1
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Large TAG, Keown W, Gary JB, Chiang L, Stack TDP. Imidazolate-Stabilized Cu(III): Dioxygen to Oxides at Type 3 Copper Sites. Angew Chem Int Ed Engl 2025; 64:e202416967. [PMID: 39420537 DOI: 10.1002/anie.202416967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2024] [Revised: 10/11/2024] [Accepted: 10/14/2024] [Indexed: 10/19/2024]
Abstract
Imidazole ligation of metals through histidine is extensive among metalloproteins, yet the role of the imidazolate conjugate base is often neglected, despite its potential accessibility when bonded to an oxidized metal center. Using synthetic models of oxygenated tyrosinase enzymes ligated exclusively by monodentate imidazoles, we find that deprotonation of the μ2-η2:η2-peroxidodicopper(II) species triggers redox isomerization to an imidazolate-ligated bis(μ2-oxido)dicopper(III) species. Formal two-electron oxidation to Cu(III) remains biologically unprecedented, yet is effected readily by addition of base. Spectrophotometric titrations by UV/Visible/near-IR and copper K-edge X-ray absorption spectroscopies are interpreted most simply as two cooperative, 2H+ transformations in which the peroxide O-O is cleaved in the first step. Elaboration from simple imidazoles to a protected histidine extends this isomerization into an amino acid environment. The role of phenolate as a base suggests this four-electron reduction of O2 is energetically viable in a biological context and requires only two copper centers, which act as two-electron shuttles when imidazole deprotonation assists. This existential precedent of viable imidazolate intermediates invites speculation into an alternative mechanism for phenol hydroxylation not previously considered at Type 3 copper sites such as tyrosinases. Structural biological evidence suggests imidazolate ligation of copper may be more widespread than generally understood.
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Affiliation(s)
- Tao A G Large
- Department of Chemistry, Stanford University Stanford, California, 94305, USA
| | - William Keown
- Department of Chemistry, Stanford University Stanford, California, 94305, USA
| | - J Brannon Gary
- Department of Chemistry, Stanford University Stanford, California, 94305, USA
- Department of Chemistry & Biochemistry, Stephen F. Austin State University Nacogdoches, TX, 75962, USA
| | - Linus Chiang
- Department of Chemistry, Stanford University Stanford, California, 94305, USA
- Department of Chemistry, University of the Fraser Valley Abbotsford, BC, Canada
| | - T Daniel P Stack
- Department of Chemistry, Stanford University Stanford, California, 94305, USA
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2
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Guberman-Pfeffer MJ. Assessing Thermal Response of Redox Conduction for Anti-Arrhenius Kinetics in a Microbial Cytochrome Nanowire. J Phys Chem B 2022; 126:10083-10097. [PMID: 36417757 PMCID: PMC9743091 DOI: 10.1021/acs.jpcb.2c06822] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A micrometers-long helical homopolymer of the outer-membrane cytochrome type S (OmcS) from Geobacter sulfurreducens is proposed to transport electrons to extracellular acceptors in an ancient respiratory strategy of biogeochemical and technological significance. OmcS surprisingly exhibits higher conductivity upon cooling (anti-Arrhenius kinetics), an effect previously attributed to H-bond restructuring and heme redox potential shifts. Herein, the temperature sensitivity of redox conductivity is more thoroughly examined with conventional and constant-redox and -pH molecular dynamics and quantum mechanics/molecular mechanics. A 30 K drop in temperature constituted a weak perturbation to electron transfer energetics, changing electronic couplings (⟨Hmn⟩), reaction free energies (ΔGmn), reorganization energies (λmn), and activation energies (Ea) by at most |0.002|, |0.050|, |0.120|, and |0.045| eV, respectively. Changes in ΔGmn reflected -0.07 ± 0.03 V shifts in redox potentials that were caused in roughly equal measure by altered electrostatic interactions with the solvent and protein. Changes in intraprotein H-bonding reproduced the earlier observations. Single-particle diffusion and multiparticle steady-state flux models, parametrized with Marcus theory rates, showed that biologically relevant incoherent hopping cannot qualitatively or quantitatively describe electrical conductivity measured by atomic force microscopy in filamentous OmcS. The discrepancy is attributed to differences between solution-phase simulations and solid-state measurements and the need to model intra- and intermolecular vibrations explicitly.
