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Kumar R, Ansari A, Comba P, Rajaraman G. Rebound or Cage Escape? The Role of the Rebound Barrier for the Reactivity of Non-Heme High-Valent Fe IV =O Species. Chemistry 2024; 30:e202303300. [PMID: 37929771 DOI: 10.1002/chem.202303300] [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: 10/09/2023] [Revised: 11/03/2023] [Accepted: 11/06/2023] [Indexed: 11/07/2023]
Abstract
Owing to their high reactivity and selectivity, variations in the spin ground state and a range of possible pathways, high-valent FeIV =O species are popular models with potential bioinspired applications. An interesting example of a structure-reactivity pattern is the detailed study with five nonheme amine-pyridine pentadentate ligand FeIV =O species, including N4py: [(L1 )FeIV =O]2+ (1), bntpen: [(L2 )FeIV =O]2+ (2), py2 tacn: [(L3 )FeIV =O]2+ (3), and two isomeric bispidine derivatives: [(L4 )FeIV =O]2+ (4) and [(L5 )FeIV =O]2+ (5). In this set, the order of increasing reactivity in the hydroxylation of cyclohexane differs from that with cyclohexadiene as substrate. A comprehensive DFT, ab initio CASSCF/NEVPT2 and DLPNO-CCSD(T) study is presented to untangle the observed patterns. These are well reproduced when both activation barriers for the C-H abstraction and the OH rebound are taken into account. An MO, NBO and deformation energy analysis reveals the importance of π(pyr) → π*xz (FeIII -OH) electron donation for weakening the FeIII -OH bond and thus reducing the rebound barrier. This requires that pyridine rings are oriented perpendicularly to the FeIII -OH bond and this is a subtle but crucial point in ligand design for non-heme iron alkane hydroxylation.
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Affiliation(s)
- Ravi Kumar
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Powai, 400076, India
| | - Azaj Ansari
- Department of Chemistry, Central University of Haryana, Haryana, 123031, India
| | - Peter Comba
- Institute of Inorganic Chemistry &, Interdisciplinary Center for Scientific Computing, Heidelberg University, 69120, Heidelberg, Germany
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Powai, 400076, India
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2
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Li Y, Singh R, Sinha A, Lisensky GC, Haukka M, Nilsson J, Yiga S, Demeshko S, Gross SJ, Dechert S, Gonzalez A, Farias G, Wendt OF, Meyer F, Nordlander E. Nonheme Fe IV═O Complexes Supported by Four Pentadentate Ligands: Reactivity toward H- and O- Atom Transfer Processes. Inorg Chem 2023; 62:18338-18356. [PMID: 37913548 PMCID: PMC10647104 DOI: 10.1021/acs.inorgchem.3c02526] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 10/06/2023] [Accepted: 10/11/2023] [Indexed: 11/03/2023]
Abstract
Four new pentadentate N5-donor ligands, [N-(1-methyl-2-imidazolyl)methyl-N-(2-pyridyl)-methyl-N-(bis-2-pyridylmethyl)-amine] (L1), [N-bis(1-methyl-2-imidazolyl)methyl-N-(bis-2-pyridylmethyl)amine] (L2), (N-(isoquinolin-3-ylmethyl)-1,1-di(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine (L3), and N,N-bis(isoquinolin-3-ylmethyl)-1,1-di(pyridin-2-yl)methanamine (L4), have been synthesized based on the N4Py ligand framework, where one or two pyridyl arms of the N4Py parent are replaced by (N-methyl)imidazolyl or N-(isoquinolin-3-ylmethyl) moieties. Using these four pentadentate ligands, the mononuclear complexes [FeII(CH3CN)(L1)]2+ (1a), [FeII(CH3CN)(L2)]2+ (2a), [FeII(CH3CN)(L3)]2+ (3a), and [FeII(CH3CN)(L4)]2+ (4a) have been synthesized and characterized. The half-wave potentials (E1/2) of the complexes become more positive in the order: 2a < 1a < 4a ≤ 3a ≤ [Fe(N4Py)(CH3CN)]2+. The order of redox potentials correlates well with the Fe-Namine distances observed by crystallography, which are 2a > 1a ≥ 4a > 3a ≥ [Fe(N4Py)(CH3CN)]2+. The corresponding ferryl complexes [FeIV(O)(L1)]2+ (1b), [FeIV(O)(L2)]2+ (2b), [FeIV(O)(L3)]2+ (3b), and [FeIV(O)(L4)]2+ (4b) were prepared by the reaction of the ferrous complexes with isopropyl 2-iodoxybenzoate (IBX ester) in acetonitrile. The greenish complexes 3b and 4b were also isolated in the solid state by the reaction of the ferrous complexes in CH3CN with ceric ammonium nitrate in water. Mössbauer spectroscopy and magnetic measurements (using superconducting quantum interference device) show that the four complexes 1b, 2b, 3b, and 4b are low-spin (S = 1) FeIV═O complexes. UV/vis spectra of the four FeIV═O complexes in acetonitrile show typical long-wavelength absorptions of around 700 nm, which are expected for FeIV═O complexes with N4Py-type ligands. The wavelengths of these absorptions decrease in the following order: 721 nm (2b) > 706 nm (1b) > 696 nm (4b) > 695 nm (3b) = 695 nm ([FeIV(O) (N4Py)]2+), indicating that the replacement of the pyridyl arms with (N-methyl) imidazolyl moieties makes L1 and L2 exert weaker ligand fields than the parent N4Py ligand, while the ligand field strengths of L3 and L4 are similar to the N4Py parent despite the replacement of the pyridyl arms with N-(isoquinolin-3-ylmethyl) moieties. Consequently, complexes 1b and 2b tend to be less stable than the parent [FeIV(O)(N4Py)]2+ complex: the half-life sequence at room temperature is 1.67 h (2b) < 16 h (1b) < 45 h (4b) < 63 h (3b) ≈ 60 h ([FeIV(O)(N4Py)]2+). Compared to the parent complex, 1b and 2b exhibit enhanced reactivity in both the oxidation of thioanisole in the oxygen atom transfer (OAT) reaction and the oxygenation of C-H bonds of aromatic and aliphatic substrates, presumed to occur via an oxygen rebound process. Furthermore, the second-order rate constants for hydrogen atom transfer (HAT) reactions affected by the ferryl complexes can be directly related to the C-H bond dissociation energies of a range of substrates that have been studied. Using either IBX ester or H2O2 as an oxidant, all four new FeII complexes display good performance in catalytic reactions involving both HAT and OAT reactions.
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Affiliation(s)
- Yong Li
- Chemical
Physics, Department of Chemistry, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Reena Singh
- Chemical
Physics, Department of Chemistry, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Arup Sinha
- Chemical
Physics, Department of Chemistry, Lund University, Box 124, Lund SE-221 00, Sweden
| | - George C. Lisensky
- Department
of Chemistry, Beloit College, 700 College Street, Beloit, Wisconsin 53511, United States
| | - Matti Haukka
- Department
of Chemistry, University of Jyväskylä, P.O. Box-35, Jyväskylä FI-40014, Finland
| | - Justin Nilsson
- Chemical
Physics, Department of Chemistry, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Solomon Yiga
- Centre
for Analysis and Synthesis, Department of Chemistry, Lund University, P.O. Box 124, Lund SE-22100, Sweden
| | - Serhiy Demeshko
- Georg-August
Universität Göttingen, Institut
für Anorganische Chemie, Tammanstrasse 4, Göttingen D-37077, Germany
| | - Sophie Jana Gross
- Georg-August
Universität Göttingen, Institut
für Anorganische Chemie, Tammanstrasse 4, Göttingen D-37077, Germany
| | - Sebastian Dechert
- Georg-August
Universität Göttingen, Institut
für Anorganische Chemie, Tammanstrasse 4, Göttingen D-37077, Germany
| | - Ana Gonzalez
- MAX IV Laboratory, Lund University, P.O.
