Superoxide dismutase enhances chain-breaking antioxidant capability of hydroquinones

2-tert-butyl-(1), 2,6-dimethyl-(2), 2,5-dimethyl-(3), trimethyl-(4), and 2,3-dimethoxy-5-methyl-(5) substituted p-hydroquinones (QH₂) were tested as a chainbreaking antioxidant during the oxidation of methyl linoleate (ML) in dodecyl sulfate micellar solution, pH 7.40, at 37°C. In the absence of superoxide dismutase (SOD), all the studied QH₂ displayed very moderate if any antioxidant capability. When 5–25 U/ml SOD was added, QH₂ showed a pronounced ability to inhibit ML oxidation. The stoichiometric factor of inhibition was found to be about one for all the tested QH₂ in the presence of SOD. The reactivities of QH₂ to the ML peroxy radical increase in the order QH₂5 < QH₂ 3 < QH₂1≈QH₂2 < QH₂4; reactivity of QH₂4 exceds that reported for the majority of phenolic antioxidants. The features of QH₂ as an antioxidant in aqueous environment is likely associated with the reactivity of semiquinone (O^·-) formed due to attack of the peroxy radical to QH₂. O^·- reacts readily with molecular oxygen with formation of superoxide (O^·-₂); in turn, O^·-₂ attacks both to QH₂ and ML (likely, as HO^·₂) that results in fast depleting QH₂ and chain propagation, respectively. The addition of SOD results in purging a reaction mixture from O^·-₂ and, as a corollary, in depressing undesirable reactions with the participation of O^·-₂. Under these conditions, QH₂ displays the theoretically highest inhibitory activity which is determined solely by the reactivity of QH₂ to the peroxy radical.     

Superoxide dismutase

Eric James here discusses the molecular forms of superoxide dismutase and looks at its potential role in the pathogenesis of parasitic infections.     

Superoxide dismutase in ruminal bacteria.

Of 13 species of anaerobic ruminal bacteria examined, 11 were found to contain measurable levels of superoxide dismutase activity. Four of five other strict anaerobic species studied for comparison were found to contain superoxide dismutase activity.     

Superoxide dismutase activity of cytochrome oxidase.

Cytochrome oxidase preparations have weak but not negligible superoxide dismutase activity which is inhibited by cyanide and azide as well as alkaline and thermal treatments. The activity does not depend on lipid content of cytochrome oxidase preparations. The activity, probably, cannot be explained by extraneous copper.     

Superoxide dismutase as multipotent therapeutic antioxidant enzyme: Role in human diseases

Biotechnology Letters - Reactive oxygen species (ROS) is consistently recognized as a threat to living organisms, especially for human beings. For proper working of cellular signaling, functioning,...     

Superoxide dismutase in anaerobes: survey.

Superoxide dismutase (SOD) was present in 23 of 28 strains of the genus Bacteroides tested. Several clostridia, anaerobic cocci, and anaerobic, grampositive, nonsporing rods contained measureable SOD, but the frequency of SOD occurrence was much lower than in the bacteroides. These data indicate that there is a large variation in SOD levels between genera and among species within a genus of anaerobic bacteria. There was also no correlation between source of isolate, SOD levels, and presumed pathogenicity of the isolate.     

Superoxide dismutase activity in copper-deficient swine.

These experiments demonstrate the dependency of cuprozinc superoxide dismutase activity in red cells and liver on an adequate dietary intake of copper. The superoxide dismutase activity in red cells decreased to 15% of control values and, therefore, these cells may be used as a convenient model for studying the physiologic consequences of free radicals     

Labile sulfur in human Superoxide dismutase.

