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1.
The possible involvement of superoxide anions in the hydroxylation of tyrosine by mushroom tyrosinase was studied. Superoxide dismutase and scavengers of superoxide ions of smaller MW than superoxide dismutase, such as nitroblue tetrazolium and copper salicylate, had no direct effect on the monohydroxyphenolase activity of mushroom tyrosinase. The kinetics of tyrosine hydroxylation, but not of DOPA oxidation, by mushroom tyrosinase was atrected by the addition of a xanthine-xanthine oxidase system. In the presence of the xanthine-xanthine oxidase system, the lag period of tyrosine hydroxylation was shortened compared to the lag period in the absence of the xanthine-xanthine oxidase system. The xanthine- xanthine oxidase system alone (without mushroom tyrosinase) had no effect on tyrosine conversion to dopachrome. Superoxide dismutase, catalase and hydroxyl radical scavengers counteracted to some extent the shortening of the lag period of tyrosine hydroxylation by mushroom tyrosinase caused by the xanthin e-xanthine oxidase system. It is suggested that the shortening of the lag period is due mainly to hydroxyl radicals generated by the xanthine-xanthine oxidase system via interaction of O2?. and hydrogen paroxide (a Haber-Weiss type reaction). The data do not support the direct participation of superoxide anions in tyrosine hydroxylation by mushroom tyrosinase. 相似文献
2.
Magnus Ingelman-Sundberg Gunilla Ekström 《Biochemical and biophysical research communications》1982,106(2):625-631
Hydroxylation of aniline, catalyzed by rabbit liver microsomal cytochromes P-450 in reconstituted systems, was inhibited by catalase, superoxide dismutase, catechol, mannitol, hydroquinone, dimethylsulfoxide and benzoate, whereas the cytochrome P-450-catalyzed O-demethylation of paranitroanisole, measured under the same conditions, was unaffected by these agents. A similar inhibition profile of the hydroxylation reaction was observed in reconstituted systems where cytochrome P-450 had been replaced by hemoglobin. The results indicate that aniline hydroxylation is mediated by hydroxyl radicals generated in an iron-catalyzed Haber-Weiss reaction between O2? and H2O2 and may explain some of the special properties of this reaction previously described. 相似文献
3.
Cytochrome c reduction by semiquinone radicals can be indirectly inhibited by superoxide dismutase 总被引:4,自引:0,他引:4
C C Winterbourn 《Archives of biochemistry and biophysics》1981,209(1):159-167
The inhibition by superoxide dismutase of cytochrome c reduction by a range of semiquinone radicals has been studied. The semiquinones were produced from the parent quinones by reduction with xanthine and xanthine oxidase. Most of the quinones studied were favored over O2 as the enzyme substrate, and in air as well as N2, semiquinone radicals rather than superoxide were produced and they caused the cytochrome c reduction. With all but one of the quinones (benzoquinone), cytochrome c reduction in air was inhibited by superoxide dismutase, but the amount of enzyme required for inhibition was up to 100 times greater than that required to inhibit reduction by superoxide. It was highest for the quinones with the highest redox potential. These results demonstrate how superoxide dismutase can inhibit cytochrome c reduction by species other than superoxide. They can be explained by the dismutase displacing the equilibrium: semiquinone + O2 ? quinone + O2? to the right, thereby allowing the forward reaction to out-compete other reactions of the semiquinone. The implication from these findings that superoxide dismutase-inhibitable reduction of cytochrome c may not be a specific test for superoxide production is discussed. 相似文献
4.
