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Results for “OXIDASE AND PEROXIDASE”

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At least 361 records · Page 20Linked to original sources
PubMed1991

Assessment of the antioxidant/prooxidant status of murine skin following topical treatment with 12-O-tetradecanoylphorbol-13-acetate and throughout the ontogeny of skin cancer. Part I: Quantitation of superoxide dismutase, catalase, glutathione peroxidase and xanthine oxidase.

The activities of several enzymes involved in reactive oxygen production and detoxification were quantified in murine skin during the ontogeny of chemically induced skin cancer. Relative to solvent-treated controls, the specific activities of epidermal superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) were reduced approximately 45, approximately 60 and approximately 24% respectively, 24 h after the fourth or tenth topical application of 1 microgram of 12-O-tetradecanoylphorbol-13-acetate (TPA) to the dorsal skin of SENCAR mice. The specific activity of epidermal xanthine oxidase (XO) increased approximately 350% during the same period. SOD and CAT specific activities in papillomas and carcinomas generated in an initiation-promotion protocol were approximately 15 and approximately 40% respectively of the activities measured in age-matched, non-treated mice. CAT and SOD activities were also significantly suppressed in the skin adjacent to the papillomas for several weeks following the cessation of TPA promotion, but eventually recovered to the levels measured in age-matched controls. XO specific activities in papillomas and squamous cell carcinomas (SCC) were approximately 85-350% greater than the activities determined in skin adjacent to the tumors. The increases in XO and the decreases in SOD and CAT activities measured in the tumors were independent of continued treatment with TPA, and thus characteristic of the tumor phenotype. GPX activities in papillomas were comparable to normal, untreated skin, but reduced approximately 22-41% in SCC. Collectively, these studies demonstrate that TPA orchestrates changes in the activities of several enzymes involved in reactive oxygen metabolism that are characteristic of the papilloma and SCC phenotype.

Administration, Topical↗
PubMed1998

Expression of phanerochaete chrysosporium genes encoding lignin peroxidases, manganese peroxidases, and glyoxal oxidase in wood

Expression of Phanerochaete chrysosporium genes encoding ligninolytic enzymes was assessed in wood. Poly(A) RNA was extracted from colonized wood chips by magnetic capture, and specific transcripts were quantified by competitive reverse transcriptase PCR. mRNA levels varied substantially among lignin peroxidase genes, and transcript patterns were dramatically different from those in previous studies with defined media.

Journal Article↗
PubMed1980

Peroxide Levels and the Activities of Catalase, Peroxidase, and Indoleacetic Acid Oxidase during and after Chilling Cucumber Seedlings.

The activities of catalase, peroxidase, indoleacetic acid (IAA) oxidase and peroxide levels in cucumber plants during and after chilling were determined. During 96 hours at 5 C and 85% relative humidity, catalase activity declined, IAA oxidase activity increased, and peroxide concentrations increased. Peroxidase activity was not affected by chilling. When chilled plants were returned to 25 C to recover, enzyme activities and peroxide concentration were restored to their prechilling levels. The increase in peroxide and IAA oxidase activity may inactivate or destroy IAA and thus retard growth.

Journal Article↗
PubMed1994

High-sensitive chemiluminescent assay for cholesterol.

Chemiluminescent measurement of cholesterol can be performed in various biological tissues and fluids. The method described in this study has a sensitivity of 54 pmol. The tissue samples used for the determination of cholesterol can be reduced to as little as 1 mg and assay can be performed on diluted biological fluids, allowing sampling of plasma or serum as little as 5 microliters. Cholesterol is solubilized in sodium cholate and aliquots are added to a reaction mixture containing cholesterol oxidase, luminol and peroxidase. Cholesterol oxidase, in the presence of cholesterol yields H2O2 which produces light in presence of luminol and peroxidase. Emitted light is quantified at a wavelength of 420 nm by means of a photomultiplier. Optimal conditions of the assay were determined and examples of cholesterol determinations, in blood plasma and nervous tissues, are presented.

Animals↗
PubMed2004

Improving the reproducibility of hydrogel-coated glutamate microsensors by using an automated dipcoater.

