• Molecules and Cells
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• v.39 no.1
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• pp.20-25
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• 2016

Photosynthesis is a highly robust process allowing for rapid adjustment to changing environmental conditions. The efficient acclimation depends on balanced redox metabolism and control of reactive oxygen species release which triggers signaling cascades and potentially detrimental oxidation reactions. Thiol peroxidases of the peroxiredoxin and glutathione peroxidase type, and ascorbate peroxidases are the main peroxide detoxifying enzymes of the chloroplast. They use different electron donors and are linked to distinct redox networks. In addition, the peroxiredoxins serve functions in redox regulation and retrograde signaling. The complexity of plastid peroxidases is discussed in context of suborganellar localization, substrate preference, metabolic coupling, protein abundance, activity regulation, interactions, signaling functions, and the conditional requirement for high antioxidant capacity. Thus the review provides an opinion on the advantage of linking detoxification of peroxides to different enzymatic systems and implementing mechanisms for their inactivation to enforce signal propagation within and from the chloroplast.

• Molecules and Cells
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• v.39 no.1
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• pp.26-30
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• 2016

Peroxiredoxins are ubiquitous thiol proteins that catalyse the breakdown of peroxides and regulate redox activity in the cell. Kinetic analysis of their reactions is required in order to identify substrate preferences, to understand how molecular structure affects activity and to establish their physiological functions. Various approaches can be taken, including the measurement of rates of individual steps in the reaction pathway by stopped flow or competitive kinetics, classical enzymatic analysis and measurement of peroxidase activity. Each methodology has its strengths and they can often give complementary information. However, it is important to understand the experimental conditions of the assay so as to interpret correctly what parameter is being measured. This brief review discusses different kinetic approaches and the information that can be obtained from them.

• Molecules and Cells
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• v.39 no.1
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• pp.1-5
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• 2016

Peroxiredoxins (Prxs) are a very large and highly conserved family of peroxidases that reduce peroxides, with a conserved cysteine residue, designated the "peroxidatic" Cys ($C_P$) serving as the site of oxidation by peroxides (Hall et al., 2011; Rhee et al., 2012). Peroxides oxidize the $C_P$-SH to cysteine sulfenic acid ($C_P$-SOH), which then reacts with another cysteine residue, named the "resolving" Cys ($C_R$) to form a disulfide that is subsequently reduced by an appropriate electron donor to complete a catalytic cycle. This overview summarizes the status of studies on Prxs and relates the following 10 minireviews.

• Proceedings of the Zoological Society Korea Conference
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• 1999.10b
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• pp.12-12
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• 1999

No Abstract, See Full Text

• Journal of Plant Biotechnology
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• v.33 no.1
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• pp.1-9
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• 2006

Peroxiredoxins (Prxs) are ubiquitously distributed and play important functions in diverse cellular signaling systems. The proteins are largely classified into three groups, such as typical 2-Cys Prx, atypical 2-Cys Prx, and 1-Cys Prx, that are distinguished by their catalytic mechanisms and number of Cys residues. From the three classes of Prxs, the typical 2-Cys Prx containing the two-conserved Cys residues at its N-terminus and C-terminus catalyzes $H_2O_2$ with the use of thioredoxin (Trx) as an electron donor. During the catalytic cycle, the N-terminal Cys residue undergoes a peroxide-dependent oxidation to sulfenic acid, which can be further oxidized to sulfinic acid at the presence of high concentrations of $H_2O_2$ and a Trx system containing Trx, Trx reductase, and NADPH. The sulfinic acid form of 2-Cys Prx is reduced by the action of sulfiredoxin which requires ATP as an energy source. Under the strong oxidative or heat shock stress conditions, 2-Cys Prx in eukaryotes rapidly switches its protein structure from low-molecular-weight species to high-molecular-weight protein structures. In accordance with its structural changes, the protein concomitantly triggers functional switching from a peroxidase to a molecular chaperone, which can protect its substrate denaturation from external stress. In addition to its N-terminal active site, the C-terminal domain including 'YF-motif' of 2-Cys Prx plays a critical role in the structural changes. Therefore, the C-terminal truncated 2-Cys Prxs are not able to regulate their protein structures and highly resistant to $H_2O_2$-dependent hyperoxidation, suggesting that the reaction is guided by the peroxidatic Cys residue. Based on the results, it may be concluded that the peroxidatic Cys of 2-Cys Prx acts as an '$H_2O_2$-sensor' in the cells. The oxidative stress-dependent regulation of 2-Cys Prx provides a means of defense systems in cells to adapt stress conditions by activating intracellular defense signaling pathways. Particularly, 2-Cys Prxs in plants are localized in chloroplasts with a dynamic protein structure. The protein undergoes conformational changes again oxidative stress. Depending on a redox-potential of the chloroplasts, the plant 2-Cys Prx forms super-molecular weight protein structures, which attach to the thylakoid membranes in a reversible manner.

