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At least 343 records · Page 19Linked to original sources
PubMed1986

Inactivation of peroxidase and glucose oxidase by H2O2 and iodide during in vitro thyroglobulin iodination.

Thyroglobulin iodination and thyroxine synthesis in vitro require the presence of peroxidase, H2O2 and iodide. H2O2 is usually continuously generated by glucose oxidase (GO) and glucose. The aim of this study was to investigate whether the two enzymes could possibly be inactivated by a particular concentration of H2O2 or iodide present during incubation. The results revealed that both enzymes were indeed inactivated under two distinct conditions: Lactoperoxidase and thyroid peroxidase were inactivated by modest concentrations of H2O2 accumulating during incubation. Glucose oxidase was inactivated by an oxidized species of iodine or singlet oxygen produced in the catalytic cycle. The results may explain some hitherto unsolved discrepancies between different iodination procedures. Moreover they may have an impact on the regulation of in vivo thyroglobulin iodination and hormone synthesis.

Glucose Oxidase↗
PubMed1984

Intracortical termination of the retino-geniculo-striate pathway studied with transsynaptic tracer (wheat germ agglutinin-horseradish peroxidase) and cytochrome oxidase staining in the macaque monkey.

The tracer, wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP), was used as a transneuronal marker in the macaque monkey to study retino-geniculo-striate pathway terminals in area 17. Concomitantly, we stained matching sections for metabolic capacity using the cytochrome oxidase staining technique. Terminal labeling by WGA-HRP and cytochrome oxidase activity staining revealed duplicate patterns in layers II and III, IVA, IVC alpha, IVC beta, and VI. The absence of WGA-HRP-labeled neuronal cell bodies in area 17 supports the conclusion that WGA-HRP is a transsynaptic marker in the macaque visual pathways.

Animals↗
PubMed2000

Discrete analysis of plasma oxalate with alkylamine glass bound sorghum oxalate oxidase and horseradish peroxidase.

We have reported a simple method of determination of plasma oxalate using a Cl(-) and NO(3)(-) insensitive oxalate oxidase purified from grain sorghum leaf and commercially available peroxidase from horseradish [Pundir et al., Ind. J. Biochem. Biophys., 35 (1998) 120-122]. The present report describes the immobilization of both the enzymes onto alkylamine glass, their kinetic properties and application for discrete analysis of plasma oxalate. In the analytic method, H(2)O(2) generated from plasma oxalate by immobilized oxalate oxidase is measured colorimetrically at 520 nm by oxidative coupling with 4-aminophenazone, and phenol catalyzed by immobilized peroxidase. The minimum detection limit of the method is 2.5 micromol/l. Analytic recovery of added oxalate in plasma was 89. 5+/-4.1% (mean+/-S.D.). The within and between day CV for plasma oxalate measurement were <9.37 and <11.0%, respectively. The normal range of plasma oxalate as measured by the present method was 3.6 to 5.7 micromol/l. The method is not only free from interference by plasma Cl(-) and NO(3)(-) but also provides the reuse of glass beads and thus reduces the cost of analysis for routine.

Adolescent↗
PubMed1995

Free radical detoxification in Giardia duodenalis.

Non-denaturing polyacrylamide gels were used to analyse superoxide dismutase (SOD), catalase, peroxidase, NADH oxidase and NADH peroxidase in the microaerophilic protozoan parasite Giardia duodenalis. A cytosolic H2O-producing NADH oxidase and membrane-associated NADH peroxidase were readily detected from G. duodenalis. In all Giardia strains investigated the NADH oxidase was present in high levels (1.2-2 U (mg protein)-1). Using the same technique, NADH oxidase activity was also detected in the microaerophilic protozoan parasites Tritrichomonas foetus, Trichomonas vaginalis and Entamoeba histolytica and in the bacterium Escherichia coli. The conventional enzymes of oxidative stress management (superoxide dismutase, catalase and peroxidase) were not detected in particulate or cytosolic extracts from recent and established strains of Giardia assayed in situ. Spectrophotometric assays also yielded negative results. The same methodology readily detected one or more of these enzyme activities in T. foetus, T. vaginalis and E. coli. Superoxide dismutase activity was not detected in lines of Giardia resistant to high levels of metronidazole or furazolidone. Furthermore, the agents 1,10 phenanthroline, diamide, MnCl2 and KNO3, which induce SOD in anaerobically cultured E. coli, did not induce SOD in Giardia. 1,10 phenanthroline has also been shown to induce iron-containing (Fe-) SOD in Entamoeba. Neither peroxidase nor catalase activities were detected in a peroxide-resistant line of Giardia. Viable trophozoites from parent lines were able to decompose H2O2 at a significant rate. It appears that the conventional SOD, catalase and peroxidase utilised in aerobic metabolism have been substituted in Giardia by NADH oxidase and NADH peroxidase, similar to anaerobic bacteria. The O2-scavenging NADH oxidase explains the previously observed futile 'respiration' in Giardia.

