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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)

The effect of regucalcin, a calcium-binding protein isolated from rat liver cytosol, on Ca2+-adenosine triphosphatase (ATPase) activity in hepatic microsomes was investigated. Mg2+-ATPase activity was clearly increased by the presence of 50 microM Ca2+. Regucalcin (1.0-4.0 microM) caused a remarkable elevation (about 3-fold) of Ca2+-ATPase activity. Also, Mg2+-ATPase activity was increased (about 1.6-fold) by the presence of regucalcin (2.0 and 4.0 microM). Guanosine-5'-O-(3-thiotriphosphate) (GTPrs; 10(-5) and 10(-4) M) and nicotinamide adenine dinucleotide phosphate oxidized form (NADP+; 10(-5) to 10(-3) M) or reduced form (NADPH; 10(-4) and 10(-3) M) significantly increased Ca2+-ATPase activity. These increases were not enhanced by the presence of regucalcin (2.0 microM). Of various metal ions, a comparatively low concentration of V5+ (10(-5) M) or Cd2+ (10(-6) M) significantly increased Ca2+-ATPase activity, while Hg2+, Zn2+, Cu2+ and Mn2+ did not have such an effect. Regucalcin (2.0 microM) did not enhance the effect of V5+ and Cd2+ on Ca2+-ATPase activity. The present finding, that regucalcin activates hepatic microsomal Ca2+-ATPase, suggests a cell physiological role of regucalcin as an activator in the microsomal Ca2+-pump activity. This action of regucalcin may not be influenced by other regulators.
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PMID:Activation of hepatic microsomal Ca2+-adenosine triphosphatase by calcium-binding protein regucalcin. 252 22

Some metal ions, e.g. Hg2+, Cd2+ and Al3+, can have the effects as ecotoxicological agents, of causing eggshell thinning and breakage in birds. In a homogenate of the Ca2+-secreting part of the eggshell gland mucosa, a study was made of the influence of Hg2+, Cd2+, Cu2+, Pb2+, methyl-Hg+, Zn2+, V3+, Al3+ and Ni2+ in different concentrations on the rate of ATP-dependent 10(-4) M Ca2+ binding. All compounds had an inhibitory action. The most potent metal (Hg2+) produced 50% inhibition (IC50) at 1.1 X 10(-6) M, whereas this value for the least potent compound (Ni2+) was 9 X 10(-4) M. The specific Ca2+-Mg2+-ATPase activity was also inhibited by the tested metal ions. In all cases except methyl-Hg+ the IC50 for this activity was lower than that for Ca2+ binding. The most potent ion in this respect was Cd2+, with an IC50 of 8 X 10(-8) M, and the least potent was methyl-Hg+, with an IC50 of 1.4 X 10(-3) M. Pb2+ and Cd2+ in a concentration range of 10(-5)-10(-4) stimulated the Mg2+-ATPase activity, however, to almost the same extent as 10(-4) M Ca2+. A possible explanation for this effect is that these ions may have an affinity for sites of Ca2+ binding of the polypeptide calmodulin and thereby influence the Ca2+ metabolism of the shell gland mucosa.
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PMID:Effect of some metal compounds on the Ca2+ binding and Ca2+-Mg2+-ATPase activity of eggshell gland mucosa homogenate from the domestic fowl. 294 86

Acetylcholinesterase (AchE: EC 3.1.1.7) was identified and purified from the hemolymph of the scorpion Heterometrus bengalensis. The purity of the enzyme was determined by polyacrylamide gel electrophoresis (PAGE). The molecular weight of the enzyme, determined by sodium dodecyl sulfate-PAGE, was 80,000. The purified AchE hydrolysed acetylthiocholine iodide, but it did not react with butyrylthiocholine iodide. BW284C51, a specific inhibitor of AchE, strongly inhibited the enzyme. The known inhibitor (tetramonoisopropylpyrophosphortetramide) of pseudocholinesterase did not produce any inhibition of the enzyme activity. The purified AchE of scorpion hemolymph was vulnerable to high substrate concentration. The presence of Cu2+ and Ni2+ reduced the enzyme activity, whereas the metal ion, Sn2+, enhanced AchE activity. Ca2+ produced neither inhibition nor activation. (Na+, K+)-ATPase and Mg2+-ATPase activities were greatly enhanced by the purified AchE.
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PMID:Acetylcholinesterase (EC 3.1.1.7), a neurotransmitter enzyme in scorpion hemolymph. 296 37

