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Mao YW, Zhang X, Li HB, Pei S, Wang AJ, Zhao T, Jin Z, Feng JJ. Confined synthesis of ternary FeCoMn single-atom nanozyme in N-doped hollow mesoporous carbon nanospheres for synergistic chemotherapy and chemodynamic cancer therapy. Biomater Adv 2023; 154:213618. [PMID: 37725871 DOI: 10.1016/j.bioadv.2023.213618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Revised: 08/19/2023] [Accepted: 09/03/2023] [Indexed: 09/21/2023]
Abstract
Recently, nanozymes show increasing biological applications and promising possibilities for therapeutic intervention, while their mediated therapeutic outcomes are severely compromised due to their insufficient catalytic activity and specificity. Herein, ternary FeCoMn single atoms were incorporated into N-doped hollow mesoporous carbon nanospheres by in situ confinement pyrolysis at 800 °C as high-efficiency nanozyme. The confinement strategy endows the as-prepared nanozyme with the enhanced catalase- and oxidase-like activities. Specifically, the FeCoMn TSAs/N-HCSs nanozyme can decompose intracellular H2O2 to generate O2 and subsequently convert O2 to cytotoxic superoxide radicals (O2∙-), which can initiate cascade enzymatic reactions in tumor microenvironment (TME) for chemodynamic therapy (CDT). Moreover, the cancer therapy was largely enhanced by loading with doxorubicin (DOX). Impressively, the FeCoMn TSAs/N-HCSs nanozyme-mediated CDT and the DOX-induced chemotherapy endow the DOX@FeCoMn TSAs/N-HCSs with effective tumor inhibition, showing the superior therapeutic efficacy.
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Affiliation(s)
- Yan-Wen Mao
- Key laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Materials Science, College of Life Science, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
| | - Xu Zhang
- Key laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Materials Science, College of Life Science, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China; Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou 310015, China
| | - Heng-Bo Li
- Key laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Materials Science, College of Life Science, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
| | - Song Pei
- Key laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Materials Science, College of Life Science, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
| | - Ai-Jun Wang
- Key laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Materials Science, College of Life Science, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
| | - Tiejun Zhao
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou 310015, China
| | - Zhigang Jin
- Key laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Materials Science, College of Life Science, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China.
| | - Jiu-Ju Feng
- Key laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Materials Science, College of Life Science, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China.
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Jannesari M, Akhavan O, Madaah Hosseini HR, Bakhshi B. Oxygen-Rich Graphene/ZnO 2-Ag nanoframeworks with pH-Switchable Catalase/Peroxidase activity as O 2 Nanobubble-Self generator for bacterial inactivation. J Colloid Interface Sci 2023; 637:237-250. [PMID: 36701869 DOI: 10.1016/j.jcis.2023.01.079] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 01/10/2023] [Accepted: 01/15/2023] [Indexed: 01/20/2023]
Abstract
The oxygen-rich organic/inorganic (reduced graphene oxide (rGO)/ZnO2-Ag) nanoframeworks as suppliers of O2 nanobubbles (NBs) with dual pH-and-temperature-sensitive behavior were developed to suppress bacterial growth. It was demonstrated that not only the rate but also the final product of oxygen-rich ZnO2 decomposition (to an intermediate product of H2O2) rate was dramatically controlled by pH adjustment. Furthermore, in the presence of Ag nanoparticles, ̇OH radical generation switched to O2 NBs evolution by shifting the pH from acidic to basic/neutral conditions, demonstrating an adjustable nanozyme function-ability between catalase and peroxidase-like activity, respectively. Antibacterial properties of the in-situ generated O2 NBs substantially enhanced against bacterial models including methicillin-resistant Staphylococcus aureus in the presence of rGO. In fact, deflecting the electrons from their main respiratory chain to an oxygen-rich bypath through rGO significantly stimulated reactive oxygen species (ROS) generation, combating bacteria more efficiently. Moreover, NIR laser irradiation-induced temperature rise (due to the inherent photothermal properties of rGO) facilitated ZnO2 decomposition and accelerated growth and collapse of NBs. The simultaneous microscale thermal and mechanical destructions induced stronger antibacterial behavior. These results hold great promises for designing simple organic/inorganic nanoframeworks as solid sources of NBs with tunable enzyme-like ability in response to environmental conditions suitable for forthcoming graphene-based bio-applications.
