Globin's structure and function in vesicomyid bivalves from the Gulf of Guinea cold seeps as an adaptation to life in reduced sediments

Vesicomyid bivalves form dense clam beds in both deep-sea cold seeps and hydrothermal vents. The species diversity within this family raises questions about niche separation and specific adaptations. To compare their abilities to withstand hypoxia, we have studied the structure and function of erythrocyte hemoglobin (Hb) and foot myoglobin (Mb) from two vesicomyid species, Christineconcha regab and Laubiericoncha chuni, collected from the Regab pockmark in the Gulf of Guinea at a depth of 3,000 m. Laubiericoncha chuni possesses three monomeric globins, G1 (15,361 Da), G2 (15,668 Da), and G3 (15,682 Da) in circulating erythrocytes (Hb), and also three globins, G1, G3, and G4 (14,786 Da) in foot muscle (Mb). Therefore, globins G2 and G4 appear to be specific for erythrocytes and muscle, respectively, but globins G1 and G3 are common. In contrast, C. regab lacks erythrocyte Hb completely and possesses only globin monomers G1' (14,941 Da), G2' (15,169 Da), and G3' (15,683 Da) in foot muscle. Thus, these two vesicomyid species, C. regab and L. chuni, show a remarkable diversity in globin expression when examined by electrospray ionization mass spectrometry. Oxygen-binding affinities reveal extremely high oxygen affinities (P50 < 1 Torr, from 5° to 15°C at pH 7.5), in particular L. chuni globins, which might be an advantage allowing L. chuni to dig deeply for sulfides and remain buried for long periods in reduced sediments.

Analysis of monoclonal antibody by a novel CE-UV/MALDI-MS interface

mAbs are highly complex proteins that present a wide range of microheterogeneity that requires multiple analytical methods for full structure assessment and quality control. As a consequence, the characterization of mAbs on different levels is particularly product- and time-consuming. CE-MS couplings, especially to MALDI, appear really attractive methods for the characterization of biological samples. In this work, we report the last instrumental development and performance of the first totally automated off-line CE-UV/MALDI-MS/MS. This interface is based on the removal of the original UV cell of the CE apparatus, modification of the spotting device geometry, and creation of an integrated delivery matrix system. The performance of the method was evaluated with separation of five intact proteins and a tryptic digest mixture of nine proteins. Intact protein application shows the acquisition of electropherograms with high resolution and high repeatability. In the peptide mapping approach, a total number of 154 unique identified peptides were characterized using MS/MS spectra corresponding to average sequence coverage of 64.1%. Comparison with NanoLC/MALDI-MS/MS showed complementarity at the peptide level with an increase of 42% when using CE/MALDI-MS coupling. Finally, this work represents the first analysis of intact mAb charge variants by CZE using an MS detection. Moreover, using a peptide mapping approach CE-UV/MALDI-MS/MS fragmentation allowed 100% sequence coverage of the light chain and 92% of the heavy chain, and the separation of four major glycosylated peptides and their structural characterization.

Oxidative stress response: a proteomic view

The oxidative stress response is characterized by various effects on a range of biologic molecules. When examined at the protein level, both expression levels and protein modifications are altered by oxidative stress. While these effects have been studied in the past by classic biochemical methods, the recent onset of proteomics methods has allowed the oxidative stress response to be studied on a much wider scale. The input of proteomics in the study of oxidative stress response and in the evidence of an oxidative stress component in biologic phenomena is reviewed in this paper.

Rapid and multi-level characterization of trastuzumab using sheathless capillary electrophoresis-tandem mass spectrometry

Monoclonal antibodies (mAbs) are highly complex proteins that display a wide range of microheterogeneity that requires multiple analytical methods for full structure assessment and quality control. As a consequence, the characterization of mAbs on different levels is particularly product - and time - consuming. This work presents the characterization of trastuzumab sequence using sheathless capillary electrophoresis (referred as CESI) – tandem mass spectrometry (CESI-MS/MS). Using this bottom-up proteomic-like approach, CESI-MS/MS provided 100% sequence coverage for both heavy and light chain via peptide fragment fingerprinting (PFF) identification. The result was accomplished in a single shot, corresponding to the analysis of 100 fmoles of digest. The same analysis also enabled precise characterization of the post-translational hot spots of trastuzumab, used as a representative widely marketed therapeutic mAb, including the structural confirmation of the five major N-glycoforms.

