Thiol Peroxidase Research Articles

Tsa1 is the dominant peroxide scavenger and a source of H2O2-dependent GSSG production in yeast

Hydrogen peroxide (H2O2) is an important biological molecule, functioning both as a second messenger in cell signaling and, especially at higher concentrations, as a cause of cell damage. Cells harbor multiple enzymes that have peroxide reducing activity in vitro. However, the contribution of each of these enzymes towards peroxide scavenging in vivo is less clear. Therefore, to directly investigate in vivo peroxide scavenging, we used the genetically encoded peroxide sensors, roGFP2-Tsa2ΔCR and HyPer7, to systematically screen the peroxide scavenging capacity of baker’s yeast thiol and heme peroxidase mutants. We show that the 2-Cys peroxiredoxin Tsa1 alone is responsible for almost all exogenous H2O2 and tert-butyl hydroperoxide scavenging. Furthermore, Tsa1 can become an important source of H2O2-dependent cytosolic glutathione disulfide production. The two catalases and cytochrome c peroxidase only produce observable scavenging defects at higher H2O2 concentrations when these three heme peroxidases are deleted in combination. We also analyzed the reduction of Tsa1 in vitro, revealing that the enzyme is efficiently reduced by thioredoxin-1 with a rate constant of 2.8×106 M–1s–1 but not by glutaredoxin-2. Tsa1 reduction by reduced glutathione occurs nonenzymatically with a rate constant of 2.9 M–1s–1. Hence, the observed Tsa1-dependent glutathione disulfide production in yeast probably requires the oxidation of thioredoxins. Our findings clarify the importance of the various thiol and heme peroxidases for peroxide removal and suggest that most thiol peroxidases have alternative or specialized functions in specific subcellular compartments.

Benzoimidazolyl Organoseleniums: Antioxidant Activity and Catalysts for Selective Iodination of Arenes and Nitro-Michael Reaction.

Here, the synthesis and catalytic activities of benzoimidazole-derived organoselenium compounds have been explored. The synthesized bis(2-benzoimidazolyl) diselenide, having increased Lewis acidity on the selenium center, outperforms simple phenyl and N-phenyl benzamide-based diselenides when compared for thiol peroxidase hydrogen peroxide decomposing antioxidant activity with a reduction rate of 18.6 ± 1.9 μM/s. The synthesized diselenide also acted as an efficient catalyst for the activation of N-iodo-succinimide toward the regioselective, monoiodination of electron-rich arenes and activation of nitro-alkene for nitro-Michael reactions for the first time.

Identification of the organic peroxide scavenging system of Yersinia pseudotuberculosis and its regulation by OxyR.

Oxidative stress caused by reactive oxygen species (ROS) is inevitable for all aerobic microorganisms as ROS are the byproducts of aerobic respiration. For gut pathogens, ROS are an integrated part of colonization resistance which protects the host against bacteria invasion. Alkyl hydroperoxide reductase (AhpR) and organic hydroperoxide resistance (Ohr) proteins are considered as the main enzymes responsible for the degradation of organic peroxides (OPs) in most bacteria. To elucidate how enteric pathogen Yersinia pseudotuberculosis YPIII deals with oxidative stress induced by OPs, we performed transcriptomic analysis and identified the OP scavenging system, which is composed of glutathione peroxidase (Gpx), thiol peroxidase (Tpx), and AhpR. Gpx serves as the main scavenger of OPs, and Tpx assists in the degradation of OPs. Transcriptional factor OxyR regulates Gpx expression, suggesting that OxyR is the regulator mediating the cellular response to OPs. Although AhpR has little influence on OP degradation, its deletion would greatly impair the scavenging ability of OPs in the absence of gpx or tpx. In addition, we found that catalase KatG and KatE are responsive to OPs but do not participate in the removal of OPs.IMPORTANCEIn bacteria, oxidative stress caused by ROS is a continuously occurring cellular response and requires multiple genes to participate in this process. The elimination of OPs is mainly dependent on AhpR and Ohr protein. Here, we carried out transcriptomic analysis to search for enzymes responsible for the removal of organic peroxides in Yersinia pseudotuberculosis. We found that Gpx was the primary OP scavenger in bacteria, which was positively regulated by the oxidative stress regulator OxyR. The OP scavenging system in Y. pseudotuberculosis was composedof Gpx, Tpx, and AhpR. OxyR is the critical global regulator mediating gene expression involved in OPs and H2O2 stress. These findings suggest that Y. pseudotuberculosis has a unique defense system in response to oxidative stress.

