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:1.11.1.7 (peroxidase)
65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

T-cell populations from guinea-pigs sensitized to the protein antigens purified protein derivative of Mycobacterium tuberculosis, ovalbumin, or horseradish perioxidase can be selectively depleted of cells capable of initiating antigen-specific macrophage-lymphocyte clusters in vitro. The depletion is achieved by incubating the T cells on a monolayer of antigen-pulsed macrophages in a Petri dish for some hours and then gently aspirating the cells not adhering to the bottom of the dish. When subsequently assayed, the aspirated cells were found to be depleted of cluster-initiating lymphocytes committed to horseradish peroxidase, monolayers of macrophages pulsed with that antigen must be used. The optimum time for incubation on the absorbing monolayer appears to be 4 h, and two successive incubations are more effective than one. The cell density of the absorbing monolayer and the handling of the Petri dish may be critical for effective removal of the cluster-initating lymphocytes. With optimum procedure we have achieved up to 90% depletion of specific cells with no depletion of cells committed to a control antigen.
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PMID:Macrophage-lymphocyte clusters in the immune response to soluble protein antigen in vitro. IX. Antigen-pulsed macrophages as a tool for specific absorption of cluster-initiating T cells. 9 61

At sub-bactericidal concentrations of hydrogen peroxide, Mycobacterium tuberculosis was killed by hydrogen peroxide/peroxidase/halide microbicidal systems. The halide cofactor could be either iodide or, with much lower efficiency, chloride. Omission of any one of the reactants eliminated the tuberculocidal effect. Differences in susceptibility between different strains of M. tuberculosis did not correlate with virulence differences. The observations are discussed in the context of host defence mechanisms against tuberculosis.
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PMID:Virulence of Mycobacterium tuberculosis and susceptibility to peroxidative killing systems. 9 84

Peroxidase from Mycobacterium tuberculosis H37Rv was purified to homogeneity. The homogeneous protein exhibits catalase and Y (Youatt's)-enzyme activities in addition to peroxidase activity. Further confirmation that the three activities are due to a single enzyme was accomplished by other criteria, such as differential thermal inactivation, sensitivity to different inhibitors, and co-purification. The Y enzyme (peroxidase) was separated from NADase (NAD+ glycohydrolase) inhibitor by gel filtration on Sephadex G-200. The molecular weights of peroxidase and NADase inhibitor, as determined by gel filtration, are 240000 and 98000 respectively. The Y enzyme shows two Km values for both isoniazid (isonicotinic acid hydrazide) and NAD at low and high concentrations. Analysis of the data by Hill plots revealed that the enzyme has one binding site at lower substrate concentrations and more than one at higher substrate concentration. The enzyme contains 6g-atoms of iron/mol. Highly purified preparations of peroxidases from different sources catalyse the Y-enzyme reaction, suggesting that the nature of the reaction may be a peroxidatic oxidation of isoniazid. Moreover, the Y-enzyme reaction is enhanced by O2. Isoniazid-resistant mutants do not exhibit Y-enzyme, peroxidase or catalase activities, and do not take up isoniazid. The Y-enzyme reaction is therefore implicated in the uptake of the drug.
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PMID:The purification and properties of peroxidase in Mycobacterium tuberculosis H37Rv and its possible role in the mechanism of action of isonicotinic acid hydrazide. 24 21

The polymerase chain reaction (PCR was used to identify M. tuberculosis in specimens from patients with suspected pulmonary tuberculosis. A segment of the IS 6110 sequence and of the Cro EL gene were amplified and identified by hybridization with specific probes labeled with peroxidase. The results are in agreement with those obtained using standard microbiological techniques or clinical criteria. The PCR method allowed the detection of M. tuberculosis in 22 out of 58 samples that were acid fast staining negative. The number of patients with at least one positive sample by PCR was much higher in the group with suspicion of tuberculosis (14/28) than in the control group (3/23). This demonstrates the possibility of using PCR technology in endemic areas for tuberculosis.
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PMID:[Diagnosis of tuberculosis by specific DNA amplification directly in samples]. 134 93

INH-resistant mutants of Mycobacterium aurum and M. smegmatis were isolated and characterized in an attempt to provide fresh insight into the activity of isoniazid (INH), a key antibiotic in the treatment of tuberculosis. In both cases, high levels of resistance were accompanied by slower growth rate, by loss of peroxidase and reduced catalase activities, although mycolic acid production was unaffected. A gene homologous to the katG gene of M. tuberculosis, encoding peroxidase-catalase, was detected in wild-type and INH-resistant strains and it appears that INH resistance may stem from the loss of its product.
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PMID:Isolation and characterization of isoniazid-resistant mutants of Mycobacterium smegmatis and M. aurum. 148 56

