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Superoxide reductase activity
About: Superoxide reductase activity is a(n) research topic. Over the lifetime, 12 publication(s) have been published within this topic receiving 708 citation(s).
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TL;DR: In this article, the authors showed that desulfoferrodoxin behaves as a superoxide reductase enzyme and thus provides new insights into the biological mechanisms designed for protection from oxidative stresses.
Abstract: Desulfoferrodoxin is a small protein found in sulfate-reducing bacteria that contains two independent mononuclear iron centers, one ferric and one ferrous Expression of desulfoferrodoxin from Desulfoarculus baarsii has been reported to functionally complement a superoxide dismutase deficient Escherichia coli strain To elucidate by which mechanism desulfoferrodoxin could substitute for superoxide dismutase in E coli, we have purified the recombinant protein and studied its reactivity toward O-(2) Desulfoferrodoxin exhibited only a weak superoxide dismutase activity (20 units mg(-1)) that could hardly account for its antioxidant properties UV-visible and electron paramagnetic resonance spectroscopy studies revealed that the ferrous center of desulfoferrodoxin could specifically and efficiently reduce O-(2), with a rate constant of 6-7 x 10(8) M(-1) s(-1) In addition, we showed that membrane and cytoplasmic E coli protein extracts, using NADH and NADPH as electron donors, could reduce the O-(2) oxidized form of desulfoferrodoxin Taken together, these results strongly suggest that desulfoferrodoxin behaves as a superoxide reductase enzyme and thus provide new insights into the biological mechanisms designed for protection from oxidative stresses
131 citations
TL;DR: UV-visible and electron paramagnetic resonance spectroscopy studies revealed that the ferrous center of desulfoferrodoxin could specifically and efficiently reduce O⨪2, with a rate constant of 6–7 × 108 m −1 s−1, and it was shown that membrane and cytoplasmic E. coli protein extracts, using NADH and NADPH as electron donors, could reduce the O⩪2oxidized form of des sulfuroferrod toxin.
Abstract: Desulfoferrodoxin is a small protein found in sulfate-reducing bacteria that contains two independent mononuclear iron centers, one ferric and one ferrous. Expression of desulfoferrodoxin from Desulfoarculus baarsii has been reported to functionally complement a superoxide dismutase deficient Escherichia coli strain. To elucidate by which mechanism desulfoferrodoxin could substitute for superoxide dismutase in E. coli, we have purified the recombinant protein and studied its reactivity toward O-(2). Desulfoferrodoxin exhibited only a weak superoxide dismutase activity (20 units mg(-1)) that could hardly account for its antioxidant properties. UV-visible and electron paramagnetic resonance spectroscopy studies revealed that the ferrous center of desulfoferrodoxin could specifically and efficiently reduce O-(2), with a rate constant of 6-7 x 10(8) M(-1) s(-1). In addition, we showed that membrane and cytoplasmic E. coli protein extracts, using NADH and NADPH as electron donors, could reduce the O-(2) oxidized form of desulfoferrodoxin. Taken together, these results strongly suggest that desulfoferrodoxin behaves as a superoxide reductase enzyme and thus provide new insights into the biological mechanisms designed for protection from oxidative stresses.
126 citations
TL;DR: This finding, the first description of a T. pallidum iron-binding protein, indicates that the syphilis spirochete copes with oxidative stress via a primitive mechanism, which, thus far, has not been described in pathogenic bacteria.
Abstract: Treponema pallidum, the causative agent of venereal syphilis, is a microaerophilic obligate pathogen of humans. As it disseminates hematogenously and invades a wide range of tissues, T. pallidum presumably must tolerate substantial oxidative stress. Analysis of the T. pallidum genome indicates that the syphilis spirochete lacks most of the iron-binding proteins present in many other bacterial pathogens, including the oxidative defense enzymes superoxide dismutase, catalase, and peroxidase, but does possess an orthologue (TP0823) for neelaredoxin, an enzyme of hyperthermophilic and sulfate-reducing anaerobes shown to possess superoxide reductase activity. To analyze the potential role of neelaredoxin in treponemal oxidative defense, we examined the biochemical, spectroscopic, and antioxidant properties of recombinant T. pallidum neelaredoxin. Neelaredoxin was shown to be expressed in T. pallidum by reverse transcriptase-polymerase chain reaction and Western blot analysis. Recombinant neelaredoxin is a 26-kDa alpha(2) homodimer containing, on average, 0.7 iron atoms/subunit. Mossbauer and EPR analysis of the purified protein indicates that the iron atom exists as a mononuclear center in a mixture of high spin ferrous and ferric oxidation states. The fully oxidized form, obtained by the addition of K(3)(Fe(CN)(6)), exhibits an optical spectrum with absorbances at 280, 320, and 656 nm; the last feature is responsible for the protein's blue color, which disappears upon ascorbate reduction. The fully oxidized protein has a A(280)/A(656) ratio of 10.3. Enzymatic studies revealed that T. pallidum neelaredoxin is able to catalyze a redox equilibrium between superoxide and hydrogen peroxide, a result consistent with it being a superoxide reductase. This finding, the first description of a T. pallidum iron-binding protein, indicates that the syphilis spirochete copes with oxidative stress via a primitive mechanism, which, thus far, has not been described in pathogenic bacteria.
