Peroxidase System Research Articles

Biochemical Analysis and Toxicity Assessment of Utilization of Argon Oxygen Decarbonization Slag as a Mineral Fertilizer for Tall Fescue (Festuca arundinacea Schreb) Planting

Argon oxygen decarbonization (AOD) slag refers to a byproduct of stainless steel (SS) production, which has caused considerable environmental stress. Finding an effective approach for recycling AOD slag is essential to environmental safety. In this work, batch leaching tests were carried out to explore the leaching behavior of AOD slag and soil. Pot experiments was conducted to analyze the fertilization effect of AOD slag for tall fescue (Festuca arundinacea Schreb) planting. The plant height, biomass, total root length (TRL), root surface area (RSA), root tips (RT), root hairs (RH)), chlorophyll content, malondialdehyde (MDA) content, and antioxidant enzyme activities of the tall fescue seedlings were measured. As indicated from the results, adding AOD slag into soil increased soil pH. The leaching concentration of Ca, Si, Al, Cr of the AOD slag was higher than the original soil, while that of Mg, Mn, and Fe was lower. Low addition rate (≤1%) of AOD slag fertilization was good for plant height, biomass, root growth, and chlorophyll synthesis, whereas high addition rate (≥2%) exerted an opposite effect. Elevating the rate of AOD slag fertilization increased the Cr accumulation in the tall fescue seedling that aggravated damage of reactive oxygen species (ROS). When the AOD slag fertilization was at a low rate (≤1%), ROS scavenging was attributed to the synergistic effects of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) defense systems, while at a high rate (≥2%) of AOD slag fertilization, scavenging of excessive ROS could be mainly due to the CAT defense system.

Cold Exposure Memory Reduces Pathogen Susceptibility in Arabidopsis Based on a Functional Plastid Peroxidase System.

Chloroplasts serve as cold priming hubs modulating the transcriptional response of Arabidopsis thaliana to a second cold stimulus for several days by postcold accumulation of thylakoid ascorbate peroxidases (tAPX). In an attempt to investigate cross-priming effects of cold on plant pathogen protection, we show here that such a single 24-h cold treatment at 4°C decreased the susceptibility of Arabidopsis to virulent Pseudomonas syringae pv. tomato DC3000 but did not alter resistance against the avirulent P. syringae pv. tomato avRPM1 and P. syringae pv. tomato avrRPS4 strains or the effector-deficient P. syringae pv. tomato strain hrcC-. The effect of cold priming against P. syringae pv. tomato was active immediately after cold exposure and memorized for at least 5 days. The priming benefit was established independent of the immune regulator Enhanced Disease Susceptibility 1 (EDS1) or activation of the immune-related genes NHL10, FRK1, ICS1 and PR1 but required thylakoid-bound as well as stromal ascorbate peroxidase activities because the effect was absent or weak in corresponding knock-out-lines. Suppression of tAPX postcold regulation in a conditional-inducible tAPX-RNAi line led to increased bacterial growth numbers. This highlights that the plant immune system benefits from postcold regeneration of the protective chloroplast peroxidase system.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Anti-cancer effects of high-dose selenium via lipid peroxidation in ovarian cancer.

e17547 Background: Selenium is an essential trace element and act as a regulator in the oxidation-reduction system. Selenium deficiency is observed in various cancers. Therefore, we investigated the relevance of high-dose selenium with the anticancer effect of ovarian cancer. Methods: We evaluated cytotoxicity and cell death by MTT assay and Annexin V-FITC/PI-labeled flow cytometry and biological function by invasion assay, ROS assay, immunoblotting, and FACS analysis. Using SKOV3-bearing xenograft mouse models, we evaluated the anti-cancer effect of high-dose selenium. Selenium toxicity was evaluated by the amount of ALT, AST, BUN and creatinine in the serum of C57BL/6 mice. Results: We observed that high-dose selenium, which was exposed to ovarian cancer cells, significantly increases the generation of reactive-species oxygen (ROS), leading to more significant cell death and cytotoxicity compared to low doses. We found that high-dose selenium triggers lipid peroxidation-mediated cell deaths and causes a reduction of glutathione peroxidase (GPX) systems. As a result of examining the lethal dose of selenium to the C57BL/6 nude mouse, it occurred in the concentration range of 3000 μg/Kg or more. SKOV3-bearing mouse models revealed the high-dose selenium administration (2000 μg/Kg) significantly reduced the ovarian tumor growth (p < 0.05). Moreover, we confirmed that high-dose selenium inhibited the expression of increased GPX in SKOV3-bearing mice. Conclusions: Our results suggest that high-dose selenium induces an anticancer effect through lipid peroxidation regulation according to the GPX redox system. Furthermore, we can suggest that chemotherapy based on high-dose selenium may have the effect of maximizing therapeutic efficacy and reducing anticancer drug resistance in ovarian cancer.

