Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.3 (topoisomerase)
 9,911 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Resistance of Streptococcus pneumoniae to fluoroquinolones is caused predominantly by amino acid substitutions at positions Ser79 of ParC and Ser81 of GyrA to either Phe or Tyr encoded in the quinolone resistance-determining regions of the parC topoisomerase IV and gyrA DNA gyrase genes. Analysis of highly resistant clinical isolates identified novel second-step substitutions, Ser79Leu (ParC) and Ser81Ile (GyrA). To determine contributions of these new mutations to fluoroquinolone resistance either alone or in combination with other Ser79/81 alleles, the substitutions Ser79Leu/Phe/Tyr in ParC and Ser81Ile/Phe/Tyr in GyrA were introduced into the R6 background, resulting in 15 isogenic strains. Their level of fluoroquinolone resistance was determined by susceptibility testing for ciprofloxacin, levofloxacin, moxifloxacin, gatifloxacin, gemifloxacin, garenoxacin, and norfloxacin. Leu79 and Ile81 alone as well as 79/81Phe/Tyr substitutions did not contribute significantly to resistance, with fluoroquinolone MICs increasing two- to fourfold compared to wild type for all agents tested. Fluoroquinolone MICs for double transformants ParC Ser79Phe/Tyr/Leu-GyrA Ser81Phe/Tyr were uniformly increased by 8- to 64-fold regardless of pairs of amino acid substitutions. However, combinations including Ile81 conferred two- to fourfold-higher levels of resistance than did combinations including any other Ser81 GyrA substitution, thus demonstrating the differential effects of diverse amino acid substitutions at particular hotspots on fluoroquinolone MICs.
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PMID:Novel Ser79Leu and Ser81Ile substitutions in the quinolone resistance-determining regions of ParC topoisomerase IV and GyrA DNA gyrase subunits from recent fluoroquinolone-resistant Streptococcus pneumoniae clinical isolates. 1591 50

We report the synthesis of an original series of oxoazabenzo[de]anthracenes conjugated to an amino acid: Ala, Phe, Pro, Lys, or Gly (4a-e, respectively). The compounds, derived from 1,8-dihydroxyanthracene-9,10-dione, were studied for DNA binding and cytotoxicity. Melting temperature, fluorescence quenching, and surface plasmon resonance methods all indicated that the lysine derivative 4d binds to DNA much more strongly that the Pro, Ala, and Gly conjugates whereas the Phe analogue showed the lowest DNA binding capacity. These compounds form intercalation complexes with DNA, as judged from electric linear dichroism and topoisomerase I-based DNA unwinding experiments. Preferential binding of 4d to defined sequences such as 5'-CTAAAGG and 5'-ATGC was evidenced by DNase I footprinting. This Lys conjugate was found to be over 20 times more cytotoxic to CEM human leukemia cells than the other conjugates, with an IC50 in the submicromolar range. A high antiproliferative activity, likely attributable to the enhanced DNA binding capacity, is maintained despite the incapacity of the compound to stabilize topoisomerase-DNA covalent complexes. The cell cycle effects of 4d consisted in an S phase accumulation of cells coupled with a pro-apoptotic action (appearance of hypodiploid sub-G1 cells) which were confirmed by measuring the inhibition of BrdU incorporation into DNA and labeling of phosphatidylserine residues with annexin V-FITC by means of flow cytometry. Altogether, the work provides interesting structure-activity relationships in the oxoazabenzo[de]anthracene-amino acid conjugate series and identifies the lysine derivative 4d as a promising candidate for further in vivo evaluation and drug design.
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PMID:Oxoazabenzo[de]anthracenes conjugated to amino acids: synthesis and evaluation as DNA-binding antitumor agents. 1602 36

The presence of fluoroquinolone resistance-associated mutations within the quinolone resistance-determining region of DNA gyrase and topoisomerase IV was investigated genetically in clinical isolates of Proteus mirabilis recovered from patients with urinay tract infections. Two isolates of fluoroquinolone-resistant P. mirabilis possessed the mutations in GyrA (Ser-83 --> Arg or Ile), GyrB (Ser-464 --> Tyr or Phe) and ParC (Ser-80 --> Ile). A novel mutation with Glu-87 --> Lys in GyrA, where suggested to be responsible for fluoroquinolone resistance, was identified. These results demonstrate that the presence of an additional mutation at Glu-87 in GyrA may contribute to high-level fluoroquinolone resistance, too.
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PMID:[Mutations of DNA gyrase and topoisomerase IV in clinical isolates of fluoroquinolone-resistant Proteus mirabilis]. 1667 82