Cell-free extracts of Lactobacillus plantarum contain non-proteinaceous compounds which mimic superoxide dismutase activity. Using the test system in which O
2
–
is generated by xanthine oxidase, superoxide dismutase activity is found in cell-free extracts, where proteins are removed by precipitation. This activity is strongly decreased after dialysis of cell-free extracts. Superoxide dismutase activity was also investigated by means of pulse radiolysis. Cell-free extracts of Escherichia coli were also investigated as a comparison, which were known to contain superoxide dismutase. With cell-free extracts of both L. plantarum and E. coli the decay of O
2
–
was markedly increased. However, the type of reaction of the O
2
–
decay was of first order in the presence of E. coli extracts due to superoxide dismutase(s), and of second order in the presence of L. plantarum extracts, indicating that O
2
–
elimination is not an enzymic reaction. Mn2+ phosphate(s) might be responsible for the observed elimination of O
2
–
. The production of O
2
–
is not detectable during NADH-, lactate- or pyruvate oxidase reactions in L. plantarum extracts. 相似文献
5.
The relationship between the degradation reaction of cytochrome and lipid peroxidation was studied utilizing bovine adrenal cortex mitochondria. The two reactions were found to be closely correlated in terms of their response to storage of the mitochondrial preparation, stimulation by Fe2+, inhibition by EDTA and their initiation by cumene hydroperoxide. Both reactions were also found not to be inhibited by catalase, superoxide dismutase, 1,4-diazabicyclo-(2,2,2)-octane and alcohols, indicating that H2O2, superoxide, singlet oxygen and hydroxyl radicals do not participate in these reactions. Yet, diphenylamine proved to be a powerful inhibitor for both reactions, suggesting the involvement of a radical species. Cumene hydroperoxide could induce these two reactions at below 0.1 mM concentrations in the presence of molecular oxygen. The chemiluminescence observed during the Fe2+-mediated lipid peroxidation reaction which was not inhibited by either superoxide dismutase or 1,4-diazabicyclo-(2,2,2)-octane, was biphasic: one was a rapid burst; and the other was a slowly increasing emission. The latter portion of the emission of light coincided with the formation of malondialdehyde. These results indicate that in adrenal cortex mitochondria the degradation of cytochrome is closely related to lipid peroxidation. 相似文献
6.
The hypothesis of superoxide anion generation as a direct bactericidal mechanism exercised by hypersensitive tobacco leaf tissue against an incompatible phytopathogenic pseudomonad was tested. The detection of O2? was made directly by reducing Cytochrome c and by producing nitrite from hydroxylamine chloride and indirectly by measuring the death of endophytic bacteria in the presence of superoxide dismutase. At 4 h and 6 h the low net specific reduction of Cytochrome c in the hypersensitive tissue was not confirmed by the specific production of nitrite. At the same time active superoxide dismutase did not give significant protection to the incompatible bacteria as compared to inactive superoxide dismutase. The protection provided by active superoxide dismutase as compared with the controls (bovine serum albumine treated tissue and non-treated tissue) at 4 h and at 6 h was not correlated to its superoxide anion scavenger activity. The results indicated that the death of the incompatible pseudomonad during the hypersensitive reaction was not directly linked to O2? generation. 相似文献
7.
Characterization of a Manganese Superoxide Dismutase from the Higher Plant Pisum sativum 总被引:1,自引:1,他引:0
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A manganese-containing superoxide dismutase (EC 1.15.1.1) was fully characterized from leaves of the higher plant Pisum sativum L., var. Lincoln. The amino acid composition determined for the enzyme was compared with that of a wide spectrum of superoxide dismutases and found to have a highest degree of homology with the mitochondrial manganese superoxide dismutases from rat liver and yeast. The enzyme showed an apparent pH optimum of 8.6 and at 25°C had a maximum stability at alkaline pH values. By kinetic competition experiments, the rate constant for the disproportionation of superoxide radicals by pea leaf manganese superoxide dismutase was found to be 1.61 × 109 molar−1·second−1 at pH 7.8 and 25°C. The enzyme was not sensitive to NaCN or to H2O2, but was inhibited by N3−. The sulfhydryl reagent p-hydroxymercuribenzoate at 1 mm concentration produced a nearly complete inhibition of the manganese superoxide dismutase activity. The metal chelators o-phenanthroline, EDTA, and diethyldithiocarbamate all inhibited activity slightly in decreasing order of intensity. A comparative study between this higher plant manganese superoxide dismutase and other dismutases from different origins is presented. 相似文献
8.