Tuberculosis is responsible for one in four of all avoidable adult deaths in developing countries. Increased frequency and accelerated fatality of the disease among individuals infected with human immunodeficiency virus has raised worldwide concern that control programmes may be inadequate, and the emergence of multidrug-resistant strains of Mycobacterium tuberculosis has resulted in several recent fatal outbreaks in the United States. Isonicotinic acid hydrazide (isoniazid, INH) forms the core of antituberculosis regimens; however, clinical isolates that are resistant to INH show reduced catalase activity and a relative lack of virulence in guinea-pigs. Here we use mycobacterial genetics to study the molecular basis of INH resistance. A single M. tuberculosis gene, katG, encoding both catalase and peroxidase, restored sensitivity to INH in a resistant mutant of Mycobacterium smegmatis, and conferred INH susceptibility in some strains of Escherichia coli. Deletion of katG from the chromosome was associated with INH resistance in two patient isolates of M. tuberculosis.
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PMID:The catalase-peroxidase gene and isoniazid resistance of Mycobacterium tuberculosis. 150 8

The antibody response to individual epitopes has previously been analysed by competition assay using 125I- or enzyme labelled monoclonal antibodies. A modification of the test is described in which competition of human sera with unlabelled mouse monoclonal antibodies at the limiting dilution is revealed by peroxidase labelled antimouse IgG conjugate. Analysis of 54 sera from patients with pulmonary (36) and extra-pulmonary (18) tuberculosis and 31 controls indicated that the modified test compares favourably with the test based upon directly labelled antibodies. Diagnostic sensitivity for five monoclonal antibodies evaluated was 11.1% (TB78), 35.2% (TB23 and TB68), 37.0% (TB71) and 61.1% (TB72) at 97.5% specificity. For TB72, sensitivity was highest for pulmonary disease (69.7%). The modified assay is also easier to standardise for screening new monoclonal antibodies using a single enzyme-labelled conjugate.
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PMID:A rapid, simple enzyme immunoassay for detection of antibody to individual epitopes in the serodiagnosis of tuberculosis. 171 68

Quantitative microdilution plate hybridization was used to identify 22 Mycobacterium species. DNAs of clinical strains were rapidly extracted and labeled with photoreactive biotin. Labeled DNAs were distributed into wells of a microdilution plate in which reference DNAs had been immobilized. After 2 h of hybridization, hybridized DNAs were quantitatively detected with peroxidase-conjugated streptavidin and the substrate, tetramethylbenzidine. This method could differentiate among 20 of the 22 Mycobacterium species tested. The type strains of Mycobacterium tuberculosis and M. bovis were genetically highly related and could not be differentiated by this method. Of 194 biochemically identified human clinical strains, 178 (90%) were genetically identified within 3 h of the small-scale DNA extraction.
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PMID:Application of colorimetric microdilution plate hybridization for rapid genetic identification of 22 Mycobacterium species. 176 80

A double antibody sandwich ELISA was carried out with commercially available anti-BCG and peroxidase labeled anti-BCG, for the detection of mycobacterial antigens. By using purified protein derivative of tuberculin (PPD) as the antigen, the lowest detection limit of the assay was found to be 0.05 microgram/ml. At the cut off level of absorbance index (Al) greater than or equal to 5. positive results of ELISA were obtained from 24/25 sputum specimens which were positive for staining of acid fast bacilli (AFB), 5/16 specimens positive for culture of Mycobacterium tuberculosis and 67/69 specimens positive for both tests. The assay was positive in only 11/164 specimens negative for both staining of AFB and culture of M. tuberculosis. 4 of which were known to have tuberculosis. Thus, with sputum specimens, the sensitivity, specificity, efficiency, positive predictive value and negative predictive value of the ELISA were 87.27, 93.29, 90.88, 89.72 and 91.62 percent respectively. Positive results were also obtained in 2/111 sputum specimens which were positive for other bacteria but the presence of AFB in these specimens could not be ruled out. With pleural fluid specimens, positive ELISA with Al greater than 1 was found in 3/26 specimens of patients with tuberculous pleurisy and 0/11 of those with malignancy. Twenty-six sera and urine specimens of tuberculous patients and also all control specimens (138 sera and 86 urine specimens) assayed, gave negative ELISA results (Al less than 1).
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PMID:Value of an ELISA for mycobacterial antigen detection as a routine diagnostic test of pulmonary tuberculosis. 211 52

The heat-labile T class of mycobacterial catalase exhibits peroxidase activity with some substrates. Most species of mycobacteria produce T-catalase, which is serologically characterized by a combination of shared epitopes and unique, species-specific epitopes. Antibodies to T-catalases from Mycobacterium tuberculosis, Mycobacterium avium, and Mycobacterium intracellulare have been cross absorbed with T-catalases from heterologous species and applied as dots to nitrocellulose membranes. When these membranes were incubated with crude sonic extracts of 93 strains of mycobacteria that produce sufficient T-catalase, and were then exposed to 3,3'-diaminobenzidine peroxidase substrate, only those extracts made from one of the three species represented yielded a discrete brown dot at the site of the corresponding globulin. The sensitivity of the test was at least 96.5%, and the specificity was in excess of 99.5%.
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PMID:Intrinsic catalase dot blot immunoassay for identification of Mycobacterium tuberculosis, Mycobacterium avium, and Mycobacterium intracellulare. 244 31


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