Synthesis of β-cyclodextrin grafted rhombohedral-CuO antioxidant nanozyme for detection of dopamine and hexavalent chromium through off–on strategy of peroxidase mimicking activity

For the last few decades, peroxidase mimicking inorganic nanoparticles are widely used as compared to natural peroxidase due to some basic advantages especially high durability, stability in harsh conditions, easy and cost-effective synthesis, and easy storage. However, most of these peroxidase mimicking nanoparticles are not always effective in a neutral medium, most of the show high activity in an acidic medium which seriously impedes their uses in bioanalytical applications. In the current study, we have developed an inorganic β-cyclodextrin (β-CD) grafted rhombohedral cupric oxide (R-CuO) nanozyme which showed high catalytic activity at neutral conditions (pH = 7) and also exhibited catalytic activity in a wide range of pH with enzymatic substrate TMB (3,3–5,5 tetramethylbenzidine).The current nanozyme has exhibited outstanding peroxidase mimic activity with low Km and very high Vmax value which was calculated by the double reciprocal Lineweaver Burk plot. Considering the R-CuO NPs as a heterogeneous catalyst, a one-pot simple colorimetric system has been developed for dopamine detection, as dopamine turns off the catalytic activity of the R-CuO NPs-TMB peroxidase system. The sensitivity of this current probe to dopamine was promising with a linear range of 2– 24 µM and had a low detection limit of 1.91 µM. More surprisingly, the R-CuO-TMB /dopamine system undergoes recovery of peroxidase activity upon introduction of Cr (+6) (dichromate).The method displays a good selectivity towards Cr (+6) (dichromate) over all the other metal ions with a wide linear relationship in the range of 2 μM–10 μM, and a low detection limit of 0.47 μM. Moreover, the present Nano system was not only applicable for toxic metal and bioactive molecules detection they also used as a ROS scavenger. Our Nano system exhibited scavenging activity for OH radical, O2–. species and metal chelation activity which was investigated calorimetrically. So, the present Nano system is used as a colorimetric probe for dopamine and Cr (+6) (dichromate) detection and consumption of reactive oxygen species as well.

Adherence to the Mediterranean Diet Has a Protective Role against Metabolic and DNA Damage Markers in Colorectal Cancer Patients.

Oxidative stress (OS) and inflammation have been related to colorectal cancer (CRC), but the influence of the Mediterranean diet (MD) on these parameters is unknown. Therefore, the aim of this study was to determine the association between adherence to the MD and markers of OS and DNA damage in CRC patients and to study the influence of adherence to the MD on metabolic and tumor-related factors. This prospective observational study included a total of 80 patients diagnosed with CRC. Adherence to the MD was estimated by the 14-item Mediterranean Diet Adherence Screener (MEDAS) questionnaire. The levels of OS markers (catalase, glutathione peroxidase, and glutathione system in serum; 8-oxo-7′8-dihydro-2′-deoxyguanosine and F2-isoprotanes in urine) and tumor and metabolic factors were determined. A total of 51.2% of our CRC patients showed a high adherence to the MD. These patients presented decreased levels of 8-oxodG, increased GPX and HDL–cholesterol levels, and a downward trend in the GSSG/GSH ratio with respect to patients with low adherence to the MD. In addition, a high adherence to the MD was associated with a lower histological grade of the tumor and a lower presence of synchronous adenomas. We conclude that a high adherence to the MD has a protective role against metabolic and oxidative DNA damage and improves antioxidant systems in CRC patients.