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Affiliation(s)
- Marziyeh Jannesari
- Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588, 89694, Tehran, Iran; School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4, Ireland
| | - Omid Akhavan
- Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588, 89694, Tehran, Iran; Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran, Iran.
| | - Hamid R Madaah Hosseini
- Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11155-9466, Tehran, Iran
| | - Bita Bakhshi
- Department of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran
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Li X, Ji Q, Yan C, Zhu Z, Yan Z, Chen P, Wang Y, Song L. H 2O 2/pH Dual-Responsive Biomimetic Nanoenzyme Drugs Delivery System for Enhanced Tumor Photodynamic Therapy. Nanoscale Res Lett 2022; 17:103. [PMID: 36308645 PMCID: PMC9618007 DOI: 10.1186/s11671-022-03738-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 10/17/2022] [Indexed: 06/16/2023]
Abstract
Phototherapy has been recognized as a photochemical process to treat tumor via induce cancer cells necrosis and death, with minimal invasiveness, higher selectivity, and few side effects. However, the therapy effects of phototherapy are often compromised by the hypoxia, high levels of hydrogen peroxide, and glutathione of tumor microenvironment (TME). Therefore, we constructed a catalase-like activity bionic metal-organic framework drugs delivery system (FA-EM@MnO2/ZIF-8/ICG) with tumor microenvironment controllable releasing. In this system, photosensitizer indocyanine green (ICG) was introduced into zeolite imidazole salt skeleton 8 (ZIF-8) by one-step methods, forming ZIF-8/ICG nano-platform, which can effectively avoid ICG-induced phototoxicity and aggregation-induced quenching during transport. MnO2 with catalase-like activity was coated on the surface of ZIF-8/ICG nano-platform, which made it have the ability of self-supplying O2 under the condition of H2O2 in TME. Exposure under near-infrared light can alleviate the anoxic TME, thus improving the phototherapy efficiency. In addition, folate-functionalized erythrocyte membrane is coated on the surface of MnO2/ZIF-8/ICG, which can endow FA-EM@MnO2/ZIF-8/ICG with the ability of targeted drug administration and immune elimination avoidance. Therefore, FA-EM@MnO2/ZIF-8/ICG nano-platform has the catalase-like activity, which can alleviate the oxidative stress state of TME and provide a beneficial environment for photodynamic therapy of tumor.
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Affiliation(s)
- Xinyuan Li
- The Affiliated Huai'an Hospital of Xuzhou Medical University and The Second People's Hospital of Huai'an, No.62, Huaihai Road (S.), Huai'an, 223002, China
| | - Qing Ji
- School of Medicine, Jiangsu University, Zhenjiang, 212013, China
| | - Chao Yan
- The Affiliated Huai'an Hospital of Xuzhou Medical University and The Second People's Hospital of Huai'an, No.62, Huaihai Road (S.), Huai'an, 223002, China
| | - Ziyu Zhu
- The Affiliated Huai'an Hospital of Xuzhou Medical University and The Second People's Hospital of Huai'an, No.62, Huaihai Road (S.), Huai'an, 223002, China
| | - Zhihui Yan
- The Affiliated Huai'an Hospital of Xuzhou Medical University and The Second People's Hospital of Huai'an, No.62, Huaihai Road (S.), Huai'an, 223002, China
| | - Ping Chen
- The Affiliated Huai'an Hospital of Xuzhou Medical University and The Second People's Hospital of Huai'an, No.62, Huaihai Road (S.), Huai'an, 223002, China
| | - Yisen Wang
- Institute of Translational Medicine, Medical College, Yangzhou University, Yangzhou, 225009, China.
| | - Li Song
- YanCheng NO.1 People's Hospital, Yancheng, 224001, China.