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Affiliation(s)
- Matthew J. Guberman-Pfeffer
- Department
of Molecular Biophysics and Biochemistry, Yale University, 333 Cedar St., New Haven, Connecticut06510, United States,Microbial
Sciences Institute, Yale University, 840 West Campus Drive, West Haven, Connecticut06516, United States,
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3
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Di Rocco G, Battistuzzi G, Borsari M, Bortolotti CA, Ranieri A, Sola M. The enthalpic and entropic terms of the reduction potential of metalloproteins: Determinants and interplay. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.214071] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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4
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Schachinger F, Chang H, Scheiblbrandner S, Ludwig R. Amperometric Biosensors Based on Direct Electron Transfer Enzymes. Molecules 2021; 26:molecules26154525. [PMID: 34361678 PMCID: PMC8348568 DOI: 10.3390/molecules26154525] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/19/2021] [Accepted: 07/23/2021] [Indexed: 11/16/2022] Open
Abstract
The accurate determination of analyte concentrations with selective, fast, and robust methods is the key for process control, product analysis, environmental compliance, and medical applications. Enzyme-based biosensors meet these requirements to a high degree and can be operated with simple, cost efficient, and easy to use devices. This review focuses on enzymes capable of direct electron transfer (DET) to electrodes and also the electrode materials which can enable or enhance the DET type bioelectrocatalysis. It presents amperometric biosensors for the quantification of important medical, technical, and environmental analytes and it carves out the requirements for enzymes and electrode materials in DET-based third generation biosensors. This review critically surveys enzymes and biosensors for which DET has been reported. Single- or multi-cofactor enzymes featuring copper centers, hemes, FAD, FMN, or PQQ as prosthetic groups as well as fusion enzymes are presented. Nanomaterials, nanostructured electrodes, chemical surface modifications, and protein immobilization strategies are reviewed for their ability to support direct electrochemistry of enzymes. The combination of both biosensor elements-enzymes and electrodes-is evaluated by comparison of substrate specificity, current density, sensitivity, and the range of detection.
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5
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Paradisi A, Lancellotti L, Borsari M, Bellei M, Bortolotti CA, Di Rocco G, Ranieri A, Sola M, Battistuzzi G. Met80 and Tyr67 affect the chemical unfolding of yeast cytochrome c: comparing the solution vs.immobilized state. RSC Chem Biol 2020. [DOI: 10.1039/d0cb00115e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The motional regime affects the unfolding propensity and axial heme coordination of the Met80Ala and Met80Ala/Tyr67Ala variants of yeast iso-1 cytochromec.
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Affiliation(s)
| | - Lidia Lancellotti
- Department of Chemistry and Geology
- University of Modena and Reggio Emilia
- 41126 Modena
- Italy
| | - Marco Borsari
- Department of Chemistry and Geology
- University of Modena and Reggio Emilia
- 41126 Modena
- Italy
| | - Marzia Bellei
- Department of Life Sciences
- University of Modena and Reggio Emilia
- 41126 Modena
- Italy
| | | | - Giulia Di Rocco
- Department of Life Sciences
- University of Modena and Reggio Emilia
- 41126 Modena
- Italy
| | - Antonio Ranieri
- Department of Life Sciences
- University of Modena and Reggio Emilia
- 41126 Modena
- Italy
| | - Marco Sola
- Department of Life Sciences
- University of Modena and Reggio Emilia
- 41126 Modena
- Italy
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6
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Redox thermodynamics of B-class dye-decolorizing peroxidases. J Inorg Biochem 2019; 199:110761. [PMID: 31325671 DOI: 10.1016/j.jinorgbio.2019.110761] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 06/22/2019] [Accepted: 07/08/2019] [Indexed: 11/23/2022]
Abstract
