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:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The involvement of membrane (Na+ + K+)-ATPase (Mg2+-dependent, (Na+ + K+)-activated ATP phosphohydrolase, E.C. 3.6.1.3) in the oxygen consumption of rat brain cortical slices was studied in order to determine whether (Na+ + K+)-ATPase activity in intact cells can be estimated from oxygen consumption. The stimulation of brain slice respiration with K+ required the simultaneous presence of Na+. Ouabain, a specific inhibitor of (Na+ + K+)-ATPase, significantly inhibited the (Na+ + K+)-stimulation of respiration. These observations suggest that the (Na+ + K+)-stimulation of brain slice respiration is related to ADP production as a result of (Na+ + K+)-ATPase activity. However, ouabain also inhibited non-K+ -stimulated respiration. Additionally, ouabain markedly reduced the stimulation of respiration by 2,4-dinitrophenol in a high (Na+ + K+)-medium. Thus, ouabain depresses brain slice respiration by reducing the availability of ADP through (Na+ + K+)-ATPase inhibition and acts additionally by increasing the intracellular Na+ concentration. These studies indicate that the use of ouabain results in an over-estimation of the respiration related to (Na+ + K+)-ATPase activity. This fraction of the respiration can be estimated more precisely from the difference between slice respiration in high Na+ and K+ media and that in choline, K+ media. Studies were performed with two (Na+ + K+)-ATPase inhibitors to determine whether administration of these agents to intact rats would produce changes in brain respiration and (Na+ + K+)-ATPase activity. The intraperitoneal injection of digitoxin in rats caused an inhibition of brain (Na+ + K+)-ATPase and related respiration, but chlorpromazine failed to alter either (Na+ + K+)-ATPase activity or related respiration.
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PMID:Control of brain slice respiration by (Na+ + K+)-activated adenosine triphosphate and the effects of enzyme inhibitors. 13 40

The calcium activation of the ATPase (ATP phosphohydrolase, EC 3.6.1.3) activity of cardiac actomyosin reconstituted from bovine cardiac myosin and a complex of actin-tropomyosin-troponin extracted from bovine cardiac muscle at 37 degrees C was studied and compared with similar proteins from rabbit fast skeletal muscle. The proteins of the actin complex were identified by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. Half-maximal activation of the cardiac actomyosin was seen at a calcium concentration of 1.2 +/- 0.002 (S.E. of mean) muM. A hybridized reconstituted actomyosin made with cardiac myosin and the actin-tropomyosin-troponin complex extracted from rabbit skeletal muscle was also activated by calcium but the half-maximal value was shifted to 0.65 +/- 0.02 (S.E. of mean) muM Ca2+. Homologous rabbit skeletal actomyosin showed half-maximal activation at 0.90 +/- 0.01 (S.E. of mean) muM Ca2+ and the value for a hybridized actomyosin made with rabbit skeletal myosin and the actin-complex from cardiac muscle was found at 1.4 +/- 0.03 (S.E. of mean) muM Ca2+ concentration. Kinetic analysis of the Ca2+ activated ATPase activity of reconstituted bovine cardiac actomyosin indicated some degree of cooperativity with respect to calcium. Double reciprocal plots of reconstituted actomyosins made with bovine cardiac actin complex were curvilinear and significantly different than those of reconstituted actomyosins made with the rabbit fast skeletal actin complex. The Ca2+-dependent cooperativity was of a mixed type as determined from Hill plots for homologous reconstituted bovine cardiac and rabbit fast skeletal actomyosin. The results show that cooperative interactions in reconstituted actomyosins were greater when the actin-tropomyosin-troponin complex was derived from cardiac than skeletal muscle.
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PMID:Cooperative interactions between the contractile proteins of cardiac and skeletal muscle. 13 46

beta-Naphthoquinone-4-sulfonate was used for chemical modification of amino groups of myosin. The reagent was found to affect also the sulfhydryl groups if the reaction was not prevented by previous disulfide exchange with cystamine. When cystamine protection was employed the ATPase (ATP phosphohydrolase, EC3.6.1.3) activity was enhanced in the presence of Mg2+ and decreased in the presence of K+ or Ca2+, a pattern typical of myosin with blocked essential amino groups. On addition of ATP or ADP a blueshift was observed in the fluorescent emission spectrum of beta-naphthoquinone-4-sulfonate bound by myosin, presumably owing to conformational changes in the environment of essential amino groups induced by the binding of nucleotides.
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PMID:Studies on the amino groups of myosin ATPase. III. Effect of nucleotides on the fluorescence of beta-naphthoquinone-4-sulfonate bound to amino groups of myosin. 13 47

