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)

Bacillus subtilis W23 was infected with a clear-plaque variant of SP-10 phage, namely, SP-10c. Exogenous thymidine was not incorporated into phage DNA (even in the presence of deoxyadenosine), nor was there any transfer of thymidine nucleotides from bacterial to viral DNA. The lytic program was unaffected by concentrations of 5-fluorodeoxyuridine sufficient to reduce bacterial DNA synthesis by greater than 95%. Although these data are consistent with the interpretation that thymidine nucleotides are excluded from phage DNA, formic acid digests of SP-10c DNA contained what appeared to be the four conventional bases; however, adenine and thymine were not recovered in equimolar yields. DNA-RNA hybridization and hybridization competition experiments were done. Synthesis of host RNA started to wane moments postinfection and stopped completely by 36 min. SP-10c coded for discrete classes of early and late RNA. The possibility of discrete subclasses of early RNA exists. Replication of the bacterial genome appeared to terminate 12 min postinfection. Degradation of the host DNA to acid-soluble material started at 36 min and, by the end of the latent period, greater than 90% of the host chromosome was hydrolyzed. Four apparent phage-coded enzymes have been identified. A di- and triphosphatase degraded dUTP, dUDP, dTTP, and dTDP (and, to a lesser extent, dCDP and d CTP) to the corresponding monophosphates; the enzyme had no apparent activity on dATP and dGTP. SP10c also coded for a DNA-dependent DNA polymerase, lysozyme, and a nuclease that degrades native bacterial DNA. Judging from the dependence of enzyme synthesis on the time of addition of rifampin (an inhibitor of the initiation of RNA synthesis), messengers for the di- and triphosphatase, as well as the nuclease, are transcribed from promoters that start to function 6 min postinfection. Promoters for polymerase and lysozyme did not become functional until 8 and 16 min postinfection, respectively.
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PMID:SP-10 bacteriophage-specific nucleic acid and enzyme synthesis in Bacillus subtilis W23. 13 89

In the presence of DNA and a divalent cation, an enzyme activity in cell-free extracts of Escherichia coli readily hydrolyses dATP to dADP. dGTP is degraded to a smaller extent, dCTP and dTTP being hardly affected. The artificial template primers poly(dC) . oligo(dG) and poly(dT) . oligo(dA) are also effective cofactors for this triphosphatase activity. As a consequence, assays measuring the misincorporation, by cell-free extracts, of dATP and dGTP into these defined templates are difficult to interpret, since the triphosphate substrate is being rapidly degraded during the polymerase reaction. A partial characterization of the dATPase activity was performed, demonstrating that the optimal conditions for its activity resemble those commonly used for assaying polymerase activity. Thus in crude extracts both polymerase and dATPase compete for the same substrate. The inclusion of an ATP-generating system in the reaction mixture maintains the levels of deoxynucleoside triphosphates and changes the kinetics of misincorporation of dAMP into poly(dC) . oligo(dG). No reproducible difference in such misincorporation has been found between lysates prepared from tif-1 cells grown at either permissive or restrictive temperature.
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PMID:Assays for the fidelity of DNA polymerases in cell-free extracts of Escherichia coli are complicated by contaminating nucleoside triphosphatases. 38 Jun 54

Hydrolysis of extracellular ATP and other nucleoside phosphates by A-431 human epidermoidal carcinoma cells was studied. The hydrolysis of extracellular ATP by these cells required either Mg2+ or Ca2+, and either cation could be replaced by Co2+, Fe2+, or Mn2+. Nucleoside triphosphates (ATP, GTP, CTP, UTP, and dTTP), but not nucleoside diphosphates, were hydrolyzed by the cells with Km and Vmax values similar to those for ATP (0.9-1.1 mmol/l and 6-10 nmol Pi formed/10(6) cells, respectively). The hydrolysis of ATP was inhibited strongly by ATP-gamma S and AMPPNP, and weakly by AMPCPP and ADP-beta S, but not by AMPCPP or AMPCP. Since the hydrolysis of [gamma-32P]ATP was inhibited by all these nucleoside triphosphates, the binding site for ATP is presumed to be the same as that for the other nucleoside triphosphates. All these results indicate that ecto-ATPase activity associated with A-431 cells is due to ecto-nucleoside triphosphatase. The nucleotide specificity shown in the present study indicates that ecto-nucleoside triphosphatase associated with A-431 cells is a molecule different from P2-purinergic receptors which can be stimulated specifically with nucleoside phosphates like ATP, ADP, UTP, UDP, and GTP, but not by other nucleotides.
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PMID:Characterization of ecto-nucleoside triphosphatase on A-431 human epidermoidal carcinoma cells. 129 31