With >5000 annotated genes dye-decolorizing peroxidases (DyPs) represent a heme b peroxidase family of broad functional diversity. Bacterial B-class DyPs are poor peroxidases of unknown physiological function. Hydrogen peroxide efficiently mediates the rapid formation of Compound I in B-class DyPs, which, however, is stable and shows modest reactivity towards organic and inorganic electron donors. To understand these characteristics, we have investigated the redox thermodynamics of the one-electron reduction of the ferric high-spin form of wild-type B-class DyP from the pathogenic bacterium Klebsiella pneumoniae (KpDyP) and the variants D143A, R232A and D143A/R232A. These distal amino acids are fully conserved in all DyPs and play important roles in Compound I formation and maintenance of the heme cavity architecture and substrate access route(s). The E°' values of the respective redox couples Fe(III)/Fe(II) varied from -350 mV (wild-type KpDyP) to -299 mV (D143A/R232A) at pH 7.0. Variable-temperature spectroelectrochemical experiments revealed that the reduction reaction of B-class DyPs is enthalpically unfavored but entropically favored with significant differences in enthalpic and entropic contributions to E°' between the four proteins. Molecular dynamics simulations demonstrated the impact of solvent reorganization on the entropy change during reduction reaction and revealed the dynamics and restriction of substrate access channels. Obtained data are discussed with respect to the poor peroxidase activities of B-class DyPs and compared with heme peroxidases from other (super)families as well as with chlorite dismutases, which do not react with hydrogen peroxide but share a similar fold and heme cavity architecture.
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7
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Bellei M, Bortolotti CA, Di Rocco G, Borsari M, Lancellotti L, Ranieri A, Sola M, Battistuzzi G. The influence of the Cys46/Cys55 disulfide bond on the redox and spectroscopic properties of human neuroglobin. J Inorg Biochem 2018; 178:70-86. [DOI: 10.1016/j.jinorgbio.2017.10.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/21/2017] [Accepted: 10/09/2017] [Indexed: 12/21/2022]
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8
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Hofbauer S, Dalla Sega M, Scheiblbrandner S, Jandova Z, Schaffner I, Mlynek G, Djinović-Carugo K, Battistuzzi G, Furtmüller PG, Oostenbrink C, Obinger C. Chemistry and Molecular Dynamics Simulations of Heme b-HemQ and Coproheme-HemQ. Biochemistry 2016; 55:5398-412. [PMID: 27599156 PMCID: PMC5041162 DOI: 10.1021/acs.biochem.6b00701] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recently, a novel pathway for heme b biosynthesis in Gram-positive bacteria has been proposed. The final poorly understood step is catalyzed by an enzyme called HemQ and includes two decarboxylation reactions leading from coproheme to heme b. Coproheme has been suggested to act as both substrate and redox active cofactor in this reaction. In the study presented here, we focus on HemQs from Listeria monocytogenes (LmHemQ) and Staphylococcus aureus (SaHemQ) recombinantly produced as apoproteins in Escherichia coli. We demonstrate the rapid and two-phase uptake of coproheme by both apo forms and the significant differences in thermal stability of the apo forms, coproheme-HemQ and heme b-HemQ. Reduction of ferric high-spin coproheme-HemQ to the ferrous form is shown to be enthalpically favored but entropically disfavored with standard reduction potentials of -205 ± 3 mV for LmHemQ and -207 ± 3 mV for SaHemQ versus the standard hydrogen electrode at pH 7.0. Redox thermodynamics suggests the presence of a pronounced H-bonding network and restricted solvent mobility in the heme cavity. Binding of cyanide to the sixth coproheme position is monophasic but relatively slow (∼1 × 10(4) M(-1) s(-1)). On the basis of the available structures of apo-HemQ and modeling of both loaded forms, molecular dynamics simulation allowed analysis of the interaction of coproheme and heme b with the protein as well as the role of the flexibility at the proximal heme cavity and the substrate access channel for coproheme binding and heme b release. Obtained data are discussed with respect to the proposed function of HemQ in monoderm bacteria.
