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:1.10.3.3 (ascorbate oxidase)
778 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human colostrum contains several antioxidants which prevent the detection of human polymorphonuclear leukocyte (PMN) respiratory burst products. Using column chromatography to fractionate colostrum, two peaks of antioxidant activity were resolved away from colostral proteins and further characterized. One peak contained both cytochrome c-reducing activity and H2O2-depleting activity. This peak had the chromatographic, spectral, and antioxidant characteristics of ascorbate, and by high performance liquid chromatography (HPLC) methods, was shown to contain ascorbate as well as at least four other materials. The antioxidant activity in this peak was totally ascorbate oxidase sensitive and partially uricase sensitive. The other peak contained only H2O2-depleting activity and had the chromatographic, spectral, and antioxidant characteristics of uric acid. By HPLC, uric acid was the only component in this peak and its antioxidant activity was completely uricase sensitive and ascorbate oxidase resistant. Colostral uric acid levels were measured in eight postpartum women and found to be approximately one-third of simultaneously determined serum uric acid levels. Colostrum contains at least two separate antioxidants, one of which is ascorbate-like and the other is uric acid. We speculate that these antioxidants may function in human colostrum as traps for neutrophil-generated reactive oxygen metabolites.
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PMID:Colostral antioxidants: separation and characterization of two activities in human colostrum. 157 13

In chromaffin vesicles, the enzyme dopamine beta-monooxygenase converts dopamine to norepinephrine. It is believed that reducing equivalents for this reaction are supplied by intravesicular ascorbic acid and that the ascorbate is regenerated by importing electrons from the cytosol with cytochrome b-561 functioning as the transmembrane electron carrier. If this is true, then the ascorbate-regenerating system should be capable of providing reducing equivalents to any ascorbate-requiring enzyme, not just dopamine beta-monooxygenase. This may be tested using chromaffin-vesicle ghosts in which an exogenous enzyme, horseradish peroxidase, has been trapped. If ascorbate and peroxidase are trapped together within chromaffin-vesicle ghosts, cytochrome b-561 in the vesicle membrane is found in the reduced form. Subsequent addition of H2O2 causes the cytochrome to become partially oxidized. H2O2 does not cause this oxidation if either peroxidase or ascorbate are absent. This argues that the cytochrome is oxidized by semidehydroascorbate, the oxidation product of ascorbate, rather than by H2O2 or peroxidase directly. The semidehydroascorbate must be internal because the ascorbate from which it is formed is sequestered and inaccessible to external ascorbate oxidase. This shows that cytochrome b-561 can transfer electrons to semidehydroascorbate within the vesicles and that the semidehydroascorbate may be generated by any enzyme, not just dopamine beta-monooxygenase.
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PMID:Electron transfer in chromaffin-vesicle ghosts containing peroxidase. 162 14

It has been indicated recently that ascorbic acid is responsible for the hemoglobin-mediated oxidative damage to the central nervous system (Sadrzadeh & Eaton, J. Clin. Invest. 82:1510-1515, 1988). In this paper we describe the changes in chemiluminescence accompanying hemoglobin- and ascorbate-dependent oxidative injury to brain tissue. Addition of either hemoglobin (15 microM) or ascorbate (1 or 2 mM) to rat brain homogenates stimulated spontaneous chemiluminescence in a synergistic manner. This increase in chemiluminescence was inhibited by desferrioxamine indicating that free iron was involved in the reactions leading to lipid peroxidation. Preincubation with ascorbate oxidase inhibited both spontaneous and hemoglobin-dependent chemiluminescence, suggesting that ascorbate was required for the reactions leading to lipid peroxidation. Supplementation with aminotriazole (an irreversible inhibitor of the catalase-H2O2 complex) increased chemiluminescence in a time-dependent manner, as catalase reacted with accumulated H2O2, suggesting that ascorbic acid has a dual action being involved in the production of H2O2 and also maintaining Fe in the reduced state to catalyze a Fenton-like reaction. The excited species responsible for the chemiluminescence were partially characterized by adding specific fluorescent energy acceptors: dibromoanthracene (DBA) and diphenylanthracene (DPA). Both DBA and DPA stimulated chemiluminescence several-fold indicating that triplet and singlet species are responsible for the observed chemiluminescence. Excited singlet carbonyls (identified with DPA) may be produced during the collision of two ROO.. Singlet oxygen may also be generated during the same reaction. It decays to the triplet state (emitting chemiluminescence at 634 nm) and reacts with double bonds producing dioxetanes, which may breakdown generating triplet carbonyls (identified with DBA).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Ascorbate- and hemoglobin-dependent brain chemiluminescence. 237 61