• BMB Reports
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• v.43 no.3
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• pp.170-175
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• 2010

Chaperone;Glutathione peroxidase;Peroxiredoxin;Schizosaccharomyces pombe;Thioredoxin peroxidase;To investigate the differences in the functional roles of peroxiredoxins (Prxs) and glutathione peroxidase (GPx) of Schizosaccharomyces pombe, we examined the peroxidase and molecular chaperone properties of the recombinant proteins. TPx (thioredoxin peroxidase) exhibited a capacity for peroxide reduction with the thioredoxin system. GPx also showed thioreoxin-dependent peroxidase activity rather than GPx activity. The peroxidase activity of BCP (bacterioferritin comigratory protein) was similar to that of TPx. However, peroxidase activity was not observed for PMP20 (peroxisomal membrane protein 20). TPx, PMP20, and GPx inhibited thermal aggregation of citrate synthase at 43$^{\circ}C$, but BCP failed to inhibit the aggregation. The chaperone activities of PMP20 and GPx were weaker than that of TPx. The peroxidase and chaperone properties of TPx, BCP, and GPx of the fission yeast are similar to those of Saccharomyces cerevisiae. The fission yeast PMP20 without thioredoxin-dependent peroxidase activity may act as a molecular chaperone.

• BMB Reports
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• v.33 no.6
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• pp.514-518
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• 2000

Two open reading frames of Haemophilus influenzae, HI0572 and HI0751, showing homology to a yeast thioredoxin peroxidase II (TPx II) and an E. coli thiol peroxidase $P_{20}$, respectively, were cloned and expressed in E. coli, and then the proteins were subsequently purified and characterized. HI0751 protein showed the thioredoxin (Trx)-dependent peroxidase activity, whereas HI0572 protein showed glutathione-dependent peroxidase. The HI0572 is the first peroxiredoxin with glutathione peroxidase activity rather than thioredoxin peroxidase. Purified HI0572 and HI0751 proteins protected specifically the inactivation of glutamine synthetase by metal catalyzed oxidation (MCO) systems composed of $Fe^{3+}$, $O_2$ and mercaptans such as dithiothreitol, ${\beta}-mercaptoethanol$ and glutathione (GSH). Unlike the HI0751 protein, the HI0572 protein was more effective in protecting glutamine synthetase from inactivation by the $GSH/Fe^{3+}/O_2$ system. It seems that these unique properties of the HI0572 protein are due to the structure containing a glutaredoxin domain at it's C-terminal in addition to a peroxiredoxin domain.

• Biomolecules & Therapeutics
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• v.19 no.4
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• pp.451-459
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• 2011

Peroxiredoxins (Prxs) have a critical role in protecting cells against oxidative damage generated by reactive oxygen species (ROS). PrxI and PrxII are more than 90% homologous in their amino acid sequences, and both proteins reduce $H_2O_2$. In this study, an over-expression plasmid carrying PrxI was transfected into $PrxII^{-/-}$ mouse embryonic fibroblasts (MEFs) to investigate potential compensatory relationships between PrxI and PrxII. ROS levels induced by oxidative stress were increased in $PrxII^{-/-}$ MEFs as compared to wild-type MEFs. Moreover, exposure of $PrxII^{-/-}$ MEFs to $H_2O_2$ caused a reduction in cell viability of about 10%, and the proportion of cell death was increased compared to mock-treated $PrxII^{-/-}$ MEFs. However, transient over-expression of PrxI in $PrxII^{-/-}$ MEFs conferred increased resistance against the oxidative damage, as evidenced by increased cell viability and reduced intracellular ROS levels under $H_2O_2$ stress conditions. The findings suggest that over-expressed PrxI can partly compensate for the loss of PrxII function in PrxII-deficient MEFs.