P-101 Mitochondria-mediated apoptosis induced testicular dysfunction in bisphenol F treated rats: ameliorative effect of baicalin

Abstract Study question Will baicalin treatment ameliorate bisphenol F (BPF)-induced testicular dysfunction? Summary answer Baicalin ameliorates BPF-induced mitochondrial dysfunction-associated apoptosis What is known already BPF is a chemical presently considered a major replacement for bisphenol A and has been widely used in the canning and other food processing industries. However, a major limitation of this chemical is its gonadotoxic effect. Studies have shown that BPF disrupts testicular function via apoptotic signaling, although, its mechanism of action has not been fully explored. On the other hand, baicalin is an anti-apoptotic agent. Yet, none of these studies has reported the effect of baicalin on BPF-induced testicular injury Study design, size, duration This is a prospective experimental study using an animal model. Twenty-four sexually matured male Wistar rats of comparable weight were used for this study. All treatments were via oral gavage and lasted for 8 weeks Participants/materials, setting, methods Animals were acclimatized for two weeks, then randomized into 4 groups (n = 6); control: animals received 0.5 mL of corn oil as vehicle, BPF: animals received 30 mg/kg of BPF, baicalin: animals treated with 100 mg/kg of baicalin, BPF+ baicalin: animals treated with 30 mg/kg BPF and 100 mg/kg baicalin Main results and the role of chance : Baicalin ameliorated BPF-induced decrease in spermatogenic indices and sperm quality, circulatory levels of follicle-stimulating hormone, luteinizing hormone, and testosterone, and testicular concentrations of 3β-HSD and 17β-HSD. Also, baicalin ameliorated BPF-induced decline in testicular superoxide dismutase, catalase, total thiol, glutathione, glutathione S-transferase, and glutathione peroxidase activities and nuclear factor erythroid 2-related factor 2 concentrations. Furthermore, baicalin alleviated BPF-induced increase in testicular malondialdehyde, myeloperoxidase, TNF-α, IL-6, and NF-kB levels. These events were associated with the dampening of BPF-induced decline in NAD+/NADH and Bcl-2 activities and BPF-induced increase in Bax and caspase 3 activities by baicalin. Limitations, reasons for caution This study was conducted in a rat model; therefore the results of the present study should be extrapolated to humans with caution Wider implications of the findings The present study described the ameliorative effect of baicalin treatment on BPF-induced testicular toxicity. Trial registration number N/A

Calcium Hexacyanoferrate Nanozyme Enhances Plant Stress Resistance by Oxidative Stress Alleviation and Heavy Metal Removal.

