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:1.15.1.1 (superoxide dismutase)
58,858 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The action of xanthine oxidase upon acetaldehyde or xanthine at pH 10.2 has been shown to be accompanied by substantial accumulation of O2- during the first few minutes of the reaction. H2O2 decreases this accumulation of O2- presumably because of the Haber-Weiss reaction (H2O2+O2- leads to OH- +OH+O2) and very small amounts of superoxide dismutase eliminate it. This accumulation of O2- was demonstrated in terms of a burst of reduction of cytochrome c, seen when the latter compound was added after aerobic preincubation of xanthine oxidase with its substrate. The kinetic peculiarities of the luminescence seen in the presence of luminol, which previously led to the proposal of H2O4-, can now be satisfactorily explained entirely on the basis of known radical intermediates.
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PMID:The accumulation of superoxide radical during the aerobic action of xanthine oxidase. A requiem for H2O4. 0 44

Crude cell-free extracts of nine strains of Streptomyces tested for nitroalkane-oxidizing activity showed production of nitrous acid from 2-nitropropane, 1-nitropropane, nitroethane, nitromethane, and 3-nitropropionic acid. These substrates were utilized in most strains but to a decreasing extent in the order given, and different strains varied in their relative efficiency of oxidation. p-Nitrobenzoic acid, p-aminobenzoic acid, enteromycin, and omega-nitro-l-arginine were not attacked. d-Amino acid oxidase, glucose oxidase, glutathione S-transferase, and xanthine oxidase, enzymes potentially responsible for the observed oxidations in crude cellfree extracts, were present at concentrations too low to play any significant role. A nitroalkane-oxidizing enzyme from streptozotocin-producing Streptomyces achromogenes subsp. streptozoticus was partially purified and characterized. It catalyzes the oxidative denitrification of 2-nitropropane as follows: 2CH(3)CH(NO(2))CH(3) + O(2) --> 2CH(3)COCH(3) + 2HNO(2). At the optimum pH of 7.5 of the enzyme, 2-nitropropane was as good a substrate as its sodium salt; t-nitrobutane was not a substrate. Whereas Tiron, oxine, and nitroxyl radical acted as potent inhibitors of this enzyme, superoxide dismutase was essentially without effect. Sodium peroxide abolished a lag phase in the progress curve of the enzyme and afforded stimulation, whereas sodium superoxide did not affect the reaction. Reducing agents, such as glutathione, reduced nicotinamide adenine dinucleotide, and nicotinamide adenine dinucleotide phosphate, reduced form, as well as thiol compounds, were strongly inhibitory, but cyanide had no effect. The S. achromogenes enzyme at the present stage of purification is similar in many respects to the enzyme 2-nitropropane dioxygenase from Hansenula mrakii. The possible involvement of the nitroalkane-oxidizing enzyme in the biosynthesis of antibiotics that contain a nitrogen-nitrogen bond is discussed.
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PMID:Nitroalkane oxidation by streptomycetes. 3 65

Eosinophil and/or neutrophil leukocytes appear to have important roles in host defense against invasive, migratory helminth infestations, but the mechanisms of larval killing by leukocytes are uncertain. This study examines killing of newborn (migratory phase) larvae of Trichinella spiralis during incubation with granule preparations of human eosinophils or neutrophils and generators of hydrogen peroxide (glucose-glucose oxidase) (G-GO) or superoxide and hydrogen peroxide (xanthine-xanthine oxidase). Larvae were killed by either hydrogen peroxide-generating system in a concentration-dependent manner. Direct enumeration of surviving larvae after incubation in microtiter wells containing the appropriate reagents was used in assess larval killing. Verification of the microplate assay was demonstrated by complete loss of larval ability to incorporate [(3)H]deoxyglucose and loss of infectivity after incubation in comparable concentrations of G-GO. Larvae were highly sensitive to oxidative products; significant killing occurred after incubation with 0.12 mU glucose oxidase and complete killing occurred with 0.5 mU. Comparable killing of bacteria required over 60 mU glucose oxidase. At 5 mU glucose oxidase, killing was complete after 6 h of incubation. Killing by G-GO was inhibited by catalase but not by boiled catalase or superoxide dismutase and was enhanced by azide. Addition of peroxidase in granule pellet preparations of eosinophils or neutrophils did not enhance killing by G-GO. These data indicate a remarkable susceptibility of newborn larvae of T. spiralis to the hydrogen peroxide generated by neutrophil and eosinophil leukocytes.
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PMID:Mechanisms of killing of newborn larvae of Trichinella spiralis by neutrophils and eosinophils. Killing by generators of hydrogen peroxide in vitro. 4 Oct 2

