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:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Our purpose was to determine whether phospholipase C stimulated thymidine kinase activity of regenerating rat liver. We determined effects of phospholipase C upon TMP formation by rat liver extracts prepared at 0, 12, 24, 36 and 48 hr following partial hepatectomy. Data were obtained which supported these conclusions: (a) Commercial preparations of phospholipase C contained nucleoside phosphotransferase activity; (b) phospholipase C exerted no appreciable stimulatory influence upon thymidine kinase activity of regenerating rat liver; and (c), apparent stimulation of thymidine kinase was associated with linked activities of two enzymes, viz., liver extract-ATPase activity and nucleoside phosphotransferase activity.
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PMID:Does phospholipase C stimulate thymide kinase activity of rat liver extracts prepared after partial hepatectomy. 12 59

Mouse fibroblasts resistant to the drug rutamycin were isolated by selectively introducing BrdUrd into the mitochondrial genome of a line of mouse fibroblasts (clone 1 D) lacking a cytoplasmic thymidine kinase enzyme. The ATPase (ATP phosphohydrolase; EC 3.6.1.3) activity of mitochondria isolated from these cells was resistant to rutamycin. The rutamycin-resistant mutants were enucleated with cytochalasin B and fused with mouse A 9 cells resistant to 8-azaguanine and sensitive to rutamycin. Cytoplasmic hybrids, or cybrids, were selected as cells resistant to rutamycin and 8-azaguanine, and appeared at a high frequency. Other fusions between rutamycin-resistant nucleated cells and A 9 produced colonies at a much lower frequency. Finally, fusions between enucleated clone 1 D cells and A 9 cells produced no rutamycin-resistant colonies. These results indicate that rutamycin resistance is a cytoplasmically inherited characteristic in this cell line.
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PMID:Cytoplasmic inheritance of rutamycin resistance in mouse fibroblasts. 14 79

1. Extracts of several plant species contained nucleoside-AMP phosphotransferase activity. The ratio of activity with thymidine to that with uridine as nucleoside substrate was essentially constant, both between species and throughout plant development. Evidence is presented that the total thymidine-AMP phosphotransferase activity of the leaves of Asplenium nidus (bird's-nest fern) and of Helianthus tuberosus (Jerusalem artichoke) increases during maturation. 2. Thymidine-AMP phosphotransferase was purified 22-fold from a very rich source of this activity, extracts of A. nidus. 3. A broad specificity towards both nucleoside and nucleoside 5'-monophosphate substrates is displayed by this preparation, and the evidence suggests that all could be due to a single enzyme. 4. Nucleosides that act as substrates will also inhibit phosphotransfer to other nucleosides, with Ki values close to the corresponding Km values found when utilized as substrates. 5. Ca2+-activated ATP phosphohydrolase was separated from the phosphotransferase by differential complexing to Blue Dextran in the presence of urea, whereas an AMP phosphohydrolase activity was closely associated with thymidine-AMP phosphotransferase through all separation techniques used. 6. Metal ions did not activate either of the latter two activities, and 1,10-phenanthroline was found to inhibit the phosphotransferase. 7. Km values for AMP for the respective activities were 0.11 mM (thymidine phosphotransferase) and 0.20 mM (AMP phosphohydrolase) and for thymidine (phosphotransferase only) 0.88 mM. 8. 3':5'-Cyclic AMP was found to inhibit both phosphotransferase and AMP phosphohydrolase activities, with Ki values of 0.056 mM and 0.15 mM respectively. It is suggested that this inhibitor would be of value in revealing the existence of thymidine kinase in plant extracts with high thymidine phosphotransferase activity.
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PMID:Thymidine phosphotransferase and nucleotide phosphohydrolase of the fern Asplenium nidus. General properties and inhibition by adenosine 3':5'-cyclic monophosphate. 18 31

