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Switala J, Donald L, Ivancich A. A remarkable peroxidase-like behavior of the catalase KatA from the pathogenic bacteria Helicobacter pylori: The oxidation reaction with formate as substrate and the stabilization of an [Fe(IV) = O Trp •] intermediate assessed by multifrequency EPR spectroscopy. J Inorg Biochem 2024; 257:112594. [PMID: 38749080 DOI: 10.1016/j.jinorgbio.2024.112594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 04/15/2024] [Accepted: 05/04/2024] [Indexed: 06/09/2024]
Abstract
We have characterized the catalytic cycle of the Helicobacter pylori KatA catalase (HPC). H. pylori is a human and animal pathogen responsible for gastrointestinal infections. Multifrequency (9-285 GHz) EPR spectroscopy was applied to identify the high-valent intermediates (5 ≤ pH ≤ 8.5). The broad (2000 G) 9-GHz EPR spectrum consistent with the [Fe(IV) = O Por•+] intermediate was detected, and showed a clear pH dependence on the exchange-coupling of the radical (delocalized over the porphyrin moiety) due to the magnetic interaction with the ferryl iron. In addition, Trp• (for pH ≤ 6) and Tyr• (for 5 ≤ pH ≤ 8.5) species were distinguished by the advantageous resolution of their g-values in the 285-GHz EPR spectrum. The unequivocal identification of the high-valent intermediates in HPC by their distinct EPR spectra allowed us to address their reactivity towards substrates. The stabilization of an [Fe(IV) = O Trp•] species in HPC, unprecedented in monofunctional catalases and possibly involved in the oxidation of formate to the formyloxyl radical at pH ≤ 6, is reminiscent of intermediates previously identified in the catalytic cycle of bifunctional catalase-peroxidases. The 2e- oxidation of formate by the [Fe(IV) = O Por•+] species, both at basic and acidic pH conditions, involving a 1H+/2e- oxidation in a cytochrome P450 peroxygenase-like reaction is proposed. Our findings demonstrate that moonlighting by the H. pylori catalase includes formate oxidation, an enzymatic reaction possibly related to the unique strategy of the neutrophile bacterium for gastric colonization, that is the release of CO2 to regulate the pH in the acidic environment.
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Affiliation(s)
- Jacek Switala
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Lynda Donald
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Anabella Ivancich
- Bioénergétique et Ingénierie des Protéines, UMR 7281 and IMM FR3479, CNRS, Aix-Marseille Univ., 31 chemin Joseph Aiguier, 13009 Marseille, France.
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2
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Labecka N, Szczepanczyk M, Mojumdar E, Sparr E, Björklund S. Unraveling UVB effects: Catalase activity and molecular alterations in the stratum corneum. J Colloid Interface Sci 2024; 666:176-188. [PMID: 38593652 DOI: 10.1016/j.jcis.2024.03.200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 03/25/2024] [Accepted: 03/29/2024] [Indexed: 04/11/2024]
Abstract
AIM Ultraviolet B (UVB) radiation can compromise the functionality of the skin barrier through various mechanisms. We hypothesize that UVB induce photochemical alterations in the components of the outermost layer of the skin, known as the stratum corneum (SC), and modulate its antioxidative defense mechanisms. Catalase is a well-known antioxidative enzyme found in the SC where it acts to scavenge reactive oxygen species. However, a detailed characterization of acute UVB exposure on the activity of native catalase in the SC is lacking. Moreover, the effects of UVB irradiation on the molecular dynamics and organization of the SC keratin and lipid components remain unclear. Thus, the aim of this work is to characterize consequences of UVB exposure on the structural and antioxidative properties of catalase, as well as on the molecular and global properties of the SC matrix surrounding the enzyme. EXPERIMENTS The effect of UVB irradiation on the catalase function is investigated by chronoamperometry with a skin covered oxygen electrode, which probes the activity of native catalase in the SC matrix. Circular dichroism is used to explore changes of the catalase secondary structure, and gel electrophoresis is used to detect fragmentation of the enzyme following the UVB exposure. UVB induced alterations of the SC molecular dynamics and structural features of the SC barrier, as well as its water sorption behavior, are investigated by a complementary set of techniques, including natural abundance 13C polarization transfer solid-state NMR, wide-angle X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and dynamic vapor sorption microbalance. FINDINGS The findings show that UVB exposure impairs the antioxidative function of catalase by deactivating both native catalase in the SC matrix and lyophilized catalase. However, UVB radiation does not alter the secondary structure of the catalase nor induce any observable enzyme fragmentation, which otherwise could explain deactivation of its function. NMR measurements on SC samples show a subtle increase in the molecular mobility of the terminal segments of the SC lipids, accompanied by a decrease in the mobility of lipid chain trans-gauche conformers after high doses of UVB exposure. At the same time, the NMR data suggest increased rigidity of the polypeptide backbone of the keratin filaments, while the molecular mobility of amino acid residues in random coil domains of keratin remain unaffected by UVB irradiation. The FTIR data show a consistent decrease in absorbance associated with lipid bond vibrations, relative to the main protein bands. Collectively, the NMR and FTIR data suggest a small modification in the composition of fluid and solid phases of the SC lipid and protein components after UVB exposure, unrelated to the hydration capacity of the SC tissue. To conclude, UVB deactivation of catalase is anticipated to elevate oxidative stress of the SC, which, when coupled with subtle changes in the molecular characteristics of the SC, may compromise the overall skin health and elevate the likelihood of developing skin disorders.
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Affiliation(s)
- Nikol Labecka
- Department of Biomedical Science, Malmö University, SE-205 06 Malmö, Sweden; Biofilms Research Center for Biointerfaces, Malmö University, SE-205 06 Malmö, Sweden; Division of Physical Chemistry, Chemistry Department, Lund University, SE-221 00 Lund, Sweden
| | - Michal Szczepanczyk
- Department of Biomedical Science, Malmö University, SE-205 06 Malmö, Sweden; Biofilms Research Center for Biointerfaces, Malmö University, SE-205 06 Malmö, Sweden
| | - Enamul Mojumdar
- Department of Biomedical Science, Malmö University, SE-205 06 Malmö, Sweden; Biofilms Research Center for Biointerfaces, Malmö University, SE-205 06 Malmö, Sweden; Division of Physical Chemistry, Chemistry Department, Lund University, SE-221 00 Lund, Sweden; CR Competence AB, Box 124, 22100 Lund, Sweden
| | - Emma Sparr
- Division of Physical Chemistry, Chemistry Department, Lund University, SE-221 00 Lund, Sweden
| | - Sebastian Björklund
- Department of Biomedical Science, Malmö University, SE-205 06 Malmö, Sweden; Biofilms Research Center for Biointerfaces, Malmö University, SE-205 06 Malmö, Sweden.