9.
M Younes E Lengfelder S Zienau U Weser 《Biochemical and biophysical research communications》1978,81(2):576-580
The rate constants of the reactions between pulse radiolytically produced superoxide anions and the Cu(II) chelates of salicylate, acetylsalicylate, p-aminosalicylate and diisopropylsalicylate were determined at pH 7.5 and found to range from 0.8 to 2.4 × 109 M?1 sec?1. It was intriguing to note that they had a superoxide dismutase activity identical with that of native cuprein-copper (k245 = 1.3 × 109 M?1 sec?1 per g-atom of Cu). These measurements confirm our earlier observations using indirect assays that all copper salicylates act as perfect model superoxide dismutases and favour the proposal that the activity of anti-inflammatory agents might be assigned to their in vivo formed Cu complexes. 相似文献
10.
H.Moustafa Hassan Harry Dougherty Irwin Fridovich 《Archives of biochemistry and biophysics》1980,199(2):349-354
An extensive search resulted in the identification of pamoic acid as an inhibitor of superoxide dismutases. Pamoic acid appeared to rapidly and reversibly inhibit all types of superoxide dismutases and did so in both the cytochrome c reduction and in the dianisidine photooxidation assays, used to measure this activity. It could nevertheless be shown that pamoic acid did not at all inhibit superoxide dismutase but rather diminished the sensitivity of the assays. The mechanism proposed to account for this effect involved oxidation of pamoate, by O2?, to yield a pamoate radical which can then reduce cytochrome c or oxidize pyrogallol. Pamoate thus competes with superoxide dismutase for the available O2?, without affecting the observable effects of that O2? upon cytochrome c or upon pyrogallol. It consequently makes these assays less responsive to superoxide dismutase, while appearing to be without effect in the absence of superoxide dismutase. Several of the predicted consequences of this proposal were affirmed. Other workers, interested in finding inhibitors for superoxide dismutases, are hereby forwarned of this subtle snare. 相似文献
11.
《Archives of biochemistry and biophysics》1987,255(2):274-278
Vanadyl (V(IV)) salts autoxidize in neutral aqueous solution yielding O2− plus vanadate (V(V)) and these, in turn, cause the oxidation of NADH, by a free radical chain reaction. This oxidation of NADH was inhibited by superoxide dismutase, but not by a scavenger of HO.. When H2O2 was present V(IV)) caused rapid oxidation of NADH by a process which was unaffected by superoxide dismutase but was inhibited by a scavenger of HO.. This appeared to be dependent upon reduction of H2O2 to OH− plus HO., by V(IV)), followed by oxidation of NADH by HO.. Since there are reductants, within cells, capable of reducing V(V)) to V(IV), these reactions are likely to contribute to the toxicity of vanadate. 相似文献
12.
The oxidation of Mn2+-pyrophosphate to Mn3+ by superoxide (O2?) was quantitative as evidenced from the formation of Mn3+-pyrophosphate and hydrogen peroxide and from the inhibition by superoxide dismutase. Using the competitive relation between Mn2+-pyrophosphate and superoxide dismutase for the O2?, the rate constant of Mn2+ oxidation was estimated to be about 6 × 106m?1 s?1. The oxidation of Mn2+-pyrophosphate by illuminated chloroplasts was also indicated to be stoichiometrically induced by O2?. In the presence of saturating amounts of the Mn2+, a double enhancement of hydrogen peroxide production and triple uptake of oxygen were found, as expected from the oxidation of Mn2+-pyrophosphate by O2?. Anaerobiosis or superoxide dismutase annuled these increments. We propose that the O2? generated as the sole initial step of the Mehler reaction oxidized Mn2+-pyrophosphate, and we discuss the role of free manganese in chloroplasts. 相似文献
13.