Insights into metazoan evolution from Alvinella pompejana cDNAs

Background

Alvinella pompejana is a representative of Annelids, a key phylum for evo-devo studies that is still poorly studied at the sequence level. A. pompejana inhabits deep-sea hydrothermal vents and is currently known as one of the most thermotolerant Eukaryotes in marine environments, withstanding the largest known chemical and thermal ranges (from 5 to 105°C). This tube-dwelling worm forms dense colonies on the surface of hydrothermal chimneys and can withstand long periods of hypo/anoxia and long phases of exposure to hydrogen sulphides. A. pompejana specifically inhabits chimney walls of hydrothermal vents on the East Pacific Rise. To survive, Alvinella has developed numerous adaptations at the physiological and molecular levels, such as an increase in the thermostability of proteins and protein complexes. It represents an outstanding model organism for studying adaptation to harsh physicochemical conditions and for isolating stable macromolecules resistant to high temperatures.

Results

We have constructed four full length enriched cDNA libraries to investigate the biology and evolution of this intriguing animal. Analysis of more than 75,000 high quality reads led to the identification of 15,858 transcripts and 9,221 putative protein sequences. Our annotation reveals a good coverage of most animal pathways and networks with a prevalence of transcripts involved in oxidative stress resistance, detoxification, anti-bacterial defence, and heat shock protection. Alvinella proteins seem to show a slow evolutionary rate and a higher similarity with proteins from Vertebrates compared to proteins from Arthropods or Nematodes. Their composition shows enrichment in positively charged amino acids that might contribute to their thermostability. The gene content of Alvinella reveals that an important pool of genes previously considered to be specific to Deuterostomes were in fact already present in the last common ancestor of the Bilaterian animals, but have been secondarily lost in model invertebrates. This pool is enriched in glycoproteins that play a key role in intercellular communication, hormonal regulation and immunity.

Conclusions

Our study starts to unravel the gene content and sequence evolution of a deep-sea annelid, revealing key features in eukaryote adaptation to extreme environmental conditions and highlighting the proximity of Annelids and Vertebrates.

Structural characterization of hemoglobins from Monilifera and Frenulata tubeworms (Siboglinids): first discovery of giant hexagonal-bilayer hemoglobin in the former "Pogonophora" group

Siboglinids are symbiotic polychete annelids having hemoglobins as essential oxygen- and sulfide-carriers for their endosymbiotic bacteria. We analyzed the structure of the hemoglobins from two species of siboglinids: the monilifera Sclerolinum contortum and the frenulata Oligobrachia webbi (i.e. haakonmosbiensis) from Norwegian cold seeps. Measured by Multi-Angle Laser Light Scattering (MALLS), Sclerolinum shows a 3190+/-50 kDa hexagonal bilayer hemoglobin (HBL-Hb) and a 461+/-46 kDa ring-Hb, just as vestimentifera, whereas Oligobrachia has a 409+/-3.7 kDa ring-Hb only. Electrospray Ionization-Mass Spectrometry (ESI-MS) showed Sclerolinum HBL-Hb composed of seven monomeric globins (15-16 kDa), three disulfide-bonded globin heterodimers and three linkers. The heterodimers always contain globin-b (15814.4+/-1.5 Da). Sclerolinum ring-Hb is composed of globins and dimers with identical masses as its HBL-Hb, but lacks linkers. Oligobrachia ring-Hb has three globin monomers (14-15 kDa) only, with no disulfide-bonded dimers. Comparison of Sclerolinum hemoglobins between Storegga and Haakon Mosby Mud Volcano, using the normalized height of deconvoluted ESI-MS peaks, shows differences in globin monomers abundances that could reflect genetic differences or differential gene expression between distinct seep populations. The discovery of HBL-Hb in Sclerolinum is a new element supporting the hypothesis of monilifera being phylogenetically more closely related to vestimentifera, than to frenulata.

Power and limitations of electrophoretic separations in proteomics strategies

Proteomics can be defined as the large-scale analysis of proteins. Due to the complexity of biological systems, it is required to concatenate various separation techniques prior to mass spectrometry. These techniques, dealing with proteins or peptides, can rely on chromatography or electrophoresis. In this review, the electrophoretic techniques are under scrutiny. Their principles are recalled, and their applications for peptide and protein separations are presented and critically discussed. In addition, the features that are specific to gel electrophoresis and that interplay with mass spectrometry (i.e., protein detection after electrophoresis, and the process leading from a gel piece to a solution of peptides) are also discussed.