Oxidative damage, exacerbated by the excessive accumulation of reactive oxygen species (ROS), profoundly inhibits both crop growth and yield. Herein, a biocompatible nanozyme, calcium hexacyanoferrate nanoparticles (CaHCF NPs), targeting ROS is developed, to mitigate oxidative damage and sequestrate heavy metal ions during plant growth. Uniquely, CaHCF NPs feature multifaced enzyme-like activities, involving superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), glutathione peroxidase, thiol peroxidase, and ascorbate peroxidase, which enable them to neutralize excessive ROS. Furthermore, CaHCF NPs promote calcium-cadmium exchange process, diminishing the uptake of heavy metals. Importantly, 120µgmL-1 of CaHCF NPs alleviate the inhibitory effects of hydrogen peroxide and cadmium chloride on Arabidopsis and tomato.The activities of SOD, POD, and CAT increase by 46.2%, 74.4%, and 48.3%, respectively, meanwhile the glutathione level rises by 72.4% in Arabidopsis under cadmium stress. Moreover, CaHCF NPs boost the expression of genes associated with antioxidation, heavy metal detoxification, nutrient transport, and stress resistance. These findings unveil the significant potential of nanoplatforms equipped with nanozymes in alleviating oxidative stress in plants, which not only regulate crop growth but also substantially ameliorate yield and quality, heralding a new era in agricultural nanotechnology.

Dual-Site Biomimetic Cu/Zn-MOF for Atopic Dermatitis Catalytic Therapy via Suppressing FcγR-Mediated Phagocytosis.

Atopic dermatitis (AD) is a prevalent chronic inflammatory skin disease that carries a significant global economic burden. Elevated levels of reactive oxygen species (ROS) have been recognized as contributing to AD exacerbation, making them a potential therapeutic target for AD treatment. Here, we introduce a dual-site biomimetic copper/zinc metal-organic framework (Cu/Zn-MOF) featuring four types of enzyme-like activities for AD treatment via suppressing the Fcγ receptor (FcγR)-mediated phagocytosis signal by mimicking the bimetallic sites of natural copper-zinc superoxide dismutase (CuZn-SOD). Interestingly, the neighboring Cu and Zn sites in both Cu/Zn-MOF and CuZn-SOD are at similar distances of ∼5.98 and ∼6.3 Å from each other, respectively, and additionally, both Cu and Zn sites are coordinated to nitrogen atoms in both structures, and the coordinating ligands to Cu and Zn are both imidazole rings. Cu/Zn-MOF exhibits remarkable SOD-like activity as well as its glutathione peroxidase (GPx)-, thiol peroxidase (TPx)-, and ascorbate peroxidase (APx)-like activities to continuously consume ROS and mitigate oxidative stress in keratinocytes. Animal experiments show that Cu/Zn-MOF outperforms halcinonide solution (a potent steroid medication) in terms of preventing mechanical injuries, reducing cutaneous water loss, and inhibiting inflammatory responses while presenting favorable biosafety. Mechanistically, Cu/Zn-MOF functions through an FcγR-mediated phagocytosis signal pathway, decreasing the continuous accumulation of ROS in AD and ultimately suppressing disease progression. These findings will provide an effective paradigm for AD therapy and contribute to the development of two-site bionics (TSB).

Vanadium Carbide MXenzyme Harnessing Photothermal Effects for Targeted Lung Tumor Suppression and Inflammation Eradication

AbstractPhotothermal therapy (PTT) is increasingly favored as a treatment option for lung cancer, a leading cause of cancer‐related death. However, the effectiveness of PTT is hampered by both tumor‐associated and treatment‐related inflammatory reactions. Consequently, there is a pressing need for innovative PTT‐based platforms capable of mitigating inflammation postcancer treatment. Herein, 2D vanadium carbide (V2C) MXenzyme nanosheets via a straightforward exfoliation and intercalation process are successfully synthesized. The V2C MXenzyme demonstrates a robust photothermal effect, which varied with concentration, density, and irradiation duration when exposed to 808 nm near‐infrared light. Notably, V2C MXenzyme exhibits the ability to eliminate A549 lung cancer cells both in vitro and in vivo through PTT. Additionally, the synthesized V2C MXenzyme nanosheets exhibited various enzyme‐like activities, resembling reactive oxygen species–mimetic enzymes, including superoxide dismutase, catalase, peroxidase, glutathione peroxidase, and thiol peroxidase. V2C MXenzyme significantly curtailed inflammation in both in vitro and in vivo settings. Furthermore, gene sequencing analysis of inflammation‐related genes responding to V2C MXenzyme nanosheets is performed and identified HSPA1A as a significantly differentially expressed gene. HSPA1A expression correlated with the infiltration of various immune cells in lung adenocarcinoma. Thus, V2C MXenzyme may serve as a revalorization platform to suppress lung tumors and reduce inflammation.

