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Ansari M, Bhattacharjee S, Pantazis DA. Correlating Structure with Spectroscopy in Ascorbate Peroxidase Compound II. J Am Chem Soc 2024; 146:9640-9656. [PMID: 38530124 PMCID: PMC11009960 DOI: 10.1021/jacs.3c13169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 03/15/2024] [Accepted: 03/15/2024] [Indexed: 03/27/2024]
Abstract
Structural and spectroscopic investigations of compound II in ascorbate peroxidase (APX) have yielded conflicting conclusions regarding the protonation state of the crucial Fe(IV) intermediate. Neutron diffraction and crystallographic data support an iron(IV)-hydroxo formulation, whereas Mössbauer, X-ray absorption (XAS), and nuclear resonance vibrational spectroscopy (NRVS) studies appear consistent with an iron(IV)-oxo species. Here we examine APX with spectroscopy-oriented QM/MM calculations and extensive exploration of the conformational space for both possible formulations of compound II. We establish that irrespective of variations in the orientation of a vicinal arginine residue and potential reorganization of proximal water molecules and hydrogen bonding, the Fe-O distances for the oxo and hydroxo forms consistently fall within distinct, narrow, and nonoverlapping ranges. The accuracy of geometric parameters is validated by coupled-cluster calculations with the domain-based local pair natural orbital approach, DLPNO-CCSD(T). QM/MM calculations of spectroscopic properties are conducted for all structural variants, encompassing Mössbauer, optical, X-ray absorption, and X-ray emission spectroscopies and NRVS. All spectroscopic observations can be assigned uniquely to an Fe(IV)═O form. A terminal hydroxy group cannot be reconciled with the spectroscopic data. Under no conditions can the Fe(IV)═O distance be sufficiently elongated to approach the crystallographically reported Fe-O distance. The latter is consistent only with a hydroxo species, either Fe(IV) or Fe(III). Our findings strongly support the Fe(IV)═O formulation of APX-II and highlight unresolved discrepancies in the nature of samples used across different experimental studies.
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Affiliation(s)
- Mursaleem Ansari
- Max-Planck-Institut für
Kohlenforschung, Kaiser-Wilhelm-Platz
1, Mülheim an der Ruhr 45470, Germany
| | - Sinjini Bhattacharjee
- Max-Planck-Institut für
Kohlenforschung, Kaiser-Wilhelm-Platz
1, Mülheim an der Ruhr 45470, Germany
| | - Dimitrios A. Pantazis
- Max-Planck-Institut für
Kohlenforschung, Kaiser-Wilhelm-Platz
1, Mülheim an der Ruhr 45470, Germany
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2
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Vukić MD, Vuković NL, Mladenović M, Tomašević N, Matić S, Stanić S, Sapienza F, Ragno R, Božović M, Kačániová M. Chemical Composition of Various Nepeta cataria Plant Organs' Methanol Extracts Associated with In Vivo Hepatoprotective and Antigenotoxic Features as well as Molecular Modeling Investigations. PLANTS (BASEL, SWITZERLAND) 2022; 11:2114. [PMID: 36015417 PMCID: PMC9415533 DOI: 10.3390/plants11162114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 07/27/2022] [Accepted: 08/11/2022] [Indexed: 11/16/2022]
Abstract
This report summarizes the chemical composition analysis of Nepeta cataria L. flower, leaf, and stem methanol extracts (FME, LME, SME, respectively) as well as their hepatoprotective and antigenotoxic features in vivo and in silico. Herein, Wistar rat liver intoxication with CCl4 resulted in the generation of trichloromethyl and trichloromethylperoxy radicals, causing lipid peroxidation within the hepatocyte membranes (viz. hepatotoxicity), as well as the subsequent formation of aberrant rDNA adducts and consequent double-strand break (namely genotoxicity). Examined FME, LME, and SME administered orally to Wistar rats before the injection of CCl4 exerted the most notable pharmacological properties in the concentrations of 200, 100, and 50 mg/kg of body weight, respectively. Thus, the extracts' hepatoprotective features were determined by monitoring the catalytic activities of enzymes and the concentrations of reactive oxidative species, modulating the liver redox status. Furthermore, the necrosis of hepatocytes was assessed by means of catalytic activities of liver toxicity markers. The extracts' antigenotoxic features were quantified using the comet assay. Distinct pharmacological property features may be attributed to quercitrin (8406.31 μg/g), chlorogenic acid (1647.32 μg/g), and quinic acid (536.11 μg/g), found within the FME, rosmarinic acid (1056.14 μg/g), and chlorogenic acid (648.52 μg/g), occurring within the LME, and chlorogenic acid (1408.43 μg/g), the most abundant in SME. Hence, the plant's secondary metabolites were individually administered similar to extracts, upon which their pharmacology in vivo was elucidated in silico by means of the structure-based studies within rat catalase, as a redox marker, and rat topoisomerase IIα, an enzyme catalyzing the rat DNA double-strand break. Conclusively, the examined N. cataria extracts in specified concentrations could be used in clinical therapy for the prevention of toxin-induced liver diseases.
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Affiliation(s)
- Milena D. Vukić
- Department of Chemistry, Faculty of Science, University of Kragujevac, Radoja Domanovića 12, 34000 Kragujevac, Serbia
| | - Nenad L. Vuković
- Department of Chemistry, Faculty of Science, University of Kragujevac, Radoja Domanovića 12, 34000 Kragujevac, Serbia
| | - Milan Mladenović
- Kragujevac Center for Computational Biochemistry, Department of Chemistry, Faculty of Science, University of Kragujevac, Radoja Domanovića 12, 34000 Kragujevac, Serbia
| | - Nevena Tomašević
- Kragujevac Center for Computational Biochemistry, Department of Chemistry, Faculty of Science, University of Kragujevac, Radoja Domanovića 12, 34000 Kragujevac, Serbia
| | - Sanja Matić
- Department of Science, Institute for Information Technologies Kragujevac, University of Kragujevac, Jovana Cvijića bb, 34000 Kragujevac, Serbia
| | - Snežana Stanić
- Department of Biology and Ecology, Faculty of Science, University of Kragujevac, Radoja Domanovića 12, 34000 Kragujevac, Serbia
| | - Filippo Sapienza
- Rome Center for Molecular Design, Department of Drug Chemistry and Technology, Faculty of Pharmacy and Medicine, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Rino Ragno
- Rome Center for Molecular Design, Department of Drug Chemistry and Technology, Faculty of Pharmacy and Medicine, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Mijat Božović
- Faculty of Science and Mathematics, University of Montenegro, Džordža Vašingtona bb, 81000 Podgorica, Montenegro
| | - Miroslava Kačániová
- Institute of Horticulture, Faculty of Horticulture and Landscape Engineering, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 94976 Nitra, Slovakia
- Department of Bioenergy, Food Technology and Microbiology, Institute of Food Technology and Nutrition, University of Rzeszow, 4 Zelwerowicza St., 35601 Rzeszow, Poland
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3
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ROS as Regulators of Cellular Processes in Melanoma. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2021; 2021:1208690. [PMID: 34725562 PMCID: PMC8557056 DOI: 10.1155/2021/1208690] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 09/28/2021] [Indexed: 12/16/2022]
Abstract
In this review, we examine the multiple roles of ROS in the pathogenesis of melanoma, focusing on signal transduction and regulation of gene expression. In recent years, different studies have analyzed the dual role of ROS in regulating the redox system, with both negative and positive consequences on human health, depending on cell concentration of these agents. High ROS levels can result from an altered balance between oxidant generation and intracellular antioxidant activity and can produce harmful effects. In contrast, low amounts of ROS are considered beneficial, since they trigger signaling pathways involved in physiological activities and programmed cell death, with protective effects against melanoma. Here, we examine these beneficial roles, which could have interesting implications in melanoma treatment.