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Affiliation(s)
- Stefan Hofbauer
- Department for Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna , A-1030 Vienna, Austria
| | - Marco Dalla Sega
- Department of Material Sciences and Process Engineering, Institute of Molecular Modeling and Simulation, BOKU-University of Natural Resources and Life Sciences , A-1190 Vienna, Austria
| | - Stefan Scheiblbrandner
- Department of Food Science and Technology, Food Biotechnology Laboratory, BOKU-University of Natural Resources and Life Sciences , A-1190 Vienna, Austria
| | - Zuzana Jandova
- Department of Material Sciences and Process Engineering, Institute of Molecular Modeling and Simulation, BOKU-University of Natural Resources and Life Sciences , A-1190 Vienna, Austria
| | - Irene Schaffner
- Department of Chemistry, Division of Biochemistry, VIBT-Vienna Institute of BioTechnology, BOKU-University of Natural Resources and Life Sciences , A-1190 Vienna, Austria
| | - Georg Mlynek
- Department for Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna , A-1030 Vienna, Austria
| | - Kristina Djinović-Carugo
- Department for Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna , A-1030 Vienna, Austria.,Department of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana , 1000 Ljubljana, Slovenia
| | - Gianantonio Battistuzzi
- Department of Chemistry and Geology, University of Modena and Reggio Emilia , 41125 Modena, Italy
| | - Paul G Furtmüller
- Department of Chemistry, Division of Biochemistry, VIBT-Vienna Institute of BioTechnology, BOKU-University of Natural Resources and Life Sciences , A-1190 Vienna, Austria
| | - Chris Oostenbrink
- Department of Material Sciences and Process Engineering, Institute of Molecular Modeling and Simulation, BOKU-University of Natural Resources and Life Sciences , A-1190 Vienna, Austria
| | - Christian Obinger
- Department of Chemistry, Division of Biochemistry, VIBT-Vienna Institute of BioTechnology, BOKU-University of Natural Resources and Life Sciences , A-1190 Vienna, Austria
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9
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Sündermann A, Reif MM, Hofbauer S, Obinger C, Oostenbrink C. Investigation of ion binding in chlorite dismutases by means of molecular dynamics simulations. Biochemistry 2014; 53:4869-79. [PMID: 24988286 PMCID: PMC4116397 DOI: 10.1021/bi500467h] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
![]()
Chlorite
dismutases are prokaryotic heme b oxidoreductases
that convert chlorite to chloride and dioxygen. It has been postulated
that during turnover hypochlorite is formed transiently, which might
be responsible for the observed irreversible inactivation of these
iron proteins. The only charged distal residue in the heme cavity
is a conserved and mobile arginine, but its role in catalysis and
inactivation is not fully understood. In the present study, the pentameric
chlorite dismutase (Cld) from the bacterium Candidatus Nitrospira
defluvii was probed for binding of the low spin ligand cyanide,
the substrate chlorite, and the intermediate hypochlorite. Simulations
were performed with the enzyme in the ferrous, ferric, and compound
I state. Additionally, the variant R173A was studied. We report the
parametrization for the GROMOS force field of the anions ClO–, ClO2–, ClO3–, and ClO4– and describe spontaneous
binding, unbinding, and rebinding events of chlorite and hypochlorite,
as well as the dynamics of the conformations of Arg173 during simulations.
The findings suggest that (i) chlorite binding to ferric NdCld occurs
spontaneously and (ii) that Arg173 is important for recognition and
to impair hypochlorite leakage from the reaction sphere. The simulation
data is discussed in comparison with experimental data on catalysis
and inhibition of chlorite dismutase.
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Affiliation(s)
- Axel Sündermann
- Department of Material Sciences and Process Engineering, Institute of Molecular Modeling and Simulation, University of Natural Resources and Life Sciences Vienna , Muthgasse 18, A-1190 Vienna, Austria
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10
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Hofbauer S, Bellei M, Sündermann A, Pirker KF, Hagmüller A, Mlynek G, Kostan J, Daims H, Furtmüller PG, Djinović-Carugo K, Oostenbrink C, Battistuzzi G, Obinger C. Redox thermodynamics of high-spin and low-spin forms of chlorite dismutases with diverse subunit and oligomeric structures. Biochemistry 2012; 51:9501-12. [PMID: 23126649 PMCID: PMC3557923 DOI: 10.1021/bi3013033] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Chlorite dismutases (Clds) are heme b-containing
oxidoreductases that convert chlorite to chloride and dioxygen. In
this work, the thermodynamics of the one-electron reduction of the
ferric high-spin forms and of the six-coordinate low-spin cyanide
adducts of the enzymes from Nitrobacter winogradskyi (NwCld) and Candidatus “Nitrospira defluvii”
(NdCld) were determined through spectroelectrochemical experiments.