The properties of Mg2+-ATPase in the vacuole of Saccharomyces cerevisiae were studied, using purified intact vacuoles and right-side-out vacuolar membrane vesicles prepared by the method of Y. Ohsumi and Y. Anraku ((1981) J. Biol. Chem. 256, 2079). The enzyme requires Mg2+ ion but not Ca2+ in. Cu2+ and Zn2+ ions inhibit the activity. The optimal pH is at pH 7.0. The enzyme hydrolyzes ATP, GTP, UTP, and CTP in this order and the Km value for ATP was determined as 0.2 mM. It does not hydrolyze ADP, adenosyl-5'-yl imidodiphosphate, or p-nitrophenyl phosphate. ADP does not inhibit hydrolysis of ATP by the enzyme. The activities of intact vacuoles and of vacuolar membrane vesicles were stimulated 3- and 1.5-fold, respectively, by the protonophore uncoupler 3,5-di-tert-butyl-4-hydroxybenzilidenemalononitrile and the K+/H+ antiporter ionophore nigericin. Sodium azide at a concentration exerting an uncoupler effect also stimulated the activity. The activity was sensitive to the ATPase inhibitor N,N'-dicyclohexylcarbodiimide, but not to sodium vanadate. The ATP-dependent formation of an electrochemical potential difference of protons, measured by the flow-dialysis method, was determined as 180 mV, with contribution of 1.7 pH units, interior acid, and of a membrane potential of 75 mV. It is concluded that the Mg2+-ATPase of vacuoles is a new marker enzyme for these organelles and is a N,N'-dicyclohexylcarbodiimide-sensitive, H+-translocating ATPase whose catalytic site is exposed to the cytoplasm.
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PMID:Properties of H+-translocating adenosine triphosphatase in vacuolar membranes of SAccharomyces cerevisiae. 611 10

1. The plasma membrane of the flounder erythrocyte contains a Mg2+-dependent ATPase which is insensitive to ouabain. Mg2+ is part of the substrate, Mg-ATP, and Mg2+ also functions as a nonessential activator. 2. Ca2+, Mn2+ and Co2+ can replace Mg2+ as an activator of ATP hydrolysis. Cu2+ and Zn2+ abolish the Mg-dependent activity. It is shown that Ca2+ and Mg2+ activate the same enzyme and that Mg-ATP and Ca-ATP are mutually competitive. 3. The hydrolysis of ATP obeys Michaelis-Menten kinetics whether or not the Mg2+-ATPase is fully activated by Mg2+. The KM values for Mg-ATP were found to be 0.13 and 0.43 mM respectively. 4. Free ATP acts as a competitive inhibitor towards Mg-ATP and the dissociation constant for the enzyme-ATP complex was determined to be about 0.55 mM. 5. The Mg2+ -ATPase has a low specificity and reacts with the common nucleoside triphosphates GTP, ITP, UTP and CTP. 6. The enzyme has a broad pH optimum ranging from 6.5 to 7.2 and an energy of activation of 13.5 kcal/mol between 0 and 30 degrees C. 7. The effect of some activators and inhibitors of membrane-bound ATPases are reported.
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PMID:The Mg2+-dependent ATPase from the erythrocyte plasma membrane of the flounder Platichthys flesus L. General properties and some observations on the steady state kinetics. 613 79

The effect of manganese on brain microsomal Mg2+-Na+K+-ATPase was examined both in vitro and in vivo. Daily intraperitoneal administration of MnCl2 . 4H2O (Mn2+, 6 mg/kg) to the rats for a period of 90 days produced 10% (P less than 0.05) inhibition in the activity of Mg2+-ATPase, and 72 and 63% increases in the contents of manganese and copper, respectively, in the microsomal fraction of brain. In in vitro studies, lower concentrations of Mn2+ activated while higher concentrations inhibited the activity of brain microsomal ATPase. Addition of equal concentrations of Mn2+ + Cu2+ (8 mM) in vitro produced 8% inhibition in the activity of Mg2+-ATPase and 83% inhibition in Na+-K+-ATPase. Free Cu2+ ions were able to antagonize the effect of Mn2+ on ATPase in vitro and inhibited the activity of Mg2+-Na+-K+-ATPase with more pronounced effect of Na+-K+-ATPase. The lack of change in the activity of Na+-K+-ATPase in the brain microsomes of rats administered manganese, in spite of a significant increase in copper, could not be explained. It is, however, evident that a manganese-induced elevation in brain copper was not responsible for initiating biochemical changes in manganese neurotoxicity.
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PMID:Effects of manganese on rat brain microsomal Mg2+-Na+-K+-ATPase: in vivo and in vitro studies. 613 60

Effects of chlorpromazine, metals and I-ascorbic acid (AA) on Ca2+-ATPase and Mg2+-ATPase in microsomal and granular fractions obtained from the bovine adrenal medulla were studied. Marker enzyme analysis on microsomal subfractions in a discontinuous sucrose density gradient showed a correlation of distribution between ATPase activities and plasma membrane. The two ATPase activities in such plasma membrane-rich microsomes were reduced by chlorpromazine, Hg2+ and Cu2+ (0.3 mM of each), and their effects were greater on the Mg2+-ATPase activity. Zn2+ (0.3 mM) also reduced only the Mg2+-ATPase activity. AA (3 mM) reduced the two ATPase activities to an equal extent. Nevertheless, the inhibitions of ATPases by Hg2+, Cu2+ and Zn2+ were decreased, unaltered and additively enhanced in combination with AA, respectively. We also observed high Mg2+-ATPase activity in the granule-rich fraction, but this ATPase activity was unaffected by all of the above agents. These results indicate that Mg2+-ATPase in the plasma membrane-rich microsome of adrenal medulla is inhibited by chlorpromazine, Hg2+, Cu2+ and Zn2+ more significantly than Ca2+-ATPase, but Mg2+-ATPase in the granular fraction is unaffected, and that AA changes the potency of inhibition by some metals of ATPases diversely.
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PMID:Inhibition by chlorpromazine, metals and I-ascorbic acid of calcium-ATPase and magnesium-ATPase in bovine adrenal medullary microsomes. 614 8