Box 118, Lund SE-221 00, Sweden
| | - Giliandro Farias
- Department
of Chemistry, Federal University of Santa
Catarina, Florianópolis 88040900, Santa Catarina, Brazil
| | - Ola F. Wendt
- Centre
for Analysis and Synthesis, Department of Chemistry, Lund University, P.O. Box 124, Lund SE-22100, Sweden
| | - Franc Meyer
- Georg-August
Universität Göttingen, Institut
für Anorganische Chemie, Tammanstrasse 4, Göttingen D-37077, Germany
| | - Ebbe Nordlander
- Chemical
Physics, Department of Chemistry, Lund University, Box 124, Lund SE-221 00, Sweden
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3
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Fitzpatrick PF. The aromatic amino acid hydroxylases: Structures, catalysis, and regulation of phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase. Arch Biochem Biophys 2023; 735:109518. [PMID: 36639008 DOI: 10.1016/j.abb.2023.109518] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 01/01/2023] [Accepted: 01/06/2023] [Indexed: 01/12/2023]
Abstract
The aromatic amino acid hydroxylases phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase are non-heme iron enzymes that catalyze key physiological reactions. This review discusses the present understanding of the common catalytic mechanism of these enzymes and recent advances in understanding the relationship between their structures and their regulation.
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Affiliation(s)
- Paul F Fitzpatrick
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, 78229, USA.
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4
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Li M, Subedi BP, Fitzpatrick PF, Emerson JP. Thermodynamics of iron, tetrahydrobiopterin, and phenylalanine binding to phenylalanine hydroxylase from Chromobacterium violaceum. Arch Biochem Biophys 2022; 729:109378. [PMID: 35995215 PMCID: PMC10184773 DOI: 10.1016/j.abb.2022.109378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 08/13/2022] [Accepted: 08/16/2022] [Indexed: 11/02/2022]
Abstract
Phenylalanine hydroxylase (PheH) is a pterin-dependent, mononuclear nonheme iron(II) oxygenase that uses the oxidative power of O2 to hydroxylate phenylalanine to form tyrosine. PheH is a member of a superfamily of O2-activating enzymes that utilizes a common metal binding motif: the 2-His-1-carboxylate facial triad. Like most members of this superfamily, binding of substrates to PheH results in a reorganization of its active site to allow O2 activation. Exploring the energetics of each step before O2 activation can provide mechanistic insight into the initial steps that support the highly specific O2 activation pathway carried out by this metalloenzyme. Here the thermal stability of PheH and its substrate complexes were investigated under an anaerobic environment by using differential scanning calorimetry. In context with known binding constants for PheH, a thermodynamic cycle associated with iron(II), tetrahydrobiopterin (BH4), and phenylalanine binding to the active site was generated, showing a distinctive cooperativity between the binding of BH4 and Phe. The addition of phenylalanine and BH4 to PheH·Fe increased the stability of this enzyme (ΔTm of 8.5 (±0.7) °C with an associated δΔH of 43.0 (±2.9) kcal/mol). The thermodynamic data presented here gives insight into the complicated interactions between metal center, cofactor, and substrate, and how this interplay sets the stage for highly specific, oxidative C-H activation in this enzyme.
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Affiliation(s)
- Mingjie Li
- Department of Chemistry, Mississippi State University, Mississippi State, MS, 39762, USA
| | - Bishnu P Subedi
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX, 78229, USA
| | - Paul F Fitzpatrick
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX, 78229, USA.
| | - Joseph P Emerson
- Department of Chemistry, Mississippi State University, Mississippi State, MS, 39762, USA.
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5
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Peng W, Yan S, Zhang X, Liao L, Zhang J, Shaik S, Wang B. How Do Preorganized Electric Fields Function in Catalytic Cycles? The Case of the Enzyme Tyrosine Hydroxylase. J Am Chem Soc 2022; 144:20484-20494. [DOI: 10.1021/jacs.2c09263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Wei Peng
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Shengheng Yan
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Xuan Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Langxing Liao
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Jinyan Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem, 9190407 Jerusalem, Israel
| | - Binju Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
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6
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Li X, Xue S, Guo Y, Chang WC. Mechanism of Methyldehydrofosmidomycin Maturation: Use Olefination to Enable Chain Elongation. J Am Chem Soc 2022; 144:8257-8266. [PMID: 35482829 DOI: 10.1021/jacs.2c01924] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Utilization of mononuclear iron- and 2-oxoglutarate-dependent (Fe/2OG) enzymes to enable C-H bond functionalization is a widely used strategy to diversify the structural complexity of natural products. Besides those well-studied reactions including hydroxylation, epoxidation, and halogenation, in the biosynthetic pathway of dehydrofosmidomycin, an Fe/2OG enzyme is reported to catalyze desaturation, alkyl chain elongation, along with demethylation in which trimethyl-2-aminoethylphosphonate is converted into methyldehydrofosmidomycin. How this transformation takes place is largely unknown. Herein, we characterized the reactive species, revealed the structure of the reaction intermediate, and used mechanistic probes to investigate the reaction pathway and mechanism. These results led to the elucidation of a two-step process in which the first reaction employs a long-lived Fe(IV)-oxo species to trigger C═C bond installation. During the second reaction, the olefin installed in situ enables C-C bond formation that is accompanied with a C-N bond cleavage and hydroxylation to furnish the alkyl chain elongation and demethylation. This work expands the reaction repertoire of Fe/2OG enzymes by introducing a new pathway to the known C-C bond formation mechanisms utilized by metalloenzymes.
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Affiliation(s)
- Xiaojun Li
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Shan Xue
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Wei-Chen Chang
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
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7
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Aregbesola OA, Kumar A, Mokoena MP, Olaniran AO. Classic Pentachlorophenol Hydroxylating Phenylalanine 4-Monooxygenase from Indigenous Bacillus tropicus Strain AOA-CPS1: Cloning, Overexpression, Purification, Characterization and Structural Homology Modelling. Appl Biochem Biotechnol 2022; 194:635-658. [PMID: 34417677 DOI: 10.1007/s12010-021-03645-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 08/10/2021] [Indexed: 11/22/2022]
Abstract
The metabolically promiscuous pentachlorophenol (PCP) hydroxylating Phe4MO (represented as CpsB) was detected, amplified (from the genome of Bacillus tropicus strain AOA-CPS1), cloned, overexpressed, purified and characterized here. The 1.755-kb gene cloned in the pET15b vector expressed a ≅ 64 kDa monomeric protein which was purified to homogeneity by single-step affinity chromatography, with a total yield of 82.1%. The optimum temperature and pH of the enzyme were found to be 30 °C and 7.0, respectively. CpsB showed functional stability between pH 6.0-7.5 and temperature 25-30 °C. The enzyme-substrate reaction kinetic studies showed the allosteric nature of the enzyme and followed pre-steady state using NADH as a co-substrate with apparent vmax, Km, kcat and kcat/Km values of 0.465 μM.s-1, 140 μM, 0.099 s-1 and 7.07 × 10-4 μM-1.s-1, respectively, for the substrate PCP. The in-gel trypsin digestion experiments and bioinformatic tools confirmed that the reported enzyme is a Phe4MO with multiple putative conserved domains and metal ion-binding site. Though Phe4MO has been reported to have a diverse catalytic function, here we report, for the first time, that it functions as a PCP dehalogenase or PCP-4-monooxygenase by hydroxylating PCP. Hence, the use of this enzyme may be further explored in the bioremediation of PCP and other related xenobiotics.
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Affiliation(s)
- Oladipupo A Aregbesola
- Discipline of Microbiology, School of Life Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal (Westville Campus), Private Bag X54001, Durban, 4000, South Africa
| | - Ajit Kumar
- Discipline of Microbiology, School of Life Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal (Westville Campus), Private Bag X54001, Durban, 4000, South Africa
| | - Mduduzi P Mokoena
- Discipline of Microbiology, School of Life Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal (Westville Campus), Private Bag X54001, Durban, 4000, South Africa
| | - Ademola O Olaniran
- Discipline of Microbiology, School of Life Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal (Westville Campus), Private Bag X54001, Durban, 4000, South Africa.