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3
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Keshari K, Santra A, Velasco L, Sauvan M, Kaur S, Ugale AD, Munshi S, Marco JF, Moonshiram D, Paria S. Functional Model of Compound II of Cytochrome P450: Spectroscopic Characterization and Reactivity Studies of a Fe IV-OH Complex. JACS AU 2024; 4:1142-1154. [PMID: 38559734 PMCID: PMC10976569 DOI: 10.1021/jacsau.3c00844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 02/12/2024] [Accepted: 02/26/2024] [Indexed: 04/04/2024]
Abstract
Herein, we show that the reaction of a mononuclear FeIII(OH) complex (1) with N-tosyliminobenzyliodinane (PhINTs) resulted in the formation of a FeIV(OH) species (3). The obtained complex 3 was characterized by an array of spectroscopic techniques and represented a rare example of a synthetic FeIV(OH) complex. The reaction of 1 with the one-electron oxidizing agent was reported to form a ligand-oxidized FeIII(OH) complex (2). 3 revealed a one-electron reduction potential of -0.22 V vs Fc+/Fc at -15 °C, which was 150 mV anodically shifted than 2 (Ered = -0.37 V vs Fc+/Fc at -15 °C), inferring 3 to be more oxidizing than 2. 3 reacted spontaneously with (4-OMe-C6H4)3C• to form (4-OMe-C6H4)3C(OH) through rebound of the OH group and displayed significantly faster reactivity than 2. Further, activation of the hydrocarbon C-H and the phenolic O-H bond by 2 and 3 was compared and showed that 3 is a stronger oxidant than 2. A detailed kinetic study established the occurrence of a concerted proton-electron transfer/hydrogen atom transfer reaction of 3. Studying one-electron reduction of 2 and 3 using decamethylferrocene (Fc*) revealed a higher ket of 3 than 2. The study established that the primary coordination sphere around Fe and the redox state of the metal center is very crucial in controlling the reactivity of high-valent Fe-OH complexes. Further, a FeIII(OMe) complex (4) was synthesized and thoroughly characterized, including X-ray structure determination. The reaction of 4 with PhINTs resulted in the formation of a FeIV(OMe) species (5), revealing the presence of two FeIV species with isomer shifts of -0.11 mm/s and = 0.17 mm/s in the Mössbauer spectrum and showed FeIV/FeIII potential at -0.36 V vs Fc+/Fc couple in acetonitrile at -15 °C. The reactivity studies of 5 were investigated and compared with the FeIV(OH) complex (3).
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Affiliation(s)
- Kritika Keshari
- Department
of Chemistry, Indian Institute of Technology
Delhi, Hauz Khas, New Delhi 110016, India
| | - Aakash Santra
- Department
of Chemistry, Indian Institute of Technology
Delhi, Hauz Khas, New Delhi 110016, India
| | - Lucía Velasco
- Instituto
de Ciencia de Materiales de Madrid, Consejo
Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - Maxime Sauvan
- Instituto
de Ciencia de Materiales de Madrid, Consejo
Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - Simarjeet Kaur
- Department
of Chemistry, Indian Institute of Technology
Delhi, Hauz Khas, New Delhi 110016, India
| | - Ashok D. Ugale
- Instituto
de Ciencia de Materiales de Madrid, Consejo
Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - Sandip Munshi
- School
of Chemical Science, Indian Association
for the Cultivation of Science, Raja S C Mulliick Road, Kolkata 700032, India
| | - J. F. Marco
- Instituto
de Quimica Fisica Blas Cabrera, Consejo
Superior de Investigaciones Científicas, C. de Serrano, 119, Serrano, Madrid 28006, Spain
| | - Dooshaye Moonshiram
- Instituto
de Ciencia de Materiales de Madrid, Consejo
Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - Sayantan Paria
- Department
of Chemistry, Indian Institute of Technology
Delhi, Hauz Khas, New Delhi 110016, India
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4
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Awasthi A, Mallojjala SC, Kumar R, Eerlapally R, Hirschi JS, Draksharapu A. Altering the Localization of an Unpaired Spin in a Formal Ni(V) Species. Chemistry 2024; 30:e202302824. [PMID: 37903027 PMCID: PMC10841873 DOI: 10.1002/chem.202302824] [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: 08/30/2023] [Revised: 10/28/2023] [Accepted: 10/30/2023] [Indexed: 11/01/2023]
Abstract
The participation of both ligand and the metal center in the redox events has been recognized as one of the ways to attain the formal high valent complexes for the late 3d metals, such as Ni and Cu. Such an approach has been employed successfully to stabilize a Ni(III) bisphenoxyl diradical species in which there exist an equilibrium between the ligand and the Ni localized resultant spin. The present work, however, broadens the scope of the previously reported three oxidized equivalent species by conveying the approaches that tend to affect the reported equilibrium in CH3 CN at 233 K. Various spectroscopic characterization revealed that employing exogenous N-donor ligands like 1-methyl imidazole and pyridine favors the formation of the Ni centered localized spin though axial binding. In contrast, due to its steric hinderance, quinoline favors an exclusive ligand localized radical species. DFT studies shed light on the novel intermediates' complex electronic structure. Further, the three oxidized equivalent species with the Ni centered spin was examined for its hydrogen atom abstraction ability stressing their key role in alike reactions.
