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)

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

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

Light-activated hydrolysis of cyclic GMP is achieved through the photoexcitation of rhodopsin, a process which then triggers the replacement of GDP for GTP by a retinal guanosine 5'-triphosphatase referred to as 'transducin'. The transducin-GTP complex then switches on the phosphodiesterase [Fung, Hurley & Stryer (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 152-156]. The bovine transducin consists of an alpha-subunit (39000 Mr), which is a GTP-binding component, together with a beta-(37000 Mr) and a gamma-subunit (10000 Mr). We have purified retinal transducin from cow, pig, chick and frog. The enzyme specific activities and sodium dodecyl sulphate/polyacrylamide-gel-electrophoretic profiles indicate that this enzyme is similar in all species except the frog. Whereas the bovine, pig and chick transducins consist of major 37000- and 39000-Mr components, that of the frog consists of a single 75000-Mr component. Labelling of the GTP-binding components with the photoaffinity label 8-azidoguanosine [gamma-32P]triphosphate demonstrated that the 37000-Mr components of the cow, pig and chick and the 75000-Mr component of the frog were major GTP-binding components. In addition, peptide maps of radioiodinated tryptic peptides indicate that the frog 75000-Mr protein is highly related to the pig transducin. These results demonstrate evolutionary conservation of retinal transducin and the presence of a higher-Mr, but nonetheless highly conserved form, of transducin in the frog. The relationship of this component to the recently reported rod-outer-segment inhibitor protein [Yamazaki, Stein, Chernoff & Bitensky (1983) J. Biol. Chem. 258, 8188-8194] is discussed.
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PMID:Interspecies conservation of retinal guanosine 5'-triphosphatase. Characterization by photoaffinity labelling and tryptic-peptide mapping. 298 63

Helicase III from Escherichia coli has been purified to near homogeneity using single-stranded DNA-dependent adenosine nucleoside 5'-triphosphatase activity as an assay to monitor the purification. The denatured form of this 18.5-kilodalton polypeptide, isolated on a preparative polyacrylamide gel run in the presence of sodium dodecyl sulfate, has been used as an antigen to direct the production of rabbit anti-helicase III antibodies. The antibodies obtained fail to inhibit directly either the helicase activity or the DNA-dependent adenosine nucleoside 5'-triphosphatase activity of helicase III. However, when the antigen-antibody complex is removed from solution by binding to Staphylococcus aureus cells with subsequent sedimentation, there is excellent correlation between the loss of both enzymatic activities and the loss of the helicase III polypeptide. The anti-helicase III antibodies have been used as a reagent to probe immunologically a library of E. coli DNA fragments inserted into the plasmid pBR322 for expression of the helicase III antigen. The gene encoding helicase III has been localized on a 2.0-kilobase pair PvuII-EcoRI fragment. Bacterial cells harboring a multicopy plasmid containing this fragment overproduce the helicase III antigen approximately 100-fold.
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PMID:Production of antibodies directed against Escherichia coli helicase III and the molecular cloning of the helicase III gene. 299 49

Messenger RNA capping enzyme (GTP:mRNA guanylyltransferase) purified from yeast Saccharomyces cerevisiae consisted of two polypeptides (45 and 39 kDa) and possessed two enzymatic activities, i.e. mRNA guanylyltransferase and RNA 5'-triphosphatase (Itoh, N., Mizumoto, K., and Kaziro, Y. (1984) J. Biol. Chem. 259, 13923-13929). In this paper, we describe an improved procedure suitable for the large scale purification of the enzyme. The steps include glass beads disruption of the cells and several ion-exchange and affinity column chromatographies. The enzyme was purified from kilogram quantities of yeast cells to apparent homogeneity. The purified enzyme had an approximate Mr of 180,000 and consisted of two heterosubunits of 80 and 52 kDa and had the same two enzymatic activities as above. We consider that this is the more intact form of the enzyme. Using the in situ assays on sodium dodecyl sulfate-polyacrylamide gels, RNA 5'-triphosphatase, and mRNA guanylyltransferase activities were located on the 80- and 52-kDa chains, respectively. In agreement with this, the 52-kDa enzyme-[32P]GMP complex was formed on incubation of the enzyme with [alpha-32P]GTP. Guinea pig antisera against purified yeast capping enzyme recognized both 80- and 52-kDa chains in Western blot analysis. The antibody did not cross-react with the enzymes from rat liver. Artemia salina, or vaccinia virus. Nuclear localization of the enzyme was demonstrated by immunofluorescence microscopy.
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PMID:Messenger RNA guanylyltransferase from Saccharomyces cerevisiae. Large scale purification, subunit functions, and subcellular localization. 302 58

