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 effects of monovalent cations on calcium uptake by fragmented sarcoplasmic reticulum have been clarified. Homogenization of muscle tissue in salt-containing solutions leads to contamination of this subcellular fraction with actomyosin and mitochondrial membranes. When, in addition, inorganic cations are contributed by the microsomal suspension and in association with nucleotide triphosphate substrates there is an apparent inhibition of the calcium transport system by potassium and other cations. However, when purified preparations were obtained after homogenization in sucrose medium followed by centrifugation on a sucrose density gradient in a zonal rotor, calcium uptake and the associated adenosine triphosphatase activity were considerably activated by potassium and other univalent cations. When plotted against the log of the free calcium concentration there was only a slight increase in calcium uptake and ATPase activity in the absence of potassium ions but sigmoid-shaped curves were obtained in 100 mM K+ with half-maximal stimulation occurring at 2 muM Ca2+ for both calcium uptake and ATPase activity. The augmentation in calcium uptake was not due to an ionic strength effect as Tris cation at pH 6.6 was shown to be inactive in this respect. Other monovalent cations were effective in the order K+ greater than Na+ greater than NH4+=Rb+=Cs+ greater than Li+ with half-maximal stimulation in 11 mM K+, 16 mM Na+, 25 mM NH4+, Rb+, and Cs+ and in 50 mM Li+. There was nos synergistic action between K+ AND Na+ ions and both calcium uptak and associated ATPase were insensitive to ouabain. Thallous ions stimulate many K+-requiring enzymes and at one-tenth the concentration were nearly as effective as K+ ions in promoting calcium uptake. The ratio of Ca2+ ions transported to P1 released remained unchanged at 2 after addition of K+ ions indicating an effect on the rate of calcium uptake rather than an increased efficiency of uptake. In support of this it was found that during the stimulation of calcium uptake by Na+ ions there was a reduction in the steady state concentration of phosphorylated intermediate formed from [gamma-32P]ATP. It is considered that there is a physiological requirement for potassium ions in the relaxation process.
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PMID:Caclium uptake and associated adenosine triphosphatase activity in fragmented sarcoplasmic reticulum. Requirement for potassium ions. 1 56

Patulin (4-hydroxy-4H-furo[3,2-c]pyran-2(6H)-one), a carcinogenic lactone produced as a major metabolite by several fungi, inhibited the Mg++-dependent Na+-K+ activated adenosine triphosphatase (ATPase) activity of mouse brain microsomal fractions with an estimated IC50 of 3.0 X 10(-4) M. Inhibition was concentration dependent. Hydrolysis of ATP was linear with both time and enzyme concentration either with or without patulin in reaction mixtures. Altered pH and activity curves for Na+-K+ ATPase demonstrated comparable inhibition by patulin in buffered acidic ranges through an optimum of 7.5, followed by a reduction of toxicity to this system at higher alkaline pH. Kinetic studies of cationic-substrate activation of Na+-K+ ATPase indicated noncompetitive inhibition with respect to ATP (at low affinity nucleotide-directed sites) and Na+ (in the presence of low, noninterfering concentrations of K+). Competitive inhibition with respect to activation of the Na+-k+-stimulated activity and K+-stimulated p-nitrophenyl phosphatase activity of the enzyme system was indicated by altered binding site parameters without change in apparent Vmax in the presence of patulin. Activity was partially restored by washing. Preincubation of patulin with dithiothreitol or glutathione protected the enzyme from inhibition. Results suggest that patulin exerted its effect on Na+-K+ ATPase either directly by interfering with K+ binding or indirectly by inducing a conformational change in the enzyme.
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PMID:Effects of patulin on the kinetics of substrate and cationic ligand activation of adenosine triphosphatase in mouse brain. 2 94

The effects of acute and chronic administration of D-Galactosamine (GalN), Ethanol and Phenobarbital were investigated on the activities of lysosomal enzymes, i.e.; acid phosphatase, beta-glucuronidase and n-acetyl-beta-glucosaminidase, and others such as gamma-GTP and adenosine triphosphatase. The histochemical distribution of gamma-GTP in the liver was also studied on biopsy specimens from patients with chronic hepatitis, and gamma-GTP levels in the serum of patients receiving drugs inductable of hepatic microsomal enzymes. 1) After a single intraperitoneal injection of GalN, the lysosomal enzyme activities were lowered in the necrotic areas, but raised in the perinecrotic areas, the proliferative Kupffer cells and intra- and/or extra-cellular eosine bodies. 2) gamma-GTP activities in rat liver after chronic administration of GalN were markedly increased in bile canalicular membrane of periportal parenchymal cells, the epithelium of bile duct and ductules, and som inflammatory cells of portal fields. Levels of serum gamma-GTP were also elevated. On histochemical studies with biopsy specimens from patients with chronic active hepatitis showing elevated gamma-GTP activity, the activity was revealed a similar localization to GalN-treated rats. These data suggested that the increased activities might be reflected on the active stage in chronic hepatitis. 3) Chronic ethanol treatment in rats induced clearly-stained lysosomes varied in size, especially large-sized. The activities of hepatic gamma-GTP were slightly increased in the bile canalicular membrane of periportal parenchymal cells and the epithelium of proliferative bile ductules. 4) It has been shown by histochemical and biochemical techniques that hepatic gamma-GTP activity was increased after phenobarbital administration in rats. A significant rise in serum gamma-GTP was observed in patients on long-term treatment with anti-epileptic drugs. These data indicated that the increased activities of serum gamma-GTP might be accompanied with induction of hepatic microsomal drug-metabolizing enzymes.
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PMID:[Clinical and experimental histochemical studies on the activities of liver lysosomal enzymes and gamma-glutamyl transpeptidase (gamma-GTP) (author's transl)]. 3 25