Aldosterone: from biosynthesis to non-genomic action onto the proteome

An increased aldosterone concentration can lead to a progression of heart diseases and to myocardial fibrosis. These fatal processes can be prevented by e.g. inhibiting the mineralocorticoid receptor (MR), which is nowadays part of a commonly applied standard therapy. Moreover, selective inhibition of aldosterone synthase (CYP11B2) is a straightforward goal whereby CYP11B1, a key enzyme in glucocorticoid biosynthesis exhibiting a high structure identity with CYP11B2 should not be inhibited. Therefore, effective test systems have been developed and rather potent and selective CYP11B2 compounds like SIAS-1 have been identified by our group. In addition to finding new inhibitors, we investigated which proteins are directly influenced by aldosterone focussing on non-genomic effects. Schizosaccharomyces pombe was chosen as a model organism, since this yeast does not contain nuclear steroid receptors, but many genes and regulatory mechanisms that are close to those of mammals. Besides creating a reference map for this organism, protein spots affected by aldosterone as well as deoxycorticosterone (DOC) and corticosterone have been identified. In case of aldosterone, a regulatory effect of proteins that are connected with structural proteins, signal cascades, osmoregulation and calcium pathway as well as to general metabolism have been discovered. DOC causes overlapping but also different effects compared with aldosterone. As shown exemplarily for GAPDH, the aldosterone-mediated effects in S. pombe can also be verified in mammalian cells. These and further investigations contribute to a deeper understanding of so-called non-genomic aldosterone effects.

Supramolecular circular helicates formed by destabilisation of supramolecular dimers

The effect of changes in the angles at the connection points of linear/circular helicates is explored as a route to control the nuclearity and architecture of metallo-supramolecular arrays. This effect is probed by changing the geometry of the metal centre used to assemble bis-pyridylimine ligands that contain a 1,3-bis(aminomethyl) benzene spacer group. Tetrahedral metal ions favour linear dimers, whereas octahedral nickel(II) predominantly gives a triangular circular helicate. Five-coordinate copper(II) falls in the middle of these extremes and results in the formation of solvent-dependent mixtures of dimer and trimer. The trinuclear, triangular, circular helicate structures, which result from coordination to copper(II) and nickel(II), are structurally characterised by X-ray crystallography and reveal that the units can aggregate into hexagonal arrays that contain anion-filled tube-like channels in the solid state.

Macrotricycles Featuring a π-Basic Tetrahedral Cavity: Preference for NH4+ Detected by Electrospray Ionization Mass Spectrometry

Cation-pi interactions play an important role in biology. The title compounds are C3-symmetric macrotricycles built from resorcinol, a pi electron-rich arene. They were prepared in up to 18% yield by intramolecular cyclization of 1,3,5-trisubstituted benzene tripods bearing pendant resorcinol groups, with methylene acetal bridges. Positive ESI-MS showed that these receptors recognize NH4+ over K+, and poorly respond to the large t-BuNH3+ cation, suggesting that they bind NH4+ intramolecularly, presumably via cation-pi interactions.

Messages in molecules: ligand/cation coding and self-recognition in a constitutionally dynamic system of heterometallic double helicates

Double helicates are known to exhibit self-recognition characteristics determined by the coordination geometry of the metal involved as well as by the topicity of the ligands. Combining tridentate (terpyridine, T) or bidentate (bipyridine, B) subunits in a tritopic strand affords a set of ligands able to assemble by pairs to form double helicates, homo- or heterostranded, homo- or heterotopic, depending on the coordination properties of the metals involved. The four ligand strands, BBB, TTT, BBT, and TBT form constitutionally dynamic sets of double helicates with the metal ions Cu(I), Cu(II), and Zn(II); these helicates correspond to the correct coding of the BB, BT, and TT pairs for tetra-, penta-, and hexacoordinate Cu(I), Cu(II), and Zn(II) cations, respectively.