A Photosystem I submembrane fraction isolated from spinach was used to study the mechanism of heat-stress stimulation of oxygen uptake by the photosystem. Various artificial electron donors were shown to generate electron transport reactions with various degrees of thermally induced stimulation. A strong stimulation was observed with durohydroquinone as electron donor with a maximal effect at 50 °C. The degree of stimulation obtained was independent from the redox potential of the electron donors and from their oxidation site because the enzyme superoxide dismutase fully inhibited the stimulation. Instead, it is proposed that thermal stress causes the release of membrane bound superoxide dismutase from the thylakoids thus allowing the reduced form of electron donors with specific properties to reduce O2
– radicals to H2O2 besides the usual disproportionation of O2
– into O2 and H2O2.Abbreviations: PS
photosystem
- DCIP
2,6-dichlorophenolindophenol
- MV
methylviologen
- TMPD
N,N,N,N-tetramethylphenylenediamine
- SOD
superoxide dismutase
- Chl
chlorophyll
- DQ
duroquinone
- DAD
N,N,N,N-tetramethyl-1,4-benzenediamine
- PMS
5-methylphenazium methyl sulfate
- PC
plastocyanin 相似文献
14.
Mechanism of aromatic hydroxylation. Properties of a model for pyridine nucleotide-dependent flavoprotein hydroxylases 总被引:1,自引:0,他引:1
S D Ravindranath A A Kumar R P Kumar C S Vaidyanathan N A Rao 《Archives of biochemistry and biophysics》1974,165(2):478-484
A model (NADH-phenazine methosulfate-O2) formally similar to pyridine nucleotide-dependent flavoprotein hydroxylases catalyzed the hydroxylation of several aromatic compounds. The hydroxylation was maximal at acid pH and was inhibited by ovine Superoxide dismutase, suggesting that perhydroxyl radicals might be intermediates in this process. The stoichiometry of the reaction indicated that a univalent reduction of oxygen was occurring. The correlation between the concentration of semiquinone and hydroxylation, and the inhibition of hydroxylation by ethanol which inhibited semiquinone oxidation, suggested the involvement of phenazine methosulfate-semiquinone. Activation of hydroxylation by Fe3+ and Cu2+ supported the contention that univalently reduced species of oxygen was involved in hydroxylation. Catalase was without effect on the hydroxylation by the model, ruling out H2O2 as an intermediate. A reaction sequence, involving a two-electron reduction of phenazine methosulfate to reduced phenazine methosulfate followed by disproportionation with phenazine methosulfate to generate the semiquinone, was proposed. The semiquinone could donate an electron to O2 to generate O2 which could be subsequently protonated to form the perhydroxyl radical. 相似文献
15.
Naum I. Goldstein Roman N. Goldstein Mark N. Merzlyak 《International journal of biometeorology》1992,36(2):118-122
The physico-chemical characteristics and possible formation mechanisms of negative air ions are considered. It was found that the products of oxygen and nitrogen negative ionization reduce ferricytochromec and nitroblue tetrazolium, and that these reactions were inhibited by superoxide dismutase. The interaction of negatively ionized oxygen with water led to hydrogen peroxide accumulation, which was inhibited by tetranitromethane or catalase. Nitrogen ionization under these conditions caused the formation of the hydrated electron e
aq
—
and the superoxide anion O
2
—
. The data obtained indicate that the biological activity of negative air ions may be dependent on superoxide. The generation of reactive oxygen ions in the gas phase and also at a gas/water interface is described. A scheme for superoxide production under oxygen and nitrogen ionization is proposed. 相似文献
16.
Human copper-zinc superoxide dismutase undergoes inactivation when exposed to O2? and H2O2 generated during the oxidation of acetaldehyde by xanthine oxidase at pH 7.4 and 37° C. In contrast, human manganese superoxide dismutase is not inactivated under the same conditions. Catalase and Mn-superoxide dismutase protect CuZn superoxide dismutase from inactivation. Similar protection is observed with hydroxyl radical (OH.) scavengers, such as formate and mannitol. In contrast, other OH. scavengers such as ethanol and tert-butyl alcohol, have no protective action. The latter results indicate that “free OH.” is not responsible for the inactivation. Furthermore, H2O2 generated during the oxidation of glucose by glucose oxidase, i.e., without production of O2?, does not induce CuZn superoxide dismutase inactivation. A mechanism accounting for this -dependent inactivation of CuZn superoxide dismutase is proposed. 相似文献
17.