Protective effects of hesperidin in gastric damage caused by experimental ischemia-reperfusion injury model in rats.

This study evaluated the protective effect of hesperidin on injury induced by gastric ischemia-reperfusion. Fifty male Sprague Dawley rats (250-300g) were divided into five groups: control (C), sham (S), ischemia (I), ischemia-reperfusion (I/R) and hesperidin + ischemia-reperfusion (Hes + I/R). Hesperidin was injected intraperitoneally at the dose of 100mg/kg one hour before the experimental stomach ischemia-reperfusion. Celiac artery was ligated. After 45minutes ischemia and 60minutes reperfusion period, blood samples were obtained under anesthesia. Then, animals were sacrificed, stomach tissues were excised for biochemical, and histopathological analyses were performed. Malondialdehyde levels and superoxide dismutase, glutathione peroxidase activities and total antioxidant status (TAS), total oxidant status (TOS), protein, total thiol parameters were measured in plasma, and tissue homogenate samples. H + E, periodic acid-Schiff, hypoxia inducible factor, terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end-labeling (TUNEL), and proliferating cell nuclear antigen (PCNA) for cell proliferation as immunohistochemical parameters were determined. Upon biochemical and histopathological assessment, hesperidin decreased stomach tissue changes in comparison with IR group. Ischemia-reperfusion injury led to a considerably increase in malondialdehyde, protein, and TOS levels (p < 0.001) in stomach tissue. Hesperidin treatment significantly decreased malondialdehyde, protein, and TOS levels (p < 0.001). Hesperidin increased superoxide dismutase, TAS, total thiol and glutathione peroxidase activities in comparison with IR group. Hesperidin reduced damage and also increased TUNEL and PCNA immunoreactivity in stomach tissue. Hesperidin was able to decrease I/R injury of the stomach tissue due to inhibition of lipid peroxidation and protein oxidation, duration of antioxidant, and free radical scavenger properties. Consequently, hesperidin can provide a beneficial therapeutic choice for preventing stomach tissue ischemia-reperfusion injury in clinical application.

Zingerone Alleviates Morphine Tolerance and Dependence in Mice by Reducing Oxidative Stress-Mediated NLRP3 Inflammasome Activation.

Morphine (MPH) is widely used for pain management; however, long-term MPH therapy results in antinociceptive tolerance and physical dependence, limiting its clinical use. Zingerone (ZIN) is a natural phenolic compound with neuroprotective effects. We investigated the effects of single and repeated doses of ZIN on MPH-induced tolerance, dependence, and underlying biochemical mechanisms. After a dose-response experiment, tolerance was developed to MPH (10mg/kg, i.p.) for seven days. In the single-dose study, ZIN was administered on day seven. In the repeated-dose study, ZIN was administered for seven days. Naloxone (5mg/kg, i.p., 120min after MPH) was injected to assess withdrawal signs on day seven. The levels of thiobarbituric acid reactive substances (TBARS), nitric oxide (NO), total thiol (TT), and glutathione peroxidase (GPx) were measured in the prefrontal cortex. The protein levels of interleukin-1 beta (IL-1β) and NLRP3-ASC-Caspase-1 axis were assessed by ELISA and Western blotting, respectively. Results showed that ZIN (100mg/kg) had no antinociceptive activity, and subsequent experiments were performed at this dose. Repeated ZIN reversed MPH antinociceptive tolerance, whereas single ZIN did not. Single and repeated ZIN attenuated naloxone-induced jumping. In addition, repeated ZIN significantly inhibited weight loss. Repeated ZIN suppressed the MPH-induced increase in TBARS, NO, IL-1β, NLRP3, ASC, and Caspase-1. It also inhibited MPH-induced TT and GPx reduction. In contrast, single ZIN had no effect. Findings suggest that ZIN reduces MPH-induced tolerance and dependence by suppressing oxidative stress and NLRP3 inflammasome activation. This study provides a novel therapeutic approach to reduce the side effects of MPH.

