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:3.6.1.25 (triphosphatase)
1,529 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A nucleoside triphosphatase (NTPase) activity appeared to be associated with a highly purified nuclear preparation from rat cardiac ventricles. Different nucleoside triphosphates (UTP greater than GTP greater than ITP greater than CTP) supported this enzymic activity, which was stimulated by Mg2+ but not by Ca2+. The nuclear NTPase activity could be down regulated by endogenous phosphorylation of a 55,000 Mr protein. Maximal phosphorylation of the 55,000 Mr protein occurred in the presence of Mg(2+)-ATP. Addition of cAMP, cGMP, Ca2+, Ca2+/phospholipid, Ca2+/calmodulin, and catalytic subunit of cAMP-dependent protein kinase was not associated with any further phosphorylation of the 55,000 Mr protein. However, in the presence of Ca2+/calmodulin or the catalytic subunit of the cAMP-dependent protein kinase additional proteins became phosphorylated, but these had no effect on the Mg(2+)-NTPase activity. These results indicate that a protein with Mr 55,000 may be involved in the regulation the Mg(2+)-NTPase activity associated with rat cardiac nuclei.
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PMID:Regulation of rat cardiac nuclei-associated Mg(2+)-NTPase by phosphorylation. 165 81

An enzyme able to cleave dinucleoside triphosphates has been purified 3,750-fold from Saccharomyces cerevisiae. Contrary to the enzymes previously shown to catabolize Ap4A in yeast, this enzyme is a hydrolase rather than a phosphorylase. The dinucleoside triphosphatase molecular ratio estimated by gel filtration is 55,000. Dinucleoside triphosphatase activity is strongly stimulated by the presence of divalent cations. Mn2+ displays the strongest stimulating effect, followed by Mg2+, Co2+, Cd2+, and Ca2+. The Km value for Ap3A is 5.4 microM (50 mM Tris-HCl [pH 7.8], 5 mM MgCl2, and 0.1 mM EDTA; 37 degrees C). Dinucleoside polyphosphates are substrates of this enzyme, provided that they contain more than two phosphates and that at least one of the two bases is a purine (Ap3A, Ap3G, Ap3C, Gp3G, Gp3C, m7Gp3A, m7Gp3G, Ap4A, Ap4G, Ap4C, Ap4U, Gp4G, and Ap5A are substrates; AMP, ADP, ATP, Ap2A, and Cp4U are not). Among the products, a nucleoside monophosphate is always formed. The specificity of cleavage of methylated dinucleoside triphosphates and the molecular weight of dinucleoside triphosphatase indicate that this enzyme is different from the mRNA decapping enzyme previously characterized (A. Stevens, Mol. Cell. Biol. 8:2005-2010, 1988).
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PMID:Isolation and characterization of a dinucleoside triphosphatase from Saccharomyces cerevisiae. 165 9

Addition of ATP or ATP analog to the incubation media is shown to result in cell death in experiments with different cultured cell lines as evidenced by the results of several independent assays, both in the absence or presence of extracellular Ca2+. Cytolytic T-lymphocyte (CTL) clone itself was not only resistant to cytolytic effects of ATP, but was able to "rescue" antigen-nonbearing 51Cr-labeled cells from lytic effects of extracellular ATP (but not from lytic effects of adenosine 5'-thiotriphosphate) when present during assay. To test whether the resistance of CTL to ATP is due to a high activity of ecto-ATPase, four independent assays of ATPase activity were utilized to demonstrate the presence and relatively high activity of the ecto-ATPase(s) on CTL surface. Studies of substrate specificity of CTL ecto-ATPase suggest that there is more than one nucleoside 5'-triphosphatase on the surface of CTL. The enzyme(s) activity is Ca2+- and Mg2+-dependent and in this respect is similar to recently described hepatic cells ecto-ATPase. We tested effects of known ATP-binding site-specific reagents fluorescein 5'-isothiocyanate (FITC) and 5'-fluorosulfonylbenzoyladenosine (FSBA) to find covalent modification procedures to be used in studies of functional role of ecto-ATPase. FSBA, but not FITC, inhibits lymphocyte ecto-ATPase but addition of ATP together with FSBA protects ecto-ATPase activity. Inactivation of CTL ecto-ATPase by pretreatment with FSBA makes CTL susceptible to lytic effects of extracellular ATP, as was hypothesized for the functional role of this enzyme in CTL.
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PMID:Ecto-ATPase activity in cytolytic T-lymphocytes. Protection from the cytolytic effects of extracellular ATP. 213 37