Salmonella enterica serovar Paratyphi A is increasingly a cause of enteric fever. Sequence analysis of an Indian isolate showed a unique strain with high-level resistance to ciprofloxacin associated with double mutations in the DNA gyrase subunit gyrA (Ser83-->Phe and Asp87-->Gly) and a mutation in topoisomerase IV subunit parC (Ser80-->Arg).
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PMID:Molecular analysis of fluoroquinolone-resistant Salmonella Paratyphi A isolate, India. 1670 90

The ability of Mycoplasma hyopneumoniae to persist despite fluoroquinolone treatments was investigated with pigs. Groups of specific-pathogen-free pigs were experimentally infected with M. hyopneumoniae strain 116 and treated with marbofloxacin at the therapeutic dose (TD) or half of the therapeutic dose (TD/2) for 3 days. Results showed that, despite tissue penetration of marbofloxacin, particularly in the trachea and the tracheal secretions, the treatments did not have any influence on M. hyopneumoniae recovery from tracheal swabs. Mycoplasmas were also isolated from inner organs and tissues such as liver, spleen, kidneys, and bronchial lymph nodes. Recontamination of pigs via environment could not explain mycoplasma persistence after medication, as decontamination of pigs and allocation to a new disinfected environment did not have any significant effect on the phenomenon. A significant decrease in the susceptibility level to marbofloxacin of 12 mycoplasma clones reisolated after the treatments (TD/2 and TD) was observed. Two point mutations were found in the ParC quinolone resistance-determining region (QRDR) of DNA topoisomerase IV (Ser80-->Phe and Asp84-->Asn), and one point mutation was observed just behind the QRDR of ParC (Ala116-->Glu). This is the first time that mutations in a gene coding for topoisomerase IV have been described for M. hyopneumoniae after in vivo marbofloxacin treatments in experimentally infected pigs. However, development of resistance is not sufficient to explain M. hyopneumoniae persistence in vivo since (i) marbofloxacin concentrations were above the marbofloxacin MIC of the wild-type strain and (ii) mycoplasmas reisolated after a single injection of marbofloxacin did not display an increased marbofloxacin MIC.
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PMID:Persistence of Mycoplasma hyopneumoniae in experimentally infected pigs after marbofloxacin treatment and detection of mutations in the parC gene. 1672 52

Serial passage of a clinical isolate of Streptococcus pneumoniae, in the presence of moxifloxacin, gatifloxacin or gemifloxacin, gave rise to resistant isolates. Non-susceptibility as defined by Clinical and Laboratory Standards Institute (CLSI, formerly NCCLS) breakpoints arose on Days 10, 11, and 12 with gatifloxacin, gemifloxacin, and moxifloxacin respectively. Moxifloxacin and gatifloxacin selected for a single step quinolone-resistant-determining-region (QRDR) mutation in DNA gyrase (GyrA) on Day 4 and 7 respectively, whereas gemifloxacin selected simultaneously for multi-step mutations in gyrase and topoisomerase IV (ParC) on Day 17 and activated a non-reserpine inhibited efflux mechanism by Day 4. As found in clinical isolates, mutations included Ser-81-Phe and Glu-85-Lys in GyrA and Ser-79-Phe or Asp-83-Tyr in ParC. At high MICs, moxifloxacin showed a previously unreported 4 amino-acid deletion in GyrB as well as a more unusual substitution Ser-79-Leu/Ile in ParC. Gemifloxacin showed a 2- to 16-fold greater activity than moxifloxacin or gatifloxacin against strains with two or more QRDR mutations, however, its potency did not translate to nonsusceptibility and gemifloxacin MIC values were either at or well above the CLSI nonsusceptible breakpoint concentration.
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PMID:Relative potential for selection of quinolone-resistance-determining-region mutations in Streptococcus pneumoniae by gemifloxacin, gatifloxacin and moxifloxacin. 1702 92

DE-310 is a novel macromolecular prodrug of the topoisomerase-I inhibitor DX-8951. DX-8951 is covalently linked to carboxymethyl dextran polyalcohol (CM-Dex-PA) via a Gly-Gly-Phe-Gly (GGFG) tetrapeptide spacer. The present study was conducted to identify the portions of DX-8951 linked to DE-310, as well as to quantify the number of DX-8951 molecules associated with DE-310. Two different structures terminated with either glycolaldehyde (CM-GA-GGFG-DX-8951) or glycerol (CM-Glr-GGFG-DX-8951) are obtained when the polymer backbone is fragmented with 1 M HCl. The two products, i.e., CM-GA-GGFG-DX-8951 and CM-Glr-GGFG-DX-8951, indicate linkage of GGFG-DX-8951 with carboxymethyl (CM) group at C-2 and C-4 position of the glucose units, respectively. In the present study, CM-GA-GGFG-DX-8951 was reduced to CM-ethyleneglycol (EG)-GGFG-DX-8951 in order to improve stability prior to HPLC analysis. Hydrolysis results revealed that the amount of CM-GA-GGFG-DX-8951 liberated was 84.7 nmol/mg DE-310 and the amount of CM-Glr-GGFG-DX-8951 was 71.8 nmol/mg DE-310. Considering the ratio of generation between CM-GA-GGFG-DX8951 and CM-Glr-GGFG-DX8951, it suggested that slightly larger amount of GGFG-DX-8951 was linked to carboxymethyl groups at the C-2 position of glucose units in DE-310. The sum of the amounts of CM-GA-GGFG-DX-8951 and CM-Glr-GGFG-DX-8951 agrees well with the amount of G-DX-8951 produced from DE-310 by alpha-chymotrypsin treatment (157.5 nmol/mg DE-310). The data indicate that the established hydrolysis give a quantitative evaluation of the DX-8951 linked to DE-310.
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PMID:Quantitative acid hydrolysis of DE-310, a macromolecular carrier system for the camptothecin analog DX-8951f. 1712 25