From biomolecules to biogeochemistry: Exploring the interaction of an indigenous bacterium with gold

Specialised microbial communities colonise the surface of gold particles in soils/sediments, and catalyse gold dissolution and re-precipitation, thereby contributing to the environmental mobility and toxicity of this ‘inert’ precious metal. We assessed the proteomic and physiological response of Serratia proteamaculans, the first metabolically active bacterium enriched and isolated directly from natural gold particles, when exposed to toxic levels of soluble Au3+ (10 μM). The results were compared to a metal-free blank, and to cultures exposed to similarly toxic levels of soluble Cu2+ (0.1 mM); Cu was chosen for comparison because it is closely associated with Au in nature due to similar geochemical properties. A total of 273 proteins were detected from the cells that experienced the oxidative effects of soluble Au, of which 139 (51%) were upregulated with either sole expression (31%) or had synthesis levels greater than the Au-free control (20%). The majority (54%) of upregulated proteins were functionally different from up-regulated proteins in the bacteria-copper treatment. These proteins were related to broad functions involving metabolism and biogenesis, followed by cellular process and signalling, indicating significant specificity for Au. This proteomic study revealed that the bacterium upregulates the synthesis of various proteins related to oxidative stress response (e.g., Monothiol-Glutaredoxin, Thiol Peroxidase, etc.) and cellular damage repair, which leads to the formation of metallic gold nanoparticles less toxic than ionic gold. Therefore, indigenous bacteria may mediate the toxicity of Au through two different yet simultaneous processes: i) repairing cellular components by replenishing damaged proteins and ii) neutralising reactive oxygen species (ROS) by up-regulating the synthesis of antioxidants. By connecting the fields of molecular bacteriology and environmental biogeochemistry, this study is the first step towards the development of biotechnologies based on indigenous bacteria applied to gold bio-recovery and bioremediation of contaminated environments.

Regeneration of cytosolic thiol peroxidases.

Three soluble type two peroxiredoxins (PRXIIB, C, D) and two glutathione peroxidase-like enzymes (GPXL2, 8) reside in the cytosol of Arabidopsis thaliana cells and function both as thiol-dependent antioxidants and redox sensors. Their primary substrate is H2 O2 , but they also accept other peroxides with a distinct preference between PRXII and GPXL. Less known is their regeneration specificity in the light of the large set of thiol reductases, namely eight annotated thioredoxin h isoforms (TRXh1-5, 7-9), a few TRX-like proteins, including CxxS1 (formerly TRXh6) and several glutaredoxins (GRX) associated with the cytosol. This study addressed this open question by in vitro enzyme tests using recombinant protein. GPXL2 and 8 exclusively accepted electrons from the TRX system, namely TRXh1-5 and TDX, while PRXIIB/C/D were efficiently regenerated with GRXC1 and C2 but not the TRX-like protein Picot1. They showed significant but low activity (<3% of GRXC2) with TRXh1-5 and TDX. A similar reduction efficiency with TRX was seen in the insulin assay, only TDX was less active. Finally, the reduction of oxidized cytosolic malate dehydrogenase 1, as measured by regained activity, showed an extremely broad ability to accept electrons from different TRXs and GRXs. The results demonstrate redundancy and specificity in the redox regulatory network of the cytosol.