These proteins belong to two phylogenetically separated lineages that
differ in subunit (21.5 and 26 kDa, respectively) and oligomeric (dimeric
and pentameric, respectively) structure but exhibit similar chlorite
degradation activity. The E°′ values
for free and cyanide-bound proteins were determined to be −119
and −397 mV for NwCld and −113 and −404 mV for
NdCld, respectively (pH 7.0, 25 °C). Variable-temperature spectroelectrochemical
experiments revealed that the oxidized state of both proteins is enthalpically
stabilized. Molecular dynamics simulations suggest that changes in
the protein structure are negligible, whereas solvent reorganization
is mainly responsible for the increase in entropy during the redox
reaction. Obtained data are discussed with respect to the known structures
of the two Clds and the proposed reaction mechanism.
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Affiliation(s)
- Stefan Hofbauer
- Department of Chemistry, Division of Biochemistry, VIBT-Vienna Institute of BioTechnology, BOKU-University of Natural Resources and Life Sciences, A-1190 Vienna, Austria
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11
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Heimdal J, Kaukonen M, Srnec M, Rulíšek L, Ryde U. Reduction potentials and acidity constants of Mn superoxide dismutase calculated by QM/MM free-energy methods. Chemphyschem 2011; 12:3337-47. [PMID: 21960467 DOI: 10.1002/cphc.201100339] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Indexed: 11/10/2022]
Abstract
We used two theoretical methods to estimate reduction potentials and acidity constants in Mn superoxide dismutase (MnSOD), namely combined quantum mechanical and molecular mechanics (QM/MM) thermodynamic cycle perturbation (QTCP) and the QM/MM-PBSA approach. In the latter, QM/MM energies are combined with continuum solvation energies calculated by solving the Poisson-Boltzmann equation (PB) or by the generalised Born approach (GB) and non-polar solvation energies calculated from the solvent-exposed surface area. We show that using the QTCP method, we can obtain accurate and precise estimates of the proton-coupled reduction potential for MnSOD, 0.30±0.01 V, which compares favourably with experimental estimates of 0.26-0.40 V. However, the calculated potentials depend strongly on the DFT functional used: The B3LYP functional gives 0.6 V more positive potentials than the PBE functional. The QM/MM-PBSA approach leads to somewhat too high reduction potentials for the coupled reaction and the results depend on the solvation model used. For reactions involving a change in the net charge of the metal site, the corresponding results differ by up to 1.3 V or 24 pK(a) units, rendering the QM/MM-PBSA method useless to determine absolute potentials. However, it may still be useful to estimate relative shifts, although the QTCP method is expected to be more accurate.