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4
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Reverse Ordered Sequential Mechanism for Lactoperoxidase with Inhibition by Hydrogen Peroxide. Antioxidants (Basel) 2021; 10:antiox10111646. [PMID: 34829517 PMCID: PMC8614691 DOI: 10.3390/antiox10111646] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 10/02/2021] [Accepted: 10/04/2021] [Indexed: 11/25/2022] Open
Abstract
Lactoperoxidase (LPO, FeIII in its resting state in the absence of substrates)—an enzyme secreted from human mammary, salivary, and other mucosal glands—catalyzes the oxidation of thiocyanate (SCN−) by hydrogen peroxide (H2O2) to produce hypothiocyanite (OSCN−), which functions as an antimicrobial agent. The accepted catalytic mechanism, called the halogen cycle, comprises a two-electron oxidation of LPO by H2O2 to produce oxoiron(IV) radicals, followed by O-atom transfer to SCN−. However, the mechanism does not explain biphasic kinetics and inhibition by H2O2 at low concentration of reducing substrate, conditions that may be biologically relevant. We propose an ordered sequential mechanism in which the order of substrate binding is reversed, first SCN− and then H2O2. The sequence of substrate binding that is described by the halogen cycle mechanism is actually inhibitory.
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5
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New Method of Determining Kinetic Parameters for Decomposition of Hydrogen Peroxide by Catalase. Catalysts 2020. [DOI: 10.3390/catal10030323] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The presented study investigates the kinetic properties of catalase during hydrogen peroxide decomposition reaction. A novel and simple method is hereby proposed for the determination of the enzyme deactivation rate constant (kd) and the decomposition of H2O2 reaction rate constant (kr). Available methods allow the kd constant to be determined only based on previously experimentally determined kr. The presented method differs from the conventional procedure. Known initial and final concentrations of hydrogen peroxide enable determination of both constants at the same time based on data from only one experiment. The correctness of the new method proposed here in determining the reaction rate constant was checked by comparing the obtained constant values with the calculated values according to the commonly used Aebi method. The method was used to analyze in detail the effect of pH (3–10) and temperature (10–45 °C) of the reaction medium on kinetic constants. The value of the constant kd increases together with the value of pH and temperature. In addition, the activation energy for decomposition reaction and deactivation reaction was found to be Er = 14 kJ mol−1 and Ed = 56.8 kJ mol−1 respectively.
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Glorieux C, Calderon PB. Catalase, a remarkable enzyme: targeting the oldest antioxidant enzyme to find a new cancer treatment approach. Biol Chem 2017; 398:1095-1108. [PMID: 28384098 DOI: 10.1515/hsz-2017-0131] [Citation(s) in RCA: 331] [Impact Index Per Article: 47.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 04/04/2017] [Indexed: 12/18/2022]
Abstract
This review is centered on the antioxidant enzyme catalase and will present different aspects of this particular protein. Among them: historical discovery, biological functions, types of catalases and recent data with regard to molecular mechanisms regulating its expression. The main goal is to understand the biological consequences of chronic exposure of cells to hydrogen peroxide leading to cellular adaptation. Such issues are of the utmost importance with potential therapeutic extrapolation for various pathologies. Catalase is a key enzyme in the metabolism of H2O2 and reactive nitrogen species, and its expression and localization is markedly altered in tumors. The molecular mechanisms regulating the expression of catalase, the oldest known and first discovered antioxidant enzyme, are not completely elucidated. As cancer cells are characterized by an increased production of reactive oxygen species (ROS) and a rather altered expression of antioxidant enzymes, these characteristics represent an advantage in terms of cell proliferation. Meanwhile, they render cancer cells particularly sensitive to an oxidant insult. In this context, targeting the redox status of cancer cells by modulating catalase expression is emerging as a novel approach to potentiate chemotherapy.
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7
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Yosca TH, Langston MC, Krest CM, Onderko EL, Grove TL, Livada J, Green MT. Spectroscopic Investigations of Catalase Compound II: Characterization of an Iron(IV) Hydroxide Intermediate in a Non-thiolate-Ligated Heme Enzyme. J Am Chem Soc 2016; 138:16016-16023. [PMID: 27960340 PMCID: PMC5987761 DOI: 10.1021/jacs.6b09693] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report on the protonation state of Helicobacter pylori catalase compound II. UV/visible, Mössbauer, and X-ray absorption spectroscopies have been used to examine the intermediate from pH 5 to 14. We have determined that HPC-II exists in an iron(IV) hydroxide state up to pH 11. Above this pH, the iron(IV) hydroxide complex transitions to a new species (pKa = 13.1) with Mössbauer parameters that are indicative of an iron(IV)-oxo intermediate. Recently, we discussed a role for an elevated compound II pKa in diminishing the compound I reduction potential. This has the effect of shifting the thermodynamic landscape toward the two-electron chemistry that is critical for catalase function. In catalase, a diminished potential would increase the selectivity for peroxide disproportionation over off-pathway one-electron chemistry, reducing the buildup of the inactive compound II state and reducing the need for energetically expensive electron donor molecules.
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Affiliation(s)
- Timothy H. Yosca
- Departments of Chemistry & Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Matthew C. Langston
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Courtney M. Krest
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Elizabeth L. Onderko
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Tyler L. Grove
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jovan Livada
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Michael T. Green
- Departments of Chemistry & Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
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8
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Barends TRM, Foucar L, Ardevol A, Nass K, Aquila A, Botha S, Doak RB, Falahati K, Hartmann E, Hilpert M, Heinz M, Hoffmann MC, Köfinger J, Koglin JE, Kovacsova G, Liang M, Milathianaki D, Lemke HT, Reinstein J, Roome CM, Shoeman RL, Williams GJ, Burghardt I, Hummer G, Boutet S, Schlichting I. Direct observation of ultrafast collective motions in CO myoglobin upon ligand dissociation. Science 2015; 350:445-50. [PMID: 26359336 DOI: 10.1126/science.aac5492] [Citation(s) in RCA: 269] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 08/26/2015] [Indexed: 11/02/2022]
Abstract
The hemoprotein myoglobin is a model system for the study of protein dynamics. We used time-resolved serial femtosecond crystallography at an x-ray free-electron laser to resolve the ultrafast structural changes in the carbonmonoxy myoglobin complex upon photolysis of the Fe-CO bond. Structural changes appear throughout the protein within 500 femtoseconds, with the C, F, and H helices moving away from the heme cofactor and the E and A helices moving toward it. These collective movements are predicted by hybrid quantum mechanics/molecular mechanics simulations. Together with the observed oscillations of residues contacting the heme, our calculations support the prediction that an immediate collective response of the protein occurs upon ligand dissociation, as a result of heme vibrational modes coupling to global modes of the protein.
