Ki 2.7 X 10(-7) M). In contrast, the enzyme activity of intact secretory granules was only sparingly inhibited by oligomycin (maximal inhibition close to 30% at 5 X 10(-4) M). However, oligomycin (5 microM) did diminish to basal levels the enhanced granule ATPase activity observed in the presence of a stimulatory anion (25 mM sodium sulfite). Other compounds known to inhibit the proton translocating mitochondrial ATPase were also tested for their ability to inhibit the secretory granule ATPase. A similar pattern of limited inhibition in granules and greater sensitivity in isolated membranes was seen with the inhibitors N,N-dicyclohexylcarbodiimide and efrapeptin. In contrast, tri-n-butyltin chloride was a potent inhibitor of the ATPase of intact granules, and the susceptibility of the enzyme to inhibition by this compound was less after isolation of membranes. These observations suggest that pituitary secretory granule membrane ATPase may have a proton pumping function similar to that of the mitochondrial enzyme. In addition, the data imply that the inhibitor binding site(s) may be masked, inaccessible, or ineffective in intact granules, but exposed (or activated) in isolated membranes. The greater sensitivity of granule ATPase to tri-n-butyltin chloride, in contrast to the greater sensitivity of membrane ATPase to the other inhibitors, indicates that the tin compound may be effective at a membrane site(s) distinct from the others, or that the mechanism of inhibition is different.
 ...
PMID:Inhibitor studies with adenohypophyseal granule membrane ATPase. Evidence for a membrane environment which modulates sensitivity to inhibitors. 614 4

Placental polypeptides present in crude preparations of transforming growth factors stimulate glycolysis when added to quiescent 3T3 cells, normal rat kidney, and chick embryo fibroblasts. The stimulation was apparent over a time period of at least 90 min and was seen at glucose concentrations ranging from 1 to 30 mM. Duramycin, an antibiotic isolated from Streptomyces cinnamomeus, inhibits the polypeptide-stimulated and nonstimulated glycolysis of intact cells, since it permeabilizes cells to Pi and nucleotides. However, duramycin also inhibits the Na+-K+-ATPase as well as the ouabain-insensitive Mg2+-ATPase of plasma membranes. Duramycin has no effect on glycolysis catalyzed by cell-free extracts of Ehrlich ascites tumor cells in the presence of mitochondrial ATPase but partially inhibits glycolysis when ADP and Pi are generated by ATPases of plasma membrane preparations.
 ...
PMID:Stimulation of glycolysis by placental polypeptides and inhibition by duramycin. 614 64