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Free Radical Biology & Medicine Sep 2022The mechanisms underlying the inactivation of Leuconostoc mesenteroides glucose 6-phosphate dehydrogenase (G6PDH) induced by peroxyl radicals (ROO) and peroxynitrite...
Role of amino acid oxidation and protein unfolding in peroxyl radical and peroxynitrite-induced inactivation of glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides.
The mechanisms underlying the inactivation of Leuconostoc mesenteroides glucose 6-phosphate dehydrogenase (G6PDH) induced by peroxyl radicals (ROO) and peroxynitrite (ONOO), were explored. G6PDH was incubated with AAPH (2,2' -azobis(2-methylpropionamidine)dihydrochloride), used as ROO source, and ONOO. Enzymatic activity was assessed by NADPH generation, while oxidative modifications were analyzed by gel electrophoresis and liquid chromatography (LC) with fluorescence and mass detection. Changes in protein conformation were studied by circular dichroism (CD) and binding of the fluorescent dye ANS (1-anilinonaphthalene-8-sulfonic acid). Incubation of G6PDH (54.4 μM) with 60 mM AAPH showed an initial phase without significant changes in enzymatic activity, followed by a secondary time-dependent continuous decrease in activity to ∼59% of the initial level after 90 min. ONOO induced a significant and concentration-dependent loss of G6PDH activity with ∼46% of the initial activity lost on treatment with 1.5 mM ONOO. CD and ANS fluorescence indicated changes in G6PDH secondary structure with exposure of hydrophobic sites on exposure to ROO, but not ONOO. LC-MS analysis provided evidence for ONOO-mediated oxidation of Tyr, Met and Trp residues, with damage to critical Met and Tyr residues underlying enzyme inactivation, but without effects on the native (dimeric) state of the protein. In contrast, studies using chloramine T, a specific oxidant of Met, provided evidence that oxidation of specific Met and Trp residues and concomitant protein unfolding, loss of dimer structure and protein aggregation are involved in G6PDH inactivation by ROO. These two oxidant systems therefore have markedly different effects on G6PDH structure and activity.
Topics: Amino Acids; Glucosephosphate Dehydrogenase; Leuconostoc mesenteroides; Oxidants; Oxidation-Reduction; Peroxides; Peroxynitrous Acid; Protein Unfolding
PubMed: 35987422
DOI: 10.1016/j.freeradbiomed.2022.08.010 -
Chemosphere Mar 2021Catalytic activation of different oxidants including peroxymonosulfate (PMS), peroxydisulfate (PDS), hydrogen peroxide (HO) and ozone (O) by MnO for degradation of...
Catalytic activation of different oxidants including peroxymonosulfate (PMS), peroxydisulfate (PDS), hydrogen peroxide (HO) and ozone (O) by MnO for degradation of sulfachloropyridazine (SCP) was investigated and the effects of different crystalline phases of MnO including nanowire α-MnO, nanorod β-MnO, nanofiber γ-MnO, and nanosphere δ-MnO on catalytic ozonation of SCP were also studied. The SCP degradation and total organic carbon removal indicated that the oxidation efficiency of the peroxide oxidants followed an order of O/MnO > PMS/MnO > PDS/MnO > HO/MnO. In catalytic ozonation, SCP degradation rate constants of different MnO phases followed an order of δ-MnO > α-MnO > γ-MnO> β-MnO. Electron paramagnetic resonance (EPR) suggested that hydroxyl radicals (·OH) and singlet oxygen (O) might be more significant for SCP degradation than sulfate (SO) and superoxide (·O) radicals. Radical competition experiments demonstrated that O and ·OH contributed to 63.16% and 28.07%, respectively, for the catalytic ozonation of SCP. It was also found that more oxygen vacancies, specific surface area and exposure of MnO edges could facilitate the activation of O for O and ·OH productions and SCP degradation. The degradation pathways of SCP could mainly follow the cleavage of S-C or S-N bond and dechlorination, accompanied by hydroxylation and oxidation.