Purified right-side-out (RSO) and inside-out (IO) plasma membrane vesicles release 35% of the total plasma membrane proteins after EDTA treatment. After such a treatment both types of vesicles exhibited the same total activity of (Na+ + K+)-stimulated Mg2+ adenosinetriphosphatase (ATPase; ATP phosphohydrolase, EC 3.6.1.3) as in their native state. The EDTA treatment increases the enzyme sensitivity to ouabain by 350-fold in IO vesicles while being without any effect RSO vesicles. Thus, proteins released only from the IO vesicles led to a change in ouabain sensitivity of the (Na+ + K+)-stimulated Mg2+ ATPase. Moreover, only proteins released from IO vesicles, when added to treated IO vesicles with divalent cations, were able to restore the original resistance of the enzyme to ouabain; released proteins from RSO vesicles failed to make such a reconstitution. Thus, we assume that these proteins detach from the inner face of the plasma membrane upon EDTA treatment and are distinct from the enzyme. Polyacrylamide gel electrophoresis indicates that these inner face plasma membrane proteins are approximately 30,000 daltons.
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PMID:Roles of proteins from inner face of plasma membranes in susceptibility of of (Na+ + K+)-stimulated Mg2+ adenosinetriphosphatase to ouabain. 13 8

The association and dissociation rate constants for the interaction of [3H]-ouabain with partially purified rat brain (Na+,K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) in vitro were estimated from the time course of the [3H]-ouabain binding observed in the presence of Na+, Mg2+ and ATP by a polynomial approximation-curve-fitting technique. The reduction of the association rate constant by K+ was greater than its reduction of the dissociation rate constant. Thus, the affinity of Na+,K+)-ATPase for ouabain was reduced by K+. The binding-site concentration was unaffected by K+. Consistent with these findings, the addition of KCl to an incubation mixture at the time when [3H]-ouabain binding to (Na+,K+)ATPase is close to equilibrium, caused an immediate decrease in bound ouabain concentration, apparently shifting towards a new, lower equilibrium concentration. Dissociation rate constants which were estimated following the termination of the ouabain-binding reaction were different from those estimated with above methods and may not be useful in predicting the ligand effects on equilibrium of the ouabain-enzyme interaction.
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PMID:Kinetics studies on the interaction between ouabain and (Na+,K+)-ATPase. 13 32

Kinetic measurement of the reaction of dynein ATPase (ATP phosphohydrolase, EC 3.6.1.3) extracted from the gills of Mytilus edulis shows that in the presence of Mg2+ there is a very rapid initial liberation of Pi from the dynein-ATP system, followed by a slower liberation in the steady state. In view of following results, we have confirmed that this phenomenon is not due to the accumulation of end products, a fall in substrate concentration, nor to the presence of labile impurities in ATP but is due to the catalytic activity of dynein ATPase. 1. The replacement of native dynein by heat denatured dynein or other kinds of Mg2+-ATPase could not produce such a burst phenomenon under the same condition. 2. Both the rate of initial burst and that of steady state were proportional to enzyme content over a wide range under our standard condition. 3. Initial burst was also observed under the constant ATP level by using a ATP generate system. 4. Preincubation of dynein with Pi prior to initiation of the reaction did not eliminate the initial burst. Some properties of the initial rapid liberation of dynein ATPase were also examined. These are shown below. 5. The free ADP liberation did not show any initial burst though the Pi liberation did in the initial phase and the rate of free ADP liberation was almost equal to that of Pi liberation of the steady state. 6. Mg2+ was more effective than Ca2+ for the appearance of the initial burst while the liberation of Pi in the steady state was activated more by Ca2+ than by Mg2+. The addition of K+ in the presence of Mg2+ resulted in a marked increase of Pi liberation in the steady state but not in the initial state. 7. The activation energy of the initial burst was 9.7 kcal, which is slightly smaller than that of myosin ATPase.
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PMID:Studies on the initial phase of dynein ATPase activity. 13 33

