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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two methods, one involving a lactoperoxidase-glucose oxidase coupled reaction and the other employing the insoluble catalyst 1,3,4,6-tetrachloro-3 alpha, 6-alpha-diphenyl-glycoluril (Iodo-Gen), were used to label the surface membrane of promastigotes of Leishmania tropica major. Both methods labelled approximately 20 proteins or glycoproteins (apparent size range 10 to 110 kDa) in a qualitatively similar manner, however the lactoperoxidase method labelled one additional constituent (260 kDa). By omission of both enzymes, or of Iodo-Gen; by comparison of radioactivity incorporated by particulate and soluble cell fractions; and through the action of proteases on live, labelled promastigotes, the surface-labelling specificity of both procedures was confirmed. Immunoprecipitation of Triton X-100 extracts of labelled cells with rabbit antisera revealed a minimum of twelve (seven major) protein antigens in the homologous system and different but cross-reactive protein species from two other isolates of L. tropica. Lectin precipitation of radiolabelled surface components was possible with concanavalin A (but not with other lectins tested) identifying a minimum of 12 glycoproteins. Two of these glycoproteins (210 and 88 kDa) were not recognized by rabbit antiserum.
Mol Biochem Parasitol 1983 Aug
PMID:Radioiodination and identification of externally disposed membrane components of Leishmania tropica. 635 41

In order to understand why different stages of Trichinella spiralis vary in their susceptibility to killing by leukocytes, the effects of artificially generated oxidants on different stages of this parasite were compared. More than 90% newborn larvae were killed after incubation in acetaldehyde-xanthine oxidase or glucose-glucose oxidase. On the other hand, fewer than 10% of adult worms or muscle larvae were killed when incubated under identical conditions. Thus, only the stages which are resistant to killing by leukocytes are resistant to killing by oxidants. The larvicidal effect of acetaldehyde-xanthine oxidase was blocked by the addition of either superoxide dismutase or catalase and was partially inhibited by radical scavengers and singlet oxygen quenchers. The oxidant resistant adults and muscle larvae contained 3-5 times more superoxide dismutase and at least five times more glutathione peroxidase than the oxidant sensitive newborn larvae. In contrast, all 3 stages lacked detectable amounts of catalase and contained roughly equivalent amounts of reduced glutathione. Accordingly, adults and muscle larvae may be more resistant to killing by leukocytes than newborn larvae because they contain better oxidant defenses.
Mol Biochem Parasitol 1984 Jan
PMID:Scavenger enzymes and resistance to oxygen mediated damage in Trichinella spiralis. 669 69

Previous electron-microscopical studies from this laboratory have shown that the thyroglobulin molecule can occur in two different conformations, one ovoid and the other cylindrical. Ovoid molecules are characteristic of well-iodinated thyroglobulin whereas cylindrical molecules are found after low-iodine diet or blocking of iodination. The present study was performed in order to elucidate the possible relation between the molecule conformation and the peroxidase-catalyzed reactions that occur in the thyroid in connection with hormone synthesis. Cylindrical thyroglobulin molecules (from PTU-exposed thyroids) were incubated in different media and the proportion of cylindrical and ovoid molecules after incubation was estimated in electron micrographs. It was found that incubation with glucose-glucose oxidase caused an extensive conversion of cylindrical molecules into ovoid molecules. Peroxidase and/or iodide were not necessary for this change of conformation. It is suggested that this in vitro molecule transformation was the result of an oxidation reaction.
Mol Cell Endocrinol 1980 Mar
PMID:Conformational change of the thyroglobulin molecule induced by oxidation in vitro. 737 74