Human colostrum manifests antioxidant properties, being capable of spontaneous reduction of cytochrome c, depletion of polymorphonuclear leukocyte-produced H2O2 and protection of epithelial cells from PMN-mediated detachment. These activities can be electrophoretically concentrated at either 3.5 kD or 50 kD dialysis membranes at mildly alkaline pH. They are progressively lost under increasingly alkaline conditions. They are resistant to 1-mM N-ethylmaleimide. Examination of a series of antioxidant compounds showed that ascorbate manifests several characteristics of colostrum, being able to reduce cytochrome c and deplete H2O2 but not altering PMN-mediated HEp2 cell detachment. Addition of ascorbate oxidase to colostrum decreased its cytochrome c-reducing activity by more than 85%, decreased its H2O2-depleting activity by nearly 50%, but did not alter its ability to protect HEp2 cells, all suggesting heterogeneity of colostral antioxidant activities. Treatment of colostrum with an enzymatic system (xanthine + xanthine oxidase) known to destroy ascorbate's cytochrome c-reducing activity yielded paradoxical results, decreasing colostral cytochrome c reduction in a dose-related manner, while increasing its H2O2-depleting activity. These studies demonstrate that a colostral component similar to ascorbate, a known antioxidant compound is responsible for the majority of colostral cytochrome c-reducing activity, for about half of its H2O2-depleting activity, and little, if any, of its protective effect on HEp2 cells. Thus colostral antioxidant activity is heterogeneous.
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PMID:Further characterization of human colostral antioxidants: identification of an ascorbate-like element as an antioxidant component and demonstration of antioxidant heterogeneity. 253 79

Titration of native ascorbate oxidase from green zucchini squash (Cucurbita pepo) with azide in 0.1 M-phosphate buffer, pH 6.8, exhibits a biphasic spectral behaviour. Binding of the anion with 'high affinity' (K greater than 5000 M-1) produces a broad increase of absorption in the 400-500 nm region (delta epsilon approximately 1000 M-1.cm-1) and c.d. activity in the 300-450 nm region, whereas azide binding with 'low affinity' (K approximately 100 M-1) is characterized by an intense absorption band at 420 nm (delta epsilon = 6000 M-1.cm-1), corresponding to negative c.d. activity and a decrease of absorption at 330 nm (delta epsilon = -2000 M-1.cm-1). The high-affinity binding involves a minor fraction of the protein containing Type 3 copper in the reduced state, and the spectral features of this azide adduct can be eliminated by treatment of the native enzyme with small amounts of H2O2, followed by dialysis before azide addition. As shown by e.s.r. spectroscopy, Type 2 copper is involved in both types of binding, its signal being converted into that of a species with small hyperfine splitting constant [12 mT (approximately 120 G)] in the case of the low-affinity azide adduct. The spectral similarities of the two types of azide adducts with the corresponding adducts formed by native laccase, which also exhibits Type 3 copper heterogeneity, are discussed.
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PMID:Azide-binding studies reveal type 3 copper heterogeneity in ascorbate oxidase from the green zucchini squash (Cucurbita pepo). 284 Aug 93

Blue light irradiation of 2-deoxyribose (DOR) in the presence of uroporphyrin I (UP), ascorbate (AH-), trace iron, and phosphate buffer resulted in a strong stimulation of hydroxyl radical (OH.)-dependent oxidation of DOR. Photostimulated generation of H2O2 was monitored after removal of residual AH- (i) by ascorbate oxidase treatment, or (ii) by anion exchange on mini-columns of DEAE-Sephadex. Irradiation of the above mixture produced a strong burst of H2O2 which was intensified by desferrioxamine and suppressed by catalase or EDTA. The mechanism suggested by these observations is one in which photoreduction of UP to the radical anion initiates the formation of H2O2, which gives rise to OH. via Fenton chemistry. This is the first known investigation of H2O2 fluxes in a Type I (free radical) photoreaction involving AH- as the electron donor.
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PMID:Light-stimulated formation of hydrogen peroxide and hydroxyl radical in the presence of uroporphyrin and ascorbate. 285 16