Ruthenium(II) Complexes with Improved Photophysical Properties Based on Planar 4‘-(2-Pyrimidinyl)-2,2‘:6‘,2‘ ‘-terpyridine Ligands

A series of new tridentate polypyridine ligands, made of terpyridine chelating subunits connected to various substituted 2-pyrimidinyl groups, and their homoleptic and heteroleptic Ru(II) complexes have been prepared and characterized. The new metal complexes have general formulas [(R-pm-tpy)Ru(tpy)]2+ and [Ru(tpy-pm-R)2]2+ (tpy = 2,2':6',2' '-terpyridine; R-pm-tpy = 4'-(2-pyrimidinyl)-2,2':6',2' '-terpyridine with R = H, methyl, phenyl, perfluorophenyl, chloride, and cyanide). Two of the new metal complexes have also been characterized by X-ray analysis. In all the R-pm-tpy ligands, the pyrimidinyl and terpyridyl groups are coplanar, allowing an extended delocalization of acceptor orbital of the metal-to-ligand charge-transfer (MLCT) excited state. The absorption spectra, redox behavior, and luminescence properties of the new Ru(II) complexes have been investigated. In particular, the photophysical properties of these species are significantly better compared to those of [Ru(tpy)2]2+ and well comparable with those of the best emitters of Ru(II) polypyridine family containing tridentate ligands. Reasons for the improved photophysical properties lie at the same time in an enhanced MLCT-MC (MC = metal centered) energy gap and in a reduced difference between the minima of the excited and ground states potential energy surfaces. The enhanced MLCT-MC energy gap leads to diminished efficiency of the thermally activated pathway for the radiationless process, whereas the similarity in ground and excited-state geometries causes reduced Franck Condon factors for the direct radiationless decay from the MLCT state to the ground state of the new complexes in comparison with [Ru(tpy)2]2+ and similar species.

Alterations of the mitochondrial proteome caused by the absence of mitochondrial DNA: A proteomic view

The proper functioning of mitochondria requires that both the mitochondrial and the nuclear genome are functional. To investigate the importance of the mitochondrial genome, which encodes only 13 subunits of the respiratory complexes, the mitochondrial rRNAs and a few tRNAs, we performed a comparative study on the 143B cell line and on its Rho-0 counterpart, i.e., devoid of mitochondrial DNA. Quantitative differences were found, of course in the respiratory complexes subunits, but also in the mitochondrial translation apparatus, mainly mitochondrial ribosomal proteins, and in the ion and protein import system, i.e., including membrane proteins. Various mitochondrial metabolic processes were also altered, especially electron transfer proteins and some dehydrogenases, but quite often on a few proteins for each pathway. This study also showed variations in some hypothetical or poorly characterized proteins, suggesting a mitochondrial localization for these proteins. Examples include a stomatin-like protein and a protein sharing homologies with bacterial proteins implicated in tyrosine catabolism. Proteins involved in apoptosis control are also found modulated in Rho-0 mitochondria.

Improved mass spectrometry compatibility is afforded by ammoniacal silver staining

Sequence coverage in MS analysis of protein digestion-derived peptides is a key issue for detailed characterization of proteins or identification at low quantities. In gel-based proteomics studies, the sequence coverage greatly depends on the protein detection method. It is shown here that ammoniacal silver detection methods offer improved sequence coverage over standard silver nitrate methods, while keeping the high sensitivity of silver staining. With the development of 2D-PAGE-based proteomics, another burden is placed on the detection methods used for protein detection on 2-D-gels. Besides the classical requirements of linearity, sensitivity, and homogeneity from one protein to another, detection methods must now take into account another aspect, namely their compatibility with MS. This compatibility is evidenced by two different and complementary aspects, which are (i) the absence of adducts and artefactual modifications on the peptides obtained after protease digestion of a protein detected and digested in - gel, and (ii) the quantitative yield of peptides recovered after digestion and analyzed by the mass spectrometer. While this quantitative yield is not very important per se, it is however a crucial parameter as it strongly influences the S/N of the mass spectrum and thus the number of peptides that can be detected from a given protein input, especially at low protein amounts. This influences in turn the sequence coverage and thus the detail of the analysis provided by the mass spectrometer.