Polystyrene microplastics biodegradation by gut bacterial Enterobacter hormaechei from mealworms under anaerobic conditions: Anaerobic oxidation and depolymerization

Synthetic plastic is used throughout daily life and industry, threatening organisms with microplastic pollution. Polystyrene is a major plastic polymer and also widely found sources of plastic wastes and microplastics. Here, we report that Enterobacter hormaechei LG3 (CP118279.1), a facultative anaerobic bacterial strain isolated from the gut of Tenebrio molitor larvae (mealworms) can oxidize and depolymerize polystyrene under anaerobic conditions. LG3 performed biodegradation while forming a biofilm on the plastic surface. PS biodegradation was characterized by analyses of surface oxidation, change in morphology and molecular weights, and production of biodegraded derivative. The biodegradation performance by LG3 was compared with PS biodegradation by Bacillus amyloliquefaciens SCGB1 under both anaerobic and aerobic conditions. In addition, through nanopore sequencing technology, we identified degradative enzymes, including thiol peroxidase (tpx), alkyl hydroperoxide reductase C (ahpC) and bacterioferritin comigratory protein (bcp). Along with the upregulation of degradative enzymes for biodegradation, changes in lipid A and biofilm-associated proteins were also observed after the cells were incubated with polystyrene microplastics. Our results provide evidence for anaerobic biodegradation by polystyrene-degrading bacteria and show alterations in gene expression patterns after polystyrene microplastics treatment in the opportunistic pathogen Enterobacter hormaechei.

Absence of proline-peptide transporter YjiY in Salmonella Typhimurium leads to secretion of factors which inhibits intra-species biofilm formation

Salmonella is a genus of widely spread Gram negative, facultative anaerobic bacteria, which is known to cause ¼th of diarrheal morbidity and mortality globally. It causes typhoid fever and gastroenteritis by gaining access to the host gut through contaminated food and water. Salmonella utilizes its biofilm lifestyle to strongly resist antibiotics and persist in the host. Although biofilm removal or dispersal has been studied widely, the inhibition of the initiation of Salmonella Typhimurium (STM WT) biofilm remains elusive. This study demonstrates the anti-biofilm property of the cell-free supernatant obtained from a carbon-starvation induced proline peptide transporter mutant (STM ΔyjiY) strain. The STM ΔyjiY culture supernatant primarily inhibits biofilm initiation by regulating biofilm-associated transcriptional network that is reversed upon complementation (STM ΔyjiY:yjiY). We demonstrate that abundance of FlgM correlates with the absence of flagella in the STM ΔyjiY supernatant treated WT cells. NusG works synergistically with the global transcriptional regulator H-NS. Relatively low abundances of flavoredoxin, glutaredoxin, and thiol peroxidase might lead to accumulation of ROS within the biofilm, and subsequent toxicity in STM ΔyjiY supernatant. This work further suggests that targeting these oxidative stress relieving proteins might be a good choice to reduce Salmonella biofilm.

Glutathione-Related Enzymes and Proteins: A Review.

The tripeptide glutathione is found in all eukaryotic cells, and due to the compartmentalization of biochemical processes, its synthesis takes place exclusively in the cytosol. At the same time, its functions depend on its transport to/from organelles and interorgan transport, in which the liver plays a central role. Glutathione is determined as a marker of the redox state in many diseases, aging processes, and cell death resulting from its properties and reactivity. It also uses other enzymes and proteins, which enables it to engage and regulate various cell functions. This paper approximates the role of these systems in redox and detoxification reactions such as conjugation reactions of glutathione-S-transferases, glyoxylases, reduction of peroxides through thiol peroxidases (glutathione peroxidases, peroxiredoxins) and thiol-disulfide exchange reactions catalyzed by glutaredoxins.

Plant thiol peroxidases as redox sensors and signal transducers in abiotic stress acclimation.