A sensitive method for evaluating extracellular parasite viability was used to determine the in vitro susceptibility of virulent Toxoplasma gondii to selected oxygen intermediates. By acridine orange fluorescent staining criteria, toxoplasmas were resistant to up to either 10(-3) M reagent H2O2 or H2O2 generated by glucose-glucose oxidase. In keeping with a lack of sensitivity to H2O2, toxoplasmas contained endogenous catalase (5.7 x 10(-4) Baudhuin units/10(6) organisms). The addition of a peroxidase and halide, however, markedly accelerated killing and lowered the H2O2 requirement by 1,000-fold. In contrast, toxoplasmas were promptly killed after exposure to products generated by xanthine (1.5 x 10(-4) M) and xanthine oxidase (50 micrograms). The inhibition of this system's microbicidal activity by scavengers of O2- (superoxide dismutase) and H2O2 (catalase) indicated that although neither O2- nor H2O2 were toxoplasmacidal, their interaction was required for parasite killing. Quenching OH. and 1O2, presumed products of O2--H2O2 interaction, by mannitol, benzoate, diazabicyclooctane, and histidine, also inhibited toxoplasma killing by xanthine-xanthine oxidase. These findings suggested that O2- and H2O2 functioned in precursor roles and that OH. and 1O2 were toxoplasmacidal. The capacity of normal peritoneal macrophages to pinocytose an oxygen intermediate scavenger, soluble catalase, was also demonstrated. Appreciable extraphagosomal concentrations of catalase were achieved by exposing macrophages to 1 mg/ml of the enzyme for 3 h. Maintenance of high intracellular levels required constant exposure because interiorized catalase was rapidly degraded.
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PMID:Macrophage oxygen-dependent antimicrobial activity. I. Susceptibility of Toxoplasma gondii to oxygen intermediates. 9 21

Superoxide dismutase from breef brain and rat liver was assayed in an enzymatic system, using xanthine oxidase, and a non-enzymatic system, based on aerobic reduction of nitro-blue tetrazolium in presence of phenazine methosulphate. The non-enzymatic assay is rapid and simple and permits simulatneous analysis of many samples. Similar results are found by the two methods of assay of superoxide dismutase.
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PMID:Enzymatic and non-enzymatic assay of superoxide dismutase. 17 Oct 1

1. Xanthine oxidase acting aerobically upon acetaldehyde was found to cause the peroxidation of linolenate. This was demonstrated by increased absorbance at 233 nm due to diene conjugation and by the detection of a lipid peroxide spot on the thin layer chromatograms. 2. Superoxide dismutase inhibited this lipid peroxidation, as did catalase, thus indicating that both O2- and H2O2 were essential intermediates. Scavengers of singlet oxygen also inhibited the peroxidation of linolenate, whereas scavengers of hydroxyl radical did not. These effects, which were observed in the absence of iron salts, led to the proposal that O2- and H2O2 can directly give rise to a singlet oxygen, as follows: O2- + H2O2 leads to OH- + OH. + O2. 3. This proposal was further supported through the use of 2,5-dimethylfuran, as an indicating scavenger of singlet oxygen. Thus, when this compound was exposed to a known source of singlet oxygen, it gave a product which was detectable by thin layer chromatography. This product was also observed when 2,5-dimethylfuran was exposed to the xanthine oxidase system, in which case its accumulation was prevented by superoxide dismutase or by catalase, but not by scavengers of hydroxyl radical.
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PMID:Superoxide, hydrogen peroxide, and singlet oxygen in lipid peroxidation by a xanthine oxidase system. 17 Dec 66

The role of superoxide anion- and myeloperoxidase-dependent reactions in the light emission by phagocytosing polymorphonuclear leukocytes has been investigated using leukocytes that lack myeloperoxidase, inhibitors (azide, superoxide dismutase), and model systems. Our earlier finding that oxygen consumption, glucose C-1 oxidation, and formate oxidation are greater in polymorphonuclear leukocytes that lack myeloperoxidase than in normal cells during phagocytosis has been confirmed with leukocytes from two newly described myeloperoxidase-deficient siblings. Although the maximal rate of superoxide anion production by myeloperoxidase-deficient leukocytes is not significantly different from that of normal cells, superoxide production falls off less rapidly with time so that with prolonged incubation, it is greater in myeloperoxidase-deficient than in normal cells. Chemiluminescence by myeloperoxidase-deficient leukocytes during the early postphagocytic period however is decreased. Light emission by normal leukocytes is strongly inhibited by both superoxide dismutase and azide, whereas that of myeloperoxidase-deficient leukocytes, while still strongly inhibited by superoxide dismutase is considerably less sensitive to azide. Zymosan, the phagocytic particle employed in the intact cell system, considerably increased the chemiluminescence of a cell-free superoxide-H2O2 generating system (xanthine-xanthine oxidase) and a system containing myeloperoxidase, H2O2, and chloride. Light emission by the xanthine oxidase model system is strongly inhibited by superoxide dismutase and is not inhibited by azide, whereas the myeloperoxidase-dependent model system is strongly inhibited by azide but only slightly inhibited by superoxide dismutase. These findings suggest that light emission by phagocytosing polymorphonuclear leukocytes is dependent on both myeloperoxidase-catalyzed reactions and the superoxide anion, and involves in part the excitation of the ingested particle. These studies are discussed in relation to the role of the superoxide anion and chemiluminescence in the microbicidal activity of the polymorphonuclear leukocyte.
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PMID:Chemiluminescence and superoxide production by myeloperoxidase-deficient leukocytes. 18 60