Animals↗
PubMed1977

Microdetermination of unbound bilirubin in icteric newborn sera: an enzymatic method employing peroxidase and glucose oxidase.

An enzymatic assay method for the microdetermination of unbound bilirubin in newborn icteric sera is described. Unbound bilirubin is oxidized to colorless compounds by peroxidase in the presence of hydrogen peroxide derived from glucose by the mediation of glucose oxidase. In this method, the bilirubin is not significantly degraded before the addition of peroxidase, in contrast to the method using hydrogen peroxide. The oxidation rate is determined by spectrophotometry and chloroform extraction is eliminated. The unbound bilirubin concentration can be determined from the initial oxidation velocity of total bilirubin. The Michaelis constant, KM, was approximately 20 micrometer. The coefficient of variation for icteric serum determination was 4.4--6.5%. The concentration of unbound bilirubin was reduced after five days of storage at -20 degrees C. The bilirubin-albumin affinity was studied with purified albumin and adult serum. The dissociation constants were 2 x 10(-8) M and 5 x 10(-9) M, respectively, at bilirubin/albuminor molar ratios below 1.0. Clinically, serum samples from 75 icteric newborn infants were analysed, and the sera of premature infants were found to have remarkably high levels of unbound bilirubin compared to those of fullterm infants. The sera of a Rhesus immunization infant and an ABO incompatibility infant were remarkably higher than that of the nonhemolytic icteric sera. The unbound bilirubin concentration was also affected, in an in vitro study, by the addition of hemolysate.

Bilirubin↗
PubMed1994

H2O2 recycling during oxidation of the arylglycerol beta-aryl ether lignin structure by lignin peroxidase and glyoxal oxidase.

Oxidative C alpha-C beta cleavage of the arylglycerol beta-aryl ether lignin model 1-(3,4-dimethoxy-phenyl)-2-phenoxypropane-1,3-diol (I) by Phanerochaete chrysosporium lignin peroxidase in the presence of limiting H2O2 was enhanced 4-5-fold by glyoxal oxidase from the same fungus. Further investigation showed that each C alpha-C beta cleavage reaction released 0.8-0.9 equiv of glycolaldehyde, a glyoxal oxidase substrate. The identification of glycolaldehyde was based on 13C NMR spectrometry of reaction product obtained from beta-, gamma-, and beta,gamma-13C-substituted I, and quantitation was based on an enzymatic NADH-linked assay. The oxidation of glycolaldehyde by glyoxal oxidase yielded 0.9 oxalate and 2.8 H2O2 per reaction, as shown by quantitation of oxalate as 2,3-dihydroxyquinoxaline after derivatization with 1,2-diaminobenzene and by quantitation of H2O2 in coupled spectrophotometric assays with veratryl alcohol and lignin peroxidase. These results suggest that the C alpha-C beta cleavage of I by lignin peroxidase in the presence of glyoxal oxidase should regenerate as many as 3 H2O2. Calculations based on the observed enhancement of LiP-catalyzed C alpha-C beta cleavage by glyoxal oxidase showed that approximately 2 H2O2 were actually regenerated per cleavage of I when both enzymes were present. The cleavage of arylglycerol beta-aryl ether structures by ligninolytic enzymes thus recycles H2O2 to support subsequent cleavage reactions.

Alcohol Oxidoreductases↗
PubMed1977

High resolution of peroxidase-indoleacetic Acid oxidase isoenzymes from horseradish by isoelectric focusing.

