scholarly journals Does superoxide anion participate in 2-oxoglutarate-dependent hydroxylation?

1982 ◽  
Vol 205 (2) ◽  
pp. 339-344 ◽  
Author(s):  
Elisabeth Holme ◽  
Göran Lindstedt ◽  
Sven Lindstedt ◽  
Ingalill Nordin
Keyword(s):  
Superoxide Dismutase ◽  
Superoxide Anion ◽  
Potent Inhibitor ◽  
Enzymic Activity ◽  
Heat Inactivation ◽  
Low Molecular Weight ◽  
Enzyme Protein ◽  
Erythrocyte Superoxide Dismutase ◽  
Rule Out

The possible role of superoxide anion in 2-oxoglutarate-coupled dioxygenase reactions has been investigated. γ-Butyrobetaine hydroxylase (EC 1.14.11.1) was inhibited by human erythrocyte superoxide dismutase (EC 1.15.1.1), probably due to release of Cu2+ or Zn2+, as the inhibition was more pronounced after heat-inactivation of the dismutase and as Cu2+ was a potent inhibitor. Bovine superoxide dismutase and the Mn2+-containing superoxide dismutase from Escherichia coli were not inhibitory. Superoxide anion generated from xanthine/xanthine oxidase was not stimulatory and could not replace ascorbate. Thymine 7-hydroxylase (EC 1.14.11.6) and thymidine 2′-hydroxylase (EC 1.14.11.3) were not inhibited by erythrocyte superoxide dismutase or stimulated by superoxide anion. γ-Butyrobetaine hydroxylase was inhibited by a number of low-molecular-weight compounds, such as tetranitromethane, Nitro Blue Tetrazolium, adrenaline and Tiron, which may act as scavengers of superoxide anion. Involvement of this radical in other oxygenase reactions has been inferred from the findings that they were inhibitory for the respective enzymes. Several of these compounds also inhibited γ-butyrobetaine hydroxylase. It could be concluded from these experiments, however, that mechanisms other than disposal of superoxide anion might equally well be operative, such as hydrophobic interaction with the enzyme protein and interaction with compounds required for full enzymic activity, e.g. iron and ascorbate. The results appear to rule out a requirement for superoxide anion generated in free solution, and have not yielded evidence for participation of enzyme-bound superoxide anion in 2-oxoglutarate-dependent hydroxylations.

Superoxide Dismutase Activity in Bovine Milk Serum

1979 ◽  
Vol 42 (11) ◽  
pp. 867-871 ◽  
Author(s):  
M. KORYCKA-DAHL ◽  
T. RICHARDSON ◽  
C. L. HICKS
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Polyacrylamide Gel Electrophoresis ◽  
Bovine Milk ◽  
Enzymic Activity ◽  
Superoxide Dismutase Activity ◽  
Bovine Erythrocyte ◽  
Milk Serum ◽  
Erythrocyte Superoxide Dismutase ◽  
Acid Whey

Superoxide dismutase activity was shown to be present in bovine milk serum and was quantified by measuring the capacity of retentate from dialyzed milk serum to inhibit reduction of cytochrome c by xanthine-xanthine oxidase-generated superoxide anion. One unit of enzyme was defined as the quantity of superoxide dismutase which inhibits cytochrome c reduction by 20%. By this definition 19,500 units of enzyme were present per liter of retentate from dialyzed milk serum. This amount is equivalent to about 2.4 mg of purified bovine erythrocyte superoxide dismutase per liter. Polyacrylamide gel electrophoresis of a partially-purified superoxide dismutase from acid whey, followed by staining for enzymic activity, confirmed the presence of the enzyme in milk serum which was identical in electrophoretic properties to those of bovine erythrocyte copper-zinc superoxide dismutase. Pasteurization at 63 C for 30 min did not decrease superoxide dismutase activity in milk serum. Heating of purified bovine erythrocyte-superoxide dismutase at 100 C for 1 min resulted in almost complete loss of enzymic activity, whereas the partially-purified superoxide dismutase from acid whey still retained 40% of the original activity under these conditions. Bovine milk superoxide dismutase may be an important naturally-occurring antioxidant for increasing oxidative stability of milk and other dairy products.

Superoxide anion is an endothelium-derived contracting factor

1989 ◽  
Vol 257 (1) ◽  
pp. H33-H37 ◽  
Author(s):  
Z. S. Katusic ◽  
P. M. Vanhoutte
Keyword(s):  
Superoxide Dismutase ◽  
Xanthine Oxidase ◽  
Superoxide Anion ◽  
Cerebral Arteries ◽  
Calcium Ionophore ◽  
Calcium Ionophore A23187 ◽  
Heat Inactivation ◽  
Ionophore A23187 ◽  
Excitatory Effect ◽  
Basilar Arteries

The calcium ionophore A23187 causes endothelium-dependent contractions in canine basilar arteries. Removal of the endothelium, or treatment with indomethacin or superoxide dismutase (SOD), prevented the endothelium-dependent excitatory effect of the calcium ionophore. Catalase and deferoxamine were without effect. Superoxide anion generated by xanthine plus xanthine oxidase in the presence of catalase caused contractions of the vascular smooth muscle, which were abolished by SOD or heat inactivation of xanthine oxidase. The A23187-induced production of prostaglandins F2 alpha and E2 and thromboxane B2 was abolished by the removal of endothelium and by treatment with indomethacin but was not affected by the presence of SOD plus catalase. These observations are consistent with the hypothesis that superoxide anion, rather than prostaglandins generated by hydroperoxidase activity of cyclooxygenase, is an endothelium-derived contracting factor in canine cerebral arteries.