1. Growth of Chlorella sorokiniana in the presence of 7.5 mM sulfite, which halved the growth rate while doubling the superoxide dismutase (SOD; EC 1.15.1.1) content per cell, rendered the cells resistant to the toxic effects of 30 M paraquat. 2. While increasing total SOD content, sulfite increased the relative amount of the H2O2-resistant manganese-containing SOD. 3. It appears that O2
– may be involved in mediating the toxicity of SO2 in this green alga.Abbreviations SOD
superoxide, dismutase
- FeSOD
ironcontaining superoxide dismutase
- MnSOD
manganese-containing superoxide dismutase 相似文献
18.
Robert E. Lynch Barry C. Cole 《Biochemical and biophysical research communications》1980,96(1):98-105
Superoxide dismutase and catalase were not detected in . and several other species of some of which consume oxygen and secrete H2O2. . in suspension formed O2? in the presence of NADH and flavins and extracts of . formed O2? in the presence of either NADH or NADPH. The lack of superoxide dismutase in . could not be attributed to superoxide dismutase in the complex medium in which the organisms were grown because organisms grown in medium in which the superoxide dismutase had been inactivated by heat still contained undetectable amounts. Mycoplasmas appear to be an exception to the rule that organisms which consume O2 synthesize superoxide dismutase. 相似文献
19.
Responses of antioxidative enzymes to elevated CO2 in leaves of beech (Fagus sylvatica L.) seedlings grown under a range of nutrient regimes 总被引:1,自引:0,他引:1
To study whether responses of antioxidative enzymes to enhanced atmospheric CO2 concentrations are affected by plant nutrition, the activities of superoxide dismutase, catalase and peroxidase were investigated in leaves of 3-year-old beech trees grown with low (0.1 × optimum), intermediate (0.5 × optimum) and high (2 × optimum) nutrient supply rates in open-top chambers at either ambient (~ 355 μmol mol?1) or elevated (700 μmol mol?1) CO2 concentrations. These treatments resulted in foliar C/N ratios of about 20 in the presence of high and > 30 in the presence of low nutrient supply rates. Pigment and malon-dialdehyde contents were determined to assess plant stress levels. Low nutrient supply rates caused pigment loss, whereas elevated CO2 had no effect on pigmentation. Guaiacol peroxidase activities did not respond to either CO2 or nutrient treatment. Catalase activity decreased with decreasing nutrient supply rate and also in response to elevated CO2. Superoxidase dismutase activity was affected by both nutrient supply and CO2 concentration. In leaves from trees grown with the high-nutrient treatment, superoxide dismutase activity was low irrespective of CO2 concentration. In chlorotic leaves, superoxide dismutase activity was increased, suggesting an enhanced need for detoxification of reactive oxygen species. Leaves from plants grown under elevated CO2 with medium nutrient supply rates showed decreased malondialdehyde contents and superoxide dismutase activities. This suggests that the intrinsic oxidative stress of leaves was decreased under these conditions. These results imply that intrinsic oxidative stress is modulated by the balance between N and C assimilation. 相似文献
20.
P M Sinet A M Michelson A Bazin J Lejeune H Jerome 《Biochemical and biophysical research communications》1975,67(3):910-915
Glutathione peroxidase activity has been measured in erythrocytes from normal subjects and from trisomy 21 patients. The latter cases show about 50 % increase of this enzyme similar to the increase observed for superoxide dismutase (erythrocuprein) suggesting either localisation of the gene for glutathione peroxidase on chromosome 21 (as is the case for erythrocuprein) or regulation of this enzyme by intracellular levels of O2, H2O2 or superoxide dismutase. 相似文献