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8
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Solomon EI, DeWeese DE, Babicz JT. Mechanisms of O 2 Activation by Mononuclear Non-Heme Iron Enzymes. Biochemistry 2021; 60:3497-3506. [PMID: 34266238 PMCID: PMC8768060 DOI: 10.1021/acs.biochem.1c00370] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Two major subclasses of mononuclear non-heme ferrous enzymes use two electron-donating organic cofactors (α-ketoglutarate or pterin) to activate O2 to form FeIV═O intermediates that further react with their substrates through hydrogen atom abstraction or electrophilic aromatic substitution. New spectroscopic methodologies have been developed, enabling the study of the active sites in these enzymes and their oxygen intermediates. Coupled to electronic structure calculations, the results of these spectroscopies provide fundamental insight into mechanism. This Perspective summarizes the results of these studies in elucidating the mechanism of dioxygen activation to form the FeIV═O intermediate and the geometric and electronic structure of this intermediate that enables its high reactivity and selectivity in product formation.
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Affiliation(s)
- Edward I. Solomon
- Department of Chemistry, Stanford University, 333 Campus Dr. Stanford, CA, 94305, United States,SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, 94025, United States
| | - Dory E. DeWeese
- Department of Chemistry, Stanford University, 333 Campus Dr. Stanford, CA, 94305, United States
| | - Jeffrey T. Babicz
- Department of Chemistry, Stanford University, 333 Campus Dr. Stanford, CA, 94305, United States
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9
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Sheng Y, Abelson CS, Prakash J, Draksharapu A, Young VG, Que L. Unmasking Steps in Intramolecular Aromatic Hydroxylation by a Synthetic Nonheme Oxoiron(IV) Complex. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202108309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Yuan Sheng
- Department of Chemistry University of Minnesota Minneapolis MN 55455 USA
| | - Chase S. Abelson
- Department of Chemistry University of Minnesota Minneapolis MN 55455 USA
| | - Jai Prakash
- Department of Chemistry University of Minnesota Minneapolis MN 55455 USA
| | | | - Victor G. Young
- Department of Chemistry University of Minnesota Minneapolis MN 55455 USA
| | - Lawrence Que
- Department of Chemistry University of Minnesota Minneapolis MN 55455 USA
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10
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Sheng Y, Abelson CS, Prakash J, Draksharapu A, Young VG, Que L. Unmasking Steps in Intramolecular Aromatic Hydroxylation by a Synthetic Nonheme Oxoiron(IV) Complex. Angew Chem Int Ed Engl 2021; 60:20991-20998. [PMID: 34292639 DOI: 10.1002/anie.202108309] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Indexed: 11/09/2022]
Abstract
In this study, a methyl group on the classic tetramethylcyclam (TMC) ligand framework is replaced with a benzylic group to form the metastable [FeIV (Osyn )(Bn3MC)]2+ (2-syn; Bn3MC=1-benzyl-4,8,11-trimethyl-1,4,8,11-tetraazacyclotetradecane) species at -40 °C. The decay of 2-syn with time at 25 °C allows the unprecedented monitoring of the steps involved in the intramolecular hydroxylation of the ligand phenyl ring to form the major FeIII -OAr product 3. At the same time, the FeII (Bn3MC)2+ (1) precursor to 2-syn is re-generated in a 1:2 molar ratio relative to 3, accounting for the first time for all the electrons involved and all the Fe species derived from 2-syn as shown in the following balanced equation: 3 [FeIV (O)(LPh )]2+ (2-syn)→2 [FeIII (LOAr )]2+ (3)+[FeII (LPh )]2+ (1)+H2 O. This system thus serves as a paradigm for aryl hydroxylation by FeIV =O oxidants described thus far. It is also observed that 2-syn can be intercepted by certain hydrocarbon substrates, thereby providing a means to assess the relative energetics of aliphatic and aromatic C-H hydroxylation in this system.
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Affiliation(s)
- Yuan Sheng
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Chase S Abelson
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Jai Prakash
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Apparao Draksharapu
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Victor G Young
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Lawrence Que
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455, USA
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11
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Srnec M, Iyer SR, Dassama LMK, Park K, Wong SD, Sutherlin KD, Yoda Y, Kobayashi Y, Kurokuzu M, Saito M, Seto M, Krebs C, Bollinger JM, Solomon EI. Nuclear Resonance Vibrational Spectroscopic Definition of the Facial Triad Fe IV═O Intermediate in Taurine Dioxygenase: Evaluation of Structural Contributions to Hydrogen Atom Abstraction. J Am Chem Soc 2020; 142:18886-18896. [PMID: 33103886 DOI: 10.1021/jacs.0c08903] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The α-ketoglutarate (αKG)-dependent oxygenases catalyze a diverse range of chemical reactions using a common high-spin FeIV═O intermediate that, in most reactions, abstract a hydrogen atom from the substrate. Previously, the FeIV═O intermediate in the αKG-dependent halogenase SyrB2 was characterized by nuclear resonance vibrational spectroscopy (NRVS) and density functional theory (DFT) calculations, which demonstrated that it has a trigonal-pyramidal geometry with the scissile C-H bond of the substrate calculated to be perpendicular to the Fe-O bond. Here, we have used NRVS and DFT calculations to show that the FeIV═O complex in taurine dioxygenase (TauD), the αKG-dependent hydroxylase in which this intermediate was first characterized, also has a trigonal bipyramidal geometry but with an aspartate residue replacing the equatorial halide of the SyrB2 intermediate. Computational analysis of hydrogen atom abstraction by square pyramidal, trigonal bipyramidal, and six-coordinate FeIV═O complexes in two different substrate orientations (one more along [σ channel] and another more perpendicular [π channel] to the Fe-O bond) reveals similar activation barriers. Thus, both substrate approaches to all three geometries are competent in hydrogen atom abstraction. The equivalence in reactivity between the two substrate orientations arises from compensation of the promotion energy (electronic excitation within the d manifold) required to access the π channel by the significantly larger oxyl character present in the pπ orbital oriented toward the substrate, which leads to an earlier transition state along the C-H coordinate.
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Affiliation(s)
- Martin Srnec
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305-5080, United States.,J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8 182 23, Czech Republic
| | - Shyam R Iyer
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305-5080, United States
| | - Laura M K Dassama
- Department of Chemistry and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Kiyoung Park
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305-5080, United States
| | - Shaun D Wong
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305-5080, United States
| | - Kyle D Sutherlin
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305-5080, United States
| | - Yoshitaka Yoda
- Japan Synchrotron Radiation Research Institute, Hyogo 679-5198, Japan
| | | | | | - Makina Saito
- Research Reactor Institute, Kyoto University, Osaka 590-0494, Japan
| | - Makoto Seto
- Research Reactor Institute, Kyoto University, Osaka 590-0494, Japan
| | - Carsten Krebs
- Department of Chemistry and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - J Martin Bollinger
- Department of Chemistry and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305-5080, United States
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12
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Abstract
Fluorochemicals are a widely distributed class of compounds and have been utilized across a wide range of industries for decades. Given the environmental toxicity and adverse health threats of some fluorochemicals, the development of new methods for their decomposition is significant to public health. However, the carbon-fluorine (C-F) bond is among the most chemically robust bonds; consequently, the degradation of fluorinated hydrocarbons is exceptionally difficult. Here, metalloenzymes that catalyze the cleavage of this chemically challenging bond are reviewed. These enzymes include histidine-ligated heme-dependent dehaloperoxidase and tyrosine hydroxylase, thiolate-ligated heme-dependent cytochrome P450, and four nonheme oxygenases, namely, tetrahydrobiopterin-dependent aromatic amino acid hydroxylase, 2-oxoglutarate-dependent hydroxylase, Rieske dioxygenase, and thiol dioxygenase. While much of the literature regarding the aforementioned enzymes highlights their ability to catalyze C-H bond activation and functionalization, in many cases, the C-F bond cleavage has been shown to occur on fluorinated substrates. A copper-dependent laccase-mediated system representing an unnatural radical defluorination approach is also described. Detailed discussions on the structure-function relationships and catalytic mechanisms provide insights into biocatalytic defluorination, which may inspire drug design considerations and environmental remediation of halogenated contaminants.