The mechanism of transport of basic amino acids into vacuoles of cells of the yeast Saccharomyces cerevisiae was investigated in vitro. Right-side-out vacuolar membrane vesicles were prepared from purified vacuoles. Arginine was taken up effectively by the vesicles only in the presence of ATP, not in the presence of ADP or AMP-adenosyl-5'-yl imidodiphosphate. It was exchangeable and was released completely by a protonophore, 3,5-di-tert-butyl-4-hydroxybenzilidenemalononitrile (SF6847). The transport required Mg2+ ion but was inhibited by Cu2+, Ca2+, or Zn2+ ions. The transport activity was sensitive to the ATPase inhibitor N,N'-dicyclohexylcarbodiimide (DCCD), but not to oligomycin or sodium vanadate. SF6847 or nigericin blocked arginine uptake completely, but valinomycin had no effect. ATP-dependent formation of a delta pH across the membrane vesicles was shown by quenching of 9-aminoacridine fluorescence. These results indicate that DCCD-sensitive, Mg2+-ATPase of vacuolar membranes is essential as an energy-donating system for the active transport, and that an electrochemical potential difference of protons is a driving force of this basic amino acid transport. Arginine transport showed saturation kinetics with a Km value of 0.6 mM and the mechanism was well explained by an H+/arginine antiport.
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PMID:Active transport of basic amino acids driven by a proton motive force in vacuolar membrane vesicles of Saccharomyces cerevisiae. 645 Jul 64

The ATPase activity of purified coupling factor 1 (CF1) of spinach chloroplasts [EC 3.6.1.3] was reversibly enhanced in some aqueous organic solvents, notably methanol, ethanol, and acetone. Pretreatment of CF1 with 20% (v/v) methanol did not affect the subsequent activity. The activity depended entirely on the final concentration of methanol in the reaction mixture. In the presence of 20% methanol, the Km of Ca2+-ATPase from ATP was lowered from 0.4 mM to 0.2 mM. Not only Ca2+, but also Cd2+, Mg2+, Mn2+, and Zn2+ supported the ATPase activity at rates of higher than 7 mumol.mg protein-1 . min-1. Co2+, Ni2+, and Pb2+ supported the activity at rates of 0.5-1.0 mumol.mg protein-1 . min-1. The activities supported by the following cations, if any, were less than 0.2 mumol.mg protein-1 . min-1; Ba2+, Cu2+, Fe2+, Hg2+, Sn2+, and Sr2+. The optimum concentration of methanol for Ca2+-ATPase and Mg2+-ATPase activities was about 30% (v/v). The optimum pH values for Ca2+-ATPase and Mg2+-ATPase activities were about 8.0 and 8.8, respectively. The enhancing effect of organic solvents appears to be associated with their relative lipophilic character as defined by the octanol-water partition coefficient. The Ca2+-ATPase activities of th trypsin-activated and the heat-activated CF1 were inhibited and their Mg2+-ATPase activities were enhanced by the presence of methanol in the reaction mixture.
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PMID:Enhancement of adenosine triphosphatase activity of purified chloroplast coupling factor 1 in aqueous organic solvent. 645 34

Mutations in ATP13A2 lead to Kufor-Rakeb syndrome, a parkinsonism with dementia. ATP13A2 belongs to the P-type transport ATPases, a large family of primary active transporters that exert vital cellular functions. However, the cellular function and transported substrate of ATP13A2 remain unknown. To discuss the role of ATP13A2 in neurodegeneration, we first provide a short description of the architecture and transport mechanism of P-type transport ATPases. Then, we briefly highlight key P-type ATPases involved in neuronal disorders such as the copper transporters ATP7A (Menkes disease), ATP7B (Wilson disease), the Na(+)/K(+)-ATPases ATP1A2 (familial hemiplegic migraine) and ATP1A3 (rapid-onset dystonia parkinsonism). Finally, we review the recent literature of ATP13A2 and discuss ATP13A2's putative cellular function in the light of what is known concerning the functions of other, better-studied P-type ATPases. We critically review the available data concerning the role of ATP13A2 in heavy metal transport and propose a possible alternative hypothesis that ATP13A2 might be a flippase. As a flippase, ATP13A2 may transport an organic molecule, such as a lipid or a peptide, from one membrane leaflet to the other. A flippase might control local lipid dynamics during vesicle formation and membrane fusion events.
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PMID:Cellular function and pathological role of ATP13A2 and related P-type transport ATPases in Parkinson's disease and other neurological disorders. 2490 74


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