Topics: Hydrogen Peroxide; Manganese Compounds; Oxidants; Oxidation-Reduction; Oxides; Ozone; Peroxides; Sulfachlorpyridazine; Water Pollutants, Chemical
PubMed: 33348268
DOI: 10.1016/j.chemosphere.2020.129287 -
Food Chemistry Dec 2022To compare the differences between direct protein oxidation (PO) and lipid-derived PO, the myofibrillar protein (MP) of obscure pufferfish was oxidatively modified by...
To compare the differences between direct protein oxidation (PO) and lipid-derived PO, the myofibrillar protein (MP) of obscure pufferfish was oxidatively modified by the hydroxyl radical oxidizing system (HOS) and the lipid-oxidizing system (LOS). The degree of oxidation, structural characteristics, and oxidation sites in MP were assessed. The results showed there was no significant thiol loss in LOS, compared with a 77.64% loss observed in case of the HOS. The secondary structure of MP was more vulnerable to HOS, but the tertiary structure was more susceptible to LOS. The cross-linking was largely attributed to the reversible disulfide links in HOS and the irreversible covalent linkages in LOS. Six amino acids and 10 specific oxidant products were identified in HOS. Only three amino acids and three specific oxidant products were identified in LOS. These findings may help deepen the understanding regarding the mechanism underlying PO in protein- and lipid-rich food materials.
Topics: Amino Acids; Hydroxyl Radical; Lipids; Myofibrils; Oxidants; Oxidation-Reduction
PubMed: 35872498
DOI: 10.1016/j.foodchem.2022.133710 -
Water Research Jan 2021Although permanganate activation by sodium sulfite (Mn(VII)/NaSO) has shown great potential for rapid abatement of organic contaminants, the limited reactivity under...
Although permanganate activation by sodium sulfite (Mn(VII)/NaSO) has shown great potential for rapid abatement of organic contaminants, the limited reactivity under alkaline conditions and undesirable Mn residual may prevent its widespread application. To solve these challenges, calcium sulfite (CaSO) was employed as a slow-release source of SO/HSO (S(IV)) to activate Mn(VII) in this study. It was found that the application of CaSO solid could extend the effective working pH range of Mn(VII)/S(IV) from ≤7.0 to ≤9.0. Moreover, due to the enhanced precipitation of MnO with the presence of Ca, very low Mn residual (<0.05 mg/L) was achieved in Mn(VII)/CaSO system. Mn(VII)/CaSO system is a unique two-stage oxidation process in terms of reaction kinetics and reactive oxidants. Specifically, Mn(VII) was rapidly consumed and reactive Mn intermediates (e.g., Mn(VI), Mn(V)), SO, and HO were produced in the first stage. However, the second stage was governed by the interaction between MnO and S(IV), with SO and HO serving as the dominant reactive oxidants. Taking advantage of an automatic titrator, excess S(IV) was found to greatly quench the generated radicals, whereas it did not cause a significant consumption of reactive Mn species. All these results improved our understanding of the Mn(VII)/S(IV) process and could thus facilitate its application.
Topics: Kinetics; Manganese Compounds; Oxidants; Oxidation-Reduction; Oxides
PubMed: 33039830
DOI: 10.1016/j.watres.2020.116481 -
The Journal of Organic Chemistry Mar 2022The synthesis of carbonyl derivatives from renewable feedstocks, by direct oxidation/functionalization of activated and unactivated C(sp)-H bonds under a controlled and...
The synthesis of carbonyl derivatives from renewable feedstocks, by direct oxidation/functionalization of activated and unactivated C(sp)-H bonds under a controlled and predictably selective fashion, especially in late stages, remains a formidable challenge. Herein, for the first time, cost-effective and widely applicable protocols for controlled and predictably selective oxidation of petroleum waste and feedstock ingredients like methyl-/alkylarenes to corresponding value-added carbonyls have been developed, using a surfactant-based oxodiperoxo molybdenum catalyst in water. The methodologies use hydrogen peroxide (HO) as an environmentally benign green oxidant, and the reactions preclude the need of any external base, additive, or cocatalyst and can be operated under mild eco-friendly conditions. The developed protocols show a wide substrate scope and eminent functional group tolerance, especially oxidation-liable and reactive boronic acid groups. Upscaled multigram synthesis of complex steroid molecules by late-stage oxidation proves the robustness and practical utility of the current protocol since it employs an inexpensive recyclable catalyst and an easily available oxidant. A plausible mechanism has been proposed with the help of few controlled experiments and kinetic and computational studies.