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Affiliation(s)
- Ayushi Awasthi
- Southern Laboratories-208 A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | | | - Rakesh Kumar
- Southern Laboratories-208 A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Raju Eerlapally
- Southern Laboratories-208 A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Jennifer S Hirschi
- Department of Chemistry, Binghamton University, Binghamton, New York, 13902, USA
| | - Apparao Draksharapu
- Southern Laboratories-208 A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
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5
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Panda S, Phan H, Karlin KD. Heme-copper and Heme O 2-derived synthetic (bioinorganic) chemistry toward an understanding of cytochrome c oxidase dioxygen chemistry. J Inorg Biochem 2023; 249:112367. [PMID: 37742491 PMCID: PMC10615892 DOI: 10.1016/j.jinorgbio.2023.112367] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 08/22/2023] [Accepted: 09/07/2023] [Indexed: 09/26/2023]
Abstract
Cytochrome c oxidase (CcO), also widely known as mitochondrial electron-transport-chain complex IV, is a multi-subunit transmembrane protein responsible for catalyzing the last step of the electron transport chain, dioxygen reduction to water, which is essential to the establishment and maintenance of the membrane proton gradient that drives ATP synthesis. Although many intermediates in the CcO catalytic cycle have been spectroscopically and/or computationally authenticated, the specifics regarding the IP intermediate, hypothesized to be a heme-Cu (hydro)peroxo species whose O-O bond homolysis is supported by a hydrogen-bonding network of water molecules, are largely obscured by the fast kinetics of the A (FeIII-O2•-/CuI/Tyr) → PM (FeIV=O/CuII-OH/Tyr•) step. In this review, we have focused on the recent advancements in the design, development, and characterization of synthetic heme-peroxo‑copper model complexes, which can circumvent the abovementioned limitation, for the investigation of the formation of IP and its O-O cleavage chemistry. Novel findings regarding (a) proton and electron transfer (PT/ET) processes, together with their contributions to exogenous phenol induced O-O cleavage, (b) the stereo-electronic tunability of the secondary coordination sphere (especially hydrogen-bonding) on the geometric and spin state alteration of the heme-peroxo‑copper unit, and (c) a plausible mechanism for the Tyr-His cofactor biogenesis, are discussed in great detail. Additionally, since the ferric-superoxide and the ferryl-oxo (Compound II) species are critically involved in the CcO catalytic cycle, this review also highlights a few fundamental aspects of these heme-only (i.e., without copper) species, including the structural and reactivity influences of electron-donating trans-axial ligands and Lewis acid-promoted H-bonding.
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Affiliation(s)
- Sanjib Panda
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Hai Phan
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Kenneth D Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA.
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6
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Lindahl PA, Vali SW. Mössbauer-based molecular-level decomposition of the Saccharomyces cerevisiae ironome, and preliminary characterization of isolated nuclei. Metallomics 2022; 14:mfac080. [PMID: 36214417 PMCID: PMC9624242 DOI: 10.1093/mtomcs/mfac080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 09/23/2022] [Indexed: 11/25/2022]
Abstract
One hundred proteins in Saccharomyces cerevisiae are known to contain iron. These proteins are found mainly in mitochondria, cytosol, nuclei, endoplasmic reticula, and vacuoles. Cells also contain non-proteinaceous low-molecular-mass labile iron pools (LFePs). How each molecular iron species interacts on the cellular or systems' level is underdeveloped as doing so would require considering the entire iron content of the cell-the ironome. In this paper, Mössbauer (MB) spectroscopy was used to probe the ironome of yeast. MB spectra of whole cells and isolated organelles were predicted by summing the spectral contribution of each iron-containing species in the cell. Simulations required input from published proteomics and microscopy data, as well as from previous spectroscopic and redox characterization of individual iron-containing proteins. Composite simulations were compared to experimentally determined spectra. Simulated MB spectra of non-proteinaceous iron pools in the cell were assumed to account for major differences between simulated and experimental spectra of whole cells and isolated mitochondria and vacuoles. Nuclei were predicted to contain ∼30 μM iron, mostly in the form of [Fe4S4] clusters. This was experimentally confirmed by isolating nuclei from 57Fe-enriched cells and obtaining the first MB spectra of the organelle. This study provides the first semi-quantitative estimate of all concentrations of iron-containing proteins and non-proteinaceous species in yeast, as well as a novel approach to spectroscopically characterizing LFePs.
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Affiliation(s)
- Paul A Lindahl
- Department of Chemistry, Texas A&M University, College Station, TX,USA
- Department of Biochemistry and Biophysics, Texas A&M University, College Station TX,USA
| | - Shaik Waseem Vali
- Department of Chemistry, Texas A&M University, College Station, TX,USA
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7
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Lučić M, Wilson MT, Tosha T, Sugimoto H, Shilova A, Axford D, Owen RL, Hough MA, Worrall JAR. Serial Femtosecond Crystallography Reveals the Role of Water in the One- or Two-Electron Redox Chemistry of Compound I in the Catalytic Cycle of the B-Type Dye-Decolorizing Peroxidase DtpB. ACS Catal 2022; 12:13349-13359. [PMID: 36366763 PMCID: PMC9638988 DOI: 10.1021/acscatal.2c03754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 10/05/2022] [Indexed: 11/30/2022]
Abstract
![]()
Controlling the reactivity
of high-valent Fe(IV)–O
catalytic
intermediates, Compounds I and II, generated in heme enzymes upon
reaction with dioxygen or hydrogen peroxide, is important for function.
It has been hypothesized that the presence (wet) or absence (dry)
of distal heme pocket water molecules can influence whether Compound
I undergoes sequential one-electron additions or a concerted two-electron
reduction. To test this hypothesis, we investigate the role of water
in the heme distal pocket of a dye-decolorizing peroxidase utilizing
a combination of serial femtosecond crystallography and rapid kinetic
studies. In a dry distal heme site, Compound I reduction proceeds
through a mechanism in which Compound II concentration is low. This
reaction shows a strong deuterium isotope effect, indicating that
reduction is coupled to proton uptake. The resulting protonated Compound
II (Fe(IV)–OH) rapidly reduces to the ferric state, giving
the appearance of a two-electron transfer process. In a wet site,
reduction of Compound I is faster, has no deuterium effect, and yields
highly populated Compound II, which is subsequently reduced to the
ferric form. This work provides a definitive experimental test of
the hypothesis advanced in the literature that relates sequential
or concerted electron transfer to Compound I in wet or dry distal
heme sites.