1. The nautre of the intense absorption band at 320 nm of the copper and zinc-containing enzyme superoxide dismutase, from human red blood cells, has been investigated. The band does not depend on the metal prosthetic groups of the enzyme, as it is still present in the apo protein. When, however, copper alone is removed from the enzyme with a treatment involving the use of cyanide, the band is also lost. Nevertheless the copper-free protein is able to recover both the enzyme activity and the native electron paramagnetic resonance spectrum as easily as the apo protein. 2. A number of other treatments are able to abolish the band. They include reaction with reducing agents such as dithiothreitol, sulfite, borohydride, exposure to denaturants such as guanidine HCl and sodium dodecyl sulfate, and exposure to pH values below pH 3 or above pH 13. 3. Four sulfur atoms per protein molecule were found to be associated to the 320-nm chromophore on the basis of quantitative determinations following reaction with cyanide or sodium borohydride. 4. A molar absorption coefficient of 1150 M-1 cm-1 was determined per each chromophoric group. In spite of this relatively high value and unusual stability, a persulfide group, R-S-SH, seems to be the most likely structure for this chromophore. 5. Bovine and equine superoxide dismutase do not show spectral or chemical evidence for such a group. This, and the recovery of activity and spectral properties of copper in the cyanide-treated human enzyme, indicate that labile sulfur is not associated with the superoxide dismutase activity of this protein.     

Superoxide dismutase isozyme activity and antioxidant responses of hydroponically cultured Lepidium sativum L. to NaCl stress

The present study was focused to assess the physiological behavior and antioxidant responses of the medicinal plant Lepidium sativum L. (commonly called Garden cress) subjected hydroponically to NaCl stress during its vegetative growth stage. The results showed that the addition of NaCl to growth medium significantly reduced plant growth. The magnitude of the response was also linked to the plant organ considered and NaCl concentration supplemented to the medium. Tissue hydration seemed unaffected by salinity. Reduction in dry weight (DW) production was associated with a high accumulation of Na⁺ and Cl^? and a significant reduction of K⁺ content in shoots. The accumulation of osmoregulatory compounds (proline and total sugars) in shoots and roots was greatly increased by NaCl. Activity staining of antioxidants after a native polyacrylamide gel electrophores (PAGE) showed four superoxide dismutase (SOD) isozymes in the extract of leaf-soluble proteins (one Mn-SOD, two Fe-SODs, and one CuZn-SOD), and three isoforms in roots (Mn-SOD, Fe-SOD, and CuZn-SOD). Four peroxidase (POD) isozymes in the roots and only one isozyme in the leaves were detected. The work demonstrated that activities of antioxidant defense enzymes changed in parallel with the increased salinity. In summary, these findings proved that L. sativum can be classified as a moderately tolerant plant to salinity.     

Superoxide dismutase: a photochemical augmentation assay.

Cell envelope vesicles containing bacteriorhodopsin, prepared from Halobacterium halobium, have previously been shown to accumulate glutamate to high concentration gradients when illuminated. This active transport is energized by a sodium gradient (Na_out⁺ ? Na_in⁺), which arises from Na⁺-efflux coupled to the light-induced H⁺-gradient. The oxidation of dimethyl phenylenediamine (DPD) by the vesicles also can drive uphill glutamate transport, and such transport is inhibited by KCN, azide, ionophores, or uncouplers. K_T for glutamate is 1.4 × 10^?7m under these conditions, as compared to 1.3 × 10^?7m for light-induced transport. The respiration-induced transport of glutamate is dependent on high Na⁺ concentrations on the vesicle exterior and requires low Na⁺ concentrations in the interior. When Na⁺ of increasing concentrations is included in the vesicles, transport proceeds with increasing lags, similarly to the case of light-driven transport. In vesicles to which DPD is added first, and then KCN at increasing time intervals (5 to 15 min), glutamate transport occurs after the addition of KCN, with increasing rates, even though respiration is inhibited. This indicates that the energy generated by DPD-oxidation is conserved over several minutes. These results suggest that in the case of respiration-dependent glutamate transport the translocation is also driven by a Na⁺-gradient; thus, there is a single glutamate transport system independent of the source of energy. The generation of such an Na⁺-gradient during DPD-oxidation implies that the respiration component involved, cytochrome oxidase, is functionally equivalent to bacteriorhodopsin, which acts as a proton pump.     

Superoxide dismutase micro assay in biological material.

