Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.1.4 (deaminase)
 5,113 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Deoxycytidine kinase, which phosphorylates deoxycytidine (CdR) and its analog, cytosine arabinoside (ara-C), has been purified 71-fold from human leukemic cells. Biochemical properties of the partially purified enzyme included a molecular weight of 68,000, Kms of 7.8 muM for CdR and 25.6 muM for ara-C, and optimal activity with ATP and GTP as phosphate donors. Ara-C phosphorylation was strongly inhibited by CdR (Ki = 0.17 muM) and dCTP (Ki = 7.3 muM) and was weakly inhibited by ara-CTP (Ki = 0.13 mM). Purification by calcium phosphate gel elution and DEAE chromatography effectively separated this enzyme from cytidine deaminase, which deaminates both CdR and ara-C, and from uridine-cytidine kinase, the enzyme which phosphorylates 5-azacytidine. CdR kinase activity was found to decrease and cytidine deaminase to increase with maturation of normal and leukemic granulocytes. Myeloblasts purified by Ficoll sedimentation revealed an average kinase activity of 15.4 U/mg protein in acute myelocytic leukemia and 12.3 U/mg protein in blastic crisis of chronic myelocytic leukemia (CML). The average ratio of CdR kinase to deaminase activity in crude cell extracts varied from 0.197 in AML and 0.089 in blastic crisis to 0.0004 in normal granulocytes, reflecting the changes which take place with cellular maturation. The absolute levels of kinase and deaminase and the ratio of these two enzymes varied considerably among patients with AML, indicating that quantitative differences may be found in the metabolism of CdR and its analogs in leukemic cells.
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PMID:Deoxycytidine kinase: properties of the enzyme from human leukemic granulocytes. 5 55

Deoxycytidine triphosphate deaminase (EC 3.5.4., dCTP aminohydrolase) of Salmonella typhimurium LT2 has been pruified 500-fold. The reaction requires the presence of Mg-2plus, Mn-2plus, Ca-2lus, or Co-2plus. Kinetics of the reaction with varying Mg-2plus concentrations, keeping the concentration of dCTP constant, suggests that the true substrate of the reaction is MgdCTP. The dependence of the rate of reaction on dCTP concentration in the presnece of 5-fold excess of Mg-2plus is sigmoid, with a Hill coefficient of 1.7. The enzyme is specifically inhibited by dTTP and dUTP. In the presence of increasing dTTP concentrations the sigmoidicity of the substrate saturation curves increases. With 0.2 and 0.4 mM dTTP the Hill coefficients are 2.6 and 3.0, respectively. Despite several attempts no dissociation of the substrate site and the inhibitor site of the enzyme was achieved.
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PMID:Deoxycytidine triphosphate deaminase of Salmonella typhimurium. Purification and characterization. 23 34

Certain D-arabinosyl nucleosides, notably arabinosyl cytosine (araC) and arabinosyl adenine (araA), are useful in the treatment of certain leukemias and some DNA virus infections, respectively. The compounds are lethal to animal cells and some bacteria. Despite extensive deamination, the parent nucleosides are transported within sensitive cells and phosphorylated to the mono-, di- and triphosphates. AraCTP and araATP are good specific competitive inhibitors of tumor cell of virus-induced DNA polymerases, competing with dCTP and dATP respectively. In addition to markedly inhibiting DNA synthesis, the aranucleotides enter newly formed DNA in internucleotide linkage. Sensitivity to the nucleosides appears to correlate with the relative ratio of formation of the triphosphate via a nucleoside kinase to degradation of the nucleoside via a nucleoside deaminase. Inhibition of the deaminase increases formation of the aranucleoside triphosphate in leukemic or virus-infected cells and markedly increases the toxicity of the nucleosides. Combinations of inhibitors of the deaminases and of the aranucleoside are being explored in clinical situations. In addition, the slow penetration of aranucleotides into cells has been observed and some of these 5'-phosphates are useful antiviral agents, e.g., against herpes virus in herpetic kiratitis.
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PMID:The mechanisms of lethal action of arabinosyl cytosine (araC) and arabinosyl adenine (araA). 32 34