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Affiliation(s)
- Yifan Wang
- Department of Chemistry, University of Texas at San Antonio, 1 UTSA Circle, San Antonio, TX 78249, USA.
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13
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The oxidation of cyclo-olefin by the S = 2 ground-state complex [Fe IV(O)(TQA)(NCMe)] 2. J Biol Inorg Chem 2020; 25:371-382. [PMID: 32133579 DOI: 10.1007/s00775-020-01768-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 02/16/2020] [Indexed: 10/24/2022]
Abstract
Density functional theory calculation is used to investigate the oxidation of cyclo-olefin (cyclobutene, cyclopentene, cyclohexene, cycloheptene, and cyclo-octene) by the complex [FeIV(O)(TQA)(NCMe)]2+, which has S = 2 ground state, and the effect of electronic factors and steric hindrance on reaction barriers. Our results suggest that the oxo-iron(IV) complex can oxidise C-H and C = C bonds via a single-state mechanism, and two different ways of electron transport exist. The energy barriers initially decrease with increasing substrate size, and the trend then reverses. Comparison of the energy barrier in different systems reveals that except for the reaction between [FeIV(O)(TQA)(NCMe)]2+ and cycloheptene, oxo-iron(IV) complexes prefer epoxidation to hydroxylation. However, the hydroxylated product is more stable than the corresponding epoxidated product. This result indicates that the products of epoxidation tend to decompose first. The energy barrier of hydroxylation and epoxidation originates from the balance of orbital interaction and Pauli repulsion from the equatorial ligand and protons on the approaching substrate. In this regard, we calculate the weak interaction between two fragments (oxo-iron complex and substrates) using the independent gradient model and drawn the corresponding 3D isosurface representations of reactants.
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14
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Dantignana V, Company A, Costas M. Oxoiron(V) Complexes of Relevance in Oxidation Catalysis of Organic Substrates. Isr J Chem 2020. [DOI: 10.1002/ijch.201900161] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Valeria Dantignana
- Grup de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT), Institut de Química Computacional i Catàlisi (IQCC), Departament de Química Universitat de Girona C/M. Aurèlia Capmany 69 17003 Girona, Catalonia Spain
| | - Anna Company
- Grup de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT), Institut de Química Computacional i Catàlisi (IQCC), Departament de Química Universitat de Girona C/M. Aurèlia Capmany 69 17003 Girona, Catalonia Spain
| | - Miquel Costas
- Grup de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT), Institut de Química Computacional i Catàlisi (IQCC), Departament de Química Universitat de Girona C/M. Aurèlia Capmany 69 17003 Girona, Catalonia Spain
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15
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Dantignana V, Serrano-Plana J, Draksharapu A, Magallón C, Banerjee S, Fan R, Gamba I, Guo Y, Que L, Costas M, Company A. Spectroscopic and Reactivity Comparisons between Nonheme Oxoiron(IV) and Oxoiron(V) Species Bearing the Same Ancillary Ligand. J Am Chem Soc 2019; 141:15078-15091. [PMID: 31469954 DOI: 10.1021/jacs.9b05758] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This work directly compares the spectroscopic and reactivity properties of an oxoiron(IV) and an oxoiron(V) complex that are supported by the same neutral tetradentate N-based PyNMe3 ligand. A complete spectroscopic characterization of the oxoiron(IV) species (2) reveals that this compound exists as a mixture of two isomers. The reactivity of the thermodynamically more stable oxoiron(IV) isomer (2b) is directly compared to that exhibited by the previously reported 1e--oxidized analogue [FeV(O)(OAc)(PyNMe3)]2+ (3). Our data indicates that 2b is 4 to 5 orders of magnitude slower than 3 in hydrogen atom transfer (HAT) from C-H bonds. The origin of this huge difference lies in the strength of the O-H bond formed after HAT by the oxoiron unit, the O-H bond derived from 3 being about 20 kcal·mol-1 stronger than that from 2b. The estimated bond strength of the FeIVO-H bond of 100 kcal·mol-1 is very close to the reported values for highly active synthetic models of compound I of cytochrome P450. In addition, this comparative study provides direct experimental evidence that the lifetime of the carbon-centered radical that forms after the initial HAT by the high valent oxoiron complex depends on the oxidation state of the nascent Fe-OH complex. Complex 2b generates long-lived carbon-centered radicals that freely diffuse in solution, while 3 generates short-lived caged radicals that rapidly form product C-OH bonds, so only 3 engages in stereoretentive hydroxylation reactions. Thus, the oxidation state of the iron center modulates not only the rate of HAT but also the rate of ligand rebound.
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Affiliation(s)
- Valeria Dantignana
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Química , Universitat de Girona , C/M. Aurèlia Capmany 69 , 17003 Girona , Catalonia , Spain
| | - Joan Serrano-Plana
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Química , Universitat de Girona , C/M. Aurèlia Capmany 69 , 17003 Girona , Catalonia , Spain
| | - Apparao Draksharapu
- Department of Chemistry and Center for Metals in Biocatalysis , University of Minnesota , Minneapolis , Minnesota 55455 , United States
| | - Carla Magallón
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Química , Universitat de Girona , C/M. Aurèlia Capmany 69 , 17003 Girona , Catalonia , Spain
| | - Saikat Banerjee
- Department of Chemistry and Center for Metals in Biocatalysis , University of Minnesota , Minneapolis , Minnesota 55455 , United States
| | - Ruixi Fan
- Department of Chemistry , Carnegie Mellon University , 4400 Fifth Avenue , Pittsburgh , Pennsylvania 15213 , United States
| | - Ilaria Gamba
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Química , Universitat de Girona , C/M. Aurèlia Capmany 69 , 17003 Girona , Catalonia , Spain
| | - Yisong Guo
- Department of Chemistry , Carnegie Mellon University , 4400 Fifth Avenue , Pittsburgh , Pennsylvania 15213 , United States
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis , University of Minnesota , Minneapolis , Minnesota 55455 , United States
| | - Miquel Costas
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Química , Universitat de Girona , C/M. Aurèlia Capmany 69 , 17003 Girona , Catalonia , Spain
| | - Anna Company
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Química , Universitat de Girona , C/M. Aurèlia Capmany 69 , 17003 Girona , Catalonia , Spain
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16
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Flydal MI, Alcorlo-Pagés M, Johannessen FG, Martínez-Caballero S, Skjærven L, Fernandez-Leiro R, Martinez A, Hermoso JA. Structure of full-length human phenylalanine hydroxylase in complex with tetrahydrobiopterin. Proc Natl Acad Sci U S A 2019; 116:11229-11234. [PMID: 31118288 PMCID: PMC6561269 DOI: 10.1073/pnas.1902639116] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Phenylalanine hydroxylase (PAH) is a key enzyme in the catabolism of phenylalanine, and mutations in this enzyme cause phenylketonuria (PKU), a genetic disorder that leads to brain damage and mental retardation if untreated. Some patients benefit from supplementation with a synthetic formulation of the cofactor tetrahydrobiopterin (BH4) that partly acts as a pharmacological chaperone. Here we present structures of full-length human PAH (hPAH) both unbound and complexed with BH4 in the precatalytic state. Crystal structures, solved at 3.18-Å resolution, show the interactions between the cofactor and PAH, explaining the negative regulation exerted by BH4 BH4 forms several H-bonds with the N-terminal autoregulatory tail but is far from the catalytic FeII Upon BH4 binding a polar and salt-bridge interaction network links the three PAH domains, explaining the stability conferred by BH4 Importantly, BH4 binding modulates the interaction between subunits, providing information about PAH allostery. Moreover, we also show that the cryo-EM structure of hPAH in absence of BH4 reveals a highly dynamic conformation for the tetramers. Structural analyses of the hPAH:BH4 subunits revealed that the substrate-induced movement of Tyr138 into the active site could be coupled to the displacement of BH4 from the precatalytic toward the active conformation, a molecular mechanism that was supported by site-directed mutagenesis and targeted molecular dynamics simulations. Finally, comparison of the rat and human PAH structures show that hPAH is more dynamic, which is related to amino acid substitutions that enhance the flexibility of hPAH and may increase the susceptibility to PKU-associated mutations.