The temporal and spatial patterns of reactive oxygen species (ROS) in cells and tissues decisively determine the plant acclimation response to diverse abiotic and biotic stresses. Recent progress in developing dynamic cell imaging probes provides kinetic information on changes in parameters like H2O2, glutathione (GSH/GSSG) and NAD(P)H/NAD(P)+, that play a crucial role in tuning the cellular redox state. Central to redox-based regulation is the thiol-redox regulatory network of the cell that integrates reductive information from metabolism and oxidative ROS signals. Sensitive proteomics allow for monitoring changes in redox-related posttranslational modifications. Thiol peroxidases act as sensitive peroxide and redox sensors and play a central role in this signal transduction process. Peroxiredoxins (PRX) and glutathione peroxidases (GPX) are the two main thiol peroxidases and their function in ROS sensing and redox signaling in plants is emerging at present and summarized in this review. Depending on their redox state, PRXs and GPXs act as redox-dependent binding partners, direct oxidants of target proteins and oxidants of thiol redox transmitters that in turn oxidize target proteins. With their versatile functions, the multiple isoforms of plant thiol peroxidases play a central role in plant stress acclimation, e.g. to high light or osmotic stress, but also in ROS-mediated immunity and development.

The cytosolic thiol peroxidase PRXIIB is an intracellular sensor for H2O2 that regulates plant immunity through a redox relay.

Rapid production of H2O2 is a hallmark of plant responses to diverse pathogens and plays a crucial role in signalling downstream of various receptors that perceive immunogenic patterns. However, mechanisms by which plants sense H2O2 to regulate immunity remain poorly understood. We show that endogenous H2O2 generated upon immune activation is sensed by the thiol peroxidase PRXIIB via oxidation at Cys51, and this is essential for stomatal immunity against Pseudomonas syringae. We further show that in immune-stimulated cells, PRXIIB conjugates via Cys51 with the type 2C protein phosphatase ABA insensitive 2 (ABI2), subsequently transducing H2O2 signal to ABI2. This oxidation dramatically sensitizes H2O2-mediated inhibition of the ABI2 phosphatase activity in vitro and is required for stomatal immunity in plants. Together, our results illustrate a redox relay, with PRXIIB as a sensor for H2O2 and ABI2 as a target protein, that mediates reactive oxygen species signalling during plant immunity.

Co-metabolic biodegradation of structurally discrepant dyestuffs by Klebsiella sp. KL-1: A molecular mechanism with regards to the differential responsiveness.

In this study, an attempt was made to decipher the underlying differential response mechanism of Klebsiella sp. KL-1 induced by exposure to disparate categories of dyestuffs in xylose (Xyl) co-metabolic system. Here, representative reactive black 5 (RB5), remazol brilliant blue R (RBBR) and malachite green (MG) belonging to the azo, anthraquinone and triphenylmethane categories were employed as three model dyestuffs. Klebsiella sp. KL-1 enabled nearly 98%, 80% or 97% removal of contaminants in assays Xyl+RB5, Xyl+RBBR or Xyl+MG after 48h, which was respectively 16%, 11% or 22% higher than those in the assays devoid of xylose. LC-QTOF-MS revealed an increased formation of smaller molecular weight intermediates in assay Xyl+RB5, whereas more metabolic pathways were deduced in assay Xyl+RBBR. Metaproteomics analysis displayed remarkable proteome alteration with regards to the structural difference effect of dyestuffs by Klebsiella sp. KL-1. Significant (p-value<0.05) activation of pivotal candidate NADH-quinone oxidoreductase occurred after 48h of disparate dyestuff exposure but with varying abundance. Dominant FMN-dependent NADH-azoreductase, Cytochrome d terminal oxidase or Thiol peroxidase were likewise deemed to be responsible for the catalytic cleavage of RB5, RBBR or MG, respectively. Further, the differential response mechanism towards the structurally discrepant dyestuffs was put forward. Elevated reducing force associated with the corresponding functional proteins/enzymes was transferred to the exterior of the cell to differentially decompose the target contaminants. Overall, this study was dedicated to provide in-depth insights into the molecular response mechanism of co-metabolic degradation of refractory and structurally discrepant dyestuffs by an indigenous isolated Klebsiella strain.