Certain D-arabinosyl nucleosides, notably D-arabinosyl cytosine (araC) and D-arabinosyl adenine (araA), are useful in the treatment of certain leukemias and some DNA virus infections, respectively. The compounds are lethal to animal cells and some bacteria. Despite extensive deamination, the parent nucleosides are transported within sensitive cells and phosphorylated to the mono-, di- and triphosphates. AraCTP and araATP are good specific competitive inhibitors of tumor cell or virus-induced DNA polymerases, competing with dCTP and dATP, respectively. In addition to markedly inhibiting DNA synthesis, the aranucleotides enter newly formed DNA in internucleotide linkage. Sensitivity to the nucleosides appears to correlate with the relative ratio of formation of the triphosphate via a nucleoside kinase to degradation of the nucleoside via a nucleoside deaminase. Inhibition of the deaminase increases formation of the aranucleoside triphosphate in leukemic or virus-infected cells and markedly increases the toxicity of the nucleosides. Combinations of inhibitors of the deaminases and of the arnaucleoside are being explored in clinical situations. In addition, the slow penetration of aranucleotides into cells has been observed and some of these 5'-phosphates are useful antiviral agents, e.g. against herpes virus in herpetic keratitis.
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PMID:The lethality of aranucleotides. 82 87

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

The antiviral activity and cytotoxicity of (E)-5-(2-bromovinyl)-2'-deoxycytidine (BrVdCyd) against herpes simplex virus type 1 (HSV-1), singly and in combination with deaminase inhibitors was determined using rabbit kidney (RK-13), HEP-2, BHK-21 and VERO cells. BrVdCyd was a potent inhibitor of HSV-1 replication with ED50 values of 0.30 to 1.20 microM depending on the cell line used. In the presence of tetrahydrouridine or tetrahydrodeoxyuridine (H4dUrd), potency of BrVdCyd increased approximately two fold (ED50: 0.54 microM) in HSV-infected VERO cells. The combination of BrVdCyd and H4dUrd was also effective in decreasing virus yield. Dihydrodeoxyuridine (H2dUrd) reversed the activity of BrVdCyd (ED50: 6 to 7 microM). The effect of (E)-5-(2-bromovinyl)-2'-deoxyuridine (BrVdUrd), BrVdCyd and BrVdCyd in combination with H4dUrd on deoxyribonucleoside triphosphate (dNTP) pools was assessed in VERO cells infected with a high multiplicity of infection (10 PFU/cell). Significant differences in dNTP poll sizes (pmol/10(6) cell) were observed with different treatments. BrVdUrd and BrVdCyd treatment resulted in marked expansion of the dTTP pool (greater than 1200 pmol) compared to HSV-infected VERO cells (303 pmol). Exposure to H4dUrd resulted in a 12-fold expansion of the dCTP pool (326 pmol) and barely detectable levels of dTTP (less than 1.0 pmol). BrVdCyd plus H4dUrd treatment resulted in a slight expansion of the dTTP pool (515 pmol). These results indicate: (i) H4dUrd inhibits de novo dCyd/dCMP deaminase pathway and (ii) exposure to BrVdCyd plus H4dUrd puts a strain on viral DNA synthesis to such an extent that even though dTTP is being formed from alternative pathways, its eventual utilization as a substrate is reduced and hence it builds up.
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PMID:Antiherpes virus activity and effect on deoxyribonucleoside triphosphate pools of (E)-5-(2-bromovinyl)-2'-deoxycytidine in combination with deaminase inhibitors. 216 47

The nucleoside analog 2',3'-dideoxycytidine (ddCyd) has been shown to inhibit the infectivity and cytopathic effect of human immunodeficiency virus on human OKT4+ lymphocytes in vitro. Metabolism of ddCyd by human T-lymphoblastic cells (Molt 4) negative for human immunodeficiency virus and OKT4 was examined. Molt 4 cells accumulated ddCyd and its phosphorylated derivatives into acid-soluble and acid-insoluble material in a dose-dependent manner. For each concentration tested, 2',3'-dideoxycytidine triphosphate represented 40% of the total acid-soluble pool of ddCyd metabolites. Uptake of 5 microM ddCyd was linear for 4 h after addition of drug. Efflux of ddCyd metabolites from cells followed a biphasic course with an initial retention half-life of 2.6 h for 2',3'-dideoxycytidine triphosphate. DNA, but not RNA, of cells incubated with [3H]ddCyd became radiolabeled. Nuclease and phosphatase treatment of DNA followed by reverse-phase high pressure liquid chromatography showed that the nucleoside was incorporated into DNA in its original form. ddCyd was not susceptible to deamination by human Cyd-dCyd deaminase. It was a poor substrate for human cytoplasmic and mitochondrial dCyd kinases, with Km values of 180 +/- 30 and 120 +/- 20 microM, respectively. DNA polymerases alpha, beta, and gamma varied in their sensitivity to inhibition by ddCTP with Ki values of 110 +/- 40, 2.6 +/- 0.3, and 0.016 +/- 0.008 microM, respectively; however, inhibition was competitive with dCTP in each case.
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PMID:Cellular metabolism of 2',3'-dideoxycytidine, a compound active against human immunodeficiency virus in vitro. 243 80

