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)

1. Extracts of several plant species contained nucleoside-AMP phosphotransferase activity. The ratio of activity with thymidine to that with uridine as nucleoside substrate was essentially constant, both between species and throughout plant development. Evidence is presented that the total thymidine-AMP phosphotransferase activity of the leaves of Asplenium nidus (bird's-nest fern) and of Helianthus tuberosus (Jerusalem artichoke) increases during maturation. 2. Thymidine-AMP phosphotransferase was purified 22-fold from a very rich source of this activity, extracts of A. nidus. 3. A broad specificity towards both nucleoside and nucleoside 5'-monophosphate substrates is displayed by this preparation, and the evidence suggests that all could be due to a single enzyme. 4. Nucleosides that act as substrates will also inhibit phosphotransfer to other nucleosides, with Ki values close to the corresponding Km values found when utilized as substrates. 5. Ca2+-activated ATP phosphohydrolase was separated from the phosphotransferase by differential complexing to Blue Dextran in the presence of urea, whereas an AMP phosphohydrolase activity was closely associated with thymidine-AMP phosphotransferase through all separation techniques used. 6. Metal ions did not activate either of the latter two activities, and 1,10-phenanthroline was found to inhibit the phosphotransferase. 7. Km values for AMP for the respective activities were 0.11 mM (thymidine phosphotransferase) and 0.20 mM (AMP phosphohydrolase) and for thymidine (phosphotransferase only) 0.88 mM. 8. 3':5'-Cyclic AMP was found to inhibit both phosphotransferase and AMP phosphohydrolase activities, with Ki values of 0.056 mM and 0.15 mM respectively. It is suggested that this inhibitor would be of value in revealing the existence of thymidine kinase in plant extracts with high thymidine phosphotransferase activity.
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PMID:Thymidine phosphotransferase and nucleotide phosphohydrolase of the fern Asplenium nidus. General properties and inhibition by adenosine 3':5'-cyclic monophosphate. 18 31

The purpose of this study was to investigate the contribution of mitochondrial and cytoplasmic protein synthesis to the biogenesis of cytochrome oxidase (ferrocytochrome c:oxygen oxidoreductase EC 1.9.3.1) and rutamycin-sensitive adenosine triphosphatase (ATP phosphohydrolase EC 3.6.1.3) in cultured oocytes of the toad, Xenopus laevis. X. laevis cytochrome oxidase was purified over 23-fold with respect to specific activity and over 29-fold with respect to specific heme a content from oocyte submitochondrial particles. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate separated the enzyme into six subunits with molecular weights of 44,000, 33,000, 23,000, 17,000, 12,000 and 9,500. the synthesis of the three larger subunits is sensitive to chloramphenicol (an inhibitor of mitochondrial protein synthesis), indicating that these subunits are made on mitochondrial ribosomes; the synthesis of the three smaller subunits is sensitive to cycloheximide (an inhibitor of cytoplasmic protein synthesis) and therefore occurs on cytoplasmic ribosomes. X. laevis rutamycin-sensitive ATPase, purified over 19-fold from oocyte submitochondrial pparticles, consists of 10 subunits with molecular weights of 56,000, 53,000, 41,000, 32,000, 29,000, 24,000, 21,000, 17,500 (2), and 11,500 on sodium dodecyl sulfate-polyacrylamide gels. The 29,000, 21,000, and one of the 17,500-dalton polypeptides are synthesized in the presence of cycloheximide and are, therefore, products of mitochondrial protein synthesis; the synthesis of the remaining seven subunits occurs in the presence of chloramphenicol, indicating that these subunits are made on cytoplasmic ribosomes. The synthesis of protein by mitochondria in cultured oocytes appears to be dependent upon cytoplasmic protein synthesis. In the presence of cycloheximide, the mitoribosomal synthesis of the subunits of cytochrome oxidase and rutamycin-sensitive ATPase is detectable only after a prior inhibition of mitochondrial protein synthesis by chloramphenicol. Oocyte mitochondrial ribosomes synthesize at least nine polypeptides after chloramphenicol treatment, three of which are components of neither cytochrome oxidase nor rutamycin-sensitive ATPase.
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PMID:Synthesis of the mitochondrial inner membrane in cultured Xenopus laevis oocytes. 18 93