Evidence is presented for the existence of ectoenzymes in rat renal cortical brush-border membrane vesicles that produce adenosine as a final product using either ATP, ADP or AMP as substrate. The enzymes are insensitive to levamisole, ouabain, oligomycin and N-ethylmaleimide, and have absolute requirement for divalent cations with following order of activation Mg2+ greater than Ca2+ greater than Mn2+ greater than Ba2+ greater than Zn2+. At least two separate enzymes can be distinguished. One is capable of hydrolyzing ATP, other nucleoside triphosphates and ADP, but not AMP. The enzyme is insensitive to concanavalin A. The other enzyme hydrolyzes AMP and is strongly inhibited by this lectin. Mg2(+)-stimulated ATP hydrolysis displays saturation kinetics which is not of the simple Michaelis-Menten type, but is biphasic with a high-affinity (K'm = 0.16 mM) and low-affinity site (K'm = 9.0 mM), respectively. The low-affinity site hydrolyzes ATP, ITP and GTP to a similar extent, whereas CTP and UTP with about 40% lower rate. The high-affinity site splits ATP much better than other nucleoside triphosphates. Hydrolysis of ADP follows simple Michaelis-Menten saturation kinetic with apparent Km = 0.38 +/- 0.06 mM. Inhibition, activation and substrate specificity studies indicate that nucleoside triphosphatase and nucleoside diphosphatase may reside on the same protein. Kinetics of the AMP hydrolysis is hyperbolic with apparent Km = 76 +/- 9 microM. The cascade of ectonucleotidases in the brush-border membrane of the proximal tubule may catalyze the degradation of filtered nucleotides into adenosine and phosphate, the compounds which are thereafter probably reabsorbed by separate transport systems.
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PMID:The stepwise hydrolysis of adenine nucleotides by ectoenzymes of rat renal brush-border membranes. 217

Intraperitoneal administration of mitomycin C (40 micrograms/100 g body weight) to male Wistar rats increased the ATPase activity in hypotonic extracts of liver cell nuclei for 4 days after injection. Partially purified ATPase, obtained by the DEAE-cellulose column chromatography of these extracts, showed a 14 times higher specific activity than that found in normal rat liver nuclei. The enzymatic activity was strongly enhanced by the addition of polynucleotides, especially poly A and poly I, to the assay mixture, but was inhibited by GTP, a chelating agent, heparin and thiol-group inhibitors. Quercetin and oligomycin were less effective, and ouabain showed no inhibitory effect. Mg2+ ions were essential, but neither Ca2+, Na+ nor K+ ions were required for the manifestation of the activity. These characteristic properties of the enzyme are similar to those of a nucleoside triphosphatase found in the nuclear matrix and envelope, suggesting that some energy-providing mechanisms involved in the repair processes of DNA damage or cellular injury are induced by mitomycin C administration.
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PMID:Enhanced ATPase activity in liver cell nuclei induced by administration of mitomycin C to rats. 253 22

1. In broken red cell membranes, Mg2+ inhibition of Na+,K+-adenosine-5'-triphosphatase (Na+,K+-ATPase) activity was partially competitive with MgATP. Mg2+ inhibition of Na+,K+-ATPase activity was uncompetitive with K+ in broken red cell membranes, and Mg2+ inhibition of ouabain-sensitive K+ influx in K+-free resealed ghosts was uncompetitive with external K+. 2. When Na+,K+-ATPase activity was measured at relatively high K+ concentration, Mg2+ inhibition was partially competitive with Na+. Mg2+ inhibition of ouabain-sensitive K+ influx in K+-free resealed ghosts was competitive with cell Na+. Magnesium was a more effective inhibitor of the uncoupled Na+ efflux in low-Na+ ghosts than in high-Na+ ghosts. 3. These findings indicate that Mg2+ inhibition results from combination of the ion with the enzyme form E2K at high intracellular Na+ and K+, and from combination with the form E1 at low intracellular Na+ and K+. 4. In ghosts containing high concentrations of MgPO4, inhibition of the K+-K+ exchange by Mg2+ was more effective at high than at low nucleotide concentrations. At high MgPO4 and low Mg2+ concentration the activity of the exchange increased monotonically with nucleotide concentration, but at a higher Mg2+ concentration, nucleotide activation of the exchange was biphasic: the K+-K+ exchange rate increased, reached a maximum, and then decreased with increasing nucleotide concentration.
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PMID:Interaction of magnesium with the sodium pump of the human red cell. 284 41