Several improved techniques for isoelectric focusing of isoenzymes in polyacrylamide gel slabs were developed. Using these techniques, three commercial sources of horseradish peroxidase were each examined with three commercial sources of carrier ampholytes to determine their respective isoenzyme profiles.A much higher degree of isoenzyme resolution was obtained than reported previously. A composite of all of the various tests gave a total of 42 peroxidase isoenzymes. Commercial sources of horseradish peroxidase showed many similarities in their isoenzyme patterns, but their differences were sufficient to recognize each source easily. Isoenzyme patterns for all three sources spanned the entire pH range with all three sources of wide range carrier ampholytes. Only a few isoenzymes stained darkly. Most isoenzymes stained moderately to lightly, but all were well resolved. Gels stained for indoleacetic acid oxidase activity showed the same pattern as gels stained for peroxidase activity. This was true for all three commerial sources of the enzyme. The isoenzyme patterns obtained in each run were entirely reproducible, and linear pH gradients were obtained in all cases. Limitations in the pH range of the wide range carrier ampholytes relative to the isoelectric points of the extreme anodic and cathodic isoenzymes led to the adoption of a modified definition of focusing time. In addition, the labeling of isoenzymes commonly used in electrophoresis was adapted for labeling isoenzymes resolved by isoelectric focusing.

Journal Article↗
PubMed1980

Localization of some steroidogenic enzymes in the ovary of the rabbit.

The distribution of delta 5-3 beta-HSD, peroxidase and cytochrome oxidase in immature, sexually mature and pregnant rabbit ovary has been studied histochemically. Corpora lutea are found only in pregnant rabbits. delta 5-3 beta-HSD is present in the theca interna of mature follicles, corpora lutea and interstitial gland cells but is absent in the granulosa cells of both developing and mature follicles. The granulosa cells of mature and developing follicles, hypertrophied theca interna and the luteal cells all show intense cytochrome oxidase activity. Peroxidase is present in the corpora lutea only. It is suggested that delta 5-3 beta-HSD in the theca interna and interstitial gland cells is the enzyme responsible for steroid synthesis in the ovaries of immature as well as sexually mature rabbits, while peroxidase and delta 5-3 beta-HSD present in the corpora lutea together regulate luteal steroidogenesis during pregnancy. The intense cytochrome oxidase activity together with peroxidase and delta 5-3 beta-HSD confirms the observations that this tissue is a site of intense oxidative activity.

3-Hydroxysteroid Dehydrogenases↗
PubMed1990

Platelet glutathione peroxidase and monoamine oxidase activity in schizophrenics with CT scan abnormalities: relation to psychosocial variables.

We have previously reported that the activity in platelets of the important antioxidant enzyme glutathione peroxidase (GPx) is inversely correlated with computed tomographic (CT) measures of brain atrophy in a population of patients with chronic schizophrenia, suggesting that low GPx may be a vulnerability factor in those schizophrenic patients with structural brain abnormalities. The significance of this finding has now been explored in a larger clinical population by examining the relation of GPx and CT parameters to psychosocial variables and to the activity of platelet monoamine oxidase (MAO), which has also been reported to be altered in certain schizophrenic populations. In the present study, low platelet GPx and high brain atrophy were found to be associated with DSM-III diagnoses of nonparanoid schizophrenia, a high degree of chronicity, and a predominance of negative symptoms. Contrary to some literature reports, atrophy also correlated with age and length of illness among the schizophrenic patients, although the contribution of these factors was less than that of low GPx, which was itself not age dependent. The ventricle-brain ratio (VBR) and atrophy were highly correlated in a control group of affective disorder patients, but not in the schizophrenic group, where large VBRs were found predominantly in the DSM-III undifferentiated subgroup. The low-GPx/high-atrophy schizophrenic patients had normal platelet MAO levels, and MAO was significantly lower only in the paranoid subgroup, consistent with reported observations. There was no evidence for a neuroleptic-induced effect on either enzyme.

Adult↗
PubMed1996

Cross-reactivity between the major allergen from olive pollen and unrelated glycoproteins: evidence of an epitope in the glycan moiety of the allergen.