Identification of genes and proteins involved in the pleiotropic response to arsenic stress in Caenibacter arsenoxydans, a metalloresistant beta-proteobacterium with an unsequenced genome

The effect of high concentrations of arsenic has been investigated in Caenibacter arsenoxydans, a beta-proteobacterium isolated from an arsenic contaminated environment and able to oxidize arsenite to arsenate. As the genome of this bacterium has not yet been sequenced, the use of a specific proteomic approach based on nano-high performance liquid chromatography tandem mass spectrometry (nanoLC-MS/MS) studies and de novo sequencing to perform cross-species protein identifications was necessary. In addition, a random mutational analysis was performed. Twenty-two proteins and 16 genes were shown to be differentially accumulated and expressed, respectively, in cells grown in the presence of arsenite. Two genes involved in arsenite oxidation and one in arsenite efflux as well as two proteins responsible for arsenate reduction were identified. Moreover, numerous genes and proteins belonging to various functional classes including information and regulation pathways, intermediary metabolism, cell envelope and cellular processes were also up- or down-regulated, which demonstrates that bacterial response to arsenic is pleiotropic.

Diversity of the exoproteome of Fusarium graminearum grown on plant cell wall

The exoproteome of the fungus Fusarium graminearum grown on glucose and on hop (Humulus lupulus, L.) cell wall has been investigated. The culture medium was found to contain a higher quantity of proteins and the proteins are more diverse when the fungus is grown on cell wall. Using both 1D and 2D electrophoresis followed by mass spectrometry analysis and protein identification based on similarity searches, 84 unique proteins were identified in the cell wall-grown fungal exoproteome. Many are putatively implicated in carbohydrate metabolism, mainly in cell wall polysaccharide degradation. The predicted carbohydrate-active enzymes fell into 24 different enzymes classes, and up to eight different proteins within a same class are secreted. This indicates that fungal metabolism becomes oriented towards synthesis and secretion of a whole arsenal of enzymes able to digest almost the complete plant cell wall. Cellobiohydrolase is one of the only four proteins found both after growth on glucose and on plant cell wall and we propose that this enzyme could act as a sensor of the extracellular environment. Extensive knowledge of this very diverse F. graminearum exoproteome is an important step towards the full understanding of Fusarium/plants interactions.

Vanadium-dependent iodoperoxidases in Laminaria digitata, a novel biochemical function diverging from brown algal bromoperoxidases

The brown alga Laminaria digitata features a distinct vanadium-dependent iodoperoxidase (vIPO) activity, which has been purified to electrophoretic homogeneity. Steady-state analyses at pH 6.2 are reported for vIPO (K (m) (I-) = 2.5 mM; k (cat) (I-) = 462 s(-1)) and for the previously characterised vanadium-dependent bromoperoxidase in L. digitata (K (m) (I-) =18.1 mM; k (cat) (I-) = 38 s(-1)). Although the vIPO enzyme specifically oxidises iodide, competition experiments with halides indicate that bromide is a competitive inhibitor with respect to the fixation of iodide. A full-length complementary ANA (cDNA) was cloned and shown to be actively transcribed in L. digitata and to encode the vIPO enzyme. Mass spectrometry analyses of tryptic digests of vIPO indicated the presence of at least two very similar proteins, in agreement with Southern analyses showing that vIPOs are encoded by a multigenic family in L. digitata. Phylogenetic analyses indicated that vIPO shares a close common ancestor with brown algal vanadium-dependent bromoperoxidases. Based on a three-dimensional structure model of the vIPO active site and on comparisons with those of other vanadium-dependent haloperoxidases, we propose a hypothesis to explain the evolution of strict specificity for iodide in L. digitata vIPO.

Proteomic analysis identifies novel proteins of the Maurer's clefts, a secretory compartment delivering Plasmodium falciparum proteins to the surface of its host cell

A novel method was validated for the efficient distinction between malaria parasite-derived and host cell proteins in mass spectrometry analyses. This method was applied to a ghost fraction from Plasmodium falciparum-infected erythrocytes containing the red blood cell plasma membrane, the erythrocyte submembrane skeleton, and the Maurer's clefts, a Golgi-like apparatus linked to and addressing parasite proteins to the host cell surface. This method allowed the identification of 78 parasite proteins. Among these we identified seven novel proteins of the Maurer's clefts based on immunofluorescence studies and proteinase K digestion assays. The products of six contiguous genes located on chromosome 5 were identified, and the location within the Maurer's clefts was established for two of them. This suggests a clustering of genes encoding Maurer's cleft proteins. Our study sheds new light on the biological function of the Maurer's clefts, which are central to the pathogenesis and to the intraerythrocytic development of P. falciparum.