The H+-translocating adenosine-5'-triphosphatase (ATPase) purified from the yeast Schizosaccharomyces pombe is inactivated upon incubation with the arginine modifier 2,3-butanedione. The inactivation of the enzyme is maximal at pH values above 8.5. The modified enzyme is reactivated when incubated in the absence of borate after removal of 2,3-butanedione. The extent of inactivation is half maximal at 10 mM 2,3-butanedione for an incubation of 30 min at 30 degrees C at pH 7.0. Under the same conditions, the time-dependence of inactivation is biphasic in a semi-logarithmic plot with half-lives of 10.9 min and 65.9 min. Incubation with 2,3-butanedione lowering markedly the maximal rate of ATPase activity does not modify the Km for MgATP. These data suggest that two classes of arginyl residues play essential role in the plasma membrane ATPase activity. Magnesium adenosine 5'-triphosphate (MgATP) and magnesium adenosine 5'-diphosphate (MgADP), the specific substrate and product, protect partially against enzyme inactivation by 2,3-butanedione. Free ATP or MgGTP which are not enzyme substrates do not protect. Free magnesium, another effector of enzyme activity, exhibits partial protection at magnesium concentrations up to 0.5 mM, while increased inactivation is observed at higher Mg2+ concentrations. These protections indicate either the existence of at least one reactive arginyl in the substrate binding site or a general change of enzyme conformation induced by MgATP, MgADP or free magnesium.
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PMID:Essential arginyl residues in the H+-translocating ATPase of plasma membrane from the yeast Schizosaccharomyces pombe. 285 89

Nuclear envelopes contain a nucleoside triphosphatase. Hydrolysis of ATP or GTP by this enzyme parallels energy-dependent efflux of poly(A)-containing mRNA from nuclei in vitro. Nucleoside triphosphatase has been purified from highly purified preparations of nuclear envelopes from rat liver by three successive affinity steps. The essentially homogeneous enzyme has an apparent molecular weight of 40,000 as checked by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and displays a rather broad substrate specificity. ATP and GTP are hydrolyzed at nearly equal rates, whereas UTP and CTP are only half as active as substrates. For optimal activity, a one-to-one ratio of a divalent cation (Mg2+, Mn2+, or Ca2+) and the nucleoside triphosphate substrate, an alkaline pH and a temperature of 34 degrees C are required. In contrast to the enzyme associated with nuclear envelopes which is stimulated by synthetic poly(A) and the poly(A) segment of the natural poly(A)-containing mRNA, homogeneous nucleoside triphosphatase is unable to be modulated by this polynucleotide species.
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PMID:Purification and characterization of the major nucleoside triphosphatase from rat liver nuclear envelopes. 286 90

Adenosine triphosphatase (ATPase) activity which could be stimulated maximally by either Ca2+ or Mg2+ was identified in a synaptosomal fraction from rat brain caudate nucleus. The thermodynamic properties of the Ca2+ and Mg2+ stimulated enzymes were similar to each other. Oligomycin, sodium azide and dinitrophenol had no significant inhibitory effects on stimulation by either cation. In vitro incubation of the ATPase with cis- or trans-flupenthixol, chlorpromazine or trifluoperazine, but not with haloperidol, significantly inhibited stimulation by either cation. The DA receptor agonist 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (ADTN) inhibited stimulation of the enzyme by either cation, while d-amphetamine, SKF 38393, pergolide and LY-171555 had no significant effects. Nomifensine at 10(-3) M inhibited the cation stimulation by about 33%. In vivo administration of dopamine (DA) receptor antagonists (haloperidol, cis- and trans-flupenthixol, spiperone, chlorpromazine and trifluoperazine) and the agonist apomorphine neither inhibited nor stimulated ATPase activity. It appears from these data that the ATPase activity is not under DA receptor modulation. In addition, our tentative conclusion is that one enzyme is involved, because both Ca2+ and Mg2+ produced similar maximal stimulations, the activities as a function of temperature were similar, the enzyme could not be further stimulated with Ca2+ after maximal stimulation by Mg2+ (and vice versa), and the behaviour of the ATPase activity to all drugs tested was similar.
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PMID:Properties of a Ca2+ and Mg2+ stimulated ATPase in the rat caudate nucleus. 293 17

Adenosine triphosphatase activity stimulated by Mg2+ was greater in muscle mitochondria of fish infected with larval Anisakis simplex nematodes than in uninfected fish. When muscle mitochondria were isolated in a sucrose ethylene-glycol bis(beta-aminoethyl ether)N,N'-tetraacetic acid medium from fresh uninfected fish, they were loosely coupled, and their adenosine triphosphatase activity was comparable to that of mitochondria from rat tissue. Activity in infected fish was dose dependent, increasing with the number of worms per fish. Excretory secretory products or a cytoplasmic fraction of anisakines, when incubated with coupled rat mitochondria, also caused adenosine triphosphatase activity to increase. Storage of fish flesh caused an increase in adenosine triphosphatase activity, but such aging was not significant until 5 and 10 days after death in refrigerated and frozen samples, respectively. The Mg2+ stimulated adenosine triphosphatase activity of muscle mitochondria can be used to estimate the number of nematodes per market fish. The type of medium used to isolate the mitochondria is crucial in such studies; an ionic medium with Nagarse proteinase was optimal for fish muscle mitochondria.
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PMID:Anisakis simplex: uncoupling of oxidative phosphorylation in the muscle mitochondria of infected fish. 293 49


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