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Affiliation(s)
- Marina Lučić
- School of Life Sciences, University of Essex, Wivenhoe Park,
Essex, ColchesterCO4 3SQ, U.K
| | - Michael T. Wilson
- School of Life Sciences, University of Essex, Wivenhoe Park,
Essex, ColchesterCO4 3SQ, U.K
| | - Takehiko Tosha
- RIKEN, Spring-8 Center, 1-1-1 Kouto, Sayo, Hyogo679-5148Japan
| | | | - Anastasya Shilova
- Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire, DidcotOX11 0DE, U.K
| | - Danny Axford
- Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire, DidcotOX11 0DE, U.K
| | - Robin L. Owen
- Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire, DidcotOX11 0DE, U.K
| | - Michael A. Hough
- School of Life Sciences, University of Essex, Wivenhoe Park,
Essex, ColchesterCO4 3SQ, U.K
- Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire, DidcotOX11 0DE, U.K
| | - Jonathan A. R. Worrall
- School of Life Sciences, University of Essex, Wivenhoe Park,
Essex, ColchesterCO4 3SQ, U.K
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8
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Abstract
The Gouterman four-orbital model conceptualizes porphyrin UV-visible spectra as dominated by four frontier molecular orbitals-two nearly degenerate HOMOs and two exactly degenerate LUMOS under D 4h symmetry. These are well separated from all the other molecular orbitals, and normal spectra involve transitions among these MOs. Unusual spectra occur when additional orbitals appear in this energy range, typically as a consequence of the central coordinated atom. For example, metals with empty d orbitals in a suitable energy range may lead to charge transfer from porphyrin (ligand) to metal, that is, so-called LMCT transitions. Metals with filled p or d orbitals may lead to charge transfer from metal to porphyrin, MLCT transitions. These cases lead to additional peaks and/or significant redshifts in the spectra and were classified as hyperporphyrins by Gouterman. Cases in which spectra are blueshifted were classified as hypsoporphyrins; they are common for relatively electronegative late transition metal porphyrins. Many of the same principles apply to porphyrin analogues, especially corroles. In this Perspective, we focus on two newer classes of hyperporphyrins: one reflecting substituent effects in protonated or deprotonated free-base tetraphenyporphyrins and the other reflecting "noninnocent" interactions between central metal ions and corroles. Hyperporphyrin effects on spectra can be dramatic, yet they can be generated by relatively simple changes and subtle structural variations, such as acid-base reactions or the selection of a central metal ion. These concepts suggest strategies for engineering porphyrin or porphyrinoid dyes for specific applications, especially those requiring far-red or near-infrared absorption or emission.
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Affiliation(s)
- Carl C. Wamser
- Department
of Chemistry, Portland State University, Portland, Oregon 97207-0751, United States
| | - Abhik Ghosh
- Department
of Chemistry and Arctic Center for Sustainable Energy, UiT − The Arctic University of Norway, N-9037 Tromsø, Norway
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9
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Lučić M, Wilson MT, Svistunenko DA, Owen RL, Hough MA, Worrall JAR. Aspartate or arginine? Validated redox state X-ray structures elucidate mechanistic subtleties of Fe IV = O formation in bacterial dye-decolorizing peroxidases. J Biol Inorg Chem 2021; 26:743-761. [PMID: 34477969 PMCID: PMC8463360 DOI: 10.1007/s00775-021-01896-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 08/23/2021] [Indexed: 11/26/2022]
Abstract
Structure determination of proteins and enzymes by X-ray crystallography remains the most widely used approach to complement functional and mechanistic studies. Capturing the structures of intact redox states in metalloenzymes is critical for assigning the chemistry carried out by the metal in the catalytic cycle. Unfortunately, X-rays interact with protein crystals to generate solvated photoelectrons that can reduce redox active metals and hence change the coordination geometry and the coupled protein structure. Approaches to mitigate such site-specific radiation damage continue to be developed, but nevertheless application of such approaches to metalloenzymes in combination with mechanistic studies are often overlooked. In this review, we summarize our recent structural and kinetic studies on a set of three heme peroxidases found in the bacterium Streptomyces lividans that each belong to the dye decolourizing peroxidase (DyP) superfamily. Kinetically, each of these DyPs has a distinct reactivity with hydrogen peroxide. Through a combination of low dose synchrotron X-ray crystallography and zero dose serial femtosecond X-ray crystallography using an X-ray free electron laser (XFEL), high-resolution structures with unambiguous redox state assignment of the ferric and ferryl (FeIV = O) heme species have been obtained. Experiments using stopped-flow kinetics, solvent-isotope exchange and site-directed mutagenesis with this set of redox state validated DyP structures have provided the first comprehensive kinetic and structural framework for how DyPs can modulate their distal heme pocket Asp/Arg dyad to use either the Asp or the Arg to facilitate proton transfer and rate enhancement of peroxide heterolysis.
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Affiliation(s)
- Marina Lučić
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
| | - Michael T Wilson
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
| | - Dimitri A Svistunenko
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
| | - Robin L Owen
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE, Oxfordshire, UK
| | - Michael A Hough
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
| | - Jonathan A R Worrall
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK.
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10
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Kwon H, Basran J, Pathak C, Hussain M, Freeman SL, Fielding AJ, Bailey AJ, Stefanou N, Sparkes HA, Tosha T, Yamashita K, Hirata K, Murakami H, Ueno G, Ago H, Tono K, Yamamoto M, Sawai H, Shiro Y, Sugimoto H, Raven EL, Moody PCE. XFEL Crystal Structures of Peroxidase Compound II. Angew Chem Int Ed Engl 2021; 60:14578-14585. [PMID: 33826799 PMCID: PMC8251747 DOI: 10.1002/anie.202103010] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Indexed: 01/07/2023]
Abstract
Oxygen activation in all heme enzymes requires the formation of high oxidation states of iron, usually referred to as ferryl heme. There are two known intermediates: Compound I and Compound II. The nature of the ferryl heme-and whether it is an FeIV =O or FeIV -OH species-is important for controlling reactivity across groups of heme enzymes. The most recent evidence for Compound I indicates that the ferryl heme is an unprotonated FeIV =O species. For Compound II, the nature of the ferryl heme is not unambiguously established. Here, we report 1.06 Å and 1.50 Å crystal structures for Compound II intermediates in cytochrome c peroxidase (CcP) and ascorbate peroxidase (APX), collected using the X-ray free electron laser at SACLA. The structures reveal differences between the two peroxidases. The iron-oxygen bond length in CcP (1.76 Å) is notably shorter than in APX (1.87 Å). The results indicate that the ferryl species is finely tuned across Compound I and Compound II species in closely related peroxidase enzymes. We propose that this fine-tuning is linked to the functional need for proton delivery to the heme.