With L-15 as the base medium, drug-resistant variants were isolated from two amphibian tissue culture strains: the Xenopus laevis A8 diploid cell line and the ICR 2A cell line of Rana pipiens. Four different classes of variants were obtained: (1) A8 cells resistant to chloramphenicol, an inhibitor of mitochondrial protein synthesis; (2) A8 cells resistant to ouabain, an inhibitor of the Na+/K+-activated ATPase of the plasma membrane;(3) ICR 2A cells resistant to low (20 microgram/ml) and high (300 microgram/ml) levels of bromodeoxyuridine (BUdR), a thymidine analog which interferes with the pyrimidine salvage pathway; and (4) ICR 2A cells resistant to 2,6-diaminopurine (DAP), an adenine analog which interferes with the purine salvage pathway. Unlike the other variants, isolation of BUdR resistant cells is a 2-step process. Resistance to low levels of BUdR is phenotypically expressed by a reduction in thymidine transport activities while resistance to high levels of this compound is evidenced by greatly reduced levels of thymidine kinase activity. DAP-resistant cells, which are characterized by reduced levels of adenine phosphoribosyl transferase (APRT) activity, do not die in AAT (adenine, aminopterin, thymidine) selection medium. This suggests that these cells utilize adenine efficiently. With MEM as the base medium, an asparagine independent clone was isolated from the ICR 2A cell line. When compared with the wild type, this variant exhibited a slightly reduced growth rate in the presence or absence of asparagine.
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PMID:Amphibian cells in culture. II. Isolation of drug-resistant variants and an asparagine-independent variant. 30 57

To understand mechanisms of viral diarrhea further, we studied ileal ion transport in vitro in relation to mucosal changes and epithelial differentiation in transmissible gastroenteritis in piglets, an invasive viral enteritis thought to involve mainly proximal intestine. In infected pigs, at the height of diarrhea, short-circuited ileal epithelium failed actively to transport Na+ and Cl-, and there was a defect of glucose-mediated Na+ transport. The Cl- secretory response to theophylline remained intact. Conductance measurements indicate that paracellular permeability may be reduced and transcellular transport may be altered. A mucosal lesion was observed at the time of the transport changes, characterized by villus blunting, crypt hyperplasia, and immature crypt-type enterocytes on the villus epithelium, deficient in disaccharidase and (Na+, K+)ATPase activity but rich in thymidine kinase. Consideration of the major determinants of diarrhea in this invasive enteritis must take into account not only altered mucosal function and differentiation but also the extent of intestinal involvement, including the ileum, a major site of fluid absorption in the intestine.
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PMID:Determinants of diarrhea in viral enteritis. The role of ion transport and epithelial changes in the ileum in transmissible gastroenteritis in piglets. 75 40

Infants and young children are particularly susceptible to a recently identified viral enteritis which is highly contagious and seems both common and universal. In this disease, virus invades the upper intestinal epithelium, causing acute diarrhoea with early fever and vomiting. We studied a similar disease in pigs, infecting three-week-old animals with transmissible gastroenteritis virus (TGE), which also invades the upper intestinal epithelium. In this model, diarrhoea is massive 16-40 hours after infection, when stools contain increased electrolytes but no excess of sugar. In the jejunum of intact pigs at the 40-hour stage we found altered Na+ and water flux, decreased mucosal activities of disaccharidases and Na+, K+-ATPase, but normal adenylate cyclase activity. At the same stage the response of Na+ flux to glucose was blunted in jejunal epithelium studied in Ussing short-circuit chambers and in suspensions of villous cells; Cl- flux responded normally to theophylline, and thymidine kinase and sucrase activities of cells isolated from jejunal villi were similar to those found in crypt cells. Probably by 40 hours after infection most virus has been shed from the mucosa. Viral diarrhoea clearly differs from enterotoxigenic diarrhoea. Consideration of its pathogenesis must take into account the dynamic nature of the mucosal epithelium and the factors governing differentiation of enterocytes as they migrate from crypt to villus. Sufficient information is available now to characterize one specific and apparently prevalent viral enteritis in man and to identify additional viral enteritides. There is hope that preventative therapy can be developed. Our understanding of the mechanisms of viral diarrhoea is limited, but the availability of an animal model and the promise of others makes us optimistic that these deficiencies can be remedied. Greater understanding of the pathogenesis of viral diarrhoea should better the active therapy of affected infants and children.
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PMID:Viral gastroenteritis: recent progress, remaining problems. 104 55