Topics: Catalysis; Hydrogen Peroxide; Molybdenum; Oxidants; Water
PubMed: 35098716
DOI: 10.1021/acs.joc.1c02855 -
Journal of Inorganic Biochemistry Jan 2013Recent research has shown that nitroxyl (HNO) has important and unique biological activity, especially as a potential alternative to current treatments of cardiac...
Recent research has shown that nitroxyl (HNO) has important and unique biological activity, especially as a potential alternative to current treatments of cardiac failure. HNO is a reactive molecule that undergoes efficient dimerization and subsequent dehydration to form nitrous oxide (N(2)O), making its detection in solution or biologically relevant preparations difficult. Due to this limitation, HNO has not yet been observed in vivo, though several pathways for its endogenous generation have been postulated. Here, we investigate the oxidation of N-hydroxy-l-arginine (NOHA) by hypochlorous acid (HOCl), which is generated in vivo from hydrogen peroxide and chloride by the heme enzyme, myeloperoxidase. NOHA is an intermediate in the enzymatic production of nitric oxide (NO) by NO synthases, and has been shown previously to be chemically oxidized to either HNO or NO, depending on the oxidant employed. Using membrane inlet mass spectrometry and standard N(2)O analysis by gas chromatography, we find that NOHA is oxidized by excess HOCl to form HNO-derived N(2)O. In addition, we also observe the analogous production of HNO from the HOCl oxidation of hydroxylamine, hydroxyurea, and (to a lesser extent) acetohydroxamic acid.
Topics: Arginine; Chromatography, Gas; Horseradish Peroxidase; Hydroxylamine; Hypochlorous Acid; Kinetics; Mass Spectrometry; Nitrogen Oxides; Oxidants; Oxidation-Reduction; Peroxidase
PubMed: 23102772
DOI: 10.1016/j.jinorgbio.2012.09.024 -
The Biochemical Journal Nov 2018l-Ascorbate, dehydro-l-ascorbic acid (DHA), and 2,3-diketo-l-gulonate (DKG) can all quench reactive oxygen species (ROS) in plants and animals. The vitamin C oxidation...
l-Ascorbate, dehydro-l-ascorbic acid (DHA), and 2,3-diketo-l-gulonate (DKG) can all quench reactive oxygen species (ROS) in plants and animals. The vitamin C oxidation products thereby formed are investigated here. DHA and DKG were incubated aerobically at pH 4.7 with peroxide (HO), 'superoxide' (a ∼50 : 50 mixture of [Formula: see text] and [Formula: see text]), hydroxyl radicals (OH, formed in Fenton mixtures), and illuminated riboflavin (generating singlet oxygen, O). Products were monitored electrophoretically. quenched HO far more effectively than superoxide, but the main products in both cases were 4--oxalyl-l-threonate (4-OxT) and smaller amounts of 3-OxT and OxA + threonate. HO, but not superoxide, also yielded cyclic-OxT. Dilute Fenton mixture almost completely oxidised a 50-fold excess of DHA, indicating that it generated oxidant(s) greatly exceeding the theoretical OH yield; it yielded oxalate, threonate, and OxT. O had no effect on DHA. was oxidatively decarboxylated by HO, Fenton mixture, and O, forming a newly characterised product, 2-oxo-l--pentonate (OTP; '2-keto-l-xylonate'). Superoxide yielded negligible OTP. Prolonged HO treatment oxidatively decarboxylated OTP to threonate. Oxidation of DKG by HO, Fenton mixture, or O also gave traces of 4-OxT but no detectable 3-OxT or cyclic-OxT. In conclusion, DHA and DKG yield different oxidation products when attacked by different ROS. DHA is more readily oxidised by HO and superoxide; DKG more readily by O The diverse products are potential signals, enabling organisms to respond appropriately to diverse stresses. Also, the reaction-product 'fingerprints' are analytically useful, indicating which ROS are acting .