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Affiliation(s)
- Thomas R M Barends
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany.
| | - Lutz Foucar
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Albert Ardevol
- Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany
| | - Karol Nass
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Andrew Aquila
- European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg, Germany
| | - Sabine Botha
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - R Bruce Doak
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Konstantin Falahati
- Institut für Physikalische und Theoretische Chemie, Goethe-Universität, Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany
| | - Elisabeth Hartmann
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Mario Hilpert
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Marcel Heinz
- Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany. Institut für Physikalische und Theoretische Chemie, Goethe-Universität, Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany
| | - Matthias C Hoffmann
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Jürgen Köfinger
- Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany
| | - Jason E Koglin
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Gabriela Kovacsova
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Mengning Liang
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Despina Milathianaki
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Henrik T Lemke
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Jochen Reinstein
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Christopher M Roome
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Robert L Shoeman
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Garth J Williams
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Irene Burghardt
- Institut für Physikalische und Theoretische Chemie, Goethe-Universität, Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany
| | - Gerhard Hummer
- Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany
| | - Sébastien Boutet
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Ilme Schlichting
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany.
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9
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Masoud M, Ebrahimi F, Minai-Tehrani D. Effect of cimetidine on catalase activity of Pseudomonas aeruginosa: a suggested mechanism of action. J Mol Microbiol Biotechnol 2014; 24:196-201. [PMID: 24993120 DOI: 10.1159/000364872] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Catalase is an important enzyme for the degradation of hydrogen peroxide in cells. Bacteria have potent catalase to deal with H2O2 in their medium culture. Any chemicals that inhibit catalase activity can be harmful for cells. Histamine H2 antagonist drugs such as cimetidine and ranitidine are used for the treatment of gastrointestinal tract disorders. The present results showed that cimetidine could inhibit the catalase activity of Pseudomonas aeruginosa in a competitive inhibition. The determination of IC50 value and Ki (6.5 μM) of cimetidine demonstrated that the enzyme binds to the drug with high affinity. Binding of the drug to the enzyme was pH-dependent and no binding was observed at basic pH (>9) and acidic pH (<6). Moreover, the imidazole ring and cyanoguanidine group of cimetidine may play an important role in inhibition by binding to Fe in heme group and glutamic acid 51 residue on the enzyme, respectively. Ranitidine had no effect on the catalase activity.
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Affiliation(s)
- Masoudeh Masoud
- BioResearch Lab, Faculty of Biological Sciences, Shahid Beheshti University, GC, Tehran, Iran
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10
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Elenewski JE, Hackett JC. Cytochrome P450 compound I in the plane wave pseudopotential framework: GGA electronic and geometric structure of thiolate-ligated iron(IV)-oxo porphyrin. J Comput Chem 2013; 34:1647-60. [PMID: 23670855 PMCID: PMC3711018 DOI: 10.1002/jcc.23311] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 03/18/2013] [Accepted: 04/07/2013] [Indexed: 11/11/2022]
Abstract
The cytochromes P450 constitute a ubiquitous family of metalloenzymes, catalyzing manifold reactions of biological and synthetic importance via a thiolate-ligated iron-oxo (IV) porphyrin radical species denoted compound I (Cpd I). Experimental investigations have implicated this intermediate in a broad spectrum of biophysically interesting phenomena, further augmenting the importance of a Cpd I model system. Ab initio molecular dynamics, including Car-Parrinello and path integral methods, conjoin electronic structure theory with finite temperature simulation, affording tools most valuable to approach such enzymes. These methods are typically driven by density functional theory (DFT) in a plane-wave pseudopotential framework; however, existing studies of Cpd I have been restricted to localized Gaussian basis sets. The appropriate choice of density functional and pseudopotential for such simulations is accordingly not obvious. To remedy this situation, a systematic benchmarking of thiolate-ligated Cpd I is performed using several generalized-gradient approximation (GGA) functionals in the Martins-Troullier and Vanderbilt ultrasoft pseudopotential schemes. The resultant electronic and structural parameters are compared to localized-basis DFT calculations using GGA and hybrid density functionals. The merits and demerits of each scheme are presented in the context of reproducing existing experimental and theoretical results for Cpd I.
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Affiliation(s)
- Justin E. Elenewski
- Goodwin Research Laboratory, Massey Cancer Center, Virginia Commonwealth University, 401 College Street, Richmond, Virginia 23219-1540
| | - John C Hackett
- Goodwin Research Laboratory, Massey Cancer Center, Virginia Commonwealth University, 401 College Street, Richmond, Virginia 23219-1540
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11
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Elenewski JE, Hackett JC. A GGA+U approach to effective electronic correlations in thiolate-ligated iron-oxo (IV) porphyrin. J Chem Phys 2013; 137:124311. [PMID: 23020335 DOI: 10.1063/1.4755290] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
High-valent oxo-metal complexes exhibit correlated electronic behavior on dense, low-lying electronic state manifolds, presenting challenging systems for electronic structure methods. Among these species, the iron-oxo (IV) porphyrin denoted Compound I occupies a privileged position, serving a broad spectrum of catalytic roles. The most reactive members of this family bear a thiolate axial ligand, exhibiting high activity toward molecular oxygen activation and substrate oxidation. The default approach to such systems has entailed the use of hybrid density functionals or multi-configurational/multireference methods to treat electronic correlation. An alternative approach is presented based on the GGA+U approximation to density functional theory, in which a generalized gradient approximation (GGA) functional is supplemented with a localization correction to treat on-site correlation as inspired by the Hubbard model. The electronic structure of thiolate-ligated iron-oxo (IV) porphyrin and corresponding Coulomb repulsion U are determined both empirically and self-consistently, yielding spin-distributions, state level splittings, and electronic densities of states consistent with prior hybrid functional calculations. Comparison of this detailed electronic structure with model Hamiltonian calculations suggests that the localized 3d iron moments induce correlation in the surrounding electron gas, strengthening local moment formation. This behavior is analogous to strongly correlated electronic systems such as Mott insulators, in which the GGA+U scheme serves as an effective single-particle representation for the full, correlated many-body problem.
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Affiliation(s)
- Justin E Elenewski
- Institute for Structural Biology and Drug Discovery and Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, 800 East Leigh Street, Richmond, Virginia 23219, USA
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12
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Vidossich P, Alfonso-Prieto M, Rovira C. Catalases versus peroxidases: DFT investigation of H₂O₂ oxidation in models systems and implications for heme protein engineering. J Inorg Biochem 2012; 117:292-7. [PMID: 22883961 DOI: 10.1016/j.jinorgbio.2012.07.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2012] [Revised: 07/01/2012] [Accepted: 07/02/2012] [Indexed: 11/27/2022]
Abstract
Catalases and peroxidases are ubiquitous heme enzymes that catalyze the removal of hydrogen peroxide (H(2)O(2)). Both enzymes use one molecule of hydrogen peroxide to form a high valent iron intermediate named Compound I (Cpd I). However, whereas catalase Cpd I oxidizes a second H(2)O(2) molecule to oxygen, peroxidases use this intermediate to oxidize other substrates rather than H(2)O(2). The origin of the different reactivity of peroxidases and catalases is not known, but it is likely to be related to structural differences between the two heme active sites. Recent modeling studies suggest that the oxidation of H(2)O(2) by catalase Cpd I may take place by two hydrogen atom transfer steps. In this work, we investigate how catalases and peroxidases compare along the same hydrogen transfer steps to give hints into the question why peroxidases cannot efficiently oxidize H(2)O(2). The use of simplified models allows us to probe the direct effect of the proximal ligand (tyrosinate in catalases and histidine in peroxidases) without masking from the protein environment. We show that the nature of the fifth ligand (His in peroxidase and Tyr in catalase) has little effect on the energy barriers of the hydrogen transfer steps. On the contrary, the Cpd I-hydrogen peroxide (O(Fe)-O(peroxide)) distance affects significantly the reaction barriers. We propose that the distal side architecture of peroxidases do not allow to attain short O(Cpd I)-O(peroxide) distances, thus resulting in a lower efficiency towards H(2)O(2) oxidation.