The qnr genes are transferable genes that confer low-level quinolone resistance by protection of topoisomerase. The occurrence of mutations in DNA gyrase (gyrA, gyrB) and topoisomerase IV (parC, parE) genes in strains harbouring qnr was investigated in 28 qnrA-positive clinical isolates, among which 7 strains also harboured qnrS. Topoisomerase mutations were found in 25 (89%) of the 28 strains, with at least two mutations (gyrA and parC) in 13 strains and one mutation in 12 strains. Isolates of the Enterobacter cloacae complex were compared with reference strains of the new Enterobacter species. gyrA mutations were found at position 83 (Ser or Thr for Ile, Tyr, Leu or Phe depending on the species), and new gyrB mutations were described (S463A, S464F). qnrA had an additive effect of a 10-fold increase in the minimum inhibitory concentration (MIC) whatever the number of topoisomerase mutations, and qnrS was additive to qnrA with a further 2- to 10-fold increase in the MIC. Comparison of MICs with susceptibility breakpoints showed that strains combining qnrA and topoisomerase mutations were resistant to fluoroquinolones, but the three strains lacking a topoisomerase mutation were susceptible using ciprofloxacin and levofloxacin but not using nalidixic acid or moxifloxacin testing.
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PMID:Type II topoisomerase mutations in clinical isolates of Enterobacter cloacae and other enterobacterial species harbouring the qnrA gene. 1725 53

DE-310 is composed of the topoisomerase-I inhibitor DX-8951 (exatecan) and carboxymethyldextran polyalcohol (CM-Dex-PA) carrier, which are covalently linked via peptidyl spacer (Gly-Gly-Phe-Gly). In this study, we investigated relationship between the cathepsin activity and the drug release of DE-310 by use of human liver origin cathepsin (B, L and H) and tumor cells (murine tumor cells (Meth A and M5076), and human tumor cells (HCT116, A549, PC-12, T98G, and HL-60)). Preliminary studies indicated that human liver cathepsin B produced Glycyl DX-8951 (G-DX-8951) from DE-310 more preferentially than DX-8951, whereas human liver cathepsin L produced DX-8951 preferentially. Release of drugs from DE-310 and cathepsin activities were measured in tumor cell types. The release of both DX-8951 and G-DX-8951 from DE-310 correlated well with cathepsin B activity of tumor cells. The release of DX-8951 was weakly, but not significantly, correlated with cathepsin L activity. In M5076 (high cathepsin activity) or Meth A (low cathepsin activity) xenograft models, the levels of DX-8951 and G-DX-8951 in M5076 were higher than in Meth A after single intravenous administration of DE-310. Our findings suggest that cathepsin B is primarily responsible for drug release from DE-310 in tumor.
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PMID:Relationship between drug release of DE-310, macromolecular prodrug of DX-8951f, and cathepsins activity in several tumors. 1805 27

Sodium N-[(trimethylamineboryl)-carbonyl]-L-phenylalanine 2 and {N-[(trimethylamineboryl)-carbonyl]-L-phenylalanyl- carbxylato}-bis-{N-[(trimethylaminebryl)-carbonyl]-L-phenylalanine} dicopper (II) 3 were successfully synthesized. The agents blocked L(1210) leukemic cell DNA and RNA syntheses by inhibiting multiple enzyme activities for nucleic acid synthesis, e.g. PRPP amido transferase, IMP dehydrogenase, DNA polymerase alpha, thymidine kinase, and TMP kinase. The copper (II) complex 3 demonstrated improved ability to inhibit L(1210) partially purified DNA topoisomerase II compared to the parent compound while the sodium salt was inactive at 100 muM.
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PMID:The Synthesis and Antitumor Activity of the Sodium Salt and Copper (II) Complex of N-[(Trimethylamineboryl)-Carbonyl]-L-Phenylalanine Methyl Ester. 1847 18


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