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:2.7.1.21 (thymidine kinase)
7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using gel filtration chromatography, we find a single peak of deoxythymidine phosphorylating activity in Chlamydomonas reinhardti. This activity has characteristics of a thymidine kinase, in that (1) it will utilize ATP (or dATP) or CTP (or dCTP) as phosphoryl donor, but not AMP or phenyl phosphate, and (2) it is inhibited by dTTP (and less so by dTDP, dUTP, and dUDP) but is unaffected by 3'-5' cyclic AMP. Partially purified chlamydomonas thymidine kinase has a pH optimum near 8.5, and a molecular weight of 80,000 to 85,000 daltons. Kinetic studies indicate a ping-pong mechanism with a Km for thymidine of 1.5 x 10(-7) moles per liter. 5-Bromo- and 5-fluorodeoxyuridine, and to a lesser degree deoxyuridine, are competitive inhibitors, but significant phosphorylation of these nucleotides could not be demonstrated in vitro by thymidine kinase. While thymidine is phosphorylated to dTMP by crude Chlamydomonas extracts, greater than 80% of the product formed by the partially purified enzyme is dTTP. Further, the gel filtration elution position of the single deoxythymidylate kinase activity present in cell extracts coincides with that of thymidine kinase. These results suggest that a multifunctional enzyme, rather than three separate phosphorylating activities, may be responsible for dTTP formation.
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PMID:Characterization of thymidine kinase and phosphorylation of deoxyribonucleosides in Chlamydomonas reinhardti. 4 38

The experimental conditions were studied which allow hormonal levels to affect the incorporation of labelled deoxyribonucleosides triphosphates (dNTP's) into mitochondrial DNA by isolated liver mitochondria, obtained either from thyroidectomized young male rats (T) or from animals of the same age thyroidectomized and then treated with triiodothyronine (T + T3). It was demonstrated that: (a) extramitochondrial DNA, on which extramitochondrial DNA polymerase may act, was absent; (b) the permeability to dNTP's, the thymidine kinase activity, the energy supply, and the nuclease activities were unaffected by hormonal conditions; (c) the bacterial contaminations contribute for only 1% to incorporation. The characterization of incorporation product showed that: (a) such product was indeed DNA, as it was DNase-degradable for about 90%; (b) the labelled DNA was indeed mitochondrial DNA, as a 10 minutes preincubation with acriflavine or ethydium bromide (Eth. Br.) inhibited the synthesis by 90%.
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PMID:Effect of thyroidectomy and in vivo administration of triiodothyronine on DNA synthesis in isolated mitochondria. 18 48

Analysis of cell-free extracts of Anacystis nidulans disclosed the absence of both thymidine phosphorylase (EC 2.4.2.4) and thymidine kinase (EC 2.7.1.21) activities. Thymine and thymidine were incorporated inefficiently by intact cells of A. nidulans either in the presence or absence of deoxyguanosine (250 mug/ml). Deoxythymidine monophosphate incorporation was also inefficient. Radioactive deoxyadenosine, at a minimally toxic level (3 mug/ml), was incorporated effectively into the deoxyribonucleic acid (DNA). A cesium chloride-ethidium bromide gradient analysis of the DNA revealed that both the plasmid DNA and the principal DNA of the A. nidulans genome were labeled effectively in cells exposed to [8-14C]deoxyadenosine.
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PMID:Labeling the deoxyribonucleic acid of Anacystis nidulans. 80 13

Thymidine kinase 2 (TK2), also called mitochondrial thymidine kinase, is a pyrimidine deoxyribonucleoside kinase expressed in all cells and tissues. It was recently purified to apparent homogeneity from human leukemic spleen and the active enzyme was shown to be a monomer of a 29-kDa polypeptide. The enzyme is feedback-inhibited by both end products, dCTP and dTTP. Here we show that TK2 purified from several different sources, including purified beef heart mitochondria, could be directly photoaffinity labeled with radioactive dTTP (approximately 18% of all TK2 molecules were cross-linked to dTTP after 20 min of ultraviolet irradiation) or to a lower extent with dCTP. Photo-incorporation was inhibited by the presence of the other effector but also the phosphate donor ATP blocked photolabeling, with dTTP. Addition of nucleoside substrates gave only a marginal inhibition of photo-incorporation. There were no detectable difference in the molecular size of photolabeled TK2 isolated from human spleen, brain or placenta, monkey liver, beef heart and beef heart mitochondria. Nor was there any significant differences in the enzyme kinetic properties of these enzymes. Cleavage of labeled TK2 with cyanogen bromide showed that dTTP was incorporated into a single 3-kDa peptide. TK2 was the only pyrimidine deoxynucleoside kinase expressed in liver, heart and brain. A detailed characterization of the subunit structure and substrate specificity of this enzyme is of importance for the design of new antiviral and cytostatic therapies based on nucleoside analogs.
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PMID:Mammalian thymidine kinase 2. Direct photoaffinity labeling with [32P]dTTP of the enzyme from spleen, liver, heart and brain. 159 87