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Affiliation(s)
- Jimmy Heimdal
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P. O. Box 124, 221 00 Lund, Sweden
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12
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Battistuzzi G, Stampler J, Bellei M, Vlasits J, Soudi M, Furtmüller PG, Obinger C. Influence of the Covalent Heme–Protein Bonds on the Redox Thermodynamics of Human Myeloperoxidase. Biochemistry 2011; 50:7987-94. [DOI: 10.1021/bi2008432] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Gianantonio Battistuzzi
- Department of Chemistry, University of Modena and Reggio Emilia, via Campi 183,
41100 Modena, Italy
| | - Johanna Stampler
- Vienna
Institute of BioTechnology,
Department of Chemistry, Division of Biochemistry, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18,
A-1190 Vienna, Austria
| | - Marzia Bellei
- Department of Chemistry, University of Modena and Reggio Emilia, via Campi 183,
41100 Modena, Italy
| | - Jutta Vlasits
- Vienna
Institute of BioTechnology,
Department of Chemistry, Division of Biochemistry, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18,
A-1190 Vienna, Austria
| | - Monika Soudi
- Vienna
Institute of BioTechnology,
Department of Chemistry, Division of Biochemistry, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18,
A-1190 Vienna, Austria
| | - Paul G. Furtmüller
- Vienna
Institute of BioTechnology,
Department of Chemistry, Division of Biochemistry, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18,
A-1190 Vienna, Austria
| | - Christian Obinger
- Vienna
Institute of BioTechnology,
Department of Chemistry, Division of Biochemistry, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18,
A-1190 Vienna, Austria
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13
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Disruption of the H-bond network in the main access channel of catalase–peroxidase modulates enthalpy and entropy of Fe(III) reduction. J Inorg Biochem 2010; 104:648-56. [DOI: 10.1016/j.jinorgbio.2010.02.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 02/15/2010] [Accepted: 02/23/2010] [Indexed: 01/06/2023]
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14
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Battistuzzi G, Bellei M, Bortolotti CA, Sola M. Redox properties of heme peroxidases. Arch Biochem Biophys 2010; 500:21-36. [PMID: 20211593 DOI: 10.1016/j.abb.2010.03.002] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Revised: 03/01/2010] [Accepted: 03/02/2010] [Indexed: 10/19/2022]
Abstract
Peroxidases are heme enzymes found in bacteria, fungi, plants and animals, which exploit the reduction of hydrogen peroxide to catalyze a number of oxidative reactions, involving a wide variety of organic and inorganic substrates. The catalytic cycle of heme peroxidases is based on three consecutive redox steps, involving two high-valent intermediates (Compound I and Compound II), which perform the oxidation of the substrates. Therefore, the thermodynamics and the kinetics of the catalytic cycle are influenced by the reduction potentials of three redox couples, namely Compound I/Fe3+, Compound I/Compound II and Compound II/Fe3+. In particular, the oxidative power of heme peroxidases is controlled by the (high) reduction potential of the latter two couples. Moreover, the rapid H2O2-mediated two-electron oxidation of peroxidases to Compound I requires a stable ferric state in physiological conditions, which depends on the reduction potential of the Fe3+/Fe2+ couple. The understanding of the molecular determinants of the reduction potentials of the above redox couples is crucial for the comprehension of the molecular determinants of the catalytic properties of heme peroxidases. This review provides an overview of the data available on the redox properties of Fe3+/Fe2+, Compound I/Fe3+, Compound I/Compound II and Compound II/Fe3+ couples in native and mutated heme peroxidases. The influence of the electron donor properties of the axial histidine and of the polarity of the heme environment is analyzed and the correlation between the redox properties of the heme group with the catalytic activity of this important class of metallo-enzymes is discussed.
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Affiliation(s)
- Gianantonio Battistuzzi
- Department of Chemistry, University of Modena and Reggio Emilia, via Campi 183, 41100 Modena, Italy.
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15
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Michel LV, Ye T, Bowman SEJ, Levin BD, Hahn MA, Russell BS, Elliott SJ, Bren KL. Heme attachment motif mobility tunes cytochrome c redox potential. Biochemistry 2007; 46:11753-60. [PMID: 17900177 PMCID: PMC2606054 DOI: 10.1021/bi701177j] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Hydrogen exchange (HX) rates and midpoint potentials (Em) of variants of cytochrome c from Pseudomonas aeruginosa (Pa cyt c551) and Hydrogenobacter thermophilus (Ht cyt c552) have been characterized in an effort to develop an understanding of the impact of properties of the Cys-X-X-Cys-His pentapeptide c-heme attachment (CXXCH) motif on heme redox potential. Despite structural conservation of the CXXCH motif, Ht cyt c552 exhibits a low level of protection from HX for amide protons within this motif relative to Pa cyt c551. Site-directed mutants have been prepared to determine the structural basis for and functional implications of these variations on HX behavior. The double mutant Ht-M13V/K22M displays suppressed HX within the CXXCH motif as well as a decreased Em (by 81 mV), whereas the corresponding double mutant of Pa cyt c551 (V13M/M22K) exhibits enhanced HX within the CXXCH pentapeptide and a modest increase in Em (by 30 mV). The changes in Em correlate with changes in axial His chemical shifts in the ferric proteins reflecting the extent of histidinate character. Thus, the mobility of the CXXCH pentapeptide is found to impact the His-Fe(III) interaction and therefore the heme redox potential.