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Affiliation(s)
- Hanna Kwon
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Jaswir Basran
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
| | - Chinar Pathak
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
| | - Mahdi Hussain
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
| | - Samuel L. Freeman
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Alistair J. Fielding
- Centre for Natural Products Discovery, Pharmacy and Biomolecular SciencesLiverpool John Moores UniversityJames Parsons Building, Byrom StreetLiverpoolL3 3AFUK
| | - Anna J. Bailey
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Natalia Stefanou
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Hazel A. Sparkes
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | | | - Keitaro Yamashita
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
- Present address: MRC Laboratory of Molecular BiologyFrancis Crick Avenue, Cambridge Biomedical CampusCambridgeCB1 0QHUK
| | - Kunio Hirata
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
| | - Hironori Murakami
- Japan Synchrotron Radiation Research Institute1-1-1 KoutoSayoHyogo679-5198Japan
| | - Go Ueno
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
| | - Hideo Ago
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
| | - Kensuke Tono
- Japan Synchrotron Radiation Research Institute1-1-1 KoutoSayoHyogo679-5198Japan
| | | | - Hitomi Sawai
- Graduate School of Life ScienceUniversity of Hyogo3-2-1 Kouto, Kamigori-choAko-gunHyogo678-1297Japan
| | - Yoshitsugu Shiro
- Graduate School of Life ScienceUniversity of Hyogo3-2-1 Kouto, Kamigori-choAko-gunHyogo678-1297Japan
| | | | - Emma L. Raven
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Peter C. E. Moody
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
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11
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Kwon H, Basran J, Pathak C, Hussain M, Freeman SL, Fielding AJ, Bailey AJ, Stefanou N, Sparkes HA, Tosha T, Yamashita K, Hirata K, Murakami H, Ueno G, Ago H, Tono K, Yamamoto M, Sawai H, Shiro Y, Sugimoto H, Raven EL, Moody PCE. XFEL Crystal Structures of Peroxidase Compound II. ANGEWANDTE CHEMIE (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 133:14699-14706. [PMID: 38505375 PMCID: PMC10947387 DOI: 10.1002/ange.202103010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Indexed: 03/21/2024]
Abstract
Oxygen activation in all heme enzymes requires the formation of high oxidation states of iron, usually referred to as ferryl heme. There are two known intermediates: Compound I and Compound II. The nature of the ferryl heme-and whether it is an FeIV=O or FeIV-OH species-is important for controlling reactivity across groups of heme enzymes. The most recent evidence for Compound I indicates that the ferryl heme is an unprotonated FeIV=O species. For Compound II, the nature of the ferryl heme is not unambiguously established. Here, we report 1.06 Å and 1.50 Å crystal structures for Compound II intermediates in cytochrome c peroxidase (CcP) and ascorbate peroxidase (APX), collected using the X-ray free electron laser at SACLA. The structures reveal differences between the two peroxidases. The iron-oxygen bond length in CcP (1.76 Å) is notably shorter than in APX (1.87 Å). The results indicate that the ferryl species is finely tuned across Compound I and Compound II species in closely related peroxidase enzymes. We propose that this fine-tuning is linked to the functional need for proton delivery to the heme.
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Affiliation(s)
- Hanna Kwon
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Jaswir Basran
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
| | - Chinar Pathak
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
| | - Mahdi Hussain
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
| | - Samuel L. Freeman
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Alistair J. Fielding
- Centre for Natural Products Discovery, Pharmacy and Biomolecular SciencesLiverpool John Moores UniversityJames Parsons Building, Byrom StreetLiverpoolL3 3AFUK
| | - Anna J. Bailey
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Natalia Stefanou
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Hazel A. Sparkes
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | | | - Keitaro Yamashita
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
- Present address: MRC Laboratory of Molecular BiologyFrancis Crick Avenue, Cambridge Biomedical CampusCambridgeCB1 0QHUK
| | - Kunio Hirata
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
| | - Hironori Murakami
- Japan Synchrotron Radiation Research Institute1-1-1 KoutoSayoHyogo679-5198Japan
| | - Go Ueno
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
| | - Hideo Ago
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
| | - Kensuke Tono
- Japan Synchrotron Radiation Research Institute1-1-1 KoutoSayoHyogo679-5198Japan
| | | | - Hitomi Sawai
- Graduate School of Life ScienceUniversity of Hyogo3-2-1 Kouto, Kamigori-choAko-gunHyogo678-1297Japan
| | - Yoshitsugu Shiro
- Graduate School of Life ScienceUniversity of Hyogo3-2-1 Kouto, Kamigori-choAko-gunHyogo678-1297Japan
| | | | - Emma L. Raven
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Peter C. E. Moody
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
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12
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Bím D, Alexandrova AN. Local Electric Fields as a Natural Switch of Heme-Iron Protein Reactivity. ACS Catal 2021; 11:6534-6546. [PMID: 34413991 DOI: 10.1021/acscatal.1c00687] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Heme-iron oxidoreductases operating through the high-valent FeIVO intermediates perform crucial and complicated transformations, such as oxidations of unreactive saturated hydrocarbons. These enzymes share the same Fe coordination, only differing by the axial ligation, e.g., Cys in P450 oxygenases, Tyr in catalases, and His in peroxidases. By examining ~200 heme-iron proteins, we show that the protein hosts exert highly specific intramolecular electric fields on the active sites, and there is a strong correlation between the direction and magnitude of this field and the protein function. In all heme proteins, the field is preferentially aligned with the Fe-O bond ( Fz ). The Cys-ligated P450 oxygenases have the highest average Fz of 28.5 MV cm-1, i.e., most enhancing the oxyl-radical character of the oxo group, and consistent with the ability of these proteins to activate strong C-H bonds. In contrast, in Tyr-ligated proteins, the average Fz is only 3.0 MV cm-1, apparently suppressing single-electron off-pathway oxidations, and in His-ligated proteins, Fz is -8.7 MV cm-1. The operational field range is given by the trade-off between the low reactivity of the FeIVO Compound I at the more negative Fz , and the low selectivity at the more positive Fz . Consequently, a heme-iron site placed in the field characteristic of another heme-iron protein class loses its canonical function, and gains an adverse one. Thus, electric fields produced by the protein scaffolds, together with the nature of the axial ligand, control all heme-iron chemistry.