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Wu L, Zhou M, Wang Y, Liu J. Nanozyme and aptamer- based immunosorbent assay for aflatoxin B1. J Hazard Mater 2020; 399:123154. [PMID: 32937727 DOI: 10.1016/j.jhazmat.2020.123154] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 05/23/2020] [Accepted: 06/07/2020] [Indexed: 05/05/2023]
Abstract
Traditional enzyme-linked immunosorbent assay (ELISA) suffers from the limitations of relatively low sensitivity and stability, and enzyme-labelled antibodies are hard to be prepared and purified. Based on a nanozyme, an aptamer and Fe3O4 magnetic nanoparticles (MNP), a nanozyme and aptamer-based immunosorbent assay (NAISA) was developed for aflatoxin B1 (AFB1) detection with simpler operation and separation. In this work, mesoporous SiO2/Au-Pt (m-SAP) were prepared to act as signal labels, which showed high catalase-like activity and was denoted as nanozyme. Aptamer was adopted to specifically recognize with AFB1, and MNP facilitated to realize magnetic separation. To verify the performance of NAISA, traditional ELISA (t-ELISA) and enhanced ELISA (e-ELISA) using MNP and m-SAP nanozyme were applied in AFB1 detection. The NAISA method showed the lowest limit of detection (LOD) with 5 pg mL-1 (n = 3, ±4.2 %), 600 and 12-fold lower than that of t-ELISA (3 ng mL-1) and e-ELISA (0.06 ng mL-1), respectively. In the interference tests, AFB1 can be identified among six different interfering substances. The NAISA method, thus, can be of great importance as it allows selective and sensitive AFB1 detection, while providing the simplicity of use and need for screening hazardous materials.
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Affiliation(s)
- Long Wu
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), College of Bioengineering and Food, Hubei University of Technology, Wuhan, Hubei 430068, PR China; College of Food Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China.
| | - Min Zhou
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), College of Bioengineering and Food, Hubei University of Technology, Wuhan, Hubei 430068, PR China; College of Food Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China
| | - Yasheng Wang
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), College of Bioengineering and Food, Hubei University of Technology, Wuhan, Hubei 430068, PR China
| | - Jingmin Liu
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), College of Bioengineering and Food, Hubei University of Technology, Wuhan, Hubei 430068, PR China
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Liu R, Zuo L, Huang X, Liu S, Yang G, Li S, Lv C. Colorimetric determination of lead(II) or mercury(II) based on target induced switching of the enzyme-like activity of metallothionein-stabilized copper nanoclusters. Mikrochim Acta 2019; 186:250. [PMID: 30888507 DOI: 10.1007/s00604-019-3360-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Accepted: 03/08/2019] [Indexed: 10/27/2022]
Abstract
It is shown that metallothionein-stabilized copper nanoclusters (MT-CuNCs) display catalase-like activity. In the presence of either lead(II) or mercury(II), the catalase-like activity is converted to a peroxidase-like activity. On addition of Pb(II) or Hg(II), the inhibitory effect of MT-CuNCs on the chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB) with H2O2 is weakened. On the other hand, the catalytic effect of the nanoclusters on the chromogenic reaction is increased. The system MT-CuNCs-Pb(II)/Hg(II) exhibits high affinity for the substrates TMB and H2O2. Their catalytic behavior follows Michaelis-Menten kinetics. Based on these findings, a method was developed for visual detection (via the blue coloration formed) and spectrophotometric determination (at 450 nm) of Pb(II) and Hg(II). The linear range for Pb(II) extends from 0.7 to 96 μM, and the linear ranges for Hg(II) from 97 nM to 2.3 μM and from 3.1 μM to 15.6 μM. The detection limits are 142 nM for Pb(II) and 43.8 nM for Hg(II). Graphical abstract Metallothionein-stabilized copper nanoclusters (MT-CuNCs) display catalase-like activity. On addition of Pb(II) or Hg(II), the catalase-like activity is converted to a peroxidase-like activity. The latter catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2.