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Affiliation(s)
| | | | | | | | | | | | | | - Kara L. Bren
- To whom correspondence should be addressed: Department of Chemistry, University of Rochester, Rochester, NY 14627-0216. Telephone: (585) 275-4335. Fax: (585) 276-0205. e-mail:
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16
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Battistuzzi G, Bellei M, Casella L, Bortolotti CA, Roncone R, Monzani E, Sola M. Redox reactivity of the heme Fe3+/Fe2+ couple in native myoglobins and mutants with peroxidase-like activity. J Biol Inorg Chem 2007; 12:951-8. [PMID: 17576605 DOI: 10.1007/s00775-007-0267-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Accepted: 05/21/2007] [Indexed: 10/23/2022]
Abstract
The reaction enthalpy and entropy for the one-electron reduction of the ferric heme in horse heart and sperm whale aquometmyoglobins (Mb) have been determined exploiting a spectroelectrochemical approach. Also investigated were the T67R, T67K, T67R/S92D and T67R/S92D Mb-H variants (the latter containing a protoheme-L: -histidine methyl ester) of sperm whale Mb, which feature peroxidase-like activity. The reduction potential (E degrees ') in all species consists of an enthalpic term which disfavors Fe(3+) reduction and a larger entropic contribution which instead selectively stabilizes the reduced form. This behavior differs from that of the heme redox enzymes and electron transport proteins investigated so far. The reduction thermodynamics in the series of sperm whale Mb variants show an almost perfect enthalpy-entropy compensation, indicating that the mutation-induced changes in DeltaH(o')(rc) and DeltaS(o')(rc) are dominated by reduction-induced solvent reorganization effects. The modest changes in E degrees ' originate from the enthalpic effects of the electrostatic interactions of the heme with the engineered charged residues. The small influence that the mutations exert on the reduction potential of myoglobin suggests that the increased peroxidase activity of the variants is not related to changes in the redox reactivity of the heme iron, but are likely related to a more favored substrate orientation within the distal heme cavity.
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Affiliation(s)
- Gianantonio Battistuzzi
- Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, 41100 Modena, Italy
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Battistuzzi G, Bellei M, Dennison C, Di Rocco G, Sato K, Sola M, Yanagisawa S. Thermodynamics of the alkaline transition in phytocyanins. J Biol Inorg Chem 2007; 12:895-900. [PMID: 17569996 DOI: 10.1007/s00775-007-0245-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2007] [Accepted: 04/29/2007] [Indexed: 10/23/2022]
Abstract
The thermodynamics of the alkaline transition which influences the spectral and redox properties of the type 1 copper center in phytocyanins has been determined spectroscopically. The proteins investigated include Rhus vernicifera stellacyanin, cucumber basic protein and its Met89Gln variant, and umecyanin, the stellacyanin from horseradish roots, along with its Gln95Met variant. The changes in reaction enthalpy and entropy within the protein series show partial compensatory behavior. Thus, the reaction free energy change (hence the pK (a) value) is rather variable. This indicates that species-dependent differences in reaction thermodynamics, although containing an important contribution from changes in the hydrogen-bonding network of water molecules in the hydration sphere of the protein (which feature enthalpy-entropy compensation), are to a large extent protein-based. The data for axial ligand variants are consistent with the hypothesis of a copper-binding His as the deprotonating residue responsible for this transition.