1. Incubation of purified (Na+ + K+)-ATPase (ATP phosphohydrolase EC 3.6.1.3) from rabbit kidney outer medulla with butanedione in borate buffer leads to reversible inactivation of the (Na+ + K+)-ATPase activity. 2. The reaction shows second-outer kinetics, suggesting that modification of a single amino acid residue is involved in the inactivation of the enzyme. 3. The pH dependence of the reaction and the effect of borate ions strongly suggest that modification of an arginine residue is involved. 4. Replacement of Na+ by K+ in the butanedione medium decreases inactivation. 5. ATP, ADP and adenylyl imido diphosphate, particularly in the presence of trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid to complex Mg2+, protect the enzyme very efficiently against inactivation by butanedione. 6. The (Na+ + Mg2+)-dependent phosphorylation capacity of the enzyme is inhibited in the same degree as the (Na+ + K+)-ATPase activity by butanedione. 7. The K+-stimulated p-nitrophenylphosphatase activity is much less inhibited than the (Na+ + K+)ATPase activity. 8. The ATP stimulation of the K+-stimulated p-nitrophenylphosphatase activity is inhibited by butanedione to the same extent as the (Na+ + K+)-ATPase activity. 9. Modification of sulfhydryl groups with 5,5'-dithiobis(2-nitrobenzoic acid) protects partially against the inactivating effect of butanedione. 10. The results suggest that an arginine residue is present in the nucleotide binding centre of the enzyme.
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PMID:An essential arginine residue in the ATP-binding centre of (Na+ + K+)-ATPase. 19 70

Fragmented sarcoplasmic reticulum (SR) was reacted with a thiol-directed spin label, N-(1-oxyl-2,2,6,6,-tetramethyl-4-piperidinyl)maleimide, under various conditions. It was found that ATP inhibited the binding of the label to SR protein in the initial phase of the reaction, but as the incubation time was extended up to 18 h, the amount of label bound to SR protein in the control and ATP-containing samples became almost identical. The Ca2+-dependent ATPase control and ATP-containing samples became almost identical The Ca2+-dependent ATPase (ATP phosphohydrolase [EC 3.6.1.3]) of SR was protected by the presence of ATP during incubation with relatively low concentrations of spin label, irrespective of the total amount of label bound, although with increasing concentration of bound label the ATPase activity decreased. Deoxycholate slightly reduced the rotational freedom of the label bound to SR protein and decreased the initial rate of quenching of protein-bound nitroxide by ascorbate. From an analysis of these results, it was concluded that the binding of deoxycholate to protein decreases the accessibility of ascorbate to the protein-bound label.
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PMID:Spin-labeling of adenosine triphosphatase in sarcoplasmic reticulum membrane and change in the state of the spin labels induced by deoxycholate. 20 Jun 8

Mitoplasts, that is, mitochondria freed from their outer membranes, were prepared from pig heart. Sonication induced an inversion of these mitoplasts, giving inside-out vesicles. Added cytochrome c can be bound much better to mitoplasts than to sonicated vesicles; addition of trypsin increased adenosinetriphosphatase (ATPase) (ATP phosphohydrolase; EC 3.6.1.3) activity of sonicated vesicles without significantly affecting that of the mitoplasts. Since the site of fixation of cytochrome c was located on the outer side of the inner mitochondrial membrane and since the protein inhibitor of the mitochondrial ATPase is present on the inner face of the inner membrane and is very sensitive to trypsin, it can be concluded that mitoplasts are mainly oriented as normal mitochondria while sonicated vesicles are mainly inverted. Trypsin treatment can abolish the oligomycin sensitivity of ATPase activity of either mitoplasts or sonicated vesicles. However, trypsin induced the solubilization of the soluble F(1)-ATPase of sonicated vesicles while the ATPase activity remained with the mitoplasts after trypsin action. Therefore, trypsin destroyed the oligomycin effect by rupturing the liaison between F(1) and the membrane in sonicated vesicles. On the other hand, the effect of trypsin on mitoplasts must be attributed to the hydrolysis of a protein located near the outer surface of the inner membrane that is at least structurally involved in the oligomycin sensitivity of the ATPase complex.
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PMID:Location of protein(s) involved in oligomycin-induced inhibition of mitochondrial adenosinetriphosphatase near the outer surface of the inner membrane. 20 Sep 6