• IMMUNE NETWORK
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• v.21 no.5
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• pp.36.1-36.16
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• 2021

Peroxiredoxins (Prxs) are ubiquitously expressed peroxidases that reduce hydrogen peroxide or alkyl peroxide production in cells. Prxs are released from cells in response to various stress conditions, and they function as damage-associated molecular pattern molecules. However, the secretory mechanism of Prxs and their roles have not been elucidated. Thus, we aimed to determine whether inflammasome activation is a secretory mechanism of Prxs and subsequently identify the effect of the secreted Prxs on activation of the classical complement pathway. Using J774A.1, a murine macrophage cell line, we demonstrated that NLRP3 inflammasome activation induces Prx1, Prx2, Prx5, and Prx6 secretion in a caspase-1 dependent manner. Using HEK293T cells with a transfection system, we revealed that the release of Prx1 and Prx2 relies on gasdermin-D (GSDMD)-mediated secretion. Next, we confirmed the binding of both Prx1 and Prx2 to C1q; however, only Prx2 could induce the C1q-mediated classical complement pathway activation. Collectively, our results suggest that inflammasome activation is a secretory mechanism of Prxs and that GSDMD is a mediator of their secretion. Moreover, secreted Prx1 and Prx2 bind with C1q, but only Prx2 mediates the classical complement pathway activation.

• Tuberculosis and Respiratory Diseases
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• v.58 no.1
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• pp.31-42
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• 2005

Background : Peroxiredoxins (Prxs) are a relatively newly recognized, novel family of peroxidases that reduce $H_2O_2$ and alkylhydroperoxide into water and alcohol, respectively. There are 6 known isoforms of Prxs present in human cells. Normally, Prxs exist in a head-to-tail homodimeric state in a reduced form. However, in the presence of excess $H_2O_2$, it can be oxidized on its catalytically active cysteine site into inactive oxidized forms. This study surveyed the types of the Prx isoforms present in the pulmonary epithelial, macrophage, endothelial, and other cell lines and observed their response to oxidative stress. Methods : This study examined the effect of exogenous, excess $H_2O_2$ on the Prxs of established cell lines originating from the pulmonary epithelium, macrophages, and other cell lines, which are known to be exposed to high oxygen partial pressures or are believed to be subject to frequent oxidative stress, using non-reducing SDS polyacrylamide electrophoresis (PAGE) and 2 dimensional electrophoresis. Result : The addition of excess $H_2O_2$ to the culture media of the various cell-lines caused the immediate inactivation of Prxs, as evidenced by their inability to form dimers by a disulfide cross linkage. This was detected as a subsequent shift to its monomeric forms on the non-reducing SDS PAGE. These findings were further confirmed by 2 dimensional electrophoresis and immunoblot analysis by a shift toward a more acidic isoelectric point (pI). However, the subsequent reappearance of the dimeric Prxs with a comparable, corresponding decrease in the monomeric bands was noted on the non-reducing SDS PAGE as early as 30 minutes after the $H_2O_2$ treatment suggesting regeneration after oxidation. The regenerated dimers can again be converted to the inactivated form by a repeated $H_2O_2$ treatment, indicating that the protein is still catalytically active. The recovery of Prxs to the original dimeric state was not inhibited by a pre-treatment with cycloheximide, nor by a pretreatment with inhibitors of protein synthesis, which suggests that the reappearance of dimers occurs via a regeneration process rather than via the de novo synthesis of the active protein. Conclusion : The cells, in general, appeared to be equipped with an established system for regenerating inactivated Prxs, and this system may function as a molecular "on-off switch" in various oxidative signal transduction processes. The same mechanisms might applicable other proteins associated with signal transduction where the active catalytic site cysteines exist.