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Affiliation(s)
- Pietro Vidossich
- Unitat de Química Física, Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
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13
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The reaction mechanisms of heme catalases: an atomistic view by ab initio molecular dynamics. Arch Biochem Biophys 2012; 525:121-30. [PMID: 22516655 DOI: 10.1016/j.abb.2012.04.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 03/31/2012] [Accepted: 04/04/2012] [Indexed: 11/21/2022]
Abstract
Catalases are ubiquitous enzymes that prevent cell oxidative damage by degrading hydrogen peroxide to water and oxygen (2H(2)O(2) → 2H(2)O+O(2)) with high efficiency. The enzyme is first oxidized to a high-valent iron intermediate, known as Compound I (Cpd I, Por(·+)-Fe(IV)=O) which, at difference from other hydroperoxidases, is reduced back to the resting state by further reacting with H(2)O(2). The normal catalase activity is reduced if Cpd I is consumed in a competing side reaction, forming a species named Cpd I*. In recent years, Density Functional Theory (DFT) methods have unraveled the electronic configuration of these high-valent iron species, helping to assign the intermediates trapped in the crystal structures of oxidized catalases. It has been demonstrated that the a priori assumption that the H(+)/H(-) type of mechanism for Cpd I reduction leads to the generation of singlet oxygen is not justified. Moreover, it has been shown by ab initio metadynamics simulations that two pathways are operative for Cpd I reduction: a His-mediated mechanism (described as H·/H(+) + e(-)) in which the distal His acts as an acid-base catalyst and a direct mechanism (described as H·/H·) in which the distal His does not play a direct role. Independently of the mechanism, the reaction proceeds by two one-electron transfers rather than one two-electron transfer, as previously assumed. Electron transfer to Cpd I, regardless of whether the electron is exogenous or endogenous, facilitates protonation of the oxoferryl group, to the point that formation of Cpd I* may be controlled by the easiness of protonation of reduced Cpd I.
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14
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Nicholls P. Classical catalase: ancient and modern. Arch Biochem Biophys 2012; 525:95-101. [PMID: 22326823 DOI: 10.1016/j.abb.2012.01.015] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 01/13/2012] [Accepted: 01/24/2012] [Indexed: 10/14/2022]
Abstract
This review describes the historical difficulties in devising a kinetically satisfactory mechanism for the classical catalase after its identification as a unique catalytic entity in 1902 and prior to the breakthrough 1947 analysis by Chance and co-workers which led to the identification of peroxide compounds I and II. The role of protons in the formation of these two ferryl complexes is discussed and current problems of inhibitory ligand and hydrogen donor binding at the active site are outlined, especially the multiple roles involving formate or formic acid. A previous mechanism of NADPH-dependent catalase protection against substrate inhibition is defended. A revised model linking the catalytic ('catalatic') action and the one-electron side reactions involving compound II is suggested. And it is concluded that, contrary to an idea proposed in 1963 that eukaryotic catalase might be a 'fossil enzyme', current thinking gives it a central role in the redox protective processes of long term importance for human and other eukaryotic and prokaryotic life.
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Affiliation(s)
- Peter Nicholls
- Department of Biological Sciences, University of Essex, Colchester Essex CO4 3SQ, UK.
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15
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Alfonso-Prieto M, Oberhofer H, Klein ML, Rovira C, Blumberger J. Proton Transfer Drives Protein Radical Formation in Helicobacter pylori Catalase but Not in Penicillium vitale Catalase. J Am Chem Soc 2011; 133:4285-98. [DOI: 10.1021/ja1110706] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- M. Alfonso-Prieto
- Computer Simulation & Modeling Laboratory, Parc Científic de Barcelona, Baldiri Reixac 4, 08028 Barcelona, Spain
- Institute for Computational Molecular Science, Temple University, 1900 North 12th Street, Philadelphia, Pennsylvania 19122, United States
| | - H. Oberhofer
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - M. L. Klein
- Institute for Computational Molecular Science, Temple University, 1900 North 12th Street, Philadelphia, Pennsylvania 19122, United States
| | - C. Rovira
- Computer Simulation & Modeling Laboratory, Parc Científic de Barcelona, Baldiri Reixac 4, 08028 Barcelona, Spain
- Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, 08028 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain
| | - J. Blumberger
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
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Goyal MM, Basak A. Human catalase: looking for complete identity. Protein Cell 2010; 1:888-97. [PMID: 21204015 DOI: 10.1007/s13238-010-0113-z] [Citation(s) in RCA: 149] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 09/19/2010] [Indexed: 12/11/2022] Open
Abstract
Catalases are well studied enzymes that play critical roles in protecting cells against the toxic effects of hydrogen peroxide. The ubiquity of the enzyme and the availability of substrates made heme catalases the focus of many biochemical and molecular biology studies over 100 years. In human, this has been implicated in various physiological and pathological conditions. Advancement in proteomics revealed many of novel and previously unknown features of this mysterious enzyme, but some functional aspects are yet to be explained. Along with discussion on future research area, this mini-review compile the information available on the structure, function and mechanism of action of human catalase.
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Affiliation(s)
- Madhur M Goyal
- Department of Biochemistry, J. N. Medical College, Datta Meghe Insatitute of Medical Sciences (Deemed University), Wardha 442004, India.
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Vlasits J, Jakopitsch C, Bernroitner M, Zamocky M, Furtmüller PG, Obinger C. Mechanisms of catalase activity of heme peroxidases. Arch Biochem Biophys 2010; 500:74-81. [DOI: 10.1016/j.abb.2010.04.018] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Revised: 04/23/2010] [Accepted: 04/24/2010] [Indexed: 11/15/2022]
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18
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Leopold JA, Loscalzo J. Oxidative risk for atherothrombotic cardiovascular disease. Free Radic Biol Med 2009; 47:1673-706. [PMID: 19751821 PMCID: PMC2797369 DOI: 10.1016/j.freeradbiomed.2009.09.009] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2009] [Revised: 08/31/2009] [Accepted: 09/06/2009] [Indexed: 02/07/2023]
Abstract
In the vasculature, reactive oxidant species, including reactive oxygen, nitrogen, or halogenating species, and thiyl, tyrosyl, or protein radicals may oxidatively modify lipids and proteins with deleterious consequences for vascular function. These biologically active free radical and nonradical species may be produced by increased activation of oxidant-generating sources and/or decreased cellular antioxidant capacity. Once formed, these species may engage in reactions to yield more potent oxidants that promote transition of the homeostatic vascular phenotype to a pathobiological state that is permissive for atherothrombogenesis. This dysfunctional vasculature is characterized by lipid peroxidation and aberrant lipid deposition, inflammation, immune cell activation, platelet activation, thrombus formation, and disturbed hemodynamic flow. Each of these pathobiological states is associated with an increase in the vascular burden of free radical species-derived oxidation products and, thereby, implicates increased oxidant stress in the pathogenesis of atherothrombotic vascular disease.