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Affiliation(s)
| | - Martín Alcorlo-Pagés
- Department of Crystallography and Structural Biology, Instituto de Química-Física "Rocasolano," Consejo Superior de Investigaciones Científicas (CSIC), 28006 Madrid, Spain
| | | | | | - Lars Skjærven
- Department of Biomedicine, University of Bergen, 5009 Bergen, Norway
| | - Rafael Fernandez-Leiro
- Structural Biology Programme, Spanish National Cancer Research Centre (CNIO), 28029 Madrid, Spain
| | - Aurora Martinez
- Department of Biomedicine, University of Bergen, 5009 Bergen, Norway;
| | - Juan A Hermoso
- Department of Crystallography and Structural Biology, Instituto de Química-Física "Rocasolano," Consejo Superior de Investigaciones Científicas (CSIC), 28006 Madrid, Spain;
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17
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Reilley DJ, Popov KI, Dokholyan NV, Alexandrova AN. Uncovered Dynamic Coupling Resolves the Ambiguous Mechanism of Phenylalanine Hydroxylase Oxygen Binding. J Phys Chem B 2019; 123:4534-4539. [PMID: 31038957 DOI: 10.1021/acs.jpcb.9b02893] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Phenylalanine hydroxylase (PAH) is an iron enzyme catalyzing the oxidation of l-Phe to l-Tyr during phenylalanine catabolism. Dysfunction of PAH leads to the debilitating condition phenylketonuria (PKU), which prompted research into the structure and function of PAH over the last 50 years. Despite intensive study, there is no consensus on the atomistic details of the mechanism of O2 binding and splitting by wild-type (WT) PAH and how it varies with PKU-inducing mutations, Arg158Gln and Glu280Lys. We studied structures involved in a proposed mechanism for the WT and mutants using extensive mixed quantum-classical molecular dynamics simulations. Simulations reveal a previously unobserved dynamic coupling between the active site and the mutation sites, suggesting how they can affect the catalytic performance of PAH. Furthermore, the effect of the coupling on the PAH structure agrees with and expands our understanding of the experimentally observed differences in activity between the WT and mutants.
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Affiliation(s)
- David J Reilley
- Department of Chemistry and Biochemistry , University of California, Los Angeles , Los Angeles , California 90095-1569 , United States
| | - Konstantin I Popov
- Department of Biochemistry and Biophysics , University of North Carolina at Chapel Hill , Chapel Hill , North Carolina 27599 , United States
| | - Nikolay V Dokholyan
- Department of Biochemistry and Biophysics , University of North Carolina at Chapel Hill , Chapel Hill , North Carolina 27599 , United States.,Department of Pharmacology, Department of Biochemistry & Molecular Biology , Penn State University College of Medicine , Hershey , Pennsylvania 17033 , United States
| | - Anastassia N Alexandrova
- Department of Chemistry and Biochemistry , University of California, Los Angeles , Los Angeles , California 90095-1569 , United States.,California NanoSystems Institute, Los Angeles , California 90095-1569 , United States
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18
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Guo M, Corona T, Ray K, Nam W. Heme and Nonheme High-Valent Iron and Manganese Oxo Cores in Biological and Abiological Oxidation Reactions. ACS CENTRAL SCIENCE 2019; 5:13-28. [PMID: 30693322 PMCID: PMC6346628 DOI: 10.1021/acscentsci.8b00698] [Citation(s) in RCA: 226] [Impact Index Per Article: 45.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Indexed: 05/23/2023]
Abstract
Utilization of O2 as an abundant and environmentally benign oxidant is of great interest in the design of bioinspired synthetic catalytic oxidation systems. Metalloenzymes activate O2 by employing earth-abundant metals and exhibit diverse reactivities in oxidation reactions, including epoxidation of olefins, functionalization of alkane C-H bonds, arene hydroxylation, and syn-dihydroxylation of arenes. Metal-oxo species are proposed as reactive intermediates in these reactions. A number of biomimetic metal-oxo complexes have been synthesized in recent years by activating O2 or using artificial oxidants at iron and manganese centers supported on heme or nonheme-type ligand environments. Detailed reactivity studies together with spectroscopy and theory have helped us understand how the reactivities of these metal-oxygen intermediates are controlled by the electronic and steric properties of the metal centers. These studies have provided important insights into biological reactions, which have contributed to the design of biologically inspired oxidation catalysts containing earth-abundant metals like iron and manganese. In this Outlook article, we survey a few examples of these advances with particular emphasis in each case on the interplay of catalyst design and our understanding of metalloenzyme structure and function.
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Affiliation(s)
- Mian Guo
- Department
of Chemistry and Nano Science, Ewha Womans
University, Seoul 03760, Korea
| | - Teresa Corona
- Department
of Chemistry, Humboldt-Universität
zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany
| | - Kallol Ray
- Department
of Chemistry, Humboldt-Universität
zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany
| | - Wonwoo Nam
- Department
of Chemistry and Nano Science, Ewha Womans
University, Seoul 03760, Korea
- State
Key Laboratory for Oxo Synthesis and Selective Oxidation, Center for
Excellence in Molecular Synthesis, Suzhou
Research Institute of LICP, Lanzhou Institute of Chemical Physics
(LICP), Chinese Academy of Sciences, Lanzhou, 730000, P. R.
China
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19
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Tian M, Gao Z, Sun W, Han H, Sun L, Hu Y. Activation role of lead ions in benzohydroxamic acid flotation of oxide minerals: New perspective and new practice. J Colloid Interface Sci 2018; 529:150-160. [DOI: 10.1016/j.jcis.2018.05.113] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Revised: 05/30/2018] [Accepted: 05/31/2018] [Indexed: 12/01/2022]
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20
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Chang WC, Liu P, Guo Y. Mechanistic Elucidation of Two Catalytically Versatile Iron(II)- and α-Ketoglutarate-Dependent Enzymes: Cases Beyond Hydroxylation. COMMENT INORG CHEM 2018. [DOI: 10.1080/02603594.2018.1509856] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Wei-chen Chang
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina, USA
| | - Pinghua Liu
- Department of Chemistry, Boston University, Boston, Massachusetts, USA
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
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21
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22
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Turcas R, Lakk-Bogáth D, Speier G, Kaizer J. Steric control and the mechanism of benzaldehyde oxidation by polypyridyl oxoiron(iv) complexes: aromatic versus benzylic hydroxylation of aromatic aldehydes. Dalton Trans 2018; 47:3248-3252. [PMID: 29446776 DOI: 10.1039/c7dt03727a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The present study describes the first example of the hydroxylation of benzaldehydes by synthetic nonheme oxoiron(iv) complexes, where the reactivity, chemoselectivity, and mechanism were strongly influenced by the ligand environment of the iron center.
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Affiliation(s)
- Ramona Turcas
- Department of Chemistry, University of Pannonia, H-8201 Veszprém, Hungary.