In-silico Screening and Identification of Novel Trypanothione Reductase Inhibitor from Leishmania

The negative effects of leishmanicidal medications are numerous, and drug resistance to all of them has been observed. As a result, new medication development and the identification of novel therapeutic targets are critical. Leishmania major trypanothione reductase (Lm-TR), a NADPH-dependent flavoprotein oxidoreductase critical for thiol metabolism, is required for parasite viability. Since it lowers trypanothione, a chemical required by Leishmania's tryparedoxin/tryparedoxin peroxidase system to neutralise hydrogen peroxide (H2O2) produced by host macrophages during infection, this enzyme is essential for parasite survival in the host.
 Because it is not found in the mammalian host, this enzyme is a promising target for novel anti-leishmania medicines. A three-dimensional model of Lm-TR was created using I-TASSER server. Virtual screening of about 5000 sigma aldrich compounds, acquired from the ZINC database, was carried out using Autodock vina tool. Top ten compounds were tabulated based on binding affinity. 
 The molecules with the ids ZINC04245710 and ZINC03869768 had the highest binding affinities of -11.4 and -11.2 kcal/mol, respectively. These compounds had the maximum binding affinity and the appropriate amount of hydrogen bonds. These molecules may be able to efficiently block the activity of the target enzyme (Lm-TR) and so serve as novel agents to combat cutaneous leishmaniasis. In search for new anti-Leishmania medications that are more effective and less cytotoxic, these molecules may provide a good starting point for a hit-to-lead procedure.

Investigation of the antioxidant activity of the peroxidase system of cell nuclei during germination of wheat embryos with different types of resistance to temperature stress

The yield of agricultural crops directly depends on their ability to adapt to a constantly changing environment, the unfavorable climatic conditions of which cause oxidative stress, accompanied by the generation of reactive oxygen species in plant cells, which can cause damage to heteropolymer cell structures, thereby leading to suppression of plant growth and a decrease in productivity grains. It has been shown that the profile of the antioxidant activity of the peroxidase system in histone and non-histone blocks of structures (nucleoplasm, chromatin) of cell nuclei during germination is more pronounced in the cold-resistant variety Mironovskaya 808 (winter) compared to Mironovskaya yarovaya (spring), which correlates with the intensity of growth processes and can be associated with participation in the realization of proliferation and differentiation programs. A direct relationship between the scavenging of ROS and plant resistance to temperature stress, which is often associated with the increased activity of antioxidant enzymes that impart stress resistance to both high and low temperature stress, apparently also exists at the level of the plant cell nucleus.

Copper fumarate with high-bifunctional nanozyme activities at different pH values for glucose and epinephrine colorimetric detection in human serum.

Metal-organic frameworks (MOFs) have attracted extensive attention for the development of colorimetric detection methods due to their ease of modification and high density of active sites. However, most of the reported colorimetric sensors based on MOFs show only a single nanozyme activity. Herein, the bifunctional enzyme activities of a hexagonal prism Cu MOF with fumaric acid as the ligand (Cu FMA), namely laccase-like activity under alkaline conditions (pH = 8) and peroxidase-like activity under acidic conditions (pH = 4), were verified. The specificity of Cu FMA at different pH values may be due to the presence of the Cu+ active center introduced by the weak reducibility of FMA. At pH = 8, Cu+ active centers are beneficial for dissociating the H-O bonds of phenolic compounds for the laccase system. In contrast, the dissociation of H-O is weakened at pH = 4, which prompts the breaking of the O-O bonds of H2O2 as a Fenton-like reaction for the peroxidase system. Based on the dual enzyme activities, Cu FMA sensors exhibit outstanding detectability for epinephrine and glucose with linear ranges of 2.7-54.6 μM and 0.01-0.8 mM and detection limits of 1.1 μM and 2.28 × 10-7 M, respectively. The Cu FMA colorimetric sensor can be applied for detecting and measuring glucose and epinephrine in human serum samples. This work paves the way for Cu MOFs to be used as the basis for rational regulation of the activity of dual nanozymes and for multifunctional applications under completely independent conditions.

Investigation of the antioxidant activity of the peroxidase system of cell nuclei during germination of wheat embryos with different types of resistance to temperature stress

The yield of agricultural crops directly depends on their ability to adapt to a constantly changing environment, the unfavorable climatic conditions of which cause oxidative stress, accompanied by the generation of reactive oxygen species in plant cells, which can cause damage to heteropolymer cell structures, thereby leading to suppression of plant growth and a decrease in productivity grains. It has been shown that the profile of the antioxidant activity of the peroxidase system in histone and non-histone blocks of structures (nucleoplasm, chromatin) of cell nuclei during germination is more pronounced in the cold-resistant variety Mironovskaya 808 (winter) compared to Mironovskaya yarovaya (spring), which correlates with the intensity of growth processes and can be associated with participation in the realization of proliferation and differentiation programs. A direct relationship between the scavenging of ROS and plant resistance to temperature stress, which is often associated with the increased activity of antioxidant enzymes that impart stress resistance to both high and low temperature stress, apparently also exists at the level of the plant cell nucleus.