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Affiliation(s)
- Jane A Leopold
- Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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19
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Alfonso-Prieto M, Biarnés X, Vidossich P, Rovira C. The Molecular Mechanism of the Catalase Reaction. J Am Chem Soc 2009; 131:11751-61. [DOI: 10.1021/ja9018572] [Citation(s) in RCA: 228] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mercedes Alfonso-Prieto
- Laboratori de Simulació Computacional i Modelització (CoSMoLab), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Química Teòrica i Computacional (IQTCUB), and Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Xevi Biarnés
- Laboratori de Simulació Computacional i Modelització (CoSMoLab), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Química Teòrica i Computacional (IQTCUB), and Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Pietro Vidossich
- Laboratori de Simulació Computacional i Modelització (CoSMoLab), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Química Teòrica i Computacional (IQTCUB), and Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Carme Rovira
- Laboratori de Simulació Computacional i Modelització (CoSMoLab), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Química Teòrica i Computacional (IQTCUB), and Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
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20
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Hersleth HP, Hsiao YW, Ryde U, Görbitz CH, Andersson KK. The influence of X-rays on the structural studies of peroxide-derived myoglobin intermediates. Chem Biodivers 2008; 5:2067-2089. [PMID: 18972498 DOI: 10.1002/cbdv.200890189] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In recent years, the awareness of potential radiation damage of metal centers in protein crystals during crystallographic data collection has received increasing attention. The radiation damage can lead to radiation-induced changes and reduction of the metal sites. One of the research fields where these concerns have been comprehensively addressed is the study of the reaction intermediates of the heme peroxidase and oxygenase reaction cycles. For both the resting states and the high-valent intermediates, the X-rays used in the structure determination have given undesired side effects through radiation-induced changes to the trapped intermediates. However, X-rays have been used to generate and trap the peroxy/hydroperoxy state in crystals. In this review, the structural work and the influence of X-rays on these intermediates in myoglobin are summarized and viewed in light of analogous studies on similar intermediates in peroxidases and oxygenases.
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Affiliation(s)
- Hans-Petter Hersleth
- University of Oslo, Department of Molecular Biosciences, P. O. Box 1041 Blindern, N-0316 Oslo
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21
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Alfonso-Prieto M, Vidossich P, Rodríguez-Fortea A, Carpena X, Fita I, Loewen PC, Rovira C. Electronic State of the Molecular Oxygen Released by Catalase. J Phys Chem A 2008; 112:12842-8. [DOI: 10.1021/jp801512h] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mercedes Alfonso-Prieto
- Laboratori de Simulació Computacional i Modelització (CoSMoLab), Parc Científic de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain, Institut de Química Teòrica i Computacional de la Universitat de Barcelona (IQTCUB), Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel.lí Domingo s/n, 43007 Tarragona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain,Department
| | - Pietro Vidossich
- Laboratori de Simulació Computacional i Modelització (CoSMoLab), Parc Científic de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain, Institut de Química Teòrica i Computacional de la Universitat de Barcelona (IQTCUB), Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel.lí Domingo s/n, 43007 Tarragona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain,Department
| | - Antonio Rodríguez-Fortea
- Laboratori de Simulació Computacional i Modelització (CoSMoLab), Parc Científic de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain, Institut de Química Teòrica i Computacional de la Universitat de Barcelona (IQTCUB), Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel.lí Domingo s/n, 43007 Tarragona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain,Department
| | - Xavi Carpena
- Laboratori de Simulació Computacional i Modelització (CoSMoLab), Parc Científic de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain, Institut de Química Teòrica i Computacional de la Universitat de Barcelona (IQTCUB), Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel.lí Domingo s/n, 43007 Tarragona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain,Department
| | - Ignacio Fita
- Laboratori de Simulació Computacional i Modelització (CoSMoLab), Parc Científic de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain, Institut de Química Teòrica i Computacional de la Universitat de Barcelona (IQTCUB), Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel.lí Domingo s/n, 43007 Tarragona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain,Department
| | - Peter C. Loewen
- Laboratori de Simulació Computacional i Modelització (CoSMoLab), Parc Científic de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain, Institut de Química Teòrica i Computacional de la Universitat de Barcelona (IQTCUB), Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel.lí Domingo s/n, 43007 Tarragona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain,Department
| | - Carme Rovira
- Laboratori de Simulació Computacional i Modelització (CoSMoLab), Parc Científic de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain, Institut de Química Teòrica i Computacional de la Universitat de Barcelona (IQTCUB), Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel.lí Domingo s/n, 43007 Tarragona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain,Department
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Sicking W, Korth HG, de Groot H, Sustmann R. On the functional role of a water molecule in clade 3 catalases: a proposal for the mechanism by which NADPH prevents the formation of compound II. J Am Chem Soc 2008; 130:7345-56. [PMID: 18479132 DOI: 10.1021/ja077787e] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
X-ray structures of the 13 different monofunctional heme catalases published to date were scrutinized in order to gain insight in the mechanism by which NADPH in Clade 3 catalases may protect the reactive ferryloxo intermediate Compound I (Cpd I; por (*+)Fe (IV)O) against deactivation to the catalytically inactive intermediate Compound II (Cpd II; porFe (IV)O). Striking similarities in the molecular network of the protein subunits encompassing the heme center and the surface-bound NADPH were found for all of the Clade 3 catalases. Unique features in this region are the presence of a water molecule (W1) adjacent to the 4-vinyl group of heme and a serine residue or a second water molecule hydrogen-bonded to both W1 and the carbonyl group of a threonine-proline linkage, with the proline in van der Waals contact with the dihydronicotinamide group of NADPH. A mechanism is proposed in which a hydroxyl anion released from W1 undergoes reversible nucleophilic addition to the terminal carbon of the 4-vinyl group of Cpd I, thereby producing a neutral porphyrin pi-radical ferryloxo (HO-por (*)Fe (IV)O) species of reduced reactivity. This structure is suggested to be the elusive Cpd II' intermediate proposed in previous studies. An accompanying proton-shifting process along the hydrogen-bonded network is believed to facilitate the NADPH-mediated reduction of Cpd I to ferricatalase and to serve as a funnel for electron transfer from NADPH to the heme center to restore the catalase Fe (III) resting state. The proposed reaction paths were fully supported as chemically reasonable and energetically feasible by means of density functional theory calculations at the (U)B3LYP/6-31G* level. A particularly attractive feature of the present mechanism is that the previously discussed formation of protein-derived radicals is avoided.