Hydrogel-coated microsensors based on carbon fiber electrodes (CFEs) are promising tools for in vivo analysis of endogeneous compounds such as glutamate. However, their construction generally depends on manual fabrication, which often results in poor reproducibility. The aim of this study was to improve the reproducibility and performance of glutamate microsensors. CFEs (10 microm diameter, 300-500 microm long) were coated with a cross-linked redox-polymer hydrogel containing l-glutamate oxidase, horseradish peroxidase and ascorbate oxidase. Various parameters that are likely to influence the reproducibility of the glutamate microsensors were studied. It appeared that the most crucial step in determining the microsensor performance is the manual hydrogel-application procedure. To control this procedure an automated dipcoater was constructed, which allowed mechanical application of the hydrogel on the CFE under standardized conditions. Significant improvements in performance were seen when the CFEs were dipcoated for 10 min at 37 degrees C. Further improvements were obtained when the automated hydrogel application was combined with other cross-link methods, such as electrodeposition and electrostatic complexation. A crucial factor in determining the microsensor performance is the hydrogel thickness. Microscopic observations revealed that, despite the use of an automated dipcoater, the layer thickness was not constant. By combining the automated dipcoat technique with amperometry, the layer thickness could be indirectly monitored and controlled, which resulted in significant improvements of the reproducibility of the sensors.

Amino Acid Oxidoreductases↗
PubMed1982

Affinity chromatography purification of cytochrome c binding enzymes.

An efficient affinity chromatography procedure for the isolation of mitochondrial cytochrome c oxidase and reductase is described. Saccharomyces cerevisiae cytochrome c was used as a ligand, bound to a thiol-Sepharose 4B gel through cysteine-107. In this way, the site of interaction of cytochrome c with cytochrome oxidase and reductase remained unmodified and available for binding to a number of partner enzymes. The procedure is adequate for the purification of all those proteins having in common the property of binding with high affinity to cytochrome c--e.g., cytochrome c oxidase, reductase, and peroxidase, sulfite oxidase, and reaction centers of photosynthetic bacteria.

Animals↗
PubMed1998

Cytochrome c oxidase as a proton-pumping peroxidase: reaction cycle and electrogenic mechanism.

Cytochrome oxidase (COX) is considered to integrate in a single enzyme two consecutive mechanistically different redox activities--oxidase and peroxidase--that can be catalyzed elsewhere by separate hemoproteins. From the viewpoint of energy transduction, the enzyme is essentially a proton pumping peroxidase with a built-in auxiliary eu-oxidase module that activates oxygen and prepares in situ H2O2, a thermodynamically efficient but potentially hazardous electron acceptor for the proton pumping peroxidase. The eu-oxidase and peroxidase phases of the catalytic cycle may be performed by different structural states of COX. Resolution of the proton pumping peroxidase activity of COX and identification of individual charge translocation steps inherent in this reaction are discussed, as well as the specific role of the two input proton channels in proton translocation.

Animals↗
PubMed1987

Production of monoclonal antibodies against glucose oxidase, alkaline phosphatase and peroxidase. Their application in a highly sensitive antigen spot microassay.

The production of monoclonal antibodies against peroxidase, alkaline phosphatase and glucose oxidase and the use of the respective enzyme monoclonal anti-enzyme complexes in immunoassays are described. A micromethod using nitrocellulose membranes as solid phase was developed. This microassay has the advantage of being a rapid and simple test procedure, using only 0.2 microliter of antigen solution and 25 microliter of test reagents. A high sensitivity was achieved by repeated incubation of monoclonal enzyme anti-enzyme complexes bridged by anti-mouse immunoglobulin. As little as 200 pg human IgG and 400 pg human IgM could be detected. The glucose oxidase assay together with the alkaline phosphatase assay displays the highest sensitivity and has significant advantages including easy evaluation due to high color contrast of the enzymatic reaction, availability of non-toxic substrate reactions, and no interference with endogenous enzyme activity in mammalian antigen preparations.

Alkaline Phosphatase↗
PubMed2005

Improving glutamate microsensors by optimizing the composition of the redox hydrogel.