The protected nucleoside 1-(2-deoxy-2-fluoro-3,5-di-O-benzoyl-beta-D-arabinofuranosyl)-5-ethylura cil (10) was prepared by condensation of 3,5-dibenzoyl-2-deoxy-2-fluoro-alpha-D-arabinofuranosyl bromide (9) with 2,4-bis-O-(trimethylsilyl)-5-ethyluracil (8). The ratio in this coupling reaction has been raised to 17:1 in favor of the desired beta-anomer. Deprotection by aminolysis gave 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-ethyluracil (FEAU, 1) in 67% isolated yield from the bromo sugar 9. In vitro data show that FEAU has activity against herpes simplex virus types 1 and 2 comparable to that of 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-methyluracil (FMAU, 2), 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-iodouracil (FIAU, 3), and acyclovir (ACV, 12). The cellular toxicity of FEAU was found to be much lower than that of the other nucleoside analogues. Biochemical experiments indicate that FEAU has similar affinity toward thymidine kinases encoded by HSV 1 and 2 and a much lower affinity for cellular thymidine kinase than thymidine. The in vivo antiviral effects of FEAU, FMAU, FIAU, and ACV were evaluated against herpes infection in a systemic mouse encephalitis model and a cutaneous guinea pig model. While FEAU showed activity comparable to that of ACV in the systemic infection model, it was superior in the cutaneous herpes infection model.
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PMID:1-(2-Deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-ethyluracil. A highly selective antiherpes simplex agent. 303 44

We have developed an assay that measures the inhibition of protein synthesis and can be used in conjunction with a whole embryo bioassay that detects the ability of a chemical to cause fetotoxicity, malformation and abnormal growth. The assay involves microinjecting the herpes thymidine kinase gene into stage 6 oocytes of Xenopus laevis then exposing the oocytes to a test compound for 18-24 h. The inhibition of thymidine kinase (TK) expression caused by an inhibitor is then measured by simple enzyme assay. Protein synthesis inhibitors such as cycloheximide, puromycin and emetine all inhibited TK synthesis. Concentrations of cycloheximide (1.4 X 10(-4) mg/ml) and puromycin (0.04 mg/ml) near the 96 h embryo LC50 inhibited thymidine kinase expression by 78% and 97%, respectively but emetine (0.01 mg/ml) had no effect. However, 0.1 mg/ml emetine inhibited TK synthesis by almost 50%. The RNA synthesis inhibitor, actinomycin D (0.013 mg/ml) inhibited TK expression by 61%. DNA synthesis inhibitors hydroxyurea (2.0 mg/ml), cytosine arabinoside (2.0 mg/ml) and ethidium bromide (0.02 mg/ml) failed to inhibit the expression of the TK gene even though these concentrations were near the 96 h embryo LC50. The whole embryo bioassay cannot differentiate the DNA synthesis inhibitors from the RNA and protein synthesis inhibitors but the oocyte assay can. This type of molecular test data can help separate classes of teratogens such as DNA synthesis inhibitors from nonteratogenic compounds such as protein synthesis inhibitors and allow the extrapolation of test data to other species.
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PMID:Detection of inhibitors of protein and nucleic acid synthesis using oocytes of Xenopus laevis microinjected with the herpes thymidine kinase gene. 377 82

A temperature-sensitive simian virus 40 (SV40) mutant, tsTNG-1, has been isolated from nitrosoguanidine-treated and SV40-infected African green monkey kidney (CV-1) cultures. Replication of virus at the nonpermissive temperature (38.7 C) was 3,000-fold less than at the permissive temperature (33.5 C). Plaque formation by SV40tsTNG-1 deoxyribonucleic acid (DNA) on CV-1 monolayers occurred normally at 33.5 C but was grossly inhibited at 38.7 C. The time at which virus replication was blocked at 38.7 C was determined by temperature-shift experiments. In shift-up experiments, cultures infected for various times at 33.5 C were shifted to 38.7 C. In shift-down experiments, cultures infected for various times at 38.7 C were shifted to 33.5 C. All cultures were harvested at 96 hr postinfection (PI). No virus growth occurred when the shift-up occurred before 40 hr PI. Maximum virus yields were obtained at 96 hr PI when the shift-down occurred at 66 hr, but only about 15% of the maximum yield was obtained when the shift-down occurred at 76 hr PI. These results indicate that SV40tsTNG-1 contains a conditional lethal mutation in a late viral gene function. Mutant SV40tsTNG-1 synthesized T antigen, viral capsid antigens, and viral DNA, and induced thymidine kinase activity at either 33.5 or 38.7 C. The properties of the SV40 DNA synthesized in mutant-infected CV-1 cells at 33.5 or 38.7 C were very similar to those of SV40 DNA made in parental virus-infected cells, as determined by nitrocellulose column chromatography, cesium-chloride-ethidium bromide equilibrium centrifugation, and by velocity centrifugation in neutral sucrose gradients. Mutant SV40tsTNG-1 enhanced cellular DNA synthesis in primary cultures of mouse kidney cells at 33.5 and 38.7 C and also transformed mouse kidney cultures at 36.5 C. SV40tsTNG-1 was recovered from clonal lines of transformed cells after fusion with susceptible CV-1 cells and incubation of heterokaryons at 33.5 C, but not at 38.7 C.
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PMID:Temperature-sensitive simian virus 40 mutant defective in a late function. 432 Mar 87