Human renal (Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) preparations which exhibited a non-linear reaction rate, contained high levels of membrane-bound cyclic AMP-dependent protein kinase, while this latter activity was much less or absent in purified preparations. A non-linear reaction rate was observed in a purified preparation of (Na+ + K+)-ATPase by reconstituting the enzyme into lipid vesicles with cyclic AMP-dependent protein kinase. The addition of cyclic AMP to the ATPase assay of these lipid vesicles inactivated the (Na+ + K+)-ATPase. The cytoplasmic fraction of the cell contained a nondialyzable factor, which prevented (or reversed) the cyclic AMP-mediated inactivation of the enzyme.
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PMID:Reversible in activation of purified (Na+ + K+)-ATPase from human renal tissue by cyclic AMP-dependent protein kinase. 20 25

1. Formycin triphosphate (FTP), a fluorescent analogue of ATP, is a substrate for (Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3), with properties similar to those of ATP. 2. FTP and formycin diphosphate (FDP) bind to the enzyme with high affinity and, on binding, the nucleotide fluorescence is enhanced 3-4-fold. It is therefore possible, with a stopped-flow fluorimeter, to measure the rates of binding and release of FTP and FDP under conditions in which turnover does not occur. 3. When the enzyme-FTP complex is exposed to conditions permitting turnover (Mg2+, Na+ +/- K+), changes in fluorescence occur which can be explained by supposing that they reflect the interconversion of states with or without bound nucleotides. A rapid fall in fluorescence, that we attribute to the rapid release of FDP from newly phosphorylated enzyme, is followed by a steady state in which low fluorescence suggests that little nucleotide is bound. Eventually, exhaustion of FTP allows rebinding of FDP to the enzyme, which is signalled by a rise in fluorescence. 4. The estimated rate of FDP release from newly formed phosphoenzyme is unaffected by the presence of K+ (0-2 mM) or the concentration of FTP (1-20 micron). 5. Experiments with [gamma-32P]FTP show that about 1 mol of 32P is incorporated per mol of enzyme. The rate of phosphorylation of the enzyme by [gamma-32P]FTP has been measured with a rapid-mixing-and-quenching apparatus. 6. Kinetic data from the fluorescence and phosphorylation experiments show that the behaviour of the enzyme, at least at the low nucleotide concentrations employed, is consistent with the Albers-Post model, and is difficult to reconcile with models in which K+ acts at or before the step in which FDP is released during turnover.
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PMID:Elementary steps of the (Na+ + K+)-ATPase mechanism, studied with formycin nucleotides. 21 Aug 11