This study examined the effects of vanadate on the potassium dependent phosphatase activity present in purified human kidney microsomal (Na+ + K+)-adenosine triphosphatase. Vanadate anion inhibited the K+-dependent phosphatase at a K1 of 35 nM. This inhibition was noncompetitive with the substrate, p-nitrophenylphosphate. The inhibition by vanadate at 1 mM K+ was only 45% of the inhibition that was observed at 10 mM K+. Neither preincubation of the enzyme with vanadate, nor changing the pH of the assay from 8.2 to 7.2 had any effect on the K1 for vanadate. The inclusion of 2.5 mM isoproterenol, to complex the yanadate, reversed the inhibition, as did diluting the enzymatic reaction. Vanadate also inhibited the overall (Na+ + K+)-ATPase reaction at a K1 of 1.91 microM. This inhibition was also reversible upon inclusion of isoproterenol in the assay. Increasing the level of magnesium from 6 mM to 30 mM lowered the K1 of vanadate to 0.25 microM. The possible role of vanadate as a physiological mediator of (Na+ + k+)-atpase activity is discussed.
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PMID:The effect of vanadate on human kidney potassium dependent phosphatase. 3 61

A crude plasma membrane fraction from the homogenate of purified rat mast cells demonstrates a high degree of Ca2+-dependent and Mg2+-dependent adenosine triphosphatase (ATPase) activity. The microsomal and mitochondrial fractions show negligible amounts of the Ca2+ and Mg2+-activated ATPases. The broad ATPase inhibitor, ethacrynic acid, effectively blocks the mast cell ATPase activity while ouabain demonstrates little inhibitory effect. Correspondingly, ethacrynic acid inhibits histamine release from antigen-challenged mast cells while ouabain does not. Both ATPase inhibition and histamine release inhibition by ethacrynic acid require the presence of the olefinic bond in the ethacrynic acid molecule.
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PMID:Ethacrynic acid inhibitable Ca2+ and Mg2+-activated membrane adenosine triphosphatase in rat mast cells. 7 76

Membrane glycoproteins have been studied in the normal lactating mammary gland and R3230 AC mammary tumor of the rat. Plasma membrane-enriched fractions were obtained from these tissues by discontinuous sucrose gradient centrifugation of a microsomal preparation from the tissue homogenates. The lightest membrane fractions (F-1 and F-2) have the greatest enrichment of plasma membrane markers, with a 14- to 20-fold purification of 5'-nucleotidase and Na+-K+ -adenosine triphosphatase over the homogenate values in both tumor and normal tissues for F-1. Electron microscopy shows smooth membrane vesicles for these fractions. Polypeptide analysis by acrylamide gel electrophoresis shows essentially the same patterns for F-1 and F-2 and only relatively minor differences between membrane components of tumor and normal tissues. Glycoprotein analysis of the polyacrylamide gels by periodate-Schiff staining indicates more dramatic differences. Membrane Fraction F-1 from normal tissue contains two major glycoproteins, GP-II and GP-III, while Fractions F-2 and F-3 contain an additional glycoprotein, GP-I, with a higher apparent molecular weight. In the tumor, the component corresponding to GP-III is decreased or absent and a new component GP-IV is seen at a lower apparent molecular weight.
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PMID:Membrane glycoprotein differences between normal lactating mammary tissue and the R3230 AC mammary tumor. 12 79