The main electric organ of Electrophorus electricus is particularly rich in thiamine triphosphate, which represents 87% of the total thiamine content in this tissue. The thiamine pyrophosphate concentration, however, is very low in the eel electric organ and skeletal muscle as compared with other eel or rat tissues. Furthermore, electroplax membranes contain a whole set of enzymes responsible for the dephosphorylation of thiamine tri-, pyro- and monophosphate. Thiamine triphosphatase has a pH optimum of 6.8 and is dependent on Mg2+. The real substrate of the enzyme is probably a 1:1 complex of Mg2+ and thiamine triphosphate. Thiamine pyrophosphatase is activated by Ca2+. The apparent Km for thiamine triphosphate and Vmax are found to be, respectively, 1.76 mM and 5.95 nmol/mg of protein/min. Thiamine triphosphatase activity is inhibited at physiological K+ concentrations (up to 90 mM) and increasing Na+ concentrations (50% inhibition at 300 mM). ZnCl2 (10 mM) inhibits 90% of the enzyme activity. ATP and ITP are also strongly inhibitory. No significant effect of neurotoxins is seen. Membrane-associated thiamine triphosphatase is affected differently by proteolytic enzymes and is partially inactivated by pretreatment with phospholipase C and neuraminidase. The physiological significance of thiamine triphosphatase is discussed in relation to a specific role of thiamine in the nervous system.
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PMID:Thiamine triphosphate and membrane-associated thiamine phosphatases in the electric organ of Electrophorus electricus. 303 30

A nucleoside triphosphatase/deoxynucleoside triphosphatase associated with the chromatin fraction from a highly purified preparation of pea nuclei has been isolated and characterized. The purified enzyme has a molecular weight of 47,000 as checked by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and it has an isoelectric point of 6.6. In the presence of divalent cations (Mg2+ = Mn2+ greater than Ca2+), this enzyme hydrolyzes nucleoside triphosphates or deoxynucleoside triphosphates. Hydrolysis is optimal at pH 7.5 and is significantly inhibited by relatively low concentrations of quercetin, but is not sensitive to vanadate, nitrate, or oligomycin. The enzyme has a rather broad nucleotide substrate specificity and has a Km for MgATP2- of 0.6 mM. The enzyme activity is stimulated over 3-fold by Ca2+ and calmodulin, and the stimulation is blocked by the Ca2+ chelator EGTA and by the calmodulin antagonists compound 48/80 and chlorpromazine.
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PMID:Purification and partial characterization of a calmodulin-stimulated nucleoside triphosphatase from pea nuclei. 303 93

1. A microsomal fraction from ox cerebral cortex catalysed [(14)C]ADP-ATP exchange at a speed similar to that at which it liberated P(i) from ATP in the presence of Na(+), K(+) and Mg(2+). 2. Repeated washing the fraction with MgATP solutions solubilized most of the exchange activity and left the adenosine triphosphatase insoluble and little changed in activity. The exchange activity was accompanied by negligible adenosine-triphosphatase activity and was enriched by precipitation at chosen pH and by DEAE-Sephadex. At no stage was its activity affected by Na(+), K(+) or ouabain. 3. The washed microsomal fraction was exposed to a variety of reagents; a sodium iodide-cysteine treatment increased both adenosine-triphosphatase and exchange activities, as also did a synthetic zeolite. Preparations were obtained with exchange activities less than 3% of their Na(+)-plus-K(+)-stimulated adenosine-triphosphatase activity. Some contribution to the residual exchange activity was made by an adenylate kinase. 4. Thus over 95% of the microsomal ADP-ATP-exchange activity does not take part in the Na(+)-plus-K(+)-stimulated adenosine-triphosphatase reaction. Participation of some of the residual 3% of the ADP-ATP-exchange activity has not been excluded, but there appears no firm evidence for its participation in the adenosine triphosphatase; the bearing of this conclusion on mechanisms proposed for the Na(+)-plus-K(+)-stimulated adenosine triphosphatase is indicated.
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PMID:Separation of adenosine diphosphate--adenosine triphosphate-exchange activity from the cerebral microsomal sodium-plus-potassium ion-stimulated adenosine triphosphatase. 422 77

Rottem, Shlomo (Hebrew University, Jerusalem, Israel), and Shmuel Razin. Adenosine triphosphatase activity of mycoplasma membranes. J. Bacteriol. 92:714-722. 1966.-Adenosine triphosphatase activity of Mycoplasma laidlawii, M. gallisepticum, and Mycoplasma sp. strain 14 was confined to the cell membrane. The enzymatic activity was dependent on magnesium, but was not activated by sodium and potassium. Ouabain did not inhibit the adenosine triphosphatase activity of the mycoplasmas, and did not interfere with the active accumulation of potassium by M. laidlawii cells. Sulfhydryl-blocking reagents and fluoride inhibited the enzymatic activity, whereas 2,4-dinitrophenol was without any effect. Membranes of M. laidlawii hydrolyzed other nucleotide triphosphates and adenosine diphosphate (ADP), but at a lower rate than adenosine triphosphate (ATP). Nucleoside-2'-(3')-phosphates, ribose-5-phosphate, glucose-6-phosphate, and pyrophosphate were not hydrolyzed by the membrane preparations. It seems that the enzyme(s) involved in ATP hydrolysis by M. laidlawii membranes is strongly bound to the membrane subunits, which would account for the failure to purify the enzyme by protein fractionation techniques. The adenosine triphosphatase activity of mycoplasma membranes resembles in its properties that of similar enzymes studied in bacteria. The mycoplasma enzyme(s) seems to differ from the adenosine triphosphatase associated with ion transport in mammalian cell membranes and from mitochondrial adenosine triphosphatase.
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PMID:Adenosine triphosphatase activity of mycoplasma membranes. 422 19


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