The literature is summarised on the activity of quinolone antibacterial compounds in assays which are commonly used for risk assessment of new pharmaceuticals. These include assays for DNA damage, sister chromatid exchanges, chromosome aberrations and mutation induction. The general pattern of activity exhibited by these compounds is induction of DNA damage in both prokaryotic and eukaryotic cells, and induction of mutations in DNA repair-proficient bacteria and at the thymidine kinase locus in mammalian cells. They do not appear as a class to induce mutations at the hypoxanthine-guanine-phosphoribosyltransferase (HGPRT) or Na+,K(+)-ATPase loci or to cause chromosome aberrations. It is suggested that these actions may be the result of interference with eukaryotic topoisomerase and that this interference differs in some respects from the topoisomerase interference caused by certain antitumour compounds. The postulated mechanism of action has important implications for assessment of risk from consumption of quinolone antibacterials. The risk of adverse genotoxic events should vary directly with the concentration of drug reaching the intracellular enzyme target and the affinity of the drug for the target. Results of carcinogenicity studies conducted to date with the quinolone antibacterials suggest minimal risk from long term consumption of the newer, second-generation compounds.
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PMID:Mutagenicity of quinolone antibacterials. 150 68

A variation of the mouse lymphoma (L5178Y TK+/(-)-3.7.2c) assay has been developed using a microtiter cloning technique instead of the standard agar method. The cell line has been used to detect both gene mutations (at the Na+/K+ ATPase and thymidine kinase loci) and chromosome damage (micronucleus induction) in the same experiment. The system was validated using gamma-irradiation (a known clastogen), 2 direct-acting mutagens, ethyl and methyl methanesulphonate and an indirect-acting mutagen, benzo[a]pyrene. Using the assay, 1-methoxy-1,3,5-cycloheptatriene was shown to be a clastogenic mutagen in the presence of S9, since a clear dose-dependent increase in micronuclei was observed, mainly small colony thymidine kinase mutants were observed, and no ouabain-resistant mutants were induced, a profile very similar to gamma-irradiation. The results suggest that metabolic activation potential explains the results in the accompanying paper (Asquith et al., 1990). The implications for mutagenicity testing are discussed.
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PMID:Comparative induction of gene mutations and chromosome damage by 1-methoxy-1,3,5-cycloheptatriene (MCHT), 2. Results using L5178Y mouse lymphoma cells to detect both gene and chromosome damage; validation with ionizing radiation, methyl methanesulphonate, ethyl methanesulphonate and benzo[a]pyrene. 234

Isolation and general properties of 3'-5' exonucleases I and II (EC 3.1.4.26), which are specific to single-stranded DNA, are described. Such enzymes, being components of replication complexes, could correct replication errors. Homogeneous exonucleases I and II consist of a single subunit with molecular mass of 50 and 40 kDa, respectively. These enzymes are located preferentially in the nuclear membrane and chromatin. They form complexes with nuclear DNA polymerases and some other proteins and are not observed practically in a free state. Molecular masses of the complexes amount from 70 to 1.500 kDa. The complexes dissociate as a result of solution hydrophobization and can be reconstituted after the decrease of hydrophobization. The heavy membrane complex form of 3'----5' exonuclease I manifests enzymatic activities of DNA polymerase alpha (EC 2.7.7.7), non-specific nucleoside triphosphatase (EC 3.1.3.2), nucleotidase (EC 3.1.3.31) and faint activity of endonuclease (EC 3.1.4.5). Complexes under study do not display activity of thymidine kinase (EC 2.7.1.21), marker protein of replitase, neither in G0 nor in S-period.
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PMID:[Homogeneous 3'----5'-exonucleases and their multienzyme complexes from the rat liver]. 234 19

In experiments with CHO-AT3-2 cell culture, a study was made of the effect of potassium cyanate (KNCO) on the effect of gamma radiation and benzo(a)pyrene (BP) by the following tests: cell viability, induction of cells with micronuclei and fragmented nuclei and mutations by thymidine kinase (TK) and Na+/K+-ATPase loci. Some tests have revealed the increase in the effect of gamma radiation and BP produced by potassium cyanate. It is suggested that the sensitizing effects are related to repair system inhibition and/or changes in the cell chromatin structure produced by KNCO.
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PMID:[Potassium cyanate modification of the toxic and mutagenic effects of gamma radiation and benzo(a)pyrene]. 271 19


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