Free radicals and other reactive oxygen species (ROS) are important mediators in asbestos-induced lung toxicity. Asbestos fibers are thought to stimulate cells to generate ROS via iron that is present on fibrous silicates. The pathophysiologic responses in the lung after asbestos exposure are characterized by the accumulation of macrophages at the site of fiber deposition and the release of growth factors and proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha). We have examined the role of iron-catalyzed ROS in asbestos induction of TNF-alpha from rat alveolar macrophages. Treatment of alveolar macrophage cultures with asbestos stimulated dose-dependently TNF-alpha secretion, which was inhibited by the addition of deferoxamine, an iron chelator. Asbestos fibers, pretreated with deferoxamine to remove iron from the fibers before addition to alveolar macrophages, also significantly reduced the TNF-alpha response. Consistent with the role of iron on asbestos fibers in catalyzing hydroxyl radical generation, membrane-permeable hydroxyl radical scavengers (tetramethylthiourea, dimethyl sulfoxide) inhibited the asbestos-induced TNF-alpha response. The asbestos-induced increase in TNF-alpha, as well as in interleukin-1 alpha, and their inhibition by tetramethylthiourea occurred at the transcriptional level. The role of ROS in signaling TNF-alpha stimulation was confirmed by use of free radical-generating systems (hypoxanthine-xanthine oxidase, hydrogen peroxide, glucose-glucose oxidase, or ferrous plus hydrogen peroxide). These results suggest that intracellularly generated ROS can stimulate TNF-alpha in alveolar macrophages and that asbestos-induced TNF-alpha gene expression and secretion are mediated by iron-catalyzed product of ROS.
Am J Respir Cell Mol Biol 1995 Jun
PMID:Iron and reactive oxygen species in the asbestos-induced tumor necrosis factor-alpha response from alveolar macrophages. 753 75

Inclusion complexes of 1,1'-dimethylferrocene (DMFe) with alpha-, 2-hydroxypropyl-beta- or gamma-cyclodextrins were formed in aqueous systems. For the first time, the interacting DMFe-cyclodextrin systems have been characterized using cyclic voltammetry which enabled the estimation of the complexation order, the formation constant and the diffusivity. Cyclic voltammetry was performed at a stationary electrode, yielding complexation ratios of 1:2 for DMFe with alpha-cyclodextrin and 1:1 with the other two cyclodextrins, as expected from the known cavity dimensions for the cyclodextrins. Formation constants of 4.4 x 10(4) M-2, 1.2 x 10(3) M-1 and 2.9 x 10(2) M-1 were then determined for the complexes between DMFe and the alpha-, beta- and gamma-cyclodextrins, respectively, in relative agreement with the literature. The maximum complexation efficiency, diffusivity and solubility were observed for the DMFe:2-hydroxypropyl-beta-cyclodextrin inclusion complex, which, combined with cost factors, resulted in the selection of this form for bioelectrocatalysis studies. The efficiency of the complex as a mediator for the glucose:glucose oxidase system was determined by measuring the rate constant (ks) for reaction of the oxidized DMFe with the reduced enzyme. The ks value decreased from 3.4 x 10(4) M-1 s-1 to 1.9 x 10(4) M-1 s-1 with an increase in 2-hydroxypropyl-beta-cyclodextrin concentration from 4 mM to 10 mM. In this range, the ks value is similar to that of free ferrocene, implying a high efficiency of the DMFe:2-hydroxypropyl-beta-cyclodextrin inclusion complex.
J Mol Recognit
PMID:Characterization of interacting ferrocene-cyclodextrin systems and their role in mediated biosensors. 759 46

The aim of the research was to study the role played by extracellular O2-radicals, which are implicated in cardiac cell damage and the protective effect by cell-permeable, nitroxide, superoxide dismutase-mimics. Cardiomyocytes cultures from 1-day-old rats served as the test-system. Experiments were performed since 5th day in culture when > 80% of the cells were beating myocardial cells. Oxidative damage was induced by 0.5 mM hypoxanthine and 0.06 U/ml xanthine oxidase or by 10 mM glucose and 0.15 U/ml glucose oxidase. The parameters used to evaluate damages were spontaneous beating, lactate dehydrogenase release and ATP level. The rhythmic pulsation was followed microscopically. To determine the kinetics of cytosolic enzyme release from the cells, media samples were collected at various points of time and assayed for enzyme activity. To determine the cellular ATP, cells were washed with sodium phosphate buffer, scraped off and boiled for 3 min with sodium phosphate buffer. Following centrifugation the supernatant was collected and ATP was determined by the chemiluminogenic assay using firefly tails. The present results indicate that nitroxide stable free radicals in the millimolar concentration range, provide full protection without toxic side-effect. Unlike exogenously added SOD that failed to protect, exogenous catalase provided almost full protection. In addition, the metal-chelating agent dipyridyl, but not diethylene-triamine-pentaacetate or desferrioxamine, protected the cultured cells. The present results suggest that H2O2 is the predominant toxic species mediating the oxidative damage whereas extracellular superoxide radical does not contribute to cultured cardiomyocyte damage.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem 1995 Apr 26
PMID:Do nitroxides protect cardiomyocytes from hydrogen peroxide or superoxide? 767 30