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Affiliation(s)
- Willi Sicking
- Institut für Organische Chemie, Universität Duisburg-Essen, 45117 Essen, Germany
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23
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Chiavarino B, Cipollini R, Crestoni ME, Fornarini S, Lanucara F, Lapi A. Probing the Compound I-like reactivity of a bare high-valent oxo iron porphyrin complex: the oxidation of tertiary amines. J Am Chem Soc 2008; 130:3208-17. [PMID: 18278912 DOI: 10.1021/ja077286t] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanisms of oxidative N-dealkylation of amines by heme enzymes including peroxidases and cytochromes P450 and by functional models for the active Compound I species have long been studied. A debated issue has concerned in particular the character of the primary step initiating the oxidation sequence, either a hydrogen atom transfer (HAT) or an electron transfer (ET) event, facing problems such as the possible contribution of multiple oxidants and complex environmental effects. In the present study, an oxo iron(IV) porphyrin radical cation intermediate 1, [(TPFPP)*+ Fe(IV)=O]+ (TPFPP = meso-tetrakis (pentafluorophenyl)porphinato dianion), functional model of Compound I, has been produced as a bare species. The gas-phase reaction with amines (A) studied by ESI-FT-ICR mass spectrometry has revealed for the first time the elementary steps and the ionic intermediates involved in the oxidative activation. Ionic products are formed involving ET (A*+, the amine radical cation), formal hydride transfer (HT) from the amine ([A(-H)]+, an iminium ion), and oxygen atom transfer (OAT) to the amine (A(O), likely a carbinolamine product), whereas an ionic product involving a net initial HAT event is never observed. The reaction appears to be initiated by an ET event for the majority of the tested amines which included tertiary aliphatic and aromatic amines as well as a cyclic and a secondary amine. For a series of N,N-dimethylanilines the reaction efficiency for the ET activated pathways was found to correlate with the ionization energy of the amine. A stepwise pathway accounts for the C-H bond activation resulting in the formal HT product, namely a primary ET process forming A*+, which is deprotonated at the alpha-C-H bond forming an N-methyl-N-arylaminomethyl radical, A(-H)*, readily oxidized to the iminium ion, [A(-H)]+. The kinetic isotope effect (KIE) for proton transfer (PT) increases as the acidity of the amine radical cation increases and the PT reaction to the base, the ferryl group of (TPFPP)Fe(IV)=O, approaches thermoneutrality. The ET reaction displayed by 1 with gaseous N,N-dimethylaniline finds a counterpart in the ET reactivity of FeO+, reportedly a potent oxidant in the gas phase, and with the barrierless ET process for a model (P)*+ Fe(IV)=O species (where P is the porphine dianion) as found by theoretical calculations. Finally, the remarkable OAT reactivity of 1 with C6F5N(CH3)2 may hint to a mechanism along a route of diverse spin multiplicity.
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Affiliation(s)
- Barbara Chiavarino
- Dipartimento di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Università di Roma La Sapienza P.le A. Moro 5, I-00185, Roma, Italy
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X-ray absorption spectroscopic characterization of a cytochrome P450 compound II derivative. Proc Natl Acad Sci U S A 2008; 105:8179-84. [PMID: 18174331 DOI: 10.1073/pnas.0708299105] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cytochrome P450 enzyme CYP119, its compound II derivative, and its nitrosyl complex were studied by iron K-edge x-ray absorption spectroscopy. The compound II derivative was prepared by reaction of the resting enzyme with peroxynitrite and had a lifetime of approximately 10 s at 23 degrees C. The CYP119 nitrosyl complex was prepared by reaction of the enzyme with nitrogen monoxide gas or with a nitrosyl donor and was stable at 23 degrees C for hours. Samples of CYP119 and its derivatives were studied by x-ray absorption spectroscopy at temperatures below 140 (K) at the Advanced Photon Source of Argonne National Laboratory. The x-ray absorption near-edge structure spectra displayed shifts in edge and pre-edge energies consistent with increasing effective positive charge on iron in the series native CYP119 < CYP119 nitrosyl complex < CYP119 compound II derivative. Extended x-ray absorption fine structure spectra were simulated with good fits for k = 12 A(-1) for native CYP119 and k = 13 A(-1) for both the nitrosyl complex and the compound II derivative. The important structural features for the compound II derivative were an iron-oxygen bond length of 1.82 A and an iron-sulfur bond length of 2.24 A, both of which indicate an iron-oxygen single bond in a ferryl-hydroxide, Fe(IV)OH, moiety.
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Vidossich P, Alfonso-Prieto M, Carpena X, Loewen PC, Fita I, Rovira C. Versatility of the Electronic Structure of Compound I in Catalase-Peroxidases. J Am Chem Soc 2007; 129:13436-46. [DOI: 10.1021/ja072245i] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Pietro Vidossich
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Mercedes Alfonso-Prieto
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Xavi Carpena
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Peter C. Loewen
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Ignacio Fita
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Carme Rovira
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
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Hersleth HP, Uchida T, Røhr AK, Teschner T, Schünemann V, Kitagawa T, Trautwein AX, Görbitz CH, Andersson KK. Crystallographic and Spectroscopic Studies of Peroxide-derived Myoglobin Compound II and Occurrence of Protonated FeIV–O. J Biol Chem 2007; 282:23372-86. [PMID: 17565988 DOI: 10.1074/jbc.m701948200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
High resolution crystal structures of myoglobin in the pH range 5.2-8.7 have been used as models for the peroxide-derived compound II intermediates in heme peroxidases and oxygenases. The observed Fe-O bond length (1.86-1.90 A) is consistent with that of a single bond. The compound II state of myoglobin in crystals was controlled by single-crystal microspectrophotometry before and after synchrotron data collection. We observe some radiation-induced changes in both compound II (resulting in intermediate H) and in the resting ferric state of myoglobin. These radiation-induced states are quite unstable, and compound II and ferric myoglobin are immediately regenerated through a short heating above the glass transition temperature (<1 s) of the crystals. It is unclear how this influences our compound II structures compared with the unaffected compound II, but some crystallographic data suggest that the influence on the Fe-O bond distance is minimal. Based on our crystallographic and spectroscopic data we suggest that for myoglobin the compound II intermediate consists of an Fe(IV)-O species with a single bond. The presence of Fe(IV) is indicated by a small isomer shift of delta = 0.07 mm/s from Mössbauer spectroscopy. Earlier quantum refinements (crystallographic refinement where the molecular-mechanics potential is replaced by a quantum chemical calculation) and density functional theory calculations suggest that this intermediate H species is protonated.
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Affiliation(s)
- Hans-Petter Hersleth
- Department of Chemistry, University of Oslo, PO Box 1033, Blindern, Oslo N-0315, Norway
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27
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Horner O, Mouesca JM, Solari PL, Orio M, Oddou JL, Bonville P, Jouve HM. Spectroscopic description of an unusual protonated ferryl species in the catalase from Proteus mirabilis and density functional theory calculations on related models. Consequences for the ferryl protonation state in catalase, peroxidase and chloroperoxidase. J Biol Inorg Chem 2007; 12:509-25. [PMID: 17237942 DOI: 10.1007/s00775-006-0203-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Accepted: 12/21/2006] [Indexed: 11/24/2022]
Abstract
The catalase from Proteus mirabilis peroxide-resistant bacteria is one of the most efficient heme-containing catalases. It forms a relatively stable compound II. We were able to prepare samples of compound II from P. mirabilis catalase enriched in (57)Fe and to study them by spectroscopic methods. Two different forms of compound II, namely, low-pH compound II (LpH II) and high-pH compound II (HpH II), have been characterized by Mössbauer, extended X-ray absorption fine structure (EXAFS) and UV-vis absorption spectroscopies. The proportions of the two forms are pH-dependent and the pH conversion between HpH II and LpH II is irreversible. Considering (1) the Mössbauer parameters evaluated for four related models by density functional theory methods, (2) the existence of two different Fe-O(ferryl) bond lengths (1.80 and 1.66 A) compatible with our EXAFS data and (3) the pH dependence of the alpha band to beta band intensity ratio in the absorption spectra, we attribute the LpH II compound to a protonated ferryl Fe(IV)-OH complex (Fe-O approximately 1.80 A), whereas the HpH II compound corresponds to the classic ferryl Fe(IV)=O complex (Fe=O approximately 1.66 A). The large quadrupole splitting value of LpH II (measured 2.29 mm s(-1) vs. computed 2.15 mm s(-1)) compared with that of HpH II (measured 1.47 mm s(-1) vs. computed 1.46 mm s(-1)) reflects the protonation of the ferryl group. The relevancy and involvement of such (Fe(IV)=O/Fe(IV)-OH) species in the reactivity of catalase, peroxidase and chloroperoxidase are discussed.
