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1.
Mutations by near-ultraviolet radiation in Escherichia coli strains lacking superoxide dismutase 总被引:3,自引:0,他引:3
Om wild-type Escherichia coli, near-ultraviolet radiation (NUV) was only weakly mutagenic. However, in an allelic mutant strain (sodA sodB) that lacks both Mn- and Fe-superoxide dismutase (SOD) and assumed to have excess superoxide anion (O2−), NUV induced a 9-fold increase in mutation above the level that normally occurs in this double mutant. When a sodA sodB double mutant contained a plasmid carrying katG+ HP-I catalase), mutation by NUV was reduced to wild-type (sodA+ sodB+) levels. Also, in the sodA sodB xthA triple mutant, which lacks exonuclease III (exoIII) in addition to SOD, the mutations frequency by NUV was reduced to wild-type levels. This synergistic action of NUV and O2− suggested that pre-mutational lesions occur, with exoIII converting these lesions to stable mutants. Exposure to H2O2 induced a 2.8 fold increase in mutations in sodA sodB double mutants, but was reduced to control levels when a plasmid carrying katG+ was introduced. These results suggest that NUV, in addition to its other effects on cells, increases mutations indirectly by increasing the flux of OH. radicals, possibly by generating excess H2O2. 相似文献
2.
3.
A comparative study on the activity profile of catalase and superoxide dismutase, the two scavenging enzymes, as well as the
developmental profile of lipid peroxidation in the human fetal brain, liver and kidney have been done for gestation periods
ranging from 12 weeks to 28 weeks and beyond. The activity of the scavenging enzymes increase gradually inall the tissues with the advancement of pregnancy. Brain is an exception in case of catalase where the activity remains more
or less same throughout the developmental period except in the case of fetuses, 28 weeks and above where significant decrease
in the catalase activity is observed. A high level of lipid peroxidation is observed during early stages of development which
declines thereafter. 相似文献
4.
5.
Summary Microbodies are ubiquitous organelles in fungal cells, occurring in both vegetative hyphae and spores. They are bounded by a single membrane and may contain a crystalloid inclusion with subunits spaced at regular intervals. Typically, they contain catalase which reacts with the cytochemical stain 3,3-diaminobenzidine to yield an electron-opaque product, urate oxidase,l--hydroxy acid oxidase andd-amino acid oxidase. Their fragility and the necessity to disrupt the tough fungal cell wall before isolating them make them difficult to isolate. Analysis of enzymes in purified or partially purified microbodies from fungi indicates that they participate in fatty acid degradation, the glyoxylate cycle, purine metabolism, methanol oxidation, assimilation of nitrogenous compounds, amine metabolism and oxalate synthesis. In organisms where microbodies are known to contain enzymes of the glyoxylate cycle, they are known as glyoxysomes; where they are known to contain peroxidatic activity, they are known as peroxisomes. In some cases microbodies contain enzymes for only a portion of a pathway or cycle. Thus, they must be involved in metabolic cooperation with other organelles, particularly mitochondria. The number, size and shape of microbodies in cells, their buoyant density and their enzyme contents may vary with the composition of the medium; their proliferation in cells is regulated by the growth environment. The isolation from the same organism of microbodies with different buoyant densities and different enzymes suggests strongly that more than one type of microbody can be formed by fungi. 相似文献
6.
Effects of Nerve Growth Factor on Glutathione Peroxidase and Catalase in PC 12 Cells 总被引:4,自引:1,他引:3
Deepa Sampath George R. Jackson Karin Werrbach-Perez J. Regino Perez-Polo 《Journal of neurochemistry》1994,62(6):2476-2479
Abstract: Nerve growth factor (NGF) is a member of the neuro- trophin family and is required for the survival and maintenance of peripheral sympathetic and sensory ganglia. In the CNS, NGF regulates cholinergic expression by basal forebrain cholinergic neurons. NGF also stimulates cellular resistance to oxidative stress in the PC12 cell line and protects PC12 cells from the toxic effects of reactive oxygen species. The hypothesis that NGF protection involves changes in antioxidant enzyme expression was tested by measuring its effects on catalase and glutathione per- oxidase (GSH Px) mRNA expression in PC12 cells. NGF increased catalase and GSH Px mRNA levels in PC 12 cells in a time- and dose-dependent manner. There was also a corresponding increase in the enzyme activities of catalase and GSH Px. Thus, NGF can provide cytoprotection to PC12 cells by inducing the free radical scavenging enzymes catalase and GSH Px. 相似文献
7.