The dCTP deaminase induced by Bacillus subtilis bacteriophage PBS2, whose DNA contains uracil instead of thymine, requires metal ion and thiol activators and has a molecular weight of 125,000. The enzyme displays sigmoidal substrate saturation kinetics and inhibition by dUTP, consistent with the deaminase's proposed role of providing balanced levels of dUTP and dCTP for PBS2 uracil-DNA synthesis.
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PMID:Bacteriophage PBS2-induced deoxycytidine triphosphate deaminase in Bacillus subtilis. 421 44

The complement-fixing tumor (T) antigen induced by simian virus 40 (SV40) has been prepared from SV40-infected cell cultures, from infected cell cultures treated at the time of infection with 1-beta-d-arabinofuranosylcytosine (ara-C), and from SV40-transformed cells. Upon partial purification, the T antigen exhibited the following properties: it was tightly adsorbed by calcium phosphate gel, it was precipitated by acetic acid at pH 5 or by ammonium sulfate at about 20 to 32% saturation, and it had a molecular weight greater than 250,000, as estimated by Sephadex G-200 gel chromatography. In contrast, deoxycytidylate (dCMP) deaminase, thymidylate (dTMP) kinase, and thymidine (dT) kinase were less strongly bound to calcium phosphate and were not precipitated at pH 5; these enzymes also had much lower molecular weights than the T antigen, as did dihydrofolic (FH(2)) reductase. Furthermore, higher ammonium sulfate concentrations were required to precipitate dCMP deaminase, dTMP kinase, and FH(2) reductase activities than to precipitate the T antigen. Another difference was that the T antigen was not stabilized, but dCMP deaminase, dTMP kinase, and dT kinase, were stabilized, respectively, by dCTP, dTMP, and dT or dTTP. Deoxyribonucleic acid (DNA) polymerase activity resembled the T antigen in adsorption to calcium phosphate, in precipitation by ammonium sulfate or at pH 5, and in the rate of inactivation when incubated at 38 C. However, the polymerase activity could be partly separated from the T antigen by Sephadex G-200 gel chromatography. The cell fraction containing partially purified T antigen also contained a soluble complement-fixing antigen (presumably a subunit of the viral capsid) which reacted with hyperimmune monkey sera. The latter antigen was present in very low titers or absent from cell extracts prepared from SV40-infected monkey kidney cell cultures which had been treated with ara-C at the time of infection, or from SV40-transformed mouse kidney (mKS) or hamster tumor (H-50) cells. The T antigen, however, was present in usual amounts in SV40-transformed cells or ara-C treated, infected cells.
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PMID:Nonidentiy of some simian virus 40-induced enzymes with tumor antigen. 431 27

The activities of dCMP deaminase and DNA polymerase I increased twofold and fivefold in BHK-21/C13 cells after infection by the virus of herpes simplex. The increases were greatly diminished, and under certain conditions prevented, by inclusion of actinomycin D or cycloheximide in the cell-virus system during the infective cycle. The dCMP deaminase purified from infected cells harvested 8h after infection differed from the deaminase purified from non-infected cells inasmuch as (a) it was more resistant to heating at 37 degrees C; (b) the substrate (dCMP) concentration at half-maximum velocity was lower; (c) maximum activation was achieved by a lower concentration of dCTP; (d) it was more resistant to inhibition by dTTP; and (e) it behaved differently when assayed in the presence of a herpes-virus-specific antiserum. The DNA polymerase activity in the infected cells was markedly decreased in the presence of the herpes-virus-specific antiserum.
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PMID:Deoxycytidylate deaminase evidence for a new enzyme in cells infected by the virus of herpes simplex. 437 45


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