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Affiliation(s)
- O Horner
- Laboratoire de Physicochimie des Métaux en Biologie, UMR CEA/CNRS/Université Joseph Fourier 5155, CEA/Grenoble, 38054, Grenoble Cedex 9, France
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28
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Kirkman HN, Gaetani GF. Mammalian catalase: a venerable enzyme with new mysteries. Trends Biochem Sci 2006; 32:44-50. [PMID: 17158050 DOI: 10.1016/j.tibs.2006.11.003] [Citation(s) in RCA: 247] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Revised: 10/12/2006] [Accepted: 11/23/2006] [Indexed: 11/24/2022]
Abstract
Mammalian catalase has been the subject of many classic biochemical studies. Despite our detailed knowledge of its functional mechanisms and its three-dimensional structure, however, several unexpected features of mammalian catalase have been recently discovered. For example, some mammalian catalases seem to have oxidase activity and produce reactive oxygen species when exposed to UVB light. In addition, bovine catalase uses unbound NAD(P)H to prevent substrate inactivation without displacing catalase-bound NADP(+). Coupled with the earlier discovery of catalase-bound NADPH, these developments indicate that serendipity and new investigative approaches can reveal unexpected features, even for an enzyme that has been studied for over 100 years.
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Affiliation(s)
- Henry N Kirkman
- Department of Pediatrics, Division of Genetics and Metabolism, University of North Carolina, Chapel Hill, NC 27599-7487, USA.
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29
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Gao J, Ma S, Major DT, Nam K, Pu J, Truhlar DG. Mechanisms and free energies of enzymatic reactions. Chem Rev 2006; 106:3188-209. [PMID: 16895324 PMCID: PMC4477011 DOI: 10.1021/cr050293k] [Citation(s) in RCA: 317] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jiali Gao
- Department of Chemistry and Supercomputing Institute, Digital Technology Center, University of Minnesota, Minneapolis, Minnesota 55455
| | - Shuhua Ma
- Department of Chemistry and Supercomputing Institute, Digital Technology Center, University of Minnesota, Minneapolis, Minnesota 55455
| | - Dan T. Major
- Department of Chemistry and Supercomputing Institute, Digital Technology Center, University of Minnesota, Minneapolis, Minnesota 55455
| | - Kwangho Nam
- Department of Chemistry and Supercomputing Institute, Digital Technology Center, University of Minnesota, Minneapolis, Minnesota 55455
| | - Jingzhi Pu
- Department of Chemistry and Supercomputing Institute, Digital Technology Center, University of Minnesota, Minneapolis, Minnesota 55455
| | - Donald G. Truhlar
- Department of Chemistry and Supercomputing Institute, Digital Technology Center, University of Minnesota, Minneapolis, Minnesota 55455
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30
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Horner O, Oddou JL, Mouesca JM, Jouve HM. Mössbauer identification of a protonated ferryl species in catalase from Proteus mirabilis: Density functional calculations on related models. J Inorg Biochem 2006; 100:477-9. [PMID: 16442627 DOI: 10.1016/j.jinorgbio.2005.12.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2005] [Accepted: 12/13/2005] [Indexed: 11/30/2022]
Abstract
The Proteus mirabilis catalase is one of the most efficient heme-containing catalase and forms a relatively stable compound II. Samples of compound II were prepared from PMC enriched in (57)Fe. For the first time, two different forms of compound II, namely low pH compound II (LpH II) (43%) and high pH compound II (HpH II) (25%), have been characterized by Mössbauer spectroscopy at pH 8.3. The ratio LpH II/HpH II increases irreversibly with decreasing pH. The large quadrupole splitting value of LpH II (DeltaE(Q)=2.29 (2) mm/s, with delta(/Fe)=0.03 (2) mm/s), compared to that of HpH II (DeltaE(Q)=1.47 (2) mm/s, with delta(/Fe)=0.07 (2) mm/s), reflects the protonation of the ferryl group. Quadrupole splitting values of 1.46 and 2.15mm/s have been computed by DFT for optimized models of the ferryl compound II (model 1) and the protonated ferryl compound II (model 2), respectively, starting from the Fe(IV)O model initially published by Rovira and Fita [C. Rovira, I. Fita, J. Phys. Chem. B 107 (2003) 5300-5305]. Therefore, we attribute the LpH II compound to a protonated ferryl Fe(IV)-OH complex, whereas the HpH II compound corresponds to the classical ferryl Fe(IV)O complex.
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Affiliation(s)
- O Horner
- Laboratoire de Physicochimie des Métaux en Biologie, UMR 5155, CEA/Grenoble, 38054 Grenoble cedex 9, France
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31
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Hersleth HP, Ryde U, Rydberg P, Görbitz CH, Andersson KK. Structures of the high-valent metal-ion haem–oxygen intermediates in peroxidases, oxygenases and catalases. J Inorg Biochem 2006; 100:460-76. [PMID: 16510192 DOI: 10.1016/j.jinorgbio.2006.01.018] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Revised: 01/09/2006] [Accepted: 01/09/2006] [Indexed: 11/22/2022]
Abstract
Peroxidases, oxygenases and catalases have similar high-valent metal-ion intermediates in their respective reaction cycles. In this review, haem-based examples will be discussed. The intermediates of the haem-containing enzymes have been extensively studied for many years by different spectroscopic methods like UV-Vis, EPR (electron paramagnetic resonance), resonance Raman, Mössbauer and MCD (magnetic circular dichroism). The first crystal structure of one of these high-valent intermediates was on cytochrome c peroxidase in 1987. Since then, structures have appeared for catalases in 1996, 2002, 2003, putatively for cytochrome P450 in 2000, for myoglobin in 2002, for horseradish peroxidase in 2002 and for cytochrome c peroxidase again in 1994 and 2003. This review will focus on the most recent structural investigations for the different intermediates of these proteins. The structures of these intermediates will also be viewed in light of quantum mechanical (QM) calculations on haem models. In particular quantum refinement, which is a combination of QM calculations and crystallography, will be discussed. Only small structural changes accompany the generation of these intermediates. The crystal structures show that the compound I state, with a so called pi-cation radical on the haem group, has a relatively short iron-oxygen bond (1.67-1.76A) in agreement with a double-bond character, while the compound II state or the compound I state with a radical on an amino acid residue have a relatively long iron-oxygen bond (1.86-1.92A) in agreement with a single-bond character where the oxygen-atom is protonated.
