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)

Mitochondrial ATPases from rat liver and beef heart were used to study the effects of guanylylimidodiphosphate (GMP-P(NH)P) and adenylylimidodiphosphate (AMP-P(NH)P) on the kinetics of MgATP, MgITP, and MgGTP hydrolysis. AMP-P(NH)P was a noncompetitive inhibitor of hydrolysis of all substrates with the rat liver enzyme, whether activating anions were present or not. Also with the liver enzyme, AMP-P(NH)P caused only MgATP hydrolysis to appear to have positive cooperativity. With the beef heart enzyme, AMP-P(NH)P was a competitive inhibitor of ATPase activity and caused positive cooperativity; it gave noncompetitive patterns with GTP or ITP as substrates. In both enzyme systems, GMP-P(NH)P gave complex inhibition patterns with MgATP as the substrate, but was a competitive inhibitor of MgITP and MgGTP hydrolysis. These results are interpreted as indicating the existence of two types of nucleotide binding sites, with varying degrees of specificity and interaction on the ATPase molecules from both sources. It is postulated that MgATP and AMP-P(NH)P bind to regulatory site while MgATP, MgGTP, Mgitp, and GMP-P(NH)P bind to the catalytic site.
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PMID:Kinetic studies on rat liver and beef heart mitochondrial ATPase. Evidence for nucleotide binding at separate regulatory and catalytic sites. 12 41

In the present paper the mechanism of the adenosine formation by a mixture of nerve ending and transmitter granula fractions was invesitgated. The adenosine formation in vivo is only possible via the whole degradation chain ATP - ADP - AMP - adenosine. The enzymes involved are ATPases, adenylate kinase and 5'-nucleotidase. The ATPase and adenylate kinase effectors Ca++ and Mg++ can be regarded as trigger ions switching on and off the degradation chain. The adenylate kinase represents a key enzyme within the whole chain. In the ion-activated state a non-inhibited adenosine formation was observed, when the initial ATP concentration amounted to less than 0,1 muMol per mg synaptosomal membrane protein. Under these conditions the whole chain velocity is mainly dependent on the 5'-nucleotidase concentration, because ATPases and adenylate kinase remove the nucleotidase inhibitors ATP and ADP spontanously. The conditions for the optimal velocity of the adenosine formation at the synaptic membrane in vivo in all probability are present. A hypothesis for the mechanism of the synaptic adenosine formation in vivo was developed. The importance of this process in respect to the synaptic transmission was discussed.
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PMID:[Mechanism of synaptosomal degradation of ATP in connection with involvement of adenosine in the transmission process]. 12 26

Mitochondrial ATPase from rat liver mitochondria contains multiple nucleotide binding sites. At low concentrations ADP binds with high affinity (1 mole/mole ATPase, KD = 1-2 muM). At high concentrations, ADP inhibits ATP hydrolysis presumably by competing with ATP for the active site (KI = 240-300 muM). As isolated, mitochondrial ATPase contains between 0.6 and 2.5 moles ATP/mole ATPase. This "tightly bound" ATP can be removed by repeated precipitations with ammonium sulfate without altering hydrolytic activity of the enzyme. However, the ATP-depleted enzyme must be redissolved in high concentrations of phosphate to retain activity. AMP-PNP (adenylyl imidodiphosphate) replaces tightly bound ATP removed from the enzyme and inhibits ATP hydrolysis. AMP-PNP has little effect on high affinity binding of ADP. Kinetics studies of ATP hydrolysis reveal hyperbolic velocity vs. ATP plots, provided assays are done in bicarbonate buffer or buffers containing high concentrations of phosphate. Taken together, these studies indicate that sites on the enzyme not directly associated with ATP hydrolysis bind ATP or ADP, and that in the absence of bound nucleotide, Pi can maintain the active form of the enzyme.
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PMID:Interaction of homogeneous mitochondrial ATPase from rat liver with adenine nucleotides and inorganic phosphate. 12 85

Accelerated calcium transport into the sarcoplasmic reticulum (SR) of the heart may mediate the inotropic actions of agents that act to increase adenosine 3',5'-monophosphate (cyclic AMP) within the cell. Studies in our laboratory have shown that ATP-dependent Ca uptake by cardiac microsomes rich in SR is enhanced by pretreatment with bovine cardiac cyclic AMP-dependent protein kinase (cyclic AMP-PK). Ca2+-activated ATPase is increased concomitantly with Ca uptake, stoichiometric coupling of 2 moles of Ca2+ taken up per mole of ATP hydrolyzed remaining constant. The steady state level of Ca binding is not increased by cyclic AMP-PK pretreatment, suggesting that the turnover rate of the transport system rather than the number of transport sites is increased. Phosphorylation of the SR by protein kinase is half-maximal at approximately 10(-7) M cyclic AMP, a value similar to that which gives half-maximal stimulation of both Ca uptake and Ca2+-activated ATPase. Over 80 percent of the 32P associated with membrane protein is identifiable as phosphoserine and phosphothreonine. The 32P is incorporated into a 22,000-dalton protein as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This protein, which we have tentatively named phospholamban (lambda alpha mu beta alpha psi usilon epsilon omega = to receive) appears to particiapte in the regulation of calcium transport by the heart's SR and may play a role in the inotropic actions of drugs, such as epinephrine, which act upon the cyclic AMP-PK system.
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PMID:Phospholamban: a regulatory protein of the cardiac sarcoplasmic reticulum. 12 51