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23
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Affiliation(s)
- Paolo Pirovano
- School of Chemistry and CRANN/AMBER Nanoscience Institute; Trinity College Dublin; The University of Dublin; College Green 2 Dublin Ireland
| | - Aidan R. McDonald
- School of Chemistry and CRANN/AMBER Nanoscience Institute; Trinity College Dublin; The University of Dublin; College Green 2 Dublin Ireland
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24
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Bigelow JO, England J, Klein JEMN, Farquhar ER, Frisch JR, Martinho M, Mandal D, Münck E, Shaik S, Que L. Oxoiron(IV) Tetramethylcyclam Complexes with Axial Carboxylate Ligands: Effect of Tethering the Carboxylate on Reactivity. Inorg Chem 2017; 56:3287-3301. [DOI: 10.1021/acs.inorgchem.6b02659] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jennifer O. Bigelow
- Department of Chemistry
and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Jason England
- Department of Chemistry
and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Johannes E. M. N. Klein
- Department of Chemistry
and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Erik R. Farquhar
- Department of Chemistry
and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Jonathan R. Frisch
- Department of Chemistry
and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Marlène Martinho
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Debasish Mandal
- Institute of Chemistry and the Lise Meitner-Minerva
Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Eckard Münck
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Sason Shaik
- Institute of Chemistry and the Lise Meitner-Minerva
Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Lawrence Que
- Department of Chemistry
and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
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25
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Kal S, Que L. Dioxygen activation by nonheme iron enzymes with the 2-His-1-carboxylate facial triad that generate high-valent oxoiron oxidants. J Biol Inorg Chem 2017; 22:339-365. [PMID: 28074299 DOI: 10.1007/s00775-016-1431-2] [Citation(s) in RCA: 159] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 12/13/2016] [Indexed: 11/24/2022]
Abstract
The 2-His-1-carboxylate facial triad is a widely used scaffold to bind the iron center in mononuclear nonheme iron enzymes for activating dioxygen in a variety of oxidative transformations of metabolic significance. Since the 1990s, over a hundred different iron enzymes have been identified to use this platform. This structural motif consists of two histidines and the side chain carboxylate of an aspartate or a glutamate arranged in a facial array that binds iron(II) at the active site. This triad occupies one face of an iron-centered octahedron and makes the opposite face available for the coordination of O2 and, in many cases, substrate, allowing the tailoring of the iron-dioxygen chemistry to carry out a plethora of diverse reactions. Activated dioxygen-derived species involved in the enzyme mechanisms include iron(III)-superoxo, iron(III)-peroxo, and high-valent iron(IV)-oxo intermediates. In this article, we highlight the major crystallographic, spectroscopic, and mechanistic advances of the past 20 years that have significantly enhanced our understanding of the mechanisms of O2 activation and the key roles played by iron-based oxidants.
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Affiliation(s)
- Subhasree Kal
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Lawrence Que
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN, 55455, USA.
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26
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Subedi BP, Fitzpatrick PF. Kinetic Mechanism and Intrinsic Rate Constants for the Reaction of a Bacterial Phenylalanine Hydroxylase. Biochemistry 2016; 55:6848-6857. [DOI: 10.1021/acs.biochem.6b01012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Bishnu P. Subedi
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, San Antonio Texas 78229, United States
| | - Paul F. Fitzpatrick
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, San Antonio Texas 78229, United States
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27
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Abstract
The non-heme Fe enzymes are ubiquitous in nature and perform a wide range of functions involving O2 activation. These had been difficult to study relative to heme enzymes; however, spectroscopic methods that provide significant insight into the correlation of structure with function have now been developed. This Current Topics article summarizes both the molecular mechanism these enzymes use to control O2 activation in the presence of cosubstrates and the oxygen intermediates these reactions generate. Three types of O2 activation are observed. First, non-heme reactivity is shown to be different from heme chemistry where a low-spin FeIII-OOH non-heme intermediate directly reacts with substrate. Also, two subclasses of non-heme Fe enzymes generate high-spin FeIV═O intermediates that provide both σ and π frontier molecular orbitals that can control selectivity. Finally, for several subclasses of non-heme Fe enzymes, binding of the substrate to the FeII site leads to the one-electron reductive activation of O2 to an FeIII-superoxide capable of H atom abstraction and electrophilic attack.
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Affiliation(s)
- Edward I Solomon
- Department of Chemistry, Stanford University , Stanford, California 94305, United States.,SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
| | - Serra Goudarzi
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Kyle D Sutherlin
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
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28
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Sahu S, Zhang B, Pollock CJ, Dürr M, Davies CG, Confer AM, Ivanović-Burmazović I, Siegler MA, Jameson GNL, Krebs C, Goldberg DP. Aromatic C-F Hydroxylation by Nonheme Iron(IV)-Oxo Complexes: Structural, Spectroscopic, and Mechanistic Investigations. J Am Chem Soc 2016; 138:12791-12802. [PMID: 27656776 PMCID: PMC5628738 DOI: 10.1021/jacs.6b03346] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The synthesis and reactivity of a series of mononuclear nonheme iron complexes that carry out intramolecular aromatic C-F hydroxylation reactions is reported. The key intermediate prior to C-F hydroxylation, [FeIV(O)(N4Py2Ar1)](BF4)2 (1-O, Ar1 = -2,6-difluorophenyl), was characterized by single-crystal X-ray diffraction. The crystal structure revealed a nonbonding C-H···O═Fe interaction with a CH3CN molecule. Variable-field Mössbauer spectroscopy of 1-O indicates an intermediate-spin (S = 1) ground state. The Mössbauer parameters for 1-O include an unusually small quadrupole splitting for a triplet FeIV(O) and are reproduced well by density functional theory calculations. With the aim of investigating the initial step for C-F hydroxylation, two new ligands were synthesized, N4Py2Ar2 (L2, Ar2 = -2,6-difluoro-4-methoxyphenyl) and N4Py2Ar3 (L3, Ar3 = -2,6-difluoro-3-methoxyphenyl), with -OMe substituents in the meta or ortho/para positions with respect to the C-F bonds. FeII complexes [Fe(N4Py2Ar2)(CH3CN)](ClO4)2 (2) and [Fe(N4Py2Ar3)(CH3CN)](ClO4)2 (3) reacted with isopropyl 2-iodoxybenzoate to give the C-F hydroxylated FeIII-OAr products. The FeIV(O) intermediates 2-O and 3-O were trapped at low temperature and characterized. Complex 2-O displayed a C-F hydroxylation rate similar to that of 1-O. In contrast, the kinetics (via stopped-flow UV-vis) for complex 3-O displayed a significant rate enhancement for C-F hydroxylation. Eyring analysis revealed the activation barriers for the C-F hydroxylation reaction for the three complexes, consistent with the observed difference in reactivity. A terminal FeII(OH) complex (4) was prepared independently to investigate the possibility of a nucleophilic aromatic substitution pathway, but the stability of 4 rules out this mechanism. Taken together the data fully support an electrophilic C-F hydroxylation mechanism.
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Affiliation(s)
- Sumit Sahu
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Bo Zhang
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Christopher J. Pollock
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Maximilian Dürr
- Department of Chemistry and Pharmacy, University of Erlangen-Nürnberg, 91058 Erlangen, Germany
| | - Casey G. Davies
- Department of Chemistry & MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Alex M. Confer
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | | | - Maxime A. Siegler
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Guy N. L. Jameson
- Department of Chemistry & MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Carsten Krebs
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - David P. Goldberg
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
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29
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Sahu S, Goldberg DP. Activation of Dioxygen by Iron and Manganese Complexes: A Heme and Nonheme Perspective. J Am Chem Soc 2016; 138:11410-28. [PMID: 27576170 DOI: 10.1021/jacs.6b05251] [Citation(s) in RCA: 229] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The rational design of well-defined, first-row transition metal complexes that can activate dioxygen has been a challenging goal for the synthetic inorganic chemist. The activation of O2 is important in part because of its central role in the functioning of metalloenzymes, which utilize O2 to perform a number of challenging reactions including the highly selective oxidation of various substrates. There is also great interest in utilizing O2, an abundant and environmentally benign oxidant, in synthetic catalytic oxidation systems. This Perspective brings together recent examples of biomimetic Fe and Mn complexes that can activate O2 in heme or nonheme-type ligand environments. The use of oxidants such as hypervalent iodine (e.g., ArIO), peracids (e.g., m-CPBA), peroxides (e.g., H2O2) or even superoxide is a popular choice for accessing well-characterized metal-superoxo, metal-peroxo, or metal-oxo species, but the instances of biomimetic Fe/Mn complexes that react with dioxygen to yield such observable metal-oxygen species are surprisingly few. This Perspective focuses on mononuclear Fe and Mn complexes that exhibit reactivity with O2 and lead to spectroscopically observable metal-oxygen species, and/or oxidize biologically relevant substrates. Analysis of these examples reveals that solvent, spin state, redox potential, external co-reductants, and ligand architecture can all play important roles in the O2 activation process.