About the mechanism of interference of silver staining with peptide mass spectrometry

The mechanism by which silver staining of proteins in polyacrylamide gels interferes with mass spectrometry of peptides produced by proteolysis has been investigated. It was demonstrated that this interference increases with time between silver staining and gel processing, although the silver image is constant. This suggested an important role of the formaldehyde used in silver staining development in this interference process. Consequently, a formaldehyde-free staining protocol has been devised, using carbohydrazide as the developing agent. This protocol showed much increased peptide coverage and retained the sensitivity of silver staining. These results were however obtained at the expense of an increased background in the stained gels and of a reduced staining homogeneity.

About thiol derivatization and resolution of basic proteins in two-dimensional electrophoresis

The influence of thiol blocking on the resolution of basic proteins by two-dimensional electrophoresis was investigated. Cysteine blocking greatly increased resolution and decreased streaking, especially in the basic region of the gels. Two strategies for cysteine blocking were found to be efficient: classical alkylation with maleimide derivatives and mixed disulfide exchange with an excess of a low molecular weight disulfide. The effect on resolution was significant enough to allow correct resolution of basic proteins with in-gel rehydration on wide gradients (e.g. 3-10 and 4-12), but anodic cup-loading was still required for basic gradients (e.g. 6-12 or 8-12). These results demonstrate that thiol-related problems are not solely responsible for streaking of basic proteins on two-dimensional gels.

Carcinogenic properties of proteins with pro-inflammatory activity from Streptococcus infantarius (formerly S.bovis)

Several studies reported linkage between bacterial infections and carcinogenesis. Streptococcus bovis was traditionally considered as a lower grade pathogen frequently involved in bacteremia and endocarditis. This bacterium became important in human health as it was shown that 25-80% of patients who presented a S.bovis bacteremia had also a colorectal tumor. Moreover, in previous experiments, we demonstrated that S.bovis or S.bovis wall extracted antigens (WEA) were able to promote carcinogenesis in rats. The aim of the present study was: (i) to identify the S.bovis proteins responsible for in vitro pro-inflammatory properties; (ii) to purify them; (iii) to examine their ability to stimulate in vitro IL-8 and COX-2 expression by human colon cancer cells; and (iv) to assess in vivo their pro-carcinogenic potential in a rat model of colon carcinogenesis. The purified S300 fraction, as determined by proteomic analysis, contained 72 protein spots in two-dimensional gel electrophoresis representing 12 different proteins able to trigger human epithelial colonic Caco-2 cells and rat colonic mucosa to release CXC chemokines (human IL-8 or rat CINC/GRO) and prostaglandins E2, correlated with an in vitro over-expression of COX-2. Moreover, these proteins were highly effective in the promotion of pre-neoplastic lesions in azoxymethane-treated rats. In the presence of these proteins, Caco-2 cells exhibited enhanced phosphorylation of the three classes of MAP kinases. Our results show a relationship between the pro-inflammatory potential of S.bovis proteins and their pro-carcinogenic properties, confirming the linkage between inflammation and colon carcinogenesis. These data support the hypothesis that colonic bacteria can contribute to cancer development particularly in chronic infection/inflammation diseases where bacterial components may interfere with cell function.

Regeneration of peroxiredoxins during recovery after oxidative stress: only some overoxidized peroxiredoxins can be reduced during recovery after oxidative stress

Peroxiredoxins (prx) are redox enzymes using an activated cysteine as their active site. This activated cysteine can be easily overoxidized to cysteine sulfinic acid or cysteine sulfonic acid, especially under oxidative stress conditions. The regeneration of peroxiredoxins after a short, intense oxidative stress was studied, using a proteomics approach. Important differences in regeneration speed were found, prx2 being the fastest regenerated protein, followed by prx1, whereas prx3 and prx6 were regenerated very slowly. Further study of the mechanism of this regeneration by pulse-chase experiments using stable isotope labeling and cycloheximide demonstrated that the fast-regenerating peroxiredoxins are regenerated at least in part by a retroreduction mechanism. This demonstrates that the overoxidation can be reversible under certain conditions. The pathway of this retroreduction and the reasons explaining the various regeneration speeds of the peroxiredoxins remain to be elucidated.