Tolerance of Pseudomonas strain to the 2,4-D herbicide through a peroxidase system.

Herbicides are widely used in agricultural practices for preventing the proliferation of weeds. Upon reaching soil and water, herbicides can harm nontarget organisms, such as bacteria, which need an efficient defense mechanism to tolerate stress induced by herbicides. 2,4-Dichlorophenoxyacetic acid (2,4-D) is a herbicide that exerts increased oxidative stress among bacterial communities. Bacterial isolates were obtained from the biofilm of tanks containing washing water from the packaging of different pesticides, including 2,4-D. The Pseudomonas sp. CMA-7.3 was selected because of its tolerance against 2,4-D toxicity, among several sensitive isolates from the biofilm collection. This study aimed to evaluate the antioxidative response system of the selected strain to 2,4-D. It was analyzed the activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase GPX enzymes, that are poorly known in the literature for bacterial systems. The Pseudomonas sp. CMA-7.3 presented an efficient response system in balancing the production of hydrogen peroxide, even at 25x the dose of 2,4-D used in agriculture. The antioxidative system was composed of Fe-SOD enzymes, less common than Mn-SOD in bacteria, and through the activities of KatA and KatB isoforms, working together with APX and GPX, having their activities coordinated possibly by quorum sensing molecules. The peroxide control is poorly documented for bacteria, and this work is unprecedented for Pseudomonas and 2,4-D. Not all bacteria harbor efficient response system to herbicides, therefore they could affect the diversity and functionality of microbiome in contaminated soils, thereby impacting agricultural production, environment sustainability and human health.

Glutaredoxins and thioredoxin peroxidase involved in defense of emamectin benzoate induced oxidative stress in Grapholita molesta

Glutaredoxins (Grxs) and thioredoxin peroxidases (Tpxs) are major antioxidant enzyme families involved in regulating cellular redox homeostasis and in defense of enhanced oxidative stress through scavenging reactive oxygen species (ROS). However, the functions of these enzymes have not been reported in the oriental fruit moth, Grapholita molesta (Busck), a worldwide pest of stone and pome fruits. Here, we identified four new antioxidant genes, GmGrx, GmGrx3, GmGrx5, and GmTpx which were induced by exposure with emamectin benzoate, a commonly used biopesticide for G. molesta control. Other environmental factors (low and high temperatures, Escherichia coli and Metarhizium anisopliae) also significantly induced the expression of these genes. After GmGrx or GmTpx silenced by RNA interference (RNAi), the percentage of larval survival to emamectin benzoate were significantly decreased, demonstrating that GmGrx and GmTpx are involved in protecting G. molesta from stresses induced by emamectin benzoate. Furthermore, silenced GmGrx, GmGrx3, GmGrx5, or GmTpx significantly enhanced the enzymatic activities of superoxide dismutase (SOD) (except GmTpx) and peroxidase (POD), as well as the contents of hydrogen peroxide and metabolites ascorbate. Taken together, our results suggest that GmGrx, GmGrx3, GmGrx5, and GmTpx may play critical roles in antioxidant defense. Specially, GmGrx and GmTpx contribute to the defense of oxidative damage induced by exposure to emamectin benzoate through scavenging excessive ROS in G. molesta. Our findings provided a theoretical basis for understanding functions of insect glutaredoxin and peroxidase systems.

Spectroelectrochemical investigation of the glyoxal oxidase activation mechanism

Glyoxal oxidase (GLOX) is an extracellular source of H2O2 in white-rot secretomes, where it acts in concert with peroxidases to degrade lignin. It has been reported that GLOX requires activation prior to catalytic turnover and that a peroxidase system can fulfill this task. In this study, we verify that an oxidation product of horseradish peroxidase, the radical cation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), is an activator for GLOX. A spectroelectrochemical cell was used to generate the activating radical species, to continuously measure its concentration, and to simultaneously measure the catalytic activity of GLOX based on its O2 consumption. The results show that GLOX can undergo multiple catalytic turnovers upon activation and that activity increases with the activator concentration. However, we also found that the ABTS cation radical can serve as an electron acceptor which becomes visible in the absence of O2. Furthermore, GLOX activity is highly restrained by the naturally occurring, low O2 concentration. We conclude that GLOX is indeed an auxiliary enzyme for H2O2 production in white-rot secretomes. Its turnover rate is strongly regulated by the availability of O2 and the radical generating activity of peroxidases present in the secretome, which acts as a feedback loop for GLOX activity.