97 citations
TL;DR: It is shown that neelaredoxin (Nlr) is the main O2·− scavenger in A. fulgidus and shown that Nlr is able to both reduce and dismutate O 2·−, thus having a bifunctional reactivity towards O2 ·−.
Abstract: Archaeoglobus fulgidus is a hyperthermophilic sulphate-reducing archaeon. It has an optimum growth temperature of 83°C and is described as a strict anaerobe. Its genome lacks any homologue of canonical superoxide (O2·−) dismutases. In this work, we show that neelaredoxin (Nlr) is the main O2·− scavenger in A. fulgidus, by studying both the wild-type and recombinant proteins. Nlr is a 125-amino-acid blue-coloured protein containing a single iron atom/molecule, which in the oxidized state is high spin ferric. This iron centre has a reduction potential of +230 mV at pH 7.0. Nitroblue tetrazolium-stained gel assays of cell-soluble extracts show that Nlr is the main protein from A. fulgidus which is reactive towards O2·−. Furthermore, it is shown that Nlr is able to both reduce and dismutate O2·−, thus having a bifunctional reactivity towards O2·−. Kinetic and spectroscopic studies indicate that Nlr's superoxide reductase activity may allow the cell to eliminate O2·− quickly in a NAD(P)H-dependent pathway. On the other hand, Nlr's superoxide dismutation activity will allow the cell to detoxify O2·− independently of the cell redox status. Its superoxide dismutase activity was estimated to be 59 U mg−1 by the xanthine/xanthine oxidase assay at 25°C. Pulse radiolysis studies with the isolated and reduced Nlr proved unambiguously that it has superoxide dismutase activity; at pH 7.1 and 83°C, the rate constant is 5 × 106 M−1 s−1. Besides the superoxide dismutase activity, soluble cell extracts of A. fulgidus also exhibit catalase and NAD(P)H/oxygen oxidoreductase activities. By putting these findings together with the entire genomic data available, a possible oxygen detoxification mechanism in A. fulgidus is discussed.
66 citations
TL;DR: A gene in T. pallidum is described with sequence homologies to a new class of antioxidant systems, named superoxide reductases, recently isolated from sulfate-reducing bacteria, and the question of the importance of superoxide reductionases in mechanisms for detoxifying superoxide radicals is raised.
Abstract: Aerobic life requires the presence of antioxidant enzymes, such as superoxide dismutase, catalase, and peroxidase to eliminate deleterious oxygen derivatives. Treponema pallidum, a microaerophilic bacterium responsible for venereal syphilis, is an interesting organism because it lacks all of the above-mentioned enzymes, as deduced from its recently sequenced genome. In this paper, we describe a gene in T. pallidum with sequence homologies to a new class of antioxidant systems, named superoxide reductases, recently isolated from sulfate-reducing bacteria (Lombard, M., Fontecave, M., Touati, D., and Niviere, V. (2000) J. Biol. Chem. 275, 115-121). We report that (i) expression of the T. pallidum gene fully restored to a superoxide dismutase-deficient Escherichia coli mutant the ability to grow under aerobic conditions; (ii) the corresponding protein displays a strong superoxide reductase activity; and (iii) the T. pallidum protein contains only one mononuclear nonheme ferrous center, able to reduce superoxide selectively and efficiently, whereas previously characterized superoxide reductase from Desulfoarculus baarsii contains an additional rubredoxin-like ferric center. These results suggest that T. pallidum antioxidant defenses rely on a new class of superoxide reductase and raise the question of the importance of superoxide reductases in mechanisms for detoxifying superoxide radicals.
65 citations