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Samuni A, Maimon E, Goldstein S. Mechanism of HRP-catalyzed nitrite oxidation by H 2O 2 revisited: Effect of nitroxides on enzyme inactivation and its catalytic activity. Free Radic Biol Med 2017; 108:832-839. [PMID: 28495446 DOI: 10.1016/j.freeradbiomed.2017.05.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 05/01/2017] [Accepted: 05/07/2017] [Indexed: 10/19/2022]
Abstract
The peroxidative activity of horseradish peroxidase (HRP) undergoes progressive inactivation while catalyzing the oxidation of nitrite by H2O2. The extent of inactivation increases as the pH increases, [nitrite] decreases or [H2O2] increases, and is accompanied by a loss of the Soret peak of HRP along with yellow-greenish coloration of the solution. HRP-catalyzed nitrite oxidation by H2O2 involves not only the formation of compounds I and II as transient heme species, but also compound III, all of which in turn, oxidize nitrite yielding •NO2. The rate constant of nitrite oxidation by compound III is at least 10-fold higher than that by compound II, which is also reducible by •NO2 where its reduction by nitrite is the rate-determining step of the catalytic cycle. The extent of the loss of the Soret peak of HRP is lower than the loss of its peroxidative activity implying that deterioration of the heme moiety leading to iron release only partially contributes toward heme inactivation. Cyclic stable nitroxide radicals, such as 2,2,6,6-tetramethyl-piperidine-N-oxyl (TPO), 4-OH-TPO and 4-NH2-TPO at µM concentrations detoxify •NO2 thus protecting HRP against inactivation mediated by this radical. Hence, HRP inactivation proceeds via nitration of the porphyrin ring most probably through compound I reaction with •NO2, which partially leads to deterioration of the heme moiety. The nitroxide acts catalytically since its oxidation by •NO2 yields the respective oxoammonium cation, which is readily reduced back to the nitroxide by H2O2, superoxide ion radical, and nitrite. In addition, the nitroxide catalytically inhibits tyrosine nitration mediated by HRP/H2O2/nitrite reactions system as it efficiently competes with tyrosyl radical for •NO2. The inhibition by nitroxides of tyrosine nitration is demonstrated also in the case of microperoxidase (MP-11) and cytochrome c revealing an additional role played by nitroxide antioxidants.
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Affiliation(s)
- Amram Samuni
- Institute of Medical Research Israel-Canada, Medical School, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Eric Maimon
- Nuclear Research Centre Negev, Be'er Sheva, Israel
| | - Sara Goldstein
- Institute of Chemistry, The Accelerator Laboratory, the Hebrew University of Jerusalem, Jerusalem 91904, Israel.
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Samuni A, Maimon E, Goldstein S. Nitroxides protect horseradish peroxidase from H 2O 2-induced inactivation and modulate its catalase-like activity. Biochim Biophys Acta Gen Subj 2017; 1861:2060-2069. [PMID: 28365302 DOI: 10.1016/j.bbagen.2017.03.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 03/05/2017] [Accepted: 03/20/2017] [Indexed: 11/24/2022]
Abstract
BACKGROUND Horseradish peroxidase (HRP) catalyzes H2O2 dismutation while undergoing heme inactivation. The mechanism underlying this process has not been fully elucidated. The effects of nitroxides, which protect metmyoglobin and methemoglobin against H2O2-induced inactivation, have been investigated. METHODS HRP reaction with H2O2 was studied by following H2O2 depletion, O2 evolution and heme spectral changes. Nitroxide concentration was followed by EPR spectroscopy, and its reactions with the oxidized heme species were studied using stopped-flow. RESULTS Nitroxide protects HRP against H2O2-induced inactivation. The rate of H2O2 dismutation in the presence of nitroxide obeys zero-order kinetics and increases as [nitroxide] increases. Nitroxide acts catalytically since its oxidized form is readily reduced to the nitroxide mainly by H2O2. The nitroxide efficacy follows the order 2,2,6,6-tetramethyl-piperidine-N-oxyl (TPO)>4-OH-TPO>3-carbamoyl proxyl>4-oxo-TPO, which correlates with the order of the rate constants of nitroxide reactions with compounds I, II, and III. CONCLUSIONS Nitroxide catalytically protects HRP against inactivation induced by H2O2 while modulating its catalase-like activity. The protective role of nitroxide at μM concentrations is attributed to its efficient oxidation by P940, which is the precursor of the inactivated form P670. Modeling the dismutation kinetics in the presence of nitroxide adequately fits the experimental data. In the absence of nitroxide the simulation fits the observed kinetics only if it does not include the formation of a Michaelis-Menten complex. GENERAL SIGNIFICANCE Nitroxides catalytically protect heme proteins against inactivation induced by H2O2 revealing an additional role played by nitroxide antioxidants in vivo.