A micro assay for the rapid and convenient determination of superoxide dismutase activity in limited amounts of biological material was devised and successfully employed. The combination of the formazan derivative colour formation induced by reaction of O2theta with nitroblue tetrazolium and a suitable analytical polyacrylamide gel electrophoresis system was used. It was possible to show that the reactivity of soluble superoxide dismutases in polyacrylamide gels was proportional to the enzyme concentrations employed. Bovine erythrocyte Cu, Zn-superoxide dismutase (EC 1.15.1.1) (erythrocuprein) served as a standard throughout. To measure the degree of superoxide dismutase activity, a gel-scanning apparatus was usedThe integrated scanning curve of the unstained portions of the gel proved linearly proportional to the logarithm of the superoxide dismutase activity in the range between 10(-12) and 7 X 10(-11) mol of the bovine enzyme. Although the absolute integral is dependent on the different staining conditions, the slope of the superoxide dismutase calibration curve is highly reproducible. Superoxide dismutase added to crude liver and brain homogenates could be fully detected using this assay. Thus, biological material including nucleic acids, enzymes, lipids etc. do not inhibit this reaction.     

Superoxide dismutase inhibits lipid peroxidation in micelles.

Superoxide dismutase (SOD) taken in minor concentrations (a few U/ml) displays a pronounced inhibiting effect on the chain oxidation of methyl linoleate and methyl linolenate (but not methyl oleate) induced by 2,2'-azobis(2-amidinopropan) dihydrochloride (AAPH) in micellar solutions of sodium dodecyl sulfate and Triton X-100 in phosphate buffer, pH 7.40, at 37.0 degrees C. The inhibition is evidently caused by purging the system from O(2)*(-). The latter suggests the formation of O(2)*(-) (HO(2)* in the course of peroxidation, most likely, via beta-decay of lipid peroxy radical (LO(2)*. Thermodynamic estimations verify a rather high probability of beta-decay of LO(2)* produced from polyunsaturated fatty acids by contrast to that produced from saturated and monoenic fatty acids. It is speculated that O(2)*(-) (HO(2)*, being an amphiphilic, reactive and highly mobile species, participates in intermicellar (interliposomal) transfer of free valence during lipid peroxidation in microheterogeneous systems.     

Superoxide dismutase in ripening fruits

The levels of superoxide dismutase (SOD) activity in extracts of preclimacteric apple, banana, avocado, and tomato fruits were not greatly different than in extracts of postclimacteric fruits. The results indicate that no major quantitative change in SOD occurs in fruits with or preceding the onset of senescence. Tomato fruit SOD was studied in more detail, and was found largely in the soluble fraction, and to a lesser extent in the mitochondrial and plastid fractions. The soluble fraction was purified by ammonium sulfate fractionation, column chromatography, and isoelectric focusing. Isoelectric focusing separated SOD from contaminating peroxidases. The purified tomato SOD showed an apparent molecular weight of 31,500 determined by gel filtration. Polyacrylamide gel electrophoresis of this preparation indicated two SOD components corresponding to two protein bands, one of which stained more intensely than the other. The purified tomato enzyme was inhibited 90% by 1 mm KCN.     

Superoxide dismutase activity in nematodes

The activities of the enzymes superoxide dismutase (E.C.:1.15.1.1) and catalase (E.C.:1.11.1.6) were studied in purified extracts of four nematodes: Ascaris suum, Toxascaris leonina, Toxocara canis and T. cati adult males and females. No catalase activity was found in any of the extracts. The results reveal that the SOD activities of the four parasites presented species differences and also sexual differences within each species. Polyacrylamide gel electrophoresis pattern analysis confirmed that the mobilities, widths and band intensities varied according to the species and sex of the parasite from which the enzyme was obtained.     

Superoxide dismutase in Scenedesmus obliquus

In heterotrophically grown Scenedesmus obliquus, the specific activity of superoxide dismutase (SOD; EC 1.15.1.1) declined when glucose was abundant, increased as it was depleated, and remained steady at a high level when it was absent. Transition to autotrophic growth produced only a small (20% over 5 d) increase in specific activity above the values obtained in dark-grown cells after glucose and starch-reserve depletion. This small, but consistent, increase did, however, parallel a similar increase in photosynthetic capacity. Polyacrylamide-gel electrophoresis showed the existence of nine isoenzymes of SOD. The three major and one of the minor isoenzymes were present in all extracts while three minor isoenzymes were found only in autotrophically grown cells and two only in heterotrophically grown cells. Characterization studies indicated that two of the major isoenzymes are dimeric FeSODs the other is a tetrameric MnSOD, and of the minor isoenzymes, two are dimeric FeSODs and four are dimeric MnSODs.Abbreviation SOD superoxide dismutase