Oral peroxidases: From antimicrobial agents to ecological actors (Review).

Sialoperoxidase and myeloperoxidase are the two main peroxidase enzymes found in the oral cavity. Sialoperoxidase is present in salivary secretions and in the biofilms that line the oral surfaces, while myeloperoxidase is abundant in the dento-gingival sulcus area. In the presence of hydrogen peroxide (H2O2), oral peroxidases catalyze the oxidation of the pseudohalide anion thiocyanate (SCN−) to hypothiocyanite (OSCN−), a strong oxidant that serves an antimicrobial role. Furthermore, oral peroxidases consume bacteria-produced H2O2 and could help inactivate toxic carcinogenic and genotoxic substances. Numerous in vitro studies have reported the antibacterial, antimycotic and antiviral role of peroxidases, suggesting possible applications in oral therapy. However, the use of oral hygiene products incorporating peroxidase systems has not yet been shown to be beneficial for the treatment or prevention of oral infections. This paradox reflects our incomplete knowledge of the physiological role of peroxidases in a complex environment, such as the oral region. While hygiene is crucial for restoring oral microbiota to a symbiotic state, there are no data to suggest that the addition of a peroxidase per se can create a dysbiotic state. Recent investigations have associated the presence of peroxidase activity with gram-positive cocci microbial flora, and its insufficiency with dysbiosis has been linked to pathologies, such as caries, periodontitis or infections of the oral mucosa. Therefore, oxidants generated by oral peroxidases appear to be an essential ecological determinant for oral health through the selection of a symbiotic microbiota capable of resisting oxidative stress. The objective of the present review was to update the current knowledge of the physiological aspects and applications of oral peroxidases in clinical practice.

L-Tryptophan Interactions with the Horseradish Peroxidase-Catalyzed Generation of Triplet Acetone.

Triplet carbonyls generated by chemiexcitation are involved in typical photobiochemical processes in the absence of light. Due to their biradical nature, ultraweak light emission and long lifetime, electronically excited triplet species display typical radical reactions such as isomerization, fragmentation, cycloaddition and hydrogen abstraction. In this paper, we report chemical reactions in a set of amino acid residues induced by the isobutanal/horseradish peroxidase (IBAL/HRP) system, a well-known source of excited triplet acetone (Ac3* ). Accordingly, quenching of Ac3* by tryptophan (Trp) unveiled parallel enzyme damage and inactivation, likely explained by scavenging of IBAL tertiary radical reaction intermediate and Ac3* -derived 2-hydroxy-i-propyl radical. Quenching constants were calculated from Stern-Volmer plots, and the structure of radical adducts was revealed by mass spectrometry. As expected, a concurrent Schiff-type adduct was found to be one of the reaction by-products. These findings draw attention to potential structural and functional changes in enzymes involved in the electronic chemiexcitation of their products.

Temperature rise and copper exposure reduce heart mitochondrial reactive oxygen species scavenging capacity

Mitochondria produce and scavenge reactive oxygen species (ROS); however, whether oxidative distress due to exogenous stress arises from excessive production or impaired scavenging remains unclear. We assessed the effect of copper (Cu) and thermal stress on kinetics of ROS (H2O2) consumption in mitochondria isolated from fish heart. Mitochondria were energized with succinate, glutamate-malate or palmitoylcarnitine (PC) and incubated with 1–25 μM Cu at 11 (control) and 23 °C. We found that H2O2 consumption capacity of heart mitochondria varies with substrate and is additively reduced by temperature rise and Cu. While Cu is a potent inhibitor of H2O2 consumption in mitochondria oxidizing glutamate-malate and succinate, mitochondria oxidizing PC are resistant to the inhibitory effect of the metal. Moreover, the sensitivity of H2O2 consumption pathways to Cu depend on the substrate and are greatly impaired during oxidation of glutamate-malate. Pharmacological manipulation of mitochondrial antioxidant systems revealed that NADPH-dependent peroxidase systems are the centerpieces of ROS scavenging in heart mitochondria, with the glutathione-dependent pathway being the most prominent while catalase played a minimal role. Surprisingly, Cu is as efficacious in inhibiting thioredoxin-dependent peroxidase pathway as auranofin, a selective inhibitor of thioredoxin reductase. Taken together, our study uncovered unique mechanisms by which Cu alters mitochondrial H2O2 homeostasis including its ability to inhibit specific mitochondrial ROS scavenging pathways on a par with conventional inhibitors. Importantly, because of additive inhibitory effect on mitochondrial ROS removal mechanisms, hearts of organisms jointly exposed to Cu and thermal stress are likely at increased risk of oxidative distress.