Topics: 2,3-Diketogulonic Acid; Ascorbic Acid; Dehydroascorbic Acid; Hydrogen Peroxide; Iron; Models, Chemical; Molecular Structure; Oxidants; Oxidation-Reduction; Reactive Oxygen Species; Superoxides
PubMed: 30348642
DOI: 10.1042/BCJ20180688 -
General Physiology and Biophysics Mar 2002Oxidative stress involves the generation of a number of reactive species, among them 'reactive oxygen species' and 'reactive nitrogen species'. Recent reports have...
Oxidative stress involves the generation of a number of reactive species, among them 'reactive oxygen species' and 'reactive nitrogen species'. Recent reports have indicated that disulfide-S-monoxides (thiosulfinates) and disulfide-S-dioxides (thiosulfonates) are formed under conditions of oxidative stress. We have now been able to demonstrate that these species are highly reactive and rapidly oxidise thiols. Glutathione and cysteine were oxidised to mixed disulfides by the action of disulfide-S-oxides. Oxidative attack on the zinc/sulfur protein metallothionein with concomitant zinc release was readily accomplished by these 'reactive sulfur species' whereas hydrogen peroxide showed minimal zinc release.
Topics: Cysteine; Disulfides; Glutathione; Glutathione Disulfide; Hydrogen Peroxide; Metallothionein; Oxidants; Oxidation-Reduction; Oxidative Stress; Oxides; Reactive Oxygen Species; Sensitivity and Specificity; Sulfhydryl Compounds; Sulfur
PubMed: 12168727
DOI: No ID Found -
Environmental Science & Technology Sep 2019Flavins are ubiquitous redox-active compounds capable of producing reactive oxygen (O, OH, and HO) and flavin radical species in natural environments, yet their roles in...
Flavins are ubiquitous redox-active compounds capable of producing reactive oxygen (O, OH, and HO) and flavin radical species in natural environments, yet their roles in the redox transformations of environmental contaminants, such as arsenic (As), remain to be investigated. Here, we show that reduced flavins can be a source of effective oxidants for As(III) under both oxic and anoxic conditions. For instance, in the presence of 15 μM reduced riboflavin (RBFH), 22% of 30 μM As(III) is oxidized in aerated solution at pH 7.0. The co-oxidation of As(III) with RBFH is pH-dependent, with a faster reaction rate under mildly acidic relative to alkaline conditions. Quencher tests with 2-propanol (for OH) and catalase (for HO) indicate that As(III) oxidation under oxic conditions is likely controlled by flavin-derived OH at pH 5.2 and 7.0, and by HO at pH 9.0. Kinetic modeling further implies that flavin-derived reactive oxygen species are mainly responsible for As(III) oxidation under oxic conditions, whereas oxidation of As(III) under anoxic conditions at pH 9.0 is attributed to riboflavin radicals (RBFH) generated from co-existing oxidized and reduced riboflavin. The demonstrated ability of flavins to catalyze As(III) oxidation has potential implications for As redox cycling in the environment.
Topics: Arsenic; Dinitrocresols; Flavins; Hydrogen Peroxide; Hydrogen-Ion Concentration; Oxidants; Oxidation-Reduction
PubMed: 31419125
DOI: 10.1021/acs.est.9b03188 -
Chemosphere Apr 2016Cefazolin was demonstrated to exert high reactivity toward permanganate (Mn(VII)), a common oxidant in water pre-oxidation treatment. In this study, five transformation...
Cefazolin was demonstrated to exert high reactivity toward permanganate (Mn(VII)), a common oxidant in water pre-oxidation treatment. In this study, five transformation products were found to be classified into three categories according to the contained characteristic functional groups: three (di-)sulfoxide products, one sulfone product and one di-ketone product. Products analyses showed that two kinds of reactions including oxidation of thioether and the cleavage of unsaturated CC double bond occurred during transformation of cefazolin by Mn(VII). Subsequently, the plausible transformation pathways under different pH conditions were proposed based on the identified products and chemical reaction principles. More importantly, the simulation with real surface water matrix indicated that the proposed transformation pathways of cefazolin could be replayed in real water treatment practices.
Topics: Cefazolin; Manganese Compounds; Models, Chemical; Oxidants; Oxidation-Reduction; Oxides; Potassium Permanganate; Water; Water Pollutants, Chemical; Water Purification
PubMed: 26872071
DOI: 10.1016/j.chemosphere.2016.01.117