Euglena gracilis was found to contain a peroxidase that specifically require L-ascorbic acid as the natural electron donor in the cytosol. The presence of an oxidation-reduction system metabolizing L-ascorbic acid was demonstrated in Euglena cells. Oxidation of L-ascorbic acid by the peroxidase, and the absence of ascorbic acid oxidase activity, suggests that the system functions to remove H2O2 in E. gracilis, which lacks catalase.
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PMID:Metabolism of hydrogen peroxide in Euglena gracilis Z by L-ascorbic acid peroxidase. 676 57

Zitter rats develop a genetic spongiform encephalopathy characterized by edematous changes in their brains. In order to elucidate the involvement of reactive oxygen species in this process we examined age-related alterations of the activities of the enzymes which metabolize reactive oxygen species. Activities of superoxide dismutase (SOD), D-amino acid oxidase (D-AAO), glutathione peroxidase (GSH-Px) and catalase in the brain and the liver of zitter rats are compared with those of control SD/J rats. In the brain of adult zitter rats which show degenerative changes, significantly enhanced activities of SOD and D-AAO were obtained, whereas activity of catalase was lower than that of the SD/J rats. Prominent abnormalities in catalase and D-AAO but not in SOD activity were demonstrated before or at the same time as the appearance of the morphological vacuolation in the brain of suckling zitter rats. There was no difference in GSH-Px activity between the brains from zitter and SD/J rats. These results suggest that the alteration of hydrogen peroxide (H2O2)-metabolism in microperoxisomes may play an important role in the initiation of degenerative changes in the brain of zitter rats. Enhanced SOD activity observed in the brain of adult zitter rats may be a compensatory response to the high superoxide anion produced in the course of cell damage caused by the H2O2 stagnation. Also, more SOD might produce more H2O2.
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PMID:Antioxidant enzymes in the brain of zitter rats: abnormal metabolism of oxygen species and its relevance to pathogenic changes in the brain of zitter rats with genetic spongiform encephalopathy. 798 77

A method for the detection of ascorbate peroxidase activity in native electrophoretic gels is described. The assay is based on the ability of ascorbate peroxidase to prevent the ascorbate-dependent reduction of nitroblue tetrazolium in the presence of H2O2. The method was found to be both sensitive (detection of less than 0.01 units of ascorbate peroxidase activity) and specific for ascorbate peroxidase activity. The application of the method for the detection of ascorbate peroxidase activity in protein extracts from several plant sources was investigated by comparing staining for activities of ascorbate peroxidase, horseradish peroxidase, and ascorbate oxidase and by immunodetection of ascorbate peroxidase in these extracts.
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PMID:Detection of ascorbate peroxidase activity in native gels by inhibition of the ascorbate-dependent reduction of nitroblue tetrazolium. 821 98

A novel type of ascorbate oxidase was purified 420-fold from the cytosolic fraction of the mycelia of Pleurotus ostreatus with an overall yield of 13%. The molecular mass of the native enzyme determined by high performance gel permeation chromatography was 94 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the enzyme consists of two subunits with a molecular mass of 46 kDa. The N-terminal amino acid sequence of the enzyme was Asp-Val-Lys-Thr-Leu-Gln-Glu-His-Leu-Gln-Leu-Ala-Leu-Met-Val-. The enzyme was optimally active at pH 5.2, monitored at 37 degrees C. The enzyme had affinity toward L-ascorbic acid, D-ascorbic acid, L-erythroascorbic acid, and D-erythroascorbic acid. Under optimal conditions, the Km value of the enzyme toward L-ascorbic acid was 0.48 mm. The absorption spectra of the native enzyme exhibited a Soret maximum at 418 nm in its oxidized form and at 426 nm in its reduced form, and alpha and beta bands at 558 and 527 nm only in its reduced form, respectively. On the basis of spectral changes after treatment with cyanide and carbon monoxide, the enzyme is a hemoprotein, quite similar to b-type cytochrome, and contains 2 mol of heme per molecule. The reaction catalyzed by the enzyme was L-ascorbic acid + O2 --> dehydro-L-ascorbic acid + H2O2.
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PMID:A heme-containing ascorbate oxidase from Pleurotus ostreatus. 862 8


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