Активність та ізоферментний склад пероксидази листя Robinia pseudoacacia L. за дії Parectopa robiniella Clemens, 1963

Іn recent times R. pseudoacacia has been suffering from populations of new pests, which cause serious economic damage to this strategic species. Therefore, studying the features of plant defense responses against harmful insects is of great importance for biodiversity conservation for preserving this species in natural and artificial plantings. The aim of the study was to analyze the peculiarities of the activity and isoenzyme composition of peroxidase in R. pseudoacacia leaves during attacks by the invading insect P. robiniella. In the green plantations of Dnipro city, as the object of research, six groups of Robinia pseudoacacia L. model trees of different ages (5 and 35–40 years of age) with the existing leaf damages by P. robiniella leaf blotch miner were identified. Differences in benzidine-peroxidase activity were found in the leaves of 5- and 40-year-old R. pseudoacacia trees. In 35‒40-year-old trees with the presence of leaf blotch mi­ners, the leaves showed a tendency to increase BPOD activity by 24.6% vs control. While in young plants, a significant increase in peroxidase activity was found by 3.8 times due to mechanical damage of the leaves by the miner compared to the control. The revealed significant increase (by 63.2%) in the activity of guaiacol-peroxidase of black locust indicates its active participation in enhancing the barrier functions of leaf cells against P. robiniella, and it indicates the promising use of the enzyme as a biomarker for pest influence. The composition of benzidine-peroxidase isoenzymes was analyzed by electrofocusing. The main pattern of changes in the expressiveness of benzidine-peroxidase due to damage of leaves by a pest was a quantitative redistribution of activity between different molecular forms of peroxidase. Several enzyme isoforms from the highly acidic pH zone showed a significant activity increase in R. pseudoacacia leaves damaged by P. robiniella; this especially applies to the peroxidase system of young black locust plants. The increase in bensidine- and guajacol-peroxidase activity under the influence of leaf miner may be explained by a change in the gene expression of individual isoforms of peroxidases, which is confirmed by the results of studying the relative share of peroxidase molecular forms with isoelectrofocusing. Calculation of the internal diversity index (KD) of IEF benzidine-peroxidase spectra showed that the studied peroxidase spectra of young and medieval trees of control and experimental samples of R. pseudoacacia leaves differ significantly in the level of complexity. Under the influence of the invader the level of complexity increased. The study of the reaction of black locust and the mechanisms of its protection against mechanical damage by phytophages with the involvement of a larger range of enzymes in further research can serve as a theoretical basis for species selection and management to restore it under biotic stress.

An analyte-triggered artificial peroxidase system based on dimanganese complex for a versatile enzyme assay.

We described an analyte-activatable artificial peroxidase system (caged Mn2(bpmp)) by caging a dimanganese complex, exhibiting peroxidase-like activity, with an analyte-reactive trigger. It allowed adjustments of the detection target to be applied depending on the trigger as well as the detection modes, such as fluorescence and colorimetric, as required. This system was successfully applied to a versatile enzyme assay for leucine aminopeptidase and γ-glutamyl transpeptidase based on spectrophotometric change induced from the oxidation of the peroxidase substrate by analyte-triggered peroxidase-like activity.