Endothelial dysfunction in mesenteric resistance arteries of diabetic rats: role of free radicals

1994 ◽  
Vol 266 (3) ◽  
pp. H1153-H1161 ◽  
Author(s):  
D. Diederich ◽  
J. Skopec ◽  
A. Diederich ◽  
F. X. Dai
Keyword(s):  
Nitric Oxide ◽  
Superoxide Dismutase ◽  
Free Radicals ◽  
Endothelial Dysfunction ◽  
Hydroxyl Radicals ◽  
Superoxide Anion ◽  
Diabetic Rats ◽  
Resistance Arteries ◽  
Luminal Diameter

Diabetes was induced in rats by an injection of streptozotocin (55 mg/kg). Endothelium-dependent relaxations in mesenteric resistance arteries (luminal diameter 210 +/- 20 microns) of control and diabetic rats were compared in myographs. Acetylcholine induced endothelium-dependent relaxations that were mediated by nitric oxide (EDNO). EDNO-mediated relaxations were impaired in diabetic arteries; concentrations of acetylcholine required to produce 50% relaxation (ED50) of activated arteries were 5 nM in control and 13.5 nM in arteries from diabetic rats studied after 6 wk (P < 0.05). The impairment in relaxation worsened with duration of the diabetes; ED50 for acetylcholine increased to 63 and 100 nM in diabetic arteries studied after 16 and 24 wk of diabetes, respectively. NG-nitro-L-arginine produced 5.5- and 16-fold decreases in sensitivity of control and diabetic arteries to acetylcholine. NG-nitro-L-arginine produced at least as much inhibition of acetylcholine relaxations in diabetic arteries, indicating that the impaired relaxation noted in diabetic arteries does not result from decreased production of EDNO. EDNO-mediated relaxations in diabetic arteries were impaired by increased production of endothelium-derived free radicals. Superoxide dismutase, a scavenger of superoxide anion, and dimethylthiourea, a scavenger of hydroxyl radicals, normalized EDNO-mediated relaxations in diabetic arteries. The ED50 values for acetylcholine were 13.5, 5.5, and 4 nM for untreated and SOD- and DMTU-treated diabetic arteries, respectively (P < 0.05 for treated vs. untreated arteries). Superoxide anion and hydroxyl radicals appear to block EDNO-mediated relaxation by inactivating EDNO.(ABSTRACT TRUNCATED AT 250 WORDS)

Reactive forms of oxygen and chemiluminescence in phagocytizing rabbit alveolar macrophages

1978 ◽  
Vol 235 (3) ◽  
pp. C103-C108 ◽  
Author(s):  
P. R. Miles ◽  
V. Castranova ◽  
P. Lee
Keyword(s):  
Hydrogen Peroxide ◽  
Superoxide Dismutase ◽  
Hydroxyl Radical ◽  
Alveolar Macrophages ◽  
Superoxide Anion ◽  
Extracellular Fluid ◽  
Particle Uptake ◽  
O2 Production

Chemiluminescence (CL), superoxide anion (O2-) production, and particle uptake were measured to determine the role of antibacterial substances in the chemiluminescent response associated with phagocytosis in rabbit alveolar macrophages (AM). Exposure of AM to zymosan particles induced both CL and the production of extracellular O2-. CL is inhibited by superoxide dismutase, an enzyme which catalyzes the conversion of O2- to hydrogen peroxide (H2O2), by catalase, an enzyme which destroys H2O2, and by the hydroxyl radical (.OH) scavengers, benzoate and ethanol. Superoxide dismutase and catalase probably exert their effects in the extracellular fluid. CL can also be produced by the addition of NaO2 or H2O2 to zymosan in a noncellular system. The chemiluminescent response occurs before particle uptake is complete, which also indicates that CL occurs in the extracellular fluid. These results suggest that CL induced by zymosan in AM is due to the extracellular reaction between various reactive forms of oxygen and zymosan.

The response of Azotobacter chroococcum to oxygen: superoxide-mediated effects

1977 ◽  
Vol 23 (11) ◽  
pp. 1548-1553 ◽  
Author(s):  
Alfred G. Buchanan
Keyword(s):  
Hydrogen Peroxide ◽  
Superoxide Dismutase ◽  
Oxygen Uptake ◽  
Superoxide Anion ◽  
Azotobacter Chroococcum ◽  
Continuous Cultures ◽  
Whole Cells ◽  
Mediated Effects ◽  
Nitrogenase Inhibition

Nitrogenase in Azotobacter chroococcum whole cells was inhibited by enzymically generated superoxide anion (O2−), hydrogen peroxide, and ethyl hydrogen peroxide. The degree of inhibition produced by O2− was related to the quantity of oxygen supplied to the organisms in continuous cultures. O2− also inhibited oxygen uptake by whole cells. These O2−-mediated inhibitions were prevented by bovine superoxide dismutase. The quantities of superoxide dismutase (SOD), and catalase associated with cells grown under varying oxygen concentrations were determined. The role of hydrogen peroxide, and of the hydroxyl radical (∙OH) in nitrogenase inhibition was examined. The response of Azotobacter chroococcum to oxygen was evaluated with respect to the observed effects of O2− on the organism, and some explanation is given to account for nitrogenase sensitivity to oxygen.

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