Concanavalin A inhibits the (Na+-K+)-ATPase activity of isolated rat-liver plasma membranes, while leaving the Mg2+-ATPase unaffected. Glucagon and cyclic AMP act supplementary to the lectin in the inhibition. The lectin effect is counteracted by insulin and L-epinephrine, and is completely abolished by the beta-adrenergic blocking agent propranolol. Results are discussed on the basis of the known interactions of concanavalin A with plasma membrane components, including its hormone-like action.
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PMID:Studies on plasma membranes. XXIII. Hormone-like action of concanavalin A on liver plasma membranes: inhibition of (Na+-K+)ATPase. 12 72

1. Insulin stimulates the activity of membrane-bound ATPase isolated from frog skeletal muscle and from rat brain. The increase in activity of the membrane-bound ATPase system isolated from frog ranged from 9-8 to 53% at concentrations of Na+ (25 mM), K+ (10 mM), and ATP (2 mM) similar to those in in vivo experiments conducted previously (Moore, 1973). The increased activity of the membrane-bound ATPase is, therefore, at least as great as the insulin-induced increase in Na efflux (10-38%) from intact cells (Moore, 1973). If the concentration of Na+ is lowered to 4 mM and that of ATP lowered to 0-5 mM albumin, and 10(6) M, the increase in ouabain-inhibitable ATPase activity can reach as high as 400%. 2. Ouabain, at a concentration (10(-3) M) sufficient to inhibit stimulation of the frog ATPase by increasing Na from 4 to 25 mM, completely blocked the stimulation of ATPase activity due to insulin. 3. At 2 mM-ATP, 100 mM-Na+, and 20 mM-K+, conditions which maximally activate the (Na+ + K+)-ATPase, insulin did not increase the ATPase, activity. Stimulation was consistently seen at 10 mM-K+, 0-5 mM-ATP, and either 4 mM or 25 mM-Na+. 4. The finding that insulin does not stimulate the ATPase activity in conditions in which the (Na+ + K+)-ATPase component is maximally activated and especially the fact that ouabain can reproducibly inhibit insulin stimulation of the membrane-bound ATPase activity strongly suggest that interaction of insulin with its receptor upon the plasma membrane somehow stimulates the (Na+ + K+)-ATPase system (ouabain sensitive; ATP phosphohydrolase, EC (3.6.1.3). These results are consistent with previous studies of the effect of insulin upon Na efflux from intact cells (Moore, 1973) and support the previous conclusion that the component of Na efflux stimulated by insulin is active. The evidence suggests that insulin probably does not affect Vmax of the (Na+ + K+)-ATPase system, but may increase the affinity of the enzyme system to one or more effectors, most likely Na+, ATP, and perhaps K+. 5. Oxidized glutathione (2-7 X 10(-6) M), 10(-6) M, 10(-7) M, and 10(-8) M cyclic AMP did not affect the ATPase activity 10(-6)Malbumin, and . 6. The results are consistent with the view that the Na pump, (Na+ + K+)-ATPase, is intimately involved with the physiological action of insulin and may be transducer between the binding of insulin to its receptor on the plasma membrane and the cellular actions of insulin.
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PMID:Effect of insulin upon membrane-bound (Na+ + K+)-ATPase extracted from frog skeletal muscle. 12 36

A study in the enzymatic properties of muscle membranes established that sarcolemma of the rabbit skeletal muscles contains the Ca2+-ATPase system which does not require Mg2+ for manifestation of ions activity. By some kinetic properties it differs from ATPase of myosin. The complex Ca-ATP2+ is a substrate of Ca2+-ATPase. Ions of a series of bivalent metals inhibit the latter as well as the passive transport of Ca2+, that may evidence for a definite relation of Ca2+-ATPase with Ca+2 transport in skeletal muscles. Acetyl cholinesterase and AMP-aminohydrolase are strongly bound with the sarcolemma. The sarcolemma structural organization is shown to play a certain role in manifestation of their activity. On the basis of the data obtained when studying the activity in the ATPase systems and dynamics of formation and decay of the intermediate phosphorylated product in the microsomal fraction of cow and rabbit myometrium certain peculiarities are established for the active mechanisms of Ca2+ transport in smooth muscles. A problem is under discussion on the possible active participation of sarcolemma in regulation of Ca2+ concentration in the smooth muscle cells. Two ATPase systems, Mg2+-dependent and Mg2+-dependent Ca2+ activated are found in nuclei; the role of lipids of the skeletal muscles in manifestation of their activity is studied. AMP-amino hydrolase properties are characterized for different areas of the sarcoplasmatic reticulum membranes. The model of E-avitaminous muscular distrophy was used to show disturbances in the structure of sarcolemma and membranes of the sarcoplasmatic reticulum which are accompanied by changes in their ATPase and Ca2+-transporting properties.
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PMID:[Enzymatic properties in muscle membranes]. 12 74