An RNA helicase, isolated from nuclear extracts of HeLa cells, displaced duplex RNA in the presence of any one of the eight common nucleoside triphosphates. The unwinding reaction was supported most efficiently by ATP and GTP and poorly by dCTP and dTTP. The enzyme activity, purified 300-fold, contained two major protein bands of 80 and 55 kDa when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. All fractions that contained RNA helicase activity also possessed single-stranded RNA-dependent nucleoside triphosphatase activity. Purified RNA helicase fractions displaced a hybrid of U4/U6 RNAs with the same efficiency as it displaced other duplex RNA structures. In contrast, the RNA helicase did not displace duplex RNA/DNA and DNA/DNA structures. Evidence is presented that suggests that this RNA helicase can displace duplex RNA by translocating in both the 3' to 5' and the 5' to 3' directions. The properties of the RNA helicase described here differ from the deaminase RNA unwinding activity described in Xenopus oocytes (Bass, B.L., and Weintraub, H. (1987) Cell 48, 607-613) and from the p68 HeLa RNA helicase (Hirling, H., Scheffner, M., Restle, T., and Stahl, H. (1989) Nature 339, 562-564).
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PMID:The isolation and characterization of an RNA helicase from nuclear extracts of HeLa cells. 170 30

Bacteriophage T7 gene 4 protein, purified from phage-infected cells, consists of a mixture of a 56- and a 63-kDa species that provides primase and helicase activities for T7 DNA replication. The 56-kDa species has been purified 1800-fold from Escherichia coli cells containing a plasmid that encodes this gene 4 protein. The purified 56-kDa protein is homogeneous, as determined by denaturing gel electrophoresis, and is monomeric in its native form, as indicated by gel filtration. The binding of the 56-kDa protein to single-stranded DNA is stimulated by nucleoside 5'-triphosphates, as is the case for a mixture of the two molecular weight species. In the presence of DNA, the 56-kDa protein preferentially hydrolyzes dTTP (Bernstein, J. A., and Richardson, C. C. (1988) Proc. Natl. Acad. Sci. U. S. A. 85, 396-400). Since nucleoside 5'-triphosphatase activity is necessary for both helicase activity and for translocation of gene 4 protein to primase recognition sites, we have characterized this activity using the 56-kDa protein alone. In the DNA-dependent hydrolysis reaction, the enzyme displays a Km of 10 mM for dTTP, and a Vmax of 2.9 x 10(-5) M/min/mg of protein (at 2.5 micrograms/ml). There is little cooperativity with respect to dTTP binding (Hill coefficient = 1.1) except in the presence of ribonucleoside 5'-triphosphate, an inhibitor of dTTP hydrolysis (Hill coefficient greater than 1.5). The apparent KD for single-stranded circular DNA is 0.2 microM. The active species in dTTP hydrolysis is an oligomer of at least two subunits, as indicated by the effect of enzyme concentration upon the rate of DNA-dependent hydrolysis. The 56-kDa protein also catalyzes DNA-independent hydrolysis of dTTP with a Km of 0.11 mM and a Vmax of 1.3 x 10(-7) M/min/mg of protein (at 8 micrograms/ml). The active species in DNA-independent dTTP hydrolysis is also an oligomer.
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PMID:Purification of the 56-kDa component of the bacteriophage T7 primase/helicase and characterization of its nucleoside 5'-triphosphatase activity. 284 90

A nonspecific nucleoside triphosphatase was partially purified from skin and cutaneous melanoma tumors from Sinclair swine using chloroform precipitation, hydrophobic, ion-exchange and affinity chromatography techniques. The enzyme was not stimulated by Na+, K+ or Mg2+ but it was inhibited by EDTA. The enzyme was not inhibited by quercetin, proflavin, azide or ovabain. The enzyme exhibited optimal activity over a pH range of 8-9 and the activation energy was 10.4 and 9.8 kcal/mol for dUTP and ATP, respectively. The apparent Km of the enzyme for dUTP and dTTP was approximately 20 mumol/l while the apparent Km for dATP, ATP, dCTP, CTP and UTP was in the range of 65-80 mumol/l.
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PMID:Purification and properties of a nucleoside triphosphatase from Sinclair swine. 609 41