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Affiliation(s)
- Daniel Bím
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States
| | - Anastassia N. Alexandrova
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States
- California NanoSystems Institute, University of California, Los Angeles, 570 Westwood Plaza, Los Angeles, California 90095-1569, United States
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13
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Belosludov RV, Nevonen DE, Nemykin VN. Accurate Prediction of the Excited States in the Fully Conjugated Porphyrin Tapes across the Full Spectral Range: A Story of the Interplay between π-π* and Intramolecular Charge-Transfer Transitions in Soft Chromophores. J Phys Chem A 2021; 125:2480-2491. [PMID: 33734683 DOI: 10.1021/acs.jpca.1c00217] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The ability of density functional theory (DFT) and time-dependent DFT (TDDFT) methods for the accurate prediction of the energies and oscillator strengths of the excited states in a series of fully conjugated meso-meso β-β β-β triple-linked porphyrin oligomers (porphyrin tapes 2-12) was probed in the gas phase and solution using several exchange-correlation functionals. It was demonstrated that the use of the hybrid B3LYP functional provides a good compromise for the accurate prediction of the localized π-π* and intramolecular charge-transfer transitions, thus allowing confident interpretation of the UV-vis-NIR spectra of porphyrin oligomers. The TDDFT-based sum-over-state (SOS) calculations for the porphyrin tape dimer 2 and trimer 3 as well as parent monomer 1 correctly predicted the signs and shapes of the magnetic circular dichroism (MCD) signals in the low-energy region of the spectra.
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Affiliation(s)
- Rodion V Belosludov
- Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
| | - Dustin E Nevonen
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Victor N Nemykin
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.,Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
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14
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Nemykin VN, Nevonen DE, Ferch LS, Shepit M, Herbert DE, van Lierop J. Accurate Prediction of Mössbauer Hyperfine Parameters in Bis-Axially Coordinated Iron(II) Phthalocyanines Using Density Functional Theory Calculations: A Story of a Single Orbital Revealed by Natural Bond Orbital Analysis. Inorg Chem 2021; 60:3690-3706. [PMID: 33651595 DOI: 10.1021/acs.inorgchem.0c03373] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Density Functional Theory (DFT) calculations coupled with several exchange-correlation functionals were used for the prediction of Mössbauer hyperfine parameters of 36 bis-axially coordinated iron(II) phthalocyanine complexes with the general formulas PcFeL2, PcFeL'L″, and [PcFeX2]2-, including four new compounds. Both gas-phase and PCM calculations using BPW91 and MN12L exchange-correlation functionals were found to accurately predict both Mössbauer quadrupole splittings and the correct trends in experimentally observed isomer shifts. In comparison, hybrid exchange-correlation functionals underestimated quadrupole splittings, while still accurately predicted isomer shifts. Out of ∼40 exchange-correlation functionals tested, only MN12L was found to correctly reproduce quadrupole splitting trends in the PcFeL2 complexes coordinated with phosphorus-donor axial ligands (i.e., P(OnBu)3 ≈ P(OEt)3 < PMe3 < P[(CH2O)2CH2]-p-C6H4NO2 < PEt3 ≈ PnBu3). Natural Bond Orbital (NBO) analysis was successfully used to explain the general trends in the observed quadrupole splitting for all compounds of interest. In particular, the general trends in the quadrupole splitting correlate well with the axial ligand dependent, NBO-predicted population of the 3dz2 orbital of the Fe ion and are reflective of the hypothesis proposed by Ohya and co-workers ( Inorg. Chem., 1984, 23, 1303) on the adaptability of the phthalocyanine's π-system toward Fe-Lax interactions. The first X-ray crystal structure of a PcFeL2 complex with axial phosphine ligands is also reported.
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Affiliation(s)
- Victor N Nemykin
- Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.,Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Dustin E Nevonen
- Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Laura S Ferch
- Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Michael Shepit
- Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - David E Herbert
- Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Johan van Lierop
- Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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15
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Roos G, Harvey JN. Histidine versus Cysteine-Bearing Heme-Dependent Halogen Peroxidases: Parallels and Differences for Cl - Oxidation. J Phys Chem B 2021; 125:74-85. [PMID: 33350832 DOI: 10.1021/acs.jpcb.0c09409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The homodimeric myeloperoxidase (MPO) features a histidine as a proximal ligand and a sulfonium linkage covalently attaching the heme porphyrin ring to the protein. MPO is able to catalyze Cl- oxidation with about the same efficiency as chloroperoxidase at pH 7.0. In this study, we seek to explore the parallels and differences between the histidine and cysteine heme-dependent halogen peroxidases. Transition states, reaction barriers, and relevant thermodynamic properties are calculated on protein models. Together with electronic structure calculations, it gives an overview of the reaction mechanisms and of the factors that determine the selectivity between one- and two-electron paths. Conclusions point to the innate oxidizing nature of MPO with the ester and sulfonium linkages hiking up the reactivity to enable chloride oxidation. The installation of a deprotonated imidazolate as a proximal ligand does not shift the equilibrium from one- to two-electron events without influencing the chemistry of the oxidation reaction.
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Affiliation(s)
- Goedele Roos
- UGSF-Unité de Glycobiologie Structurale et Fonctionnelle, University of Lille, CNRS, UMR 8576, F-59000 Lille, France
| | - Jeremy N Harvey
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
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16
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Ansari M, Senthilnathan D, Rajaraman G. Deciphering the origin of million-fold reactivity observed for the open core diiron [HO-Fe III-O-Fe IV[double bond, length as m-dash]O] 2+ species towards C-H bond activation: role of spin-states, spin-coupling, and spin-cooperation. Chem Sci 2020; 11:10669-10687. [PMID: 33209248 PMCID: PMC7654192 DOI: 10.1039/d0sc02624g] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 06/16/2020] [Indexed: 01/26/2023] Open
Abstract
High-valent metal-oxo species have been characterised as key intermediates in both heme and non-heme enzymes that are found to perform efficient aliphatic hydroxylation, epoxidation, halogenation, and dehydrogenation reactions. Several biomimetic model complexes have been synthesised over the years to mimic both the structure and function of metalloenzymes. The diamond-core [Fe2(μ-O)2] is one of the celebrated models in this context as this has been proposed as the catalytically active species in soluble methane monooxygenase enzymes (sMMO), which perform the challenging chemical conversion of methane to methanol at ease. In this context, a report of open core [HO(L)FeIII-O-FeIV(O)(L)]2+ (1) gains attention as this activates C-H bonds a million-fold faster compared to the diamond-core structure and has the dual catalytic ability to perform hydroxylation as well as desaturation with organic substrates. In this study, we have employed density functional methods to probe the origin of the very high reactivity observed for this complex and also to shed light on how this complex performs efficient hydroxylation and desaturation of alkanes. By modelling fifteen possible spin-states for 1 that could potentially participate in the reaction mechanism, our calculations reveal a doublet ground state for 1 arising from antiferromagnetic coupling between the quartet FeIV centre and the sextet FeIII centre, which regulates the reactivity of this species. The unusual stabilisation of the high-spin ground state for FeIV[double bond, length as m-dash]O is due to the strong overlap of with the orbital, reducing the antibonding interactions via spin-cooperation. The electronic structure features computed for 1 are consistent with experiments offering confidence in the methodology chosen. Further, we have probed various mechanistic pathways for the C-H bond activation as well as -OH rebound/desaturation of alkanes. An extremely small barrier height computed for the first hydrogen atom abstraction by the terminal FeIV[double bond, length as m-dash]O unit was found to be responsible for the million-fold activation observed in the experiments. The barrier height computed for -OH rebound by the FeIII-OH unit is also smaller suggesting a facile hydroxylation of organic substrates by 1. A strong spin-cooperation between the two iron centres also reduces the barrier for second hydrogen atom abstraction, thus making the desaturation pathway competitive. Both the spin-state as well as spin-coupling between the two metal centres play a crucial role in dictating the reactivity for species 1. By exploring various mechanistic pathways, our study unveils the fact that the bridged μ-oxo group is a poor electrophile for both C-H activation as well for -OH rebound. As more and more evidence is gathered in recent years for the open core geometry of sMMO enzymes, the idea of enhancing the reactivity via an open-core motif has far-reaching consequences.