Tightly bound adenine nucleotides are removed from multiple binding sites on beef heart mitochondrial ATPase (F1) by chromatography on columns of Sephadex equilibrated with 50% glycerol. Release of nucleotides from the enzyme is associated with large decreases in sedimentation velocity (from 11.9 S to 8.4 S) which may be observed in concentrated solutions of polyols. Polyol-induced conformational changes are reversed when the enzyme is returned to dilute buffers. The nucleotide-depleted enzyme restores oxidative phosphorylation in F1-deficient submitochondrial particles. Reconstitution of nucleotide-depleted F1 with the ATP analog (adenylyl-imidodiphosphate (AMP-PNP), almost 5 moles of AMP-PNP per mole of enzyme, results in preparations with substantially inhibited ATPase activity which nevertheless restores oxidative phosphorylation and the 32Pi-ATP exchange reaction in F1-deficient submitochondrial particles. Incubation of the analog-labeled enzyme with ATP and Mg++ results in partial displacement of the analog and a time-dependent recovery of ATPase activity.
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PMID:Physical and enzymatic properties of nucleotide-depleted beef heart mitochondrial adenosine triphosphatase. 12 61

Two highly lead-sensitive ATPases, Na+,K+-ATPase and adenylate cyclase, can be demonstrated cytochemically by the lead precipitation technique in briefly prefixed tissue, provided that the free Pb2+ concentration in the incubation medium is kept below 0.1 mM by a heavy metal chelator. Under conditions suitable for Na+,K+-ATPase activity precipitation of final reaction product (lead phosphate) at the sarcolemma of cardiac muscle is abolished by 0.1-1mM ouabain. In contrast, reaction product deposition at the intramuscular part of the plasma membrane and at intracellular sites is not noticeably affected by the glycoside. These findings indicate either that the sarcolemma is the exclusive location of Na+,K+-ATPase in cardiac muscle or that the presence of the enzyme at other loci is masked by active Na+,K+-independent, ouabain resistant ATPases. Under conditions favoring adenylate cyclase activity, precipitation by Pb2+ of orthophosphate derived, with the help of added cyclic nucleotide phosphodiesterase and 5'-nucleotidase, from cyclic AMP formed from adenylyl imidodiphosphate (AMP-PNP) is seen after prolonged incubation in myocardial cells along the entire course of the plasma membrane and also at the transverse tubules and is particularly intense at the tight junction regions of the intercalated disks. Ouabain has no effect on these reactions. Reaction product deposition is also observed at the sarcolemma in red skeletal muscle and at the terminal cisternae of the sarcoplasmic reticulum in white skeletal muscle, where the reaction is intensified by adrenaline. Sarcoplasmic reticulum of cardiac and of red skeletal muscle exhibits only relatively weak staining attributable to cyclic AMP formation. These observations are in agreement with the results of tissue fractionation studies according to which the plasma membrane is the chief site of adenylate cyclase in heart and in red, but not white skeletal muscle.
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PMID:Cytochemical studies on sarcolemma: Na+, K+-adenosine triphosphatase and adenylate cyclase. 13 Jun 56

The effect of vibration (vibration level of 130 dB at a frequency of 2 Hz; 108, 118, and 105 dB at frequencies of 32, 63 and 125 Hz, respectively) combined with the noise at mid- and low-frequencies (sound pressure level of 85 dBA) was studied as applied to oxidative phosphorylation in mitochondria from skeletal muscles of the rats exposed to a single action of the mentioned factors, for a fortnight and for a month. A certain separation of oxidation and phosphorylation was observed after a fortnight action of the studied factors. The expressed changes in the process of oxidative phosphorylation were detected after the vibration-noise effect for a month. A considerable decrease of the P/O coefficient (almost twice as compared to the control one) occurs when oxygen uptake by mitochondria is intensified (1.9 times) and their phosphorylation activity is lower (by 61.5%). This is accompanied by a rise (by 2.65 times) of Mg2+-activated ATPase of mitochondria and by a deficit of adenylic system components (ATP, ADP, AMP) in the muscular tissue homogenate.
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PMID:[Oxidative phosphorylation in rat skeletal muscles in dynamics of vibration-noise effect]. 13 Jul 5


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