Historically, it has been theorized that the oxidant sensitivity of glucose-6-phosphate dehydrogenase (G6PD)-deficient erythrocytes arises as a direct consequence of an inability to maintain cellular gluthione (GSH) levels. This study alternatively hypothesizes that decreased NADPH concentration leads to impaired to catalase activity which, in turn, underlies the observed oxidant susceptibility. To investigate this hypothesis, normal and G6PD-deficient erythrocytes and hemolysates were challenged with a H2O2-generating agent. The results of this study demonstrated that catalase activity was severely impaired upon H2O2 challenge in the G6PD-deficient cell whiel only decrease was observed in normal cells. Supplmentation of either normal or G6PD-deficient hemolysates with purified NADPH was found to significantly (P < 0.001) inhibit catalase inactivation upon oxidant challenge while addition of NADP+ had no effect. Analysis of these results demonstrated direct correlation between NADPH concentration and catalase activity (r = 0.881) and an inverse correlation between catalase activity and erythrocyte oxidant sensitivity (r = 0.906). In contrast, no correlation was found to exist between glutathione concentration (r = 0.170) and oxidant sensitivity. Analysis of NADPH/NADPt ration in acatalasemic mouse erythrocytes demonstrated that NADPH maintenance alone was not sufficient to explain oxidant resistance, and that catalase activity was required. This study supports the hypothesis that impaired catalase activity underlies the enhanced oxidant sensitivity of G6PD-deficient erythrocytes and elucidates the importance of NADPH in the maintenance of normal catalase activity. 相似文献
8.
A facultative methylotrophic bacterium was isolated from enrichment cultures containing methylamine as the sole carbon source.
It was tentatively identified as an Arthrobacter species. Extracts of cells grown on methylamine or ethylamine contained high levels of amine oxidase (E.C. 1.4.3.) activity.
Glucose- or choline-grown cells lacked this enzyme. Oxidation of primary amines by the enzyme resulted in the formation of
H2O2; as a consequence high levels of catalase were present in methylamine-and ethylamine-grown cells. The significance of catalase
in vivo was demonstrated by addition of 20 mM aminotriazole (a catalase inhibitor) to exponentially growing cells. This completely
blocked growth on methylamine whereas growth on glucose was hardly affected. Cytochemical studies showed that methylamine-dependent
H2O2 production mainly occurred on invaginations of the cytoplasmic membrane. Assimilation of formaldehyde which is generated
during methylamine oxidation was by the FBP variant of the RuMP cycle of formaldehyde fixation. The absence of NAD-dependent
formaldehyde and formate dehydrogenases indicated the operation of a non-linear oxidation sequence for formal-dehyde via hexulose
phosphate synthase. Enzyme profiles of the organism grown on various substrates suggested that the synthesis of amine oxidase,
catalase and the enzymes of the RuMP cycle is not under coordinate control. 相似文献
9.
Coupling of Dopamine Oxidation (Monoamine Oxidase Activity) to Glutathione Oxidation Via the Generation of Hydrogen Peroxide in Rat Brain Homogenates 总被引:16,自引:6,他引:10
Howard S. Maker Cipora Weiss Demetra J. Silides Gerald Cohen 《Journal of neurochemistry》1981,36(2):589-593
Abstract: Homogenates of perfused rat brain generated oxidized glutathione from reduced glutathione during incubation with dopamine or serotonin. This activity was blocked by pargyline. a monoamine oxidase inhibitor, or by catalase, a scavenger of hydrogen peroxide. These results demonstrate formation of hydrogen peroxide by monoamine oxidase and the coupling of the peroxide to glutathione peroxidase activity. Oxidized glutathione was measured fluorometrically via the oxidation of NADPH by glutathione reductase. In the absence of added dopamine or serotonin, a much smaller amount of reduced glutathione was oxidized: this activity was blocked by catalase, but not by pargyline. Therefore, endogenous production of hydrogen peroxide, not linked to monoamine oxidase activity, was present. These results indicate that glutathione peroxidase (linked to hexose monophosphate shunt activity) can function to eliminate hydrogen peroxide generated by monoamine oxidase and other endogenous sources in aminergic neurons. 相似文献
10.
Abstract: Glutathione peroxidase, glutathione reductase, and catalase activities were measured to 48 h after death in mouse brains held at temperatures replicating the cooling occurring in human cadaver brain. Glutathione peroxidase was stable for 48 h; catalase was stable for 24 h and then declined 20% in activity. Glutathione reductase was stable for 4 h and then decreased to 55% of its initial activity by 48 h. Perfusion of mouse brain with 0.9% (wt/vol) NaCl did not decrease enzyme activities, indicating that erythrocyte contamination has little effect on measured brain activities. The results suggest that glutathione peroxidase would not be affected by moderate time delays in obtaining human postmortem brains but catalase activity may be affected if brains are not promptly removed. Glutathione reductase is not stable and measurements would require controls carefully matched for postmortem conditions. 相似文献