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Affiliation(s)
- Sumit Sahu
- Department of Chemistry, The Johns Hopkins University , Baltimore, Maryland 21218, United States
| | - David P Goldberg
- Department of Chemistry, The Johns Hopkins University , Baltimore, Maryland 21218, United States
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30
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Chang WC, Li J, Lee JL, Cronican AA, Guo Y. Mechanistic Investigation of a Non-Heme Iron Enzyme Catalyzed Epoxidation in (-)-4'-Methoxycyclopenin Biosynthesis. J Am Chem Soc 2016; 138:10390-3. [PMID: 27442345 DOI: 10.1021/jacs.6b05400] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mechanisms have been proposed for α-KG-dependent non-heme iron enzyme catalyzed oxygen atom insertion into an olefinic moiety in various natural products, but they have not been examined in detail. Using a combination of methods including transient kinetics, Mössbauer spectroscopy, and mass spectrometry, we demonstrate that AsqJ-catalyzed (-)-4'-methoxycyclopenin formation uses a high-spin Fe(IV)-oxo intermediate to carry out epoxidation. Furthermore, product analysis on (16)O/(18)O isotope incorporation from the reactions using the native substrate, 4'-methoxydehydrocyclopeptin, and a mechanistic probe, dehydrocyclopeptin, reveals evidence supporting oxo↔hydroxo tautomerism of the Fe(IV)-oxo species in the non-heme iron enzyme catalysis.
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Affiliation(s)
- Wei-Chen Chang
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
| | - Jikun Li
- Department of Chemistry, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
| | - Justin L Lee
- Department of Chemistry, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
| | - Andrea A Cronican
- Department of Environmental and Occupational Health, University of Pittsburgh , Pittsburgh, Pennsylvania 15219, United States
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
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31
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Mono- and binuclear non-heme iron chemistry from a theoretical perspective. J Biol Inorg Chem 2016; 21:619-44. [DOI: 10.1007/s00775-016-1357-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 04/29/2016] [Indexed: 10/21/2022]
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32
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Srnec M, Wong SD, Matthews ML, Krebs C, Bollinger JM, Solomon EI. Electronic Structure of the Ferryl Intermediate in the α-Ketoglutarate Dependent Non-Heme Iron Halogenase SyrB2: Contributions to H Atom Abstraction Reactivity. J Am Chem Soc 2016; 138:5110-22. [PMID: 27021969 DOI: 10.1021/jacs.6b01151] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Low temperature magnetic circular dichroism (LT MCD) spectroscopy in combination with quantum-chemical calculations are used to define the electronic structure associated with the geometric structure of the Fe(IV)═O intermediate in SyrB2 that was previously determined by nuclear resonance vibrational spectroscopy. These studies elucidate key frontier molecular orbitals (FMOs) and their contribution to H atom abstraction reactivity. The VT MCD spectra of the enzymatic S = 2 Fe(IV)═O intermediate with Br(-) ligation contain information-rich features that largely parallel the corresponding spectra of the S = 2 model complex (TMG3tren)Fe(IV)═O (Srnec, M.; Wong, S. D.; England, J; Que, L; Solomon, E. I. Proc. Natl. Acad. Sci. USA 2012, 109, 14326-14331). However, quantitative differences are observed that correlate with π-anisotropy and oxo donor strength that perturb FMOs and affect reactivity. Due to π-anisotropy, the Fe(IV)═O active site exhibits enhanced reactivity in the direction of the substrate cavity that proceeds through a π-channel that is controlled by perpendicular orientation of the substrate C-H bond relative to the halide-Fe(IV)═O plane. Also, the increased intrinsic reactivity of the SyrB2 intermediate relative to the ferryl model complex is correlated to a higher oxyl character of the Fe(IV)═O at the transition states resulting from the weaker ligand field of the halogenase.
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Affiliation(s)
- Martin Srnec
- Department of Chemistry, Stanford University , Stanford, California 94305-5080, United States .,J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences , Dolejškova 2155/3, 182 23 Prague 8, Czech Republic
| | - Shaun D Wong
- Department of Chemistry, Stanford University , Stanford, California 94305-5080, United States
| | - Megan L Matthews
- Department of Chemistry, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Carsten Krebs
- Department of Chemistry, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - J Martin Bollinger
- Department of Chemistry, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University , Stanford, California 94305-5080, United States
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Catalytic strategies of the non-heme iron dependent oxygenases and their roles in plant biology. Curr Opin Chem Biol 2016; 31:126-35. [PMID: 27015291 PMCID: PMC4879150 DOI: 10.1016/j.cbpa.2016.02.017] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 02/25/2016] [Accepted: 02/26/2016] [Indexed: 12/18/2022]
Abstract
Current evidence for iron-oxo reactive intermediates is reviewed. In crystallo intermediates detected in a native extradiol dioxygenase reaction. Carotenoid cleavage dioxygenases catalyse strigolactone biosynthesis. Identification of plant cysteine oxidases involved in the plant hypoxic response. Applications of enzyme manipulation to plant biology and agriculture are discussed.
Non-heme iron-dependent oxygenases catalyse the incorporation of O2 into a wide range of biological molecules and use diverse strategies to activate their substrates. Recent kinetic studies, including in crystallo, have provided experimental support for some of the intermediates used by different subclasses of this enzyme family. Plant non-heme iron-dependent oxygenases have diverse and important biological roles, including in growth signalling, stress responses and secondary metabolism. Recently identified roles include in strigolactone biosynthesis, O-demethylation in morphine biosynthesis and regulating the stability of hypoxia-responsive transcription factors. We discuss current structural and mechanistic understanding of plant non-heme iron oxygenases, and how their chemical/genetic manipulation could have agricultural benefit, for example, for improved yield, stress tolerance or herbicide development.
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34
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Yi W, Yuan L, Kun Y, Zhengwen H, Jing T, Xu F, Hong G, Yong W. What factors influence the reactivity of C-H hydroxylation and C=C epoxidation by [Fe(IV)(L(ax))(1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane)(O)](n+). J Biol Inorg Chem 2015; 20:1123-34. [PMID: 26345158 DOI: 10.1007/s00775-015-1294-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 08/26/2015] [Indexed: 11/26/2022]
Abstract
Density functional theory is used to investigate geometric structures and mechanisms for hydroxylation and epoxidation from propene for four non-heme iron complexes, [Fe(IV)(L(ax))(TMC)(O)](n+), which are the inverted isomers of [Fe(IV)(O)(TMC)(Lax)](n+) (Lax = acetonitrile (AN), monoanionic trifluoroacetate (TF), azide (N3), thiolate (SR)). The Fe(IV)O unit is found to be sterically less hindered in [Fe(IV)(L(ax))(TMC)(O)](n+) than that in [Fe(IV)(O)(TMC)(L(ax))](n+). Becke, three-parameter, Lee-Yang-Parr (B3LYP) calculations show that hydroxylation and epoxidation proceed via a two-state-reactivity on competing triplet and quintet spin surfaces; and the reactions have been invariably mediated by the S = 2 state. The reaction pathways computed reveal that 2-AN is the most reactive in the four [Fe(IV)(L(ax))(TMC)(O)](n+) complexes; along the reaction pathway, the axial ligand moves away from the iron center, and thus, the energy of the LUMO decreases. The anionic axial ligand, which is more electron releasing than neutral AN, shows a strong overlap of iron orbitals. Thus, the anionic ligand does not move away from the iron center. The H-abstraction is affected by the tunneling contribution, the more electron donation power of the axial ligand, the more effect of the tunneling contribution. Adding the tunneling correction, the relative reactivity of the hydroxylation follows the trend: 2-AN > 2-SR ≈ 2-N3 > 2-TF. However, for the epoxidation, the reactivity is in the following order of 2-AN > 2-TF > 2-N3 > 2-SR. Except for 2-AN, 2-X (L(ax) = TF, N3, SR) complexes chemoselectively hydroxylate even in the presence of a C=C double bond.