1. Fluorescence measurements have shown that formycin triphosphate (FTP) or formycin diphosphate (FDP) bound to (Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) in Na+-containing media can be displaced by the following ions (listed in order of effectiveness): Tl+, K+, Rb+, NH4+, Cs+. 2. The differences between the nucleotide affinities displayed by the enzyme in predominantly Na+ and predominantly K+ media in the absence of phosphorylation, are thought to reflect changes in enzyme conformation. These changes can therefore be monitored by observing the changes in fluorescence that accompany net binding or net release of formycin nucleotides. 3. The transition from a K+-bound form (E2-(K)) to an Na+-bound form (E1-Na) is remarkably slow at low nucleotide concentrations, but is accelerated if the nucleotide concentration is increased. This suggests that the binding of nucleotide to a low-affinity site on E2-(K) accelerates its conversion to E1-Na; it supports the hypothesis that during the normal working of the pump, ATP, acting at a low affinity site, accelerates the conversion of dephosphoenzyme, newly formed by K+-catalysed hydrolysis of E2P, to a form in which it can be phosphorylated in the presence of Na+. 4. The rate of the reverse transformation, E1-Na to E2-(K), varies roughly linearly with the K+ concentration up to the highest concentration at which the rate can be measured (15 mM). Since much lower concentrations of K+ are sufficient to displace the equilibrium to the K-form, we suggest that the sequence of events is: (i) combination of K+ with low affinity (probably internal) binding sites, followed by (ii) spontaneous conversion of the enzyme to a form, E2-(K), containing occluded K+. 5. Mg2+ or oligomycin slows the rate of conversion of E1-Na to E2-(K) but does not significantly affect the rate of conversion of E2-(K) to E1-Na. 6. In the light of these and previous findings, we propose a model for the sodium pump in which conformational changes alternate with trans-phosphorylations, and the inward and outward fluxes of both Na+ and K+ each involve the transfer of a phosphoryl group as well as a change in conformation between E1 and E2 forms of the enzyme or phosphoenzyme.
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PMID:Conformational transitions between Na+-bound and K+-bound forms of (Na+ + K+)-ATPase, studied with formycin nucleotides. 21 Aug 12

The effects of two lectins, wheat germ agglutinin and concanavalin A, were studied on a variety of parameters of two highly purified (Na+ + K+)-ATPases (ATP phosphohydrolase, EC 3.6.1.3), from the rectal salt gland of Squalus acanthias and from the electroplax of Electrophorus electricus. Both lectins agglutinated the rectal gland enzyme equally, but wheat germ agglutinin inhibited (Na+ + K+)-ATPase activity much more. The electroplax enzyme was only marginally agglutinated and inhibited by the lectins. Neuraminidase treatment of the rectal gland (Na+ + K+)-ATPase had no effect on germ agglutinin inhibition. The inhibition of the rectal gland (Na+ + K+)-ATPase by wheat germ agglutinin could be reversed by N,N'-diacetylchitobiose, which has a high affinity for wheat germ agglutinin. Neither ouabain inhibition nor ouabain binding to the rectal gland enzyme was affected by wheat germ agglutinin. The p-nitrophenylphosphatase activity of the rectal gland enzyme was not inhibited by wheat germ agglutinin. Na+-ATPase activity, which reflects ATP binding and phosphorylation at the substrate site was inhibited by wheat germ agglutinin and this inhibition was reversed by potassium. Evidence is cited (Pennington, J. and Hokin, L.E., in preparation) that the inhibition of the (Na+ + K+)-ATPase by wheat germ agglutinin is due to binding to the glycoprotein subunit.
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PMID:Effects of wheat germ agglutinin and concanavalin A on parameters of highly purified sodium-potassium adenosine triphosphatases from Squalus acanthias and Electrophorus electricus. 21 Aug 20

The mechanism of interaction between prednisolone-3,20-bisguanylhydrazone (PBGH) and Na+,K+-ATPase (ATP phosphohydrolase, EC 3.6.1.3) was studied using partially purified rat brain enzyme preparations. PBGH inhibited Na+,K+-ATPase rapidly and reversibly. The enzyme-inhibiting action of PBGH was competitively antagonized by potassium. PBGH inhibited Na+,Mg2+ and ATP-supported binding of (3H)-ouabain to the enzyme. When PBGH was added to the incubation mixture at the time when the (3H)-ouabain binding was close to its equilibrium state, the concentration of (3H)-ouabain complex was rapidly reduced and shifted to a lower equilibrium state. A double reciprocal plot analysis of the (3H)-ouabain binding data indicates that the inhibition of ouabain binding by PBGH is apparently competitive. Binding of (3H)-ouabain in the presence of Tris-phosphate and Mg2+ was also inhibited by unlabeled PBGH. Thus, it appears that the binding of PBGH precludes the binding of ouabain to Na+,K+-ATPase.
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PMID:Prednisolone-3,20-bisguanylhydrazone: the mode of interaction with rat brain sodium and potassium-activated adenosine triphosphatase. 21 75


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