Superoxide radical ions (O2-) produced by the radiolytic reduction of oxygenated formate solutions and by the xanthine oxidase-catalysed oxidation of xanthine were shown to oxidize the haem groups in oxyhaemoglobin and reduce those in methaemoglobin as in reactions (1) and (2): (see articles) Reaction (1) is suppressed by reaction (8) when [O2-]exceeds 10 muM, but consumes all the O2- generated in oxyhaemoglobin solutions when [oxyhaemoglobin] greater than 160 muM and [O2-]less than 1 nM at pH 7. The yield of reaction (2) is also maximal in methaemoglobin solutions under similar conditions, but less than one haem group is reduced per O2- radical. From studies of (a) the yield of reactions (1) and (2) at variable [haemoglobin] and rates of production of O2-, (b) their suppression by superoxide dismutase, and (c) equilibria observed with mixtures of oxyhaemoglobin and methaemoglobin, it is shown that k1/k2=0.7 +/- 0.2 and k1 = (4 +/- 1) X 10(3) M-1-S-1 At pH7, and k1 and k2 decrease with increasing pH. Concentrations and rate constants are expressed in terms of haem-group concentrations. Concentrations of superoxide dismutase observed in normal erythrocytes are sufficient to suppress reactions (1) and (2), and hence prevent the formation of excessive methaemoglobin.
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PMID:The rate of reaction of superoxide radical ion with oxyhaemoglobin and methaemoglobin. 18 29

The participation of superoxide anion (O2-) in the intracellular indoleamine 2,3-dioxygenase activity was studied using the dispersed cell suspension of the rabbit small intestine. The dioxygenase activity was assayed by measuring [14C]formate released from DL-[ring-2-14C]tryptophan. The addition of diethyldiethiocarbamate, a superoxide dismutase inhibitor, markedly accelerated the intracellular dioxygenase activity while the superoxide dismutase activity decreased concomitantly. Furthermore, substrates of xanthine oxidase such as inosine, adenosine, and hypoxanthine also increased the dioxygenase activity in the cells, particularly in the presence of methylene blue. This increase was completely abolished by the addition of allopurinol, a specific inhibitor of xanthine oxidase. These results, taken together, indicate that the intracellular accumulation of O2- results in acceleration of the in situ dioxygenase activity, and that indoleamine 2,3-dioxygenase utilizes O2- in the isolated intestinal cells.
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PMID:Intracellular utilization of superoxide anion by indoleamine 2,3-dioxygenase of rabbit enterocytes. 19 20

During the aerobic conversion of xanthine to uric acid by xanthine oxidase, superoxide anion and hydrogen peroxide are produced along with the hydroxyl radical. Our studies demonstrate that washed human platelets incubated with xanthine and xanthine oxidase aggregated and released [14C]serotonin. Aggregation and release were dependent on the duration of exposure to xanthine oxidase as well as the concentration of enzyme. Both reactions were inhibited by the superoxide scavenger enzyme superoxide dismutase but not by catalase, or the free radical scavenger mannitol, suggesting that they were induced by superoxide anion. Superoxide-dependent release was inhibited by prior incubation of platelets with 1 mM EDTA, 1 micronM prostaglandin E1, or 1 mM dibutyryl cyclic AMP, but was unaffected by 1 mM acetylsalicylic acid or 1 micronM indomethacin. After prolonged incubation with xanthine and xanthine oxidase there was also efflux of up to 15% of intraplatelet 51Cr, a cytosol marker. This leakage was prevented by the addition of catalase to the media but not by superoxide dismutase. Incubation with xanthine and xanthine oxidase did not produce malonyldialdehyde, the three-carbon fatty acid fragment produced during prostaglandin endoperoxide synthesis and lipid peroxidation. Prior exposure of platelets to low fluxes of superoxide anion lowered the threshold for release by subsequent addition of thrombin, suggesting a synergistic effect. We conclude that superoxide-dependent aggregation and release may be a physiologically important method to modulate hemostatic reactions particularly in areas of inflammation or vessel injury which could have high local concentrations of superoxide anion.
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PMID:Enhancement of platelet function by superoxide anion. 19 66


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