1. The function of mitochondria, sarcotubular membranes (heavy microsomes), sarcolemma and myofibrils from the hind-leg skeletal muscle of about 60- and 150-day-old normal and myopathic (UM-X7.1) hamsters was examined. 2. The mitochondrial calcium uptake as well as mitochondrial phosphorylation and respiratory rates were lower in 60-day-old myopathic skeletal muscle, unlike 150-day-old myopathic animals, when pyruvate-malate and glutamate-malate were used as substrates. However, mitochondria from 150-day-old myopathic animals showed depressed glutamate-dependent respiratory and phosphorylation rates and succinate-supported initial rate of calcium uptake. 3. The microsomal calcium-uptake, but not calcium-binding, and Ca2+-stimulated adenosine triphosphatase (ATPase) activity of the 150-day-old myopathic skeletal muscle were lower than the control values. Although microsomal calcium-binding, calcium-uptake and ATPase activities of the 60-day-old myopathic muscle were not depressed significantly, the initial rate of calcium uptake was less than the control. 4. The sarcolemmal Ca2+-ATPase, but not Mg2+-ATPase or Na+ +K+-ATPase, activity was higher in 60-day-old myopathic muscle whereas the activities of all these enzymes from 150-day-old myopathic animals were higher than the control. On the other hand, the Na+ +K+-ATPase activities from 60- and 150-day-old myopathic animals were inhibited by ouabain to a lesser extent in comparison with the respective control values. 5. The myofibrillar Ca2+-ATPase and Mg2+-ATPase activities as well as inhibition of Mg2+-ATPase due to Na+ and K+ in myopathic muscle were no different from the control values. 6. The results reported here give further support to the view that different membrane systems of the dystrophic muscle are defective.
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PMID:Defective membrane systems in dystrophic skeletal muscle of the UM-X7.1 strain of genetically myopathic hamster. 12 86

Sodium- and potassium-activated adenosine triphosphatase (NaK-ATPase) was purified from nasal salt glands of the duck (Anas platyrhynchos). Enzyme of specific activity 2,000 to 2,300 mumol of Pi/mg/hour was routinely obtained by sodium dodecyl sulfate treatment of a microsomal fraction of gland homogenate in the presence of 3 mM ATP followed by pelleting of the enzyme through a sucrose density gradient. Purified NaK-ATPase was stable for over 3 months at -20 degree. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration chromatography purified NaK-ATPase was shown to contain two polypeptide chains of molecular weight 94,000 and 60,000, the smaller of which was a glycoprotein. Purified enzyme of activity 2,300 mumol of Pi/mg/hour bound 3,600 pmol of ouabain/mg of enzyme protein. Reaction with [gamma-32P]ATP in the presence of Mg2+ and Na+ gave 7,025 pmol of acyl phosphate/mg of enzyme protein. The turnover number calculated from phosphorylation data was 5,460 min-1. Amino acid analysis of the polypeptide components of duck salt gland enzyme after separation by gel filtration chromatography in sodium dodecyl sulfate demonstrated strong compositional homology with highly purified NaK-ATPase preparations from other organs and species. The NH2-terminal amino acid of the 94,000-dalton component was glycine and of the 60,000-dalton component, alanine. With a combination of manual sequencing and automated Edman degradation, the NH2-terminal amino acid sequence of the 94,00-dalton catalytic subunit was found to be Gly-Arg-Asn-Lys-Tyr-Glu-Thr-Thr-Ala-()-Ser-Glu.
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PMID:Sodium- and potassium-activated adenosine triphosphatase of the nasal salt gland of the duck (Anas platyrhynchos). Purification, characterization, and NH2-terminal amino acid sequence of the phosphorylating polypeptide. 13 47

Skeletal muscles of flight rats showed no changes in the content of glycogen, adenosine triphosphatase activity of myosin and protein content in protein fractions (except the T fraction where the protein content increased on the 1st and returned to the normal on the 26th postflight day). On the 1st postflight day activities of aminotransferases and lactate dehydrogenase of sarcoplasmatic proteins were elevated and the isoenzyme spectrum of LDH was changed as if in muscular atrophy. The amount of free amino acids in muscles was lowered. On the 26 the postflight day the enzymic activity of sarcoplasmatic proteins remained increased whereas the isoenzyme spectrum of LDH returned to the normal and the amount of free amino acids grew significantly. In the microsomal fraction of muscles the phospholipid content decreased on the 1st and returned to the normal on the 26th postflight day.
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PMID:[Effect of a 22-day space flight on the metabolism of rat skeletal muscle tissue]. 13 80

The effects of CdCl2 on adenosine triphosphatase (ATPase) were studied microsomal fractions or tissue homogenates of outer cortex, inner cortex and outer medulla of dog kidney. Cd was found to be an inhibitor of Na+ +K+ Atpase with 150 value of 2.1 to 3.2 X 10(-4) M regardless of type or source of the enzyme preparation tested. Mg++ ATPase was about 10-fold less sensitive to inhibition by Cd than Na+ +K+ ATPase. The inhibition of microsomal NA+ +K+ ATPase from outer medulla was characterized by irreversible kinetics. The inhibitory effect was not altered by varying Na+ or K+ concentrations, but was decreased by disodium ethylenediaminetetracetic acid (EDTA). EDTA was more effective in preventing than in reversing the inhibition. Na+ +K+ ATPase from kidneys of several other mammalian species showed a similar sensitivity to Cd.
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PMID:Inhibition of renal adenosine triphosphatase by cadmium. 13 65


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