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Affiliation(s)
- Hans-Petter Hersleth
- Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway
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32
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Terner J, Palaniappan V, Gold A, Weiss R, Fitzgerald MM, Sullivan AM, Hosten CM. Resonance Raman spectroscopy of oxoiron(IV) porphyrin π-cation radical and oxoiron(IV) hemes in peroxidase intermediates. J Inorg Biochem 2006; 100:480-501. [PMID: 16513173 DOI: 10.1016/j.jinorgbio.2006.01.008] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Accepted: 01/04/2006] [Indexed: 11/15/2022]
Abstract
The catalytic cycle intermediates of heme peroxidases, known as compounds I and II, have been of long standing interest as models for intermediates of heme proteins, such as the terminal oxidases and cytochrome P450 enzymes, and for non-heme iron enzymes as well. Reports of resonance Raman signals for compound I intermediates of the oxo-iron(IV) porphyrin pi-cation radical type have been sometimes contradictory due to complications arising from photolability, causing compound I signals to appear similar to those of compound II or other forms. However, studies of synthetic systems indicated that protein based compound I intermediates of the oxoiron(IV) porphyrin pi-cation radical type should exhibit vibrational signatures that are different from the non-radical forms. The compound I intermediates of horseradish peroxidase (HRP), and chloroperoxidase (CPO) from Caldariomyces fumago do in fact exhibit unique and characteristic vibrational spectra. The nature of the putative oxoiron(IV) bond in peroxidase intermediates has been under discussion in the recent literature, with suggestions that the Fe(IV)O unit might be better described as Fe(IV)-OH. The generally low Fe(IV)O stretching frequencies observed for proteins have been difficult to mimic in synthetic ferryl porphyrins via electron donation from trans axial ligands alone. Resonance Raman studies of iron-oxygen vibrations within protein species that are sensitive to pH, deuteration, and solvent oxygen exchange, indicate that hydrogen bonding to the oxoiron(IV) group within the protein environment contributes to substantial lowering of Fe(IV)O frequencies relative to those of synthetic model compounds.
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Affiliation(s)
- James Terner
- Department of Chemistry, Virginia Commonwealth University, Richmond, VA 23284-2006, USA.
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33
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Kozlowski PM, Kuta J, Ohta T, Kitagawa T. Resonance Raman enhancement of FeIVO stretch in high-valent iron porphyrins: An insight from TD-DFT calculations. J Inorg Biochem 2006; 100:744-50. [PMID: 16529819 DOI: 10.1016/j.jinorgbio.2006.01.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2005] [Revised: 01/10/2006] [Accepted: 01/10/2006] [Indexed: 11/23/2022]
Abstract
Density functional theory (DFT) has been applied to explain the origin of resonance Raman enhancement associated with the Fe(IV)=O stretch observed in iron(IV)oxo porphyrins. To accomplish this electronic excitations of the Im-(Por)Fe(IV)=O model were computed in the 1.5-4.0 eV spectral range using time-dependent DFT (TD-DFT). All electronic transitions having dominant pi-->pi* character were analyzed and assigned in terms of one-electron excitations. It was found that the most intense Soret band has a multi-component character, but the pi (a(2u))-->pi*(d(xz),d(yz)) and pi (a(1u))-->pi*(d(xz),d(yz)) electronic excitations are primarily responsible for observed resonance enhancement of the Fe(IV)=O stretch.
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Affiliation(s)
- Pawel M Kozlowski
- Department of Chemistry, University of Louisville, 2330 South Brook Street, Louisville, KY 40292, USA.
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Behan RK, Green MT. On the status of ferryl protonation. J Inorg Biochem 2006; 100:448-59. [PMID: 16500711 DOI: 10.1016/j.jinorgbio.2005.12.019] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2005] [Accepted: 12/13/2005] [Indexed: 11/18/2022]
Abstract
We examine the issue of ferryl protonation in heme proteins. An analysis of the results obtained from X-ray crystallography, resonance Raman spectroscopy, and extended X-ray absorption spectroscopy (EXAFS) is presented. Fe-O bond distances obtained from all three techniques are compared using Badger's rule. The long Fe-O bond lengths found in the ferryl crystal structures of myoglobin, cytochrome c peroxidase, horseradish peroxidase, and catalase deviate substantially from the values predict by Badger's rule, while the oxo-like distances obtained from EXAFS measurements are in good agreement with the empirical formula. Density functional calculations, which suggest that Mössbauer spectroscopy can be used to determine ferryl protonation states, are presented. Our calculations indicate that the quadrupole splitting (DeltaE(Q)) changes significantly upon ferryl protonation. New resonance Raman data for horse-heart myoglobin compound II (Mb-II, pH 4.5) are also presented. An Fe-O stretching frequency of 790cm(-1) (shifting to 754cm(-1) with (18)O substitution) was obtained. This frequency provides a Badger distance of r(Fe-O)=1.66A. This distance is in agreement with the 1.69A Fe-O bond distance obtained from EXAFS measurements but is significantly shorter than the 1.93A bond found in the crystal structure of Mb-II (pH 5.2). In light of the available evidence, we conclude that the ferryl forms of myoglobin (pKa4), horseradish peroxidase (pKa4), cytochrome c peroxidase (pKa4), and catalase (pKa7) are not basic. They are authentic Fe(IV)oxos with Fe-O bonds on the order of 1.65A.
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Affiliation(s)
- Rachel K Behan
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
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35
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Conradie J, Wasbotten I, Ghosh A. Electronic ménages a trois: a molecular orbital perspective of protonated ferryl intermediates and synthetic models. J Inorg Biochem 2006; 100:502-6. [PMID: 16504302 DOI: 10.1016/j.jinorgbio.2006.01.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Revised: 01/10/2006] [Accepted: 01/10/2006] [Indexed: 11/24/2022]
Abstract
Presented here is a molecular orbital perspective of various S=1 iron(IV)-hydroxo compound II intermediates as well as of synthetic heme and nonheme analogues. A key conceptual issue concerns how the iron(IV) center in these species coexists with highly reducing alkoxide, thiolate, phenolate, and hydroperoxide ligands. We suggest that a clue to this conundrum involves a three-way splitting of the spin density among the iron and two pi-basic ligands, which effectively delocalizes the high positive charge away from the iron.
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Affiliation(s)
- Jeanet Conradie
- Department of Chemistry, University of Tromsø, Breivika, N-9037 Tromsø, Norway
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36
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Green MT. Application of Badger's Rule to Heme and Non-Heme Iron−Oxygen Bonds: An Examination of Ferryl Protonation States. J Am Chem Soc 2006; 128:1902-6. [PMID: 16464091 DOI: 10.1021/ja054074s] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To gain insight into the protonation state of enzymatic ferryl species we have examined the applicability of Badger's rule to heme and non-heme iron-oxygen bonds. Using density functional theory we have calculated r(e) and nu(e) for the Fe-O bonds of complexes with different axial ligands, iron-oxidation, oxygen-protonation, and spin states. Our results indicate that Badger's rule holds for heme and non-heme oxo and hydroxo complexes. We find that the long Fe-O bonds that have been reported in the crystal structures of the ferryl forms of myoglobin, horseradish peroxidase, cytochrome c peroxidase, and catalase deviate substantially from the values predicted by Badger's rule, while the short Fe-O bonds obtained from X-ray absorption measurements are in good agreement with Badger's rule. In light of our analysis we conclude that the ferryl forms of myoglobin, horseradish peroxidase, and cytochrome c peroxidase are authentic iron(IV)oxos with Fe-O bonds on the order of 1.66 A and pKa's < 4.
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Affiliation(s)
- Michael T Green
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA.
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