Amperometric hydrogel-coated glutamate microsensors form a promising concept to detect glutamate levels directly in brain tissue. These microsensors are constructed by coating a carbon fiber electrode (CFE) (10 microm diameter; 300-500 microm long) with a five-component redox-hydrogel, in which L-glutamate oxidase, horseradish peroxidase, and ascorbate oxidase are wired via poly(ethylene glycol) diglycidyl ether to an osmium-containing redox polymer. Coating with a thin Nafion film completes the construction. Prior to use in vivo, a reliable and reproducible construction of microsensors with a high performance is required. For an optimal microsensor performance, the balance between the five individual hydrogel components is critical. However, due to their small size, hydrogel application to CFE's need to be performed by dip-coating. Dip-coating is a difficult procedure to control and does not allow individual application of hydrogel constituents. To improve the microsensor construction and to better control the dip-coating procedure, we have recently developed an automated device. Throughout this study, automatic dip-coating was performed with premixed solutions, in which the amount of a single component was varied. This allowed us to optimize the hydrogel composition, which resulted in a significant improvement of the microsensor properties in terms of sensitivity, current density, linearity, detection limit, and interference by ascorbic acid.

Biosensing Techniques↗
PubMed2001

Resistance to cold and heat stress: accumulation of phenolic compounds in tomato and watermelon plants.

Tomato plants, Lycopersicon esculentum L. cv. Tmknvf(2), and watermelon plants, Citrullus lanatus [Thomb.] Mansf. cv. Dulce maravilla, were grown for 30 days at different temperatures (15, 25 and 35 degrees C). We analysed soluble phenolics, enzymatic activities (phenylalanine ammonia-lyase, polyphenol oxidase and peroxidase), and dry weight. The impact of the three temperatures was different in tomato and watermelon. Our results indicate that heat stress in tomato plants occurred at 35 degrees C, while chilling stress occurred in watermelon plants at 15 degrees C. Thermal stress in both plants caused: (1) decreased shoot weight; (2) accumulation of soluble phenolics; (3) highest phenylalanine ammonia-lyase activity; and (4) lowest peroxidase and polyphenol oxidase activity. These results indicate that thermal stress induces the accumulation of phenolics in the plant by activating their biosynthesis as well as inhibiting their oxidation. This could be considered an acclimation mechanism of the plant against thermal stress.

Journal Article↗
PubMed2006

Evaluation of hydrogel-coated glutamate microsensors.

Glutamate microsensors form a promising analytical tool for monitoring neuronally derived glutamate directly in the brain. However, when a microsensor is implanted in brain tissue, many factors can diminish its performance. Consequently, a thorough characterization and evaluation of a microsensor is required concerning all factors that may possibly be encountered in vivo. The present report deals with the validation of a hydrogel-coated glutamate microsensor. This microsensor is constructed by coating a carbon fiber electrode (10-microm diameter; 300-500 microm long) with a five-component redox hydrogel, in which L-glutamate oxidase, horseradish peroxidase, and ascorbate oxidase are wired via poly(ethylene glycol) diglycidyl ether to an osmium-containing redox polymer. A thin Nafion coating completes the construction. Although this microsensor was previously used in vivo, information concerning its validation is limited. In the present study, attention was given to its selectivity, specificity, calibration, oxygen dependency, biofouling, operating potential dependency, and linear range. In addition, successful microsensor experiments in microdialysate, in vitro (in organotypic hippocampal slice cultures), and in vivo (in anesthesized rats) are shown.

Animals↗
PubMedDate not supplied

[Effect of temperature on structure and functional properties of horseradish peroxidase].

The dynamics of structural and functional changes proceeding in a peroxidase molecule under the effect of temperature was studied. It was shown that peroxidase thermoinactivation proceeds in two consequent stages. Based on the analysis of enzyme peroxidase and oxidase activity and peroxidase spectral and buffer characteristics, it was established that at temperatures from 20 to 55 degrees C reversible conformation there occur changes of the hemoprotein molecule related to consequent unfolding and folding of the protein globule. The influence of temperature of 60 degrees C and above induces the protein globule unfolding and loosing of peroxidase activity.

Armoracia↗