Nuclei from baby hamster kidney cells infected with herpes simplex virus type 1 contain a virus-specific deoxyribonucleoside triphosphate degrading activity. The reaction proceeds at 4 degrees C and can thus be distinguished from host enzymes. Under these conditions the enzyme is specific for deoxyribopyrimide triphosphates and catalyzes pyrophosphate cleavage to produce the monophosphates, dUTP being the best substrate followed by dCTP and dTTP. The appearance of the activity after infection parallels that of viral DNA-synthesis-related functions. Of a series of eight temperature-sensitive mutants tested, two (tsD and tsK) exhibit significantly decreased triphosphatase levels after infection at nonpermissive temperature, whereas a viral deoxypyrimidine kinase-deficient mutant induced wild-type levels.
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PMID:Deoxyribopyrimidine triphosphatase activity specific for cells infected with herpes simplex virus type 1. 610 41

The gene 4 protein of bacteriophage T7 is both a primase and a helicase. In this paper, we present a detailed description of a third activity, single-stranded DNA-dependent nucleoside 5'-triphosphate hydrolysis, and show that this activity is coupled to the unidirectional translocation of the gene 4 protein on single-stranded DNA (Tabor, S., and Richardson, C.C. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 205-209). The competitive inhibitor of NTP hydrolysis, beta, gamma-methylene dTTP, is also a potent inhibitor of gene 4 protein-dependent, RNA-primed DNA synthesis; inhibition is not due to a direct inhibition of T7 DNA polymerase or RNA primer synthesis. We conclude that the energy derived from the hydrolysis of NTPs by the gene 4 protein is required for translocation of the protein to primase recognition sites. Measurement of the rates of hydrolysis of NTPs using a variety of DNAs of known structure and length support the unidirectional translocation of the gene 4 protein on single-stranded DNA. Duplex DNA, RNA, and single-stranded DNA coated with single-stranded DNA-binding protein do not serve as effectors for the nucleoside triphosphatase of the gene 4 protein. Kinetic data suggest that the gene 4 protein does not remain bound to newly synthesized oligoribonucleotide primers but continues to search for other primase recognition sites. Although all the predominant naturally occurring NTPs except rCTP are hydrolyzed by the gene 4 protein, the enzyme shows specificity for dTTP with a Km of 0.4 mM. In the accompanying paper (Matson, S.W., Tabor, S., and Richardson, C.C. (1983) J. Biol. Chem. 258, 14017-14024), we show that the hydrolysis of NTPs is also required for the protein to function as a helicase in duplex regions of DNA.
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PMID:DNA-dependent nucleoside 5'-triphosphatase activity of the gene 4 protein of bacteriophage T7. 613 75

RNA-dependent DNA polymerase activity of avian myeloblastosis virions as measured by the incorporation of [3H]TTP into trichloroacetic acid-precipitable material was very low. This apparent low polymerase activity was observed with virions isolated either from leukemic chicken plasma or from the supernatant of cultured leukemic myeloblasts. The inhibition of reverse transcriptase activity was caused by nucleoside triphosphatase present in avian myeloblastosis virions and could be reversed by ADP.
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PMID:Inhibition of virion-associated reverse transcription by nucleoside triphosphatase in avian myeloblastosis virus. 615 6

The nucleoside triphosphatase (EC 3.6.1.15) was isolated from rat liver cytosol and purified 600-fold. The enzyme hydrolyzes all NTPs and dNTPs, splits NDPs and dNDPs at a low rate and does not destroy NMPs and dNMPs. The phosphatase consists of a single subunit with molecular weight of 65 000. The chromatin fraction of the enzyme is fully bound to the membrane, whereas the cytosol fraction contains 15-30% of the membrane-bound enzyme. Both free and membrane-bound phosphatases possess identical functional properties. The enzymatic activity has a pH-optimum of 4.0--4.5, is increased in the presence of Me2+ and is unaffected by ouabain, Triton X-100, N-ethylmaleimide, NaF or DNA, but is inhibited by NaCl, Pi and PPi. The value of Km is equal to 20 microM for TTP splitting. Since the NTP pool is essentially changed throughout the cell cycle, it is suggested that the nucleoside triphosphatase can participate in the nucleotide pool regulation.
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PMID:[Non-specific acid nucleoside triphosphatase from cytosol and chromatin of rat liver: partial purification and general properties]. 628 41


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