Ole e 1, the major allergen from olive pollen, is a glycoprotein containing a single Asn-linked glycan moiety. Rabbit antiserum against this protein has been obtained; and its immunologic cross-reactivities in Western blotting with ascorbate oxidase, horseradish peroxidase, bromelain, ovalbumin, and honeybee venom phospholipase A2 have been studied. Ascorbate oxidase, peroxidase, and bromelain are recognized by the Ole e 1 antiserum. When these three proteins are deglycosylated by periodate treatment, such an immunologic reaction does not occur. The relative affinities of these proteins have been analyzed by direct and inhibition ELISA experiments. A commercially available antibody against horseradish peroxidase has also been considered in these studies. This antibody reacts with Ole e 1 but not with the periodate-deglycosylated allergen. Horseradish peroxidase, bromelain, and ascorbate oxidase are recognized by the IgE of sera from patients who are hypersensitive to olive tree pollen. This binding is also abolished by periodate treatment. The results are interpreted in terms of the presence of an epitope in the carbohydrate moiety of Ole e 1, which would contain a xylose involved in recognition by both IgE and IgG antibodies.

Allergens↗
PubMed2003

Superoxide dismutase, catalase, glutathione peroxidase and NADPH oxidase in lead-induced hypertension.

BACKGROUND: Earlier studies from this laboratory have revealed the presence of oxidative stress and its role in the pathogenesis of lead-induced hypertension (HTN). We have further shown evidence of increased hydroxyl radical (.OH) and superoxide production in lead-treated rats and cultured endothelial cells. This study was designed to determine whether oxidative stress in animals with lead-induced HTN is associated with dysregulation of the main antioxidant enzymes namely superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) or increased superoxide producing enzyme nicotinamide adenine dinucleotide (phosphate) oxidase [NAD(P)H]. METHODS: Male Sprague-Dawley rats were randomly assigned to lead-exposed and control groups. Animals in the lead-exposed group were provided with drinking water containing 100 ppm lead acetate for 12 weeks. The control group was provided with regular drinking water. At the conclusion of the experiment, immunodetectable Cu Zn SOD, Mn SOD, CAT, GPX and gp91 phox subunit of NAD(P)H oxidase were determined by Western analysis in the kidney, brain and left ventricle of control and lead-exposed rats. Subgroups of the study animals were treated with IV infusion (180 micromol/kg/h) of the superoxide trapping agent, tempol, and arterial pressure and urinary nitric oxide (NO) metabolite (NOx) excretion were determined. RESULTS: Lead exposure for 12 weeks resulted in a marked rise in systolic blood pressure, a significant reduction in urinary NOx excretion, a significant increase in kidney and brain Cu, Zn SOD, a significant increase in brain and insignificant increase in kidney and heart gp91 phox. In contrast, Mn SOD, CAT and GPX in the kidney, brain and left ventricle were unchanged. Incubation with lead acetate did not alter SOD activity in vitro. Infusion of tempol significantly lowered arterial pressure and raised urinary NOx excretion in the lead-exposed group (but had no effect in the control group) pointing to increased superoxide production in the lead-exposed animals. CONCLUSION: Animals with lead-induced hypertension exhibited oxidative stress which was associated with mild up-regulation of superoxide-generating enzyme, NAD(P)H oxidase, with no evidence of quantitative SOD, CAT or GPX deficiencies.

Animals↗
PubMed1985

Amperometric assays of total and free cholesterols in serum by the combined use of immobilized cholesterol esterase and cholesterol oxidase reactors and peroxidase electrode in a flow injection system.

A flow injection system for assays of total cholesterol and free cholesterol was described. The total cholesterol assay system included an amperometric peroxidase electrode to measure hexacyanoferrate(III) converted from hydrogen peroxide, which was generated by injecting a 2-microliter sample into the packed-bed reactors of immobilized cholesterol esterase and cholesterol oxidase covalently bound to silica. The free cholesterol was assayed with the same system without the cholesterol esterase reactor. The peak current was linearly related to cholesterol in the range 2-160 mg/dl and to total cholesterol in the range 3-300 mg/dl; the assay speed was about 80 samples/h for free cholesterol and 40 samples/h for total cholesterol. Reliable results were obtained in the assays of free cholesterol and total cholesterol in human sera. Both the reactors and the peroxidase electrode retained over 90% of their original activities, even after repetitive use for 4 and 2 months, respectively.

3-Hydroxysteroid Dehydrogenases↗