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Affiliation(s)
- Amram Samuni
- Institute of Medical Research Israel-Canada, Medical School, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Eric Maimon
- Nuclear Research Centre Negev, Beer Sheva, Israel
| | - Sara Goldstein
- Institute of Chemistry, The Accelerator Laboratory, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
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Samuni A, Maimon E, Goldstein S. Nitroxides catalytically inhibit nitrite oxidation and heme inactivation induced by H 2O 2, nitrite and metmyoglobin or methemoglobin. Free Radic Biol Med 2016; 101:491-499. [PMID: 27826125 DOI: 10.1016/j.freeradbiomed.2016.10.534] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 10/22/2016] [Accepted: 10/25/2016] [Indexed: 11/18/2022]
Abstract
Stable nitroxide radicals have multiple biological effects, although the mechanisms underlying them are not fully understood. Their protective effect against oxidative damage has been mainly attributed to scavenging deleterious radicals, oxidizing reduced metal ions and reducing oxyferryl centers of heme proteins. Yet, the potential of nitroxides to protect heme proteins against inactivation while suppressing or enhancing their catalytic activities has been largely overlooked. We have studied the effect of nitroxides, including TPO (2,2,6,6-tetramethylpiperidin-N-oxyl), 4-OH-TPO, 4-oxo-TPO and 3-carbamoyl proxyl, on the peroxidase-like activity of metmyoglobin (MbFeIII) and methemoglobin (HbFeIII) using nitrite as an electron donor by following heme absorption, H2O2 consumption, O2 evolution and nitrite oxidation. The results demonstrate that the peroxidase-like activity is accompanied by a progressive heme inactivation where MbFeIII is far more resistant than HbFeIII. Nitroxides convert the peroxidase-like activity into catalase-like activity while inhibiting heme inactivation and nitrite oxidation in a dose-dependent manner. The nitroxide facilitates H2O2 dismutation, yet none of its reactions with any of the intermediates formed in these systems is rate-determining, and therefore its effect on the rate of the catalysis is hardly dependent on the kind of the nitroxide derivative and its concentration. The nitroxide at µM concentrations range catalytically inhibits nitrite oxidation, and consequently prevents tyrosine nitration induced by heme protein/H2O2/nitrite due to its fast oxidation by •NO2 forming the respective oxoammonium cation, which is reduced back to the nitroxide by H2O2 and by superoxide radical. The nitroxides are superior over common antioxidants, which their reaction with •NO2 always yields secondary radicals leading eventually to consumption of the antioxidant. A mechanism is proposed, and the kinetic simulations fit very well the experimental data in the case of MbFeIII where most of the rate constants of the reactions involved are independently known.
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Affiliation(s)
- Amram Samuni
- Institute of Medical Research, Israel-Canada Medical School, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Eric Maimon
- Nuclear Research Centre Negev, Beer Sheva, Israel
| | - Sara Goldstein
- Institute of Chemistry, The Accelerator Laboratory, the Hebrew University of Jerusalem, Jerusalem 91904, Israel.
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Asadollahi K, Jasemi NS, Riazi GH, Katuli FH, Yazdani F, Sartipnia N, Moosavi MA, Rahimi A, Falahati M. A bio-mimetic zinc/tau protein as an artificial catalase. Int J Biol Macromol 2016; 92:1307-12. [PMID: 26905468 DOI: 10.1016/j.ijbiomac.2016.02.045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Revised: 02/01/2016] [Accepted: 02/03/2016] [Indexed: 11/21/2022]
Abstract
In this study, the catalase-like activity of monomeric tau protein was reported in the presence of of zinc (Zn(II)) ions at low pH value. Monomeric tau protein contains two SH groups that are a target of disulfide bond formation. However these SH groups are able to interact with Zn(II) ion at pH 7.2 which creates a thiol bond as a mimetic model of chloroperoxidase active site which performs catalase like activity at low pH. Zn(II)/tau protein complex decomposed H2O2 with a high rate (Vm) as well as an efficient turn oven number (kcat) at pH 3. This remarkable catalase like activity is may be attributed to the conformational reorientation of protein at low pH. Circular dichroism (CD) studies did not demonstrate any secondary structural changes of tau protein after addition of Zn(II) ions at pH 7.2. In addition, tau protein shows identical CD bands at pH 7.2 and 3. Moreover, fluorescence quenching of tau by Zn(II) at pH 7.2 was initiated by complex formation rather than by dynamic collision. A significant red shift (6nm) was observed in the emission maximum of the fluorescence spectra when the protein was dissolved at pH 3 compared to pH 7.2. This conformational change can provide information regarding the rearrangements of the protein structure and exposure of Cys-Zn(II) group to the solvent which induces easy access of active site to H2O2 molecules and corresponding enhanced catalytic activity of Zn(II)/tau protein complex. This study introduces tau protein as a bio-inspired high performing scaffold for transition metal encapsulation and introducing an engineered apoprotein-induced biomimetic enzyme.
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