Nitroblue tetrazolium was reduced to blue formazan during the oxidation of glucose by glucose oxidase. The rate of blue color formation was dependent on the concentrations of glucose, nitroblue tetrazolium and glucose oxidase. The rate of the reaction was negligible below pH 8.4, but sharply increased with increasing pH. The reduction of nitroblue tetrazolium was inhibited by superoxide dismutase, consistent with the participation of superoxide anion radical in the reaction.
Biochem Mol Biol Int 1994 Sep
PMID:Evidence for superoxide radical production by a simple flavoprotein: glucose oxidase. 784 33

A thermodynamic investigation was carried out on heat-induced flavin dissociation in Aspergillus niger glucose oxidase. Experimental measurements performed by difference spectroscopy showed that the dissociation of the FAD cofactors is a highly cooperative process and is probably related to the extended conformational changes resulting from protein unfolding. Microenvironmental modifications attained by the addition of polyhydric compounds (glycerol, fructose, sucrose and sorbitol) from 10 to 30% by weight were found to hinder the dissociation. The stabilizing effect provided by these substances was interpreted as a consequence of preferential exclusion phenomena, which are likely to be determined by the perturbation of the surface tension of water, in the case of sugars, or by the solvophobic effect, in the case of glycerol.
Biochem Mol Biol Int 1994 Oct
PMID:Effect of polyols and sugars on heat-induced flavin dissociation in glucose oxidase. 786 96

A gene encoding an endo-1,4-beta-xylanase from Aspergillus tubigensis was cloned by oligonucleotide screening using oligonucleotides derived from amino acid sequence data obtained from the purified protein. The isolated gene was functional as it could be expressed in the very closely related fungus Aspergillus niger. The xylanase encoded by this gene is synthesized as a protein of 211 amino acids. After cleavage of the presumed prepropeptide this results in a mature protein of 184 amino acids with a molecular weight of 19 kDa and an isoelectric point of 3.6. The regulatory region of the xlnA gene was studied with respect to the response to xylan induction and carbon catabolite repression. By deletion analysis of the 5' upstream region of the gene a 158 bp region involved in the xylan specific induction was identified. To study this regulatory element a reporter system for transcriptional activating sequences was developed that is based on the A. niger glucose oxidase-encoding gene. From the results with this reporter system it is concluded that this 158 bp fragment not only contains the information required for induction of transcription but that it also plays a role in carbon catabolite repression of the xlnA gene. The region directly upstream of this fragment contains four potential CREA target sites; deletion of this region leads to an increase in the level of transcription. These results suggest that carbon catabolite repression of the xlnA gene is controlled at two levels, directly by repression of xlnA gene transcription and indirectly by repression of the expression of a transcriptional activator. This type of mechanism would be similar to the double lock mechanism for the regulation of gene expression of alcA in Aspergillus nidulans. The reporter system was also used to study the regulation of expression via the functions located on this fragment in A. niger and in A. nidulans. Essentially the same pattern of regulation was found in both of these hosts. Therefore, regulation of xylanase gene expression is basically conserved in all three aspergilli.
Mol Microbiol 1994 May
PMID:Regulation of the xylanase-encoding xlnA gene of Aspergillus tubigensis. 806 65

The ferricenium salt FcH+BF4- behaves as a specific substrate of glucose oxidase acting instead of dioxygen with the effective parameters of the Michaelis-Menten equation kcat = 2.60 x 10(2) s-1 and KM = 2.7 x 10(-4) M at 25 degrees C, pH 6.8 and [D-glucose] = 0.001 M. The activity of glucose oxidase can easily be monitored by conventional UV-vis spectrophotometry at 617 nm following the bleaching of the ferricenium dye.
Biochem Mol Biol Int 1993 Nov
PMID:Ferricenium salts instead of dioxygen in glucose oxidase catalysis. A direct interaction and analytical implications. 829 5


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