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Affiliation(s)
- Mursaleem Ansari
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India .
| | - Dhurairajan Senthilnathan
- Center for Computational Chemistry , CRD , PRIST University , Vallam , Thanjavur , Tamilnadu 613403 , India
| | - Gopalan Rajaraman
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India .
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17
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Ehudin MA, Gee LB, Sabuncu S, Braun A, Moënne-Loccoz P, Hedman B, Hodgson KO, Solomon EI, Karlin KD. Tuning the Geometric and Electronic Structure of Synthetic High-Valent Heme Iron(IV)-Oxo Models in the Presence of a Lewis Acid and Various Axial Ligands. J Am Chem Soc 2019; 141:5942-5960. [PMID: 30860832 DOI: 10.1021/jacs.9b00795] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
High-valent ferryl species (e.g., (Por)FeIV═O, Cmpd-II) are observed or proposed key oxidizing intermediates in the catalytic cycles of heme-containing enzymes (P-450s, peroxidases, catalases, and cytochrome c oxidase) involved in biological respiration and oxidative metabolism. Herein, various axially ligated iron(IV)-oxo complexes were prepared to examine the influence of the identity of the base. These were generated by addition of various axial ligands (1,5-dicyclohexylimidazole (DCHIm), a tethered-imidazole system, and sodium derivatives of 3,5-dimethoxyphenolate and imidazolate). Characterization was carried out via UV-vis, electron paramagnetic resonance (EPR), 57Fe Mössbauer, Fe X-ray absorption (XAS), and 54/57Fe resonance Raman (rR) spectroscopies to confirm their formation and compare the axial ligand perturbation on the electronic and geometric structures of these heme iron(IV)-oxo species. Mössbauer studies confirmed that the axially ligated derivatives were iron(IV) and six-coordinate complexes. XAS and 54/57Fe rR data correlated with slight elongation of the iron-oxo bond with increasing donation from the axial ligands. The first reported synthetic H-bonded iron(IV)-oxo heme systems were made in the presence of the protic Lewis acid, 2,6-lutidinium triflate (LutH+), with (or without) DCHIm. Mössbauer, rR, and XAS spectroscopic data indicated the formation of molecular Lewis acid ferryl adducts (rather than full protonation). The reduction potentials of these novel Lewis acid adducts were bracketed through addition of outer-sphere reductants. The oxidizing capabilities of the ferryl species with or without Lewis acid vary drastically; addition of LutH+ to F8Cmpd-II (F8 = tetrakis(2,6-difluorophenyl)porphyrinate) increased its reduction potential by more than 890 mV, experimentally confirming that H-bonding interactions can increase the reactivity of ferryl species.
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Affiliation(s)
- Melanie A Ehudin
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Leland B Gee
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Sinan Sabuncu
- Department of Biochemistry & Molecular Biology , Oregon Health & Science University , Portland , Oregon 97239-3098 , United States
| | - Augustin Braun
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Pierre Moënne-Loccoz
- Department of Biochemistry & Molecular Biology , Oregon Health & Science University , Portland , Oregon 97239-3098 , United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Stanford University , Menlo Park , California 94025 , United States
| | - Keith O Hodgson
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Stanford University , Menlo Park , California 94025 , United States
| | - Edward I Solomon
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Stanford University , Menlo Park , California 94025 , United States
| | - Kenneth D Karlin
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , United States
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18
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Lu X, Li XX, Seo MS, Lee YM, Clémancey M, Maldivi P, Latour JM, Sarangi R, Fukuzumi S, Nam W. A Mononuclear Nonheme Iron(IV)-Amido Complex Relevant for the Compound II Chemistry of Cytochrome P450. J Am Chem Soc 2018; 141:80-83. [PMID: 30558411 DOI: 10.1021/jacs.8b11045] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A mononuclear nonheme iron(IV)-amido complex bearing a tetraamido macrocyclic ligand, [(TAML)FeIV(NHTs)]- (1), was synthesized via a hydrogen atom (H atom) abstraction reaction of an iron(V)-imido complex, [(TAML)FeV(NTs)]- (2), and fully characterized using various spectroscopies. We then investigated (1) the p Ka of 1, (2) the reaction of 1 with a carbon-centered radical, and (3) the H atom abstraction reaction of 1. To the best of our knowledge, the present study reports for the first time the synthesis and chemical properties/reactions of a high-valent iron(IV)-amido complex.