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Affiliation(s)
- Gianantonio Battistuzzi
- Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, 41100 Modena, Italy
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Ayala M, Roman R, Vazquez-Duhalt R. A catalytic approach to estimate the redox potential of heme-peroxidases. Biochem Biophys Res Commun 2007; 357:804-8. [PMID: 17442271 DOI: 10.1016/j.bbrc.2007.04.020] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2007] [Accepted: 04/05/2007] [Indexed: 10/23/2022]
Abstract
The redox potential of heme-peroxidases varies according to a combination of structural components within the active site and its vicinities. For each peroxidase, this redox potential imposes a thermodynamic threshold to the range of oxidizable substrates. However, the instability of enzymatic intermediates during the catalytic cycle precludes the use of direct voltammetry to measure the redox potential of most peroxidases. Here we describe a novel approach to estimate the redox potential of peroxidases, which directly depends on the catalytic performance of the activated enzyme. Selected p-substituted phenols are used as substrates for the estimations. The results obtained with this catalytic approach correlate well with the oxidative capacity predicted by the redox potential of the Fe(III)/Fe(II) couple.
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Affiliation(s)
- Marcela Ayala
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico.
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Vladimirov YA, Proskurnina EV, Izmailov DY, Novikov AA, Brusnichkin AV, Osipov AN, Kagan VE. Cardiolipin activates cytochrome c peroxidase activity since it facilitates H(2)O(2) access to heme. BIOCHEMISTRY (MOSCOW) 2006; 71:998-1005. [PMID: 17009954 DOI: 10.1134/s0006297906090082] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In this work, the effect of liposomes consisting of tetraoleyl cardiolipin and dioleyl phosphatidylcholine (1 : 1, mol/mol) on the rate of three more reactions of Cyt c heme with H2O2 was studied: (i) Cyt c (Fe2+) oxidation to Cyt c (Fe3+), (ii) Fe...S(Met80) bond breaking, and (iii) heme porphyrin ring decomposition. It was revealed that the rates of all those reactions increased greatly in the presence of liposomes containing cardiolipin and not of those consisting of only phosphatidylcholine, and approximately to the same extent as peroxidase activity. These data suggest that cardiolipin activates specifically Cyt c peroxidase activity not only because it promotes Fe...S(Met80) bond breaking but also facilitates H2O2 penetration to the reaction center.
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Affiliation(s)
- Yu A Vladimirov
- Faculty of Basic Medicine, Lomonosov Moscow State University, Moscow 117192, Russia.
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Battistuzzi G, Bellei M, De Rienzo F, Sola M. Redox properties of the Fe3+/Fe2+ couple in Arthromyces ramosus class II peroxidase and its cyanide adduct. J Biol Inorg Chem 2006; 11:586-92. [PMID: 16791642 DOI: 10.1007/s00775-006-0108-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Accepted: 04/10/2006] [Indexed: 10/24/2022]
Abstract
The thermodynamics of the one-electron reduction of the ferric heme in free and cyanide-bound Arthromyces ramosus peroxidase (ARP), a class II plant peroxidase, were determined through spectro-electrochemical experiments. The data were compared with those for class III horseradish peroxidase C (HRP) and its cyanide adduct, and were interpreted in terms of ligand binding features, electrostatic effects and solvent accessible surface area of the heme group and of catalytically relevant residues in the heme distal site. The E(o)' values for free and cyanide-bound ARP (-0.183 and -0.390 V, respectively, at 25 degrees C and pH 7) are higher than those for HRP and HRP-CN. ARP features an enthalpic stabilization of the ferrous state and a remarkably negative reduction entropy, which are both unprecedented for heme peroxidases. Once the compensatory contributions of solvent reorganization are partitioned from the measured reduction enthalpy, the resulting protein-based deltaH(o)'(rc(int)) value for ARP turns out to be less positive than that for HRP by +10 kJ mol(-1). The smaller stabilization of the oxidized heme in ARP most probably results from the less pronounced anionic character of the proximal histidine, and the decreased polarity in the heme distal site as compared with HRP, as indicated by the X-ray structures. The surprisingly negative deltaS(o)'(rc) value for ARP is the result of peculiar reduction-induced solvent reorganization effects.
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Affiliation(s)
- Gianantonio Battistuzzi
- Department of Chemistry and Centro SCS, University of Modena and Reggio Emilia, Via Campi 183, 41100, Modena, Italy
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