Sulfane Sulfur Is an Intrinsic Signal for the Organic Peroxide Sensor OhrR of Pseudomonas aeruginosa.

Sulfane sulfur, including organic persulfide and polysulfide, is a normal cellular component, and its level varies during growth. It is emerging as a signaling molecule in bacteria, regulating the gene regulator MarR in Escherichia coli, MexR in Pseudomonas aeruginosa, and MgrA of Staphylococcus aureus. They are MarR-family regulators and are often repressors for multiple antibiotic resistance genes. Here, we report that another MarR-type regulator OhrR that represses the expression of itself and a thiol peroxidase gene ohr in P. aeruginosa PAO1 also responded to sulfane sulfur. PaOhrR formed disulfide bonds between three Cys residues within a dimer after polysulfide treatment. The modification reduced its affinity to its cognate DNA binding site. An Escherichia coli reporter system, in which mKate was under the repression of OhrR, showed that PaOhrR derepressed its controlled gene when polysulfide was added, whereas the mutant PaOhrR with two Cys residues changed to Ser residues did not respond to polysulfide. The expression of the PaOhrR-repressed mKate was significantly increased when the cells enter the late log phase when cellular sulfane sulfur reached a maximum, but the mKate expression under the control of the PaOhrR-C9SC19S double mutant was not increased. Furthermore, the expression levels of ohrR and ohr in P. aeruginosa PAO1 were significantly increased when cellular sulfane sulfur was high. Thus, PaOhrR senses both exogenous and intrinsic sulfane sulfur to derepress its controlled genes. The finding also suggests that sulfane sulfur may be a common inducer of the MarR-type regulators, which may confer the bacteria to resist certain stresses without being exposed to the stresses.

Thiol peroxidases in plant redox sensing and metabolic tuning

Thiol peroxidases in plant redox sensing and metabolic tuning

Mitochondrial Peroxiredoxin-IIF (PRXIIF) Activity and Function during Seed Aging.

Mitochondria play a major role in energy metabolism, particularly in cell respiration, cellular metabolism, and signal transduction, and are also involved in other processes, such as cell signaling, cell cycle control, cell growth, differentiation and apoptosis. Programmed cell death is associated with the production of reactive oxygen species (ROS) and a concomitant decrease in antioxidant capacity, which, in turn, determines the aging of living organisms and organs and thus also seeds. During the aging process, cell redox homeostasis is disrupted, and these changes decrease the viability of stored seeds. Mitochondrial peroxiredoxin-IIF (PRXIIF), a thiol peroxidase, has a significant role in protecting the cell and sensing oxidative stress that occurs during the disturbance of redox homeostasis. Thioredoxins (TRXs), which function as redox transmitters and switch protein function in mitochondria, can regulate respiratory metabolism. TRXs serve as electron donors to PRXIIF, as shown in Arabidopsis. In contrast, sulfiredoxin (SRX) can regenerate mitochondrial PRXIIF once hyperoxidized to sulfinic acid. To protect against oxidative stress, another type of thiol peroxidases, glutathione peroxidase-like protein (GPXL), is important and receives electrons from the TRX system. They remove peroxides produced in the mitochondrial matrix. However, the TRX/PRX and TRX/GPXL systems are not well understood in mitochondria. Knowledge of both systems is important because these systems play an important role in stress sensing, response and acclimation, including redox imbalance and generation of ROS and reactive nitrogen species (RNS). The TRX/PRX and TRX/GPXL systems are important for maintaining cellular ROS homeostasis and maintaining redox homeostasis under stress conditions. This minireview focuses on the functions of PRXIIF discovered in plant cells approximately 20 years ago and addresses the question of how PRXIIF affects seed viability maintenance and aging. Increasing evidence suggests that the mitochondrial PRXIIF plays a major role in metabolic processes in seeds, which was not previously known.