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Affiliation(s)
- Xiaoyan Lu
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea
| | - Xiao-Xi Li
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea
| | - Mi Sook Seo
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea
| | - Yong-Min Lee
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea
| | - Martin Clémancey
- Université Grenoble Alpes , CEA, CNRS, BIG, LCBM , Grenoble F-38000 , France
| | - Pascale Maldivi
- Université Grenoble Alpes , CEA, CNRS, INAC, SYMMES , Grenoble F-38000 , France
| | - Jean-Marc Latour
- Université Grenoble Alpes , CEA, CNRS, BIG, LCBM , Grenoble F-38000 , France
| | - Ritimukta Sarangi
- Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Stanford , California 94025 , United States
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea
| | - Wonwoo Nam
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea.,State Key Laboratory for Oxo Synthesis and Selective Oxidation, Suzhou Research Institute of LICP , Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences , Lanzhou 730000 , China
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19
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Huang X, Groves JT. Oxygen Activation and Radical Transformations in Heme Proteins and Metalloporphyrins. Chem Rev 2018; 118:2491-2553. [PMID: 29286645 PMCID: PMC5855008 DOI: 10.1021/acs.chemrev.7b00373] [Citation(s) in RCA: 577] [Impact Index Per Article: 96.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Indexed: 12/20/2022]
Abstract
As a result of the adaptation of life to an aerobic environment, nature has evolved a panoply of metalloproteins for oxidative metabolism and protection against reactive oxygen species. Despite the diverse structures and functions of these proteins, they share common mechanistic grounds. An open-shell transition metal like iron or copper is employed to interact with O2 and its derived intermediates such as hydrogen peroxide to afford a variety of metal-oxygen intermediates. These reactive intermediates, including metal-superoxo, -(hydro)peroxo, and high-valent metal-oxo species, are the basis for the various biological functions of O2-utilizing metalloproteins. Collectively, these processes are called oxygen activation. Much of our understanding of the reactivity of these reactive intermediates has come from the study of heme-containing proteins and related metalloporphyrin compounds. These studies not only have deepened our understanding of various functions of heme proteins, such as O2 storage and transport, degradation of reactive oxygen species, redox signaling, and biological oxygenation, etc., but also have driven the development of bioinorganic chemistry and biomimetic catalysis. In this review, we survey the range of O2 activation processes mediated by heme proteins and model compounds with a focus on recent progress in the characterization and reactivity of important iron-oxygen intermediates. Representative reactions initiated by these reactive intermediates as well as some context from prior decades will also be presented. We will discuss the fundamental mechanistic features of these transformations and delineate the underlying structural and electronic factors that contribute to the spectrum of reactivities that has been observed in nature as well as those that have been invented using these paradigms. Given the recent developments in biocatalysis for non-natural chemistries and the renaissance of radical chemistry in organic synthesis, we envision that new enzymatic and synthetic transformations will emerge based on the radical processes mediated by metalloproteins and their synthetic analogs.
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Affiliation(s)
- Xiongyi Huang
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
- Department
of Chemistry, California Institute of Technology, Pasadena, California 91125, United States
| | - John T. Groves
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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20
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Abstract
Aerobic organisms have evolved to activate oxygen from the atmosphere, which allows them to catalyze the oxidation of different kinds of substrates. This activation of oxygen is achieved by a metal center (usually iron or copper) buried within a metalloprotein. In the case of iron-containing heme enzymes, the activation of oxygen is achieved by formation of transient iron-oxo (ferryl) intermediates; these intermediates are called Compound I and Compound II. The Compound I and II intermediates were first discovered in the 1930s in horseradish peroxidase, and it is now known that these same species are used across the family of heme enzymes, which include all of the peroxidases, the heme catalases, the P450s, cytochrome c oxidase, and NO synthase. Many years have passed since the first observations, but establishing the chemical nature of these transient ferryl species remains a fundamental question that is relevant to the reactivity, and therefore the usefulness, of these species in biology. This Account summarizes experiments that were conceived and conducted at Leicester and presents our ideas on the chemical nature, stability, and reactivity of these ferryl heme species. We begin by briefly summarizing the early milestones in the field, from the 1940s and 1950s. We present comparisons between the nature and reactivity of the ferryl species in horseradish peroxidase, cytochrome c peroxidase, and ascorbate peroxidase; and we consider different modes of electron delivery to ferryl heme, from different substrates in different peroxidases. We address the question of whether the ferryl heme is best formulated as an (unprotonated) FeIV═O or as a (protonated) FeIV-OH species. A range of spectroscopic approaches (EXAFS, resonance Raman, Mossbauer, and EPR) have been used over many decades to examine this question, and in the last ten years, X-ray crystallography has also been employed. We describe how information from all of these studies has blended together to create an overall picture, and how the recent application of neutron crystallography has directly identified protonation states and has helped to clarify the precise nature of the ferryl heme in cytochrome c peroxidase and ascorbate peroxidase. We draw comparisons between the Compound I and Compound II species that we have observed in peroxidases with those found in other heme systems, notably the P450s, highlighting possible commonality across these heme ferryl systems. The identification of proton locations from neutron structures of these ferryl species opens the door for understanding the proton translocations that need to occur during O-O bond cleavage.
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Affiliation(s)
- Peter C. E. Moody
- Department
of Molecular and Cell Biology and Leicester Institute of Structural
and Chemical Biology, University of Leicester, Lancaster Road, Leicester LE1 9HN, England
| | - Emma L. Raven
- Department
of Chemistry and Leicester Institute of Structural and Chemical Biology, University of Leicester, University Road, Leicester LE1 7RH, U.K
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Zaragoza JPT, Yosca TH, Siegler MA, Moënne-Loccoz P, Green MT, Goldberg DP. Direct Observation of Oxygen Rebound with an Iron-Hydroxide Complex. J Am Chem Soc 2017; 139:13640-13643. [PMID: 28930448 DOI: 10.1021/jacs.7b07979] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The rebound mechanism for alkane hydroxylation was invoked over 40 years ago to help explain reactivity patterns in cytochrome P450, and subsequently has been used to provide insight into a range of biological and synthetic systems. Efforts to model the rebound reaction in a synthetic system have been unsuccessful, in part because of the challenge in preparing a suitable metal-hydroxide complex at the correct oxidation level. Herein we report the synthesis of such a complex. The reaction of this species with a series of substituted radicals allows for the direct interrogation of the rebound process, providing insight into this uniformly invoked, but previously unobserved process.
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Affiliation(s)
- Jan Paulo T Zaragoza
- Department of Chemistry, The Johns Hopkins University , 3400 N Charles Street, Baltimore, Maryland 21218, United States
| | - Timothy H Yosca
- Department of Chemistry and Department of Molecular Biology and Biochemistry, University of California , Irvine, California 92697, United States
| | - Maxime A Siegler
- Department of Chemistry, The Johns Hopkins University , 3400 N Charles Street, Baltimore, Maryland 21218, United States
| | - Pierre Moënne-Loccoz
- Division of Environmental and Biomolecular Systems, Oregon Health & Science University , Portland, Oregon 97239, United States
| | - Michael T Green
- Department of Chemistry and Department of Molecular Biology and Biochemistry, University of California , Irvine, California 92697, United States
| | - David P Goldberg
- Department of Chemistry, The Johns Hopkins University , 3400 N Charles Street, Baltimore, Maryland 21218, United States
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