1. The effect of free Mg2+, MgEDTA and MgCDTA on the phofphorylation of the (Na+ + K+)-activated ATPase (ATP phosphohydrolase, EC 3.6.1.3) has been studied. 2. 10 mM trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CDTA) added simultaneously with [gamma-32P]ATP to a solution containing the enzyme, 1 mM Mg2+ and 150 mM Na+ does not prevent formation of phospho-enzyme. When [gamma-32P]ATP is added after CDTA the level of phospho-enzyme obtained decreases with increase in the time interval between addition of CDTA and ATP. The inability of CDTA to prevent the formation of phospho-enzyme becomes more pronounced when the medium contains MgEDTA. In the presence of CDTA the maximum amount of phospho-enzyme formed increases with the MgEDTA concentration. 3. Without CDTA the steady-state level of phospho-enzyme is directly proportional to the logarithm of free Mg2+ concentration. Neither with suboptimal nor with optimal concentrations of free Mg2+ does MgEDTA have an effect on the level of phospho-enzyme formed. 4. Using the phospho-enzyme level as a measure of free Mg2+ the experiments show that CDTA reacts slower with Mg2+ than does EDTA, but the stability constant of MgCDTA complex is higher than of MgCDTA, complex. 5. Due to the higher stability constant, of MgCDTA, as compared to MgEDTA, addition of CDTA to a medium containing free Mg2+ and MgEDTA will not only chelate the free Mg2+, but it will also shift the equilibrium from MgEDTA towards MgCDTA, i.e. MgEDTA acts as a source of free Mg2+ which is then chelated by CDTA. The experiments show that it takes minutes before Mg2+, EDTA and CDTA come to equilibrium. Provided the dissociation of MgEDTA is faster than the formation of the MgCDTA complex, the medium will contain a concentration of free Mg2+ which at any given instant is near in equilibrium with a slowly decreasing concentration of MgEDTA; this free Mg2+ can support phosphorylation. This can explain why the rate with which CDTA stops phosphorylation decreases with an increase in the MgEDTA concentration. 6. When phosphorylation is stopped by addition of unlabelled ATP, the rate of dephosphorylation is faster than when it is stopped by addition of CDTA both with and without EDTA in the medium. CDTA reacts too slowly with Mg2+ to be used as a chelator in studies where a fast removal of Mg2+ is required. 7. A previous finding has been verified, namely that the rate of spontaneous, of K+-stimulated and of ADP-stimulated dephosphorylation is independent of the Mg2+ concentration during formation of phospho-enzyme.
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PMID:The effect of chelators on Mg2+, Na+-dependent phosphorylation of (Na+ + K+)-activated ATPase. 13 34

ATP plus Mg2+ plus Na+ supported [3H]ouabain binding to canine left ventricular tissue homogenates and microsomal (Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) activity from the same tissue were measured. A linear relationship was found between the initial velocity of [3H]ouabain binding to tissue homogenates and microsomal (Na+ + K+)-ATPase activity from the same tissue in the presence and absence of in vivo bound digoxin. In vivo bound digoxin reduced both measurements. With tissue from digoxin-free hearts, a linear relationship was also obtained between the initial velocity and the maximum level of [3H]ouabain binding to tissue homogenate. Binding of [3H]ouabain to whole tissue homogenate is a convenient method for estimating (Na+ + K+)-ATPase activity in small left ventricular biopsy samples.
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PMID:Correlation between microsomal (Na+ + K+)-ATPase activity and [3H]ouabain binding to heart tissue homogenates. 13 36

The hydrolysis of [gamma-32P]ATP by porcine brain (Na+ + K+)-stimulated ATP phosphohydrolase (EC 3.6.1.3) has been studied at 28 degree C in a rapid mixing quenched-flow apparatus. An "early burst" in the release of Pi from ATP has been observed when the enzyme is mixed with ATP, Na+ and a relatively high concentration of K+ (10 mM) but the burst is less pronounced with 0.5 mM K+. This "early burst" of Pi release is suppressed when the enzyme is pre-mixed with 10 mM K+ or 20% (v/v) dimethylsulphoxide before mixing with ATP and Na+, and premixing of enzyme with Na+ antagonizes this effect of dimethylsulphoxide. The results have been analysed by a non-linear least squares regression treatment and are consistent with a mechanism involving three steps, one of which may be a relatively slow change in enzyme conformation following release of Pi from its covalent linkage with the enzyme, in addition to formation of the enzyme-substrate complex. Rate constants (and S.E.) for these steps have been calculated and the roles of phospho-enzyme and other intermediates in the reaction mechanism of the transport ATPase are dicussed.
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PMID:The pre-steady-state hydrolysis of ATP by porcine brain (Na+ + K+)-dependent ATPase. 13 37

The activity of a Ca2+-adenosinetriphosphatase (ATP phosphohydrolase, EC 3.6.1.3) increases during the mitotic phase of synchronized mouse mastocytoma P-815X2 cells. The enzyme is synchronized mouse mastocytoma P-815X2 cells. The enzyme is synthesized mainly during a distinct period of the interphase and is activated at mitosis. It is thought to regulate the formation of the mitotic apparatus by controlling the concentration of Ca2+ ions at the site of formation of the mitotic spindle.
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PMID:Synthesis and activation of mitotic Ca2+-adenosinetriphosphatase during the cell cycle of mouse mastocytoma cells. 14 Mar 77


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