Nested polymerase chain reaction (PCR) assays were developed for the detection of equine herpesvirus 2 (EHV2) and equine herpesvirus 5 (EHV5) using the nucleotide sequences from the glycoprotein B (gB) gene of EHV2 and the thymidine kinase (TK) gene of EHV5. The simultaneous use of EHV2 specific and EHV5 specific primers in one nested amplification assay (multiplex PCR) enabled a rapid, specific and sensitive diagnosis for each virus. PCR was found to be 10(3) times more sensitive than virus isolation by cell culture for EHV2 and 10(6) for EHV5. In separate PCR assays, the routine detection limit after ethidium bromide staining was 0.6 fg for EHV2 plasmid DNA and 2.3 fg for EHV5 plasmid DNA, equivalent for both viruses to approximately 100 genome copies. The detection limits in multiplex PCR were 6 pg for EHV2 and 2.3 fg for EHV5, respectively. PCR assays were applied to studies of the epidemiology of EHV2 and EHV5 infections of racehorses and breeding mares in Victoria and New South Wales, Australia. Peripheral blood leukocytes from 31% of horses were positive for EHV2, 16% positive for EHV5, 8% positive for both viruses and 63% negative for both viruses. EHV2 PCR was also successfully used to detect EHV2 DNA in nasal secretions from horses. The multiplex PCR assay proved to be a rapid and reliable method for the simultaneous detection and differentiation of 2 related equine gammaherpesviruses.
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PMID:Diagnosis of equine gammaherpesvirus 2 and 5 infections by polymerase chain reaction. 761 77

Bovine semen samples spiked with bovine herpesvirus 1 (BHV-1) were used to compare dot blot hybridization, polymerase chain reaction (PCR), and virus isolation for detection of BHV-1 in bovine semen. The PCR amplification used primers targeting the BHV-1 thymidine kinase gene and a nucleic acid releasing cocktail (GeneReleaser); the PCR product was used as the DNA probe in dot blot hybridization; virus isolation was done in primary bovine fetal testis (BFT) cell cultures. Semen diluted 1:20 in tissue culture medium had the least cytotoxicity and inhibition of viral cytopathic effects in BFT cells, allowing detection of 1 TCID50/100 microL of BHV-1 suspension by virus isolation. The presence of foreign DNA such as bovine sperm DNA or salmon sperm DNA increased the sensitivity of dot blot hybridization in detecting BHV-1, allowing detection of 20,000 TCID50/100 microL of neat semen. The inhibition of PCR amplification of BHV-1 DNA in bovine semen was eliminated by diluting the samples 1:20 in tissue culture medium. The best PCR amplification was obtained when semen was diluted 1:20 and when a reaction buffer of pH 9.0, with 1.0 mM MgCl2 was used. Under these conditions, the PCR followed by ethidium bromide staining of agarose gels could detect 1 TCID20/100 microL of sample, whereas PCR followed by Southern blot hybridization could detect 0.01 TCID50/100 microL of sample.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Comparison of dot blot hybridization, polymerase chain reaction, and virus isolation for detection of bovine herpesvirus-1 (BHV-1) in artificially infected bovine semen. 764 21

Polymerase chain reaction (PCR) for detection of bovine herpesvirus-1 (BHV-1) was developed and optimized using 22 bp sense and 20 bp antisense primers in the thymidine kinase (TK) coding region. The amplification product is 183 bp long. The PCR optimization was done using BHV-1 tissue culture supernate (BHV-1TCS), concentrated BHV-1 tissue culture supernate (cBHV-1TCS) and sucrose gradient purified BHV-1 (pBHV-1). The sensitivity of four methods of sample preparation which are standard DNA extraction, modified proteinase K (PK) digestion, GeneReleaserTM + 34 cycles or + 44 cycles, and boiling were compared with virus isolation (VI) using BHV-1TCS. The incorporation of 10% glycerol in the reaction mixture, the incubation in PK for 18 hours and predenaturation of samples and cooling in ice prior to PCR were essential for the amplification of BHV-1 DNA for samples prepared by standard DNA extraction and modified PK digestion. The preparation of samples by Gene-ReleaserTM, a proprietary nucleic acid releasing cocktail, showed 10 to 1,000-fold increase in sensitivity compared to standard DNA extraction and modified PK digestion. No amplification was observed in samples prepared by boiling. The sample preparation of BHV-1 LA strain by GeneReleaserTM showed sensitivity equivalent to virus isolation. The BHV-1 TK PCR using GeneReleaserTM has a detection limit of 1 picogram and 10 fentograms of purified BHV-1 DNA using ethidium bromide stained gel and Southern blot hybridization, respectively. It could detect viral DNA in 1,000 infected cells in a total suspension of 10,000 cells using either ethidium bromide stained gel or Southern blot hybridization.
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PMID:Establishment of conditions for the detection of bovine herpesvirus-1 by polymerase chain reaction using primers in the thymidine kinase region. 764 33


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