Development of a magnetically separable co-immobilized laccase and versatile peroxidase system for the conversion of lignocellulosic biomass to vanillin

ABSTRACT Lignin obtained from renewable biomass is a potential feedstock for the synthesis of various value-added chemicals through efficient biocatalytic routes. The ligninolytic enzymes-assisted depolymerization of lignin to vanillin constitutes the most commercially attractive and promising approach in green chemistry as vanillin constitutes the second most prevalent flavoring agent. Thus, in the present work, immobilized laccase and versatile peroxidase, and further, a co-immobilized laccase and versatile peroxidase system on magnetic silica microspheres (MSMS) were developed to generate a robust biocatalytic system that mediates the depolymerization of lignin obtained from Casuarina equisetifolia biomass. The depolymerization of lignin by free and immobilized laccase showed a vanillin yield of 24.8% and 23%, respectively, at pH 4.0 in 6 h at 30°C against a vanillin yield of 20% and 21.7% with the free and immobilized versatile peroxidase, respectively, at pH 5.0°C and 50°C. Comparatively, the system with the co-immobilized laccase and versatile peroxidase exhibited a 1-fold and 1.2-fold higher vanillin yield than the free and immobilized laccase system, respectively. On comparing with the versatile peroxidase system, the co-immobilized biocatalytic system displayed 1.3-fold and 1.2-fold increased vanillin yield than the free and immobilized versatile peroxidase system, respectively, at a pH of 6.0 in 6 h at 30°C with an enzyme concentration of 1 U/ml. The reusability studies of the co-immobilized biocatalytic system exhibited that both the enzymes retained up to 40% of its activity till sixth cycle. Implications: The waste biomass of Casuarina equisetifolia is widely available around the coastal regions of India which does not have any agricultural or industrial applications. The present work exploits the lignocellulosic content of the Casuarina biomass to extract the lignin, which provides a renewable alternative for the production of the commercially high-valued compound, vanillin. This work also integrates a co-immobilized biocatalytic process comprising of laccase and versatile peroxidase leading to an environmentally benign enzymatic process for the depolymerization of lignin to vanillin.

Reactions of kynurenic acid with hypobromous acid and hypochlorous acid.

Kynurenic acid, a tryptophan metabolite, acts as antagonist or agonist of several receptors. Hypobromous acid (HOBr) and hypochlorous acid (HOCl) are generated by eosinophils and neutrophils. At inflammation sites, kynurenic acid may encounter HOBr and HOCl to generate products. When kynurenic acid was incubated with HOBr under neutral conditions, kynurenic acid generated a single product almost exclusively. This was identified as 3-bromokynurenic acid. Kynurenic acid reacted with HOCl, generating two products. The major product was identified as 3-chlorokynurenic acid with its oxidative decarboxylation product, 3-chloro-4-hydroxy-2(1H)-quinolinone as a by-product. Free amino acids suppressed the reactions of kynurenic acid with HOBr and HOCl. Taurine suppressed the HOCl reaction but not the HOBr reaction. An eosinophil peroxidase system containing H2O2, NaCl, and NaBr reacted with kynurenic acid, generating 3-bromokynurenic acid under mildly acidic conditions. Although a myeloperoxidase system containing H2O2 and NaCl reacted with kynurenic acid to generate 3-chlorokynurenic acid under mildly acidic conditions, the product was altered to 3-bromokynurenic acid by addition of NaBr to the system. These results suggest that 3-bromokynurenic acid and 3-chlorokynurenic acid may be generated from kynurenic acid at inflammation sites in humans, although their formation will be suppressed by coexistent amino acids.

Extracellular Glutathione Peroxidase GPx3 and Its Role in Cancer

Mammalian cells possess a multifaceted antioxidant enzyme system, which includes superoxide dismutases, catalase, the peroxiredoxin/thioredoxin and the glutathione peroxidase systems. The dichotomous role of reactive oxygen species and antioxidant enzymes in tumorigenesis and cancer progression complicates the use of small molecule antioxidants, pro-oxidants, and targeting of antioxidant enzymes as therapeutic approaches for cancer treatment. It also highlights the need for additional studies to investigate the role and regulation of these antioxidant enzymes in cancer. The focus of this review is on glutathione peroxidase 3 (GPx3), a selenoprotein, and the only extracellular GPx of a family of oxidoreductases that catalyze the detoxification of hydro- and soluble lipid hydroperoxides by reduced glutathione. In addition to summarizing the biochemical function, regulation, and disease associations of GPx3, we specifically discuss the role and regulation of systemic and tumor cell expressed GPx3 in cancer. From this it is evident that GPx3 has a dichotomous role in different tumor types, acting as both a tumor suppressor and pro-survival protein. Further studies are needed to examine how loss or gain of GPx3 specifically affects oxidant scavenging and redox signaling in the extracellular tumor microenvironment, and how GPx3 might be targeted for therapeutic intervention.