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Affiliation(s)
- Wang Yi
- School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, China.
| | - Liu Yuan
- School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, China
| | - Yang Kun
- Department of Physics, Dalian Maritime University, 1 Linghai Road, Dalian, 116026, China
| | - He Zhengwen
- School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, China
| | - Tian Jing
- School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, China
| | - Fei Xu
- School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, China
| | - Guo Hong
- School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, China
| | - Wang Yong
- State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China.
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England J, Prakash J, Cranswick MA, Mandal D, Guo Y, Münck E, Shaik S, Que L. Oxoiron(IV) Complex of the Ethylene-Bridged Dialkylcyclam Ligand Me2EBC. Inorg Chem 2015; 54:7828-39. [PMID: 26244657 DOI: 10.1021/acs.inorgchem.5b00861] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We report herein the first example of an oxoiron(IV) complex of an ethylene-bridged dialkylcyclam ligand, [Fe(IV)(O)(Me2EBC)(NCMe)](2+) (2; Me2EBC = 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane). Complex 2 has been characterized by UV-vis, (1)H NMR, resonance Raman, Mössbauer, and X-ray absorption spectroscopy as well as electrospray ionization mass spectrometry, and its properties have been compared with those of the closely related [Fe(IV)(O)(TMC)(NCMe)](2+) (3; TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), the intensively studied prototypical oxoiron(IV) complex of the macrocyclic tetramethylcyclam ligand. Me2EBC has an N4 donor set nearly identical with that of TMC but possesses an ethylene bridge in place of the 1- and 8-methyl groups of TMC. As a consequence, Me2EBC is forced to deviate from the trans-I configuration typically found for Fe(IV)(O)(TMC) complexes and instead adopts a folded cis-V stereochemistry that requires the MeCN ligand to coordinate cis to the Fe(IV)═O unit in 2 rather than in the trans arrangement found in 3. However, switching from the trans geometry of 3 to the cis geometry of 2 did not significantly affect their ground-state electronic structures, although a decrease in ν(Fe═O) was observed for 2. Remarkably, despite having comparable Fe(IV/III) reduction potentials, 2 was found to be significantly more reactive than 3 in both oxygen-atom-transfer (OAT) and hydrogen-atom-transfer (HAT) reactions. A careful analysis of density functional theory calculations on the HAT reactivity of 2 and 3 revealed the root cause to be the higher oxyl character of 2, leading to a stronger O---H bond specifically in the quintet transition state.
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Affiliation(s)
- Jason England
- †Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Jai Prakash
- †Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Matthew A Cranswick
- †Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Debasish Mandal
- §Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Yisong Guo
- ‡Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Eckard Münck
- ‡Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Sason Shaik
- §Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Lawrence Que
- †Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
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36
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Kleespies ST, Oloo WN, Mukherjee A, Que L. C-H Bond Cleavage by Bioinspired Nonheme Oxoiron(IV) Complexes, Including Hydroxylation of n-Butane. Inorg Chem 2015; 54:5053-64. [PMID: 25751610 DOI: 10.1021/ic502786y] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The development of efficient and selective hydrocarbon oxidation processes with low environmental impact remains a major challenge of the 21st century because of the strong and apolar nature of the C-H bond. Naturally occurring iron-containing metalloenzymes can, however, selectively functionalize strong C-H bonds on substrates under mild and environmentally benign conditions. The key oxidant in a number of these transformations is postulated to possess an S = 2 Fe(IV)═O unit in a nonheme ligand environment. This oxidant has been trapped and spectroscopically characterized and its reactivity toward C-H bonds demonstrated for several nonheme iron enzyme classes. In order to obtain insight into the structure-activity relationships of these reactive intermediates, over 60 synthetic nonheme Fe(IV)(O) complexes have been prepared in various laboratories and their reactivities investigated. This Forum Article summarizes the current status of efforts in the characterization of the C-H bond cleavage reactivity of synthetic Fe(IV)(O) complexes and provides a snapshot of the current understanding of factors that control this reactivity, such as the properties of the supporting ligands and the spin state of the iron center. In addition, new results on the oxidation of strong C-H bonds such as those of cyclohexane and n-butane by a putative S = 2 synthetic Fe(IV)(O) species that is generated in situ using dioxygen at ambient conditions are presented.
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Affiliation(s)
- Scott T Kleespies
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Williamson N Oloo
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Anusree Mukherjee
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
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37
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Kazaryan A, Baerends EJ. Ligand Field Effects and the High Spin–High Reactivity Correlation in the H Abstraction by Non-Heme Iron(IV)–Oxo Complexes: A DFT Frontier Orbital Perspective. ACS Catal 2015. [DOI: 10.1021/cs501721y] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Andranik Kazaryan
- VU University Amsterdam, Theoretical Chemistry,
FEW, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Evert Jan Baerends
- VU University Amsterdam, Theoretical Chemistry,
FEW, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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38
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Sahu S, Quesne M, Davies CG, Dürr M, Ivanović-Burmazović I, Siegler MA, Jameson GNL, de Visser SP, Goldberg DP. Direct observation of a nonheme iron(IV)-oxo complex that mediates aromatic C-F hydroxylation. J Am Chem Soc 2014; 136:13542-5. [PMID: 25246108 PMCID: PMC4183621 DOI: 10.1021/ja507346t] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2014] [Indexed: 11/29/2022]
Abstract
The synthesis of a pentadentate ligand with strategically designed fluorinated arene groups in the second coordination sphere of a nonheme iron center is reported. The oxidatively resistant fluorine substituents allow for the trapping and characterization of an Fe(IV)(O) complex at -20 °C. Upon warming of the Fe(IV)(O) complex, an unprecedented arene C-F hydroxylation reaction occurs. Computational studies support the finding that substrate orientation is a critical factor in the observed reactivity. This work not only gives rare direct evidence for the participation of an Fe(IV)(O) species in arene hydroxylation but also provides the first example of a high-valent iron-oxo complex that mediates aromatic C-F hydroxylation.
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Affiliation(s)
- Sumit Sahu
- Department
of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Matthew
G. Quesne
- Manchester
Institute of Biotechnology and School of Chemical Engineering and
Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Casey G. Davies
- Department
of Chemistry & MacDiarmid Institute for Advanced Materials and
Nanotechnology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Maximilian Dürr
- Department
of Chemistry and Pharmacy, University of
Erlangen-Nürnberg, 91058 Erlangen, Germany
| | | | - Maxime A. Siegler
- Department
of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Guy N. L. Jameson
- Department
of Chemistry & MacDiarmid Institute for Advanced Materials and
Nanotechnology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Sam P. de Visser
- Manchester
Institute of Biotechnology and School of Chemical Engineering and
Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - David P. Goldberg
- Department
of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
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39
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Cook SA, Ziller JW, Borovik AS. Iron(II) complexes supported by sulfonamido tripodal ligands: endogenous versus exogenous substrate oxidation. Inorg Chem 2014; 53:11029-35. [PMID: 25264932 PMCID: PMC4203402 DOI: 10.1021/ic501531g] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
![]()
High-valent
iron species are known to act as powerful oxidants in both natural
and synthetic systems. While biological enzymes have evolved to prevent
self-oxidation by these highly reactive species, development of organic
ligand frameworks that are capable of supporting a high-valent iron
center remains a challenge in synthetic chemistry. We describe here
the reactivity of an Fe(II) complex that is supported by a tripodal
sulfonamide ligand with both dioxygen and an oxygen-atom transfer
reagent, 4-methylmorpholine-N-oxide (NMO). An Fe(III)–hydroxide
complex is obtained from reaction with dioxygen, while NMO gives
an Fe(III)–alkoxide product resulting from activation of a
C–H bond of the ligand. Inclusion of Ca2+ ions in
the reaction with NMO prevented this ligand activation and resulted
in isolation of an Fe(III)–hydroxide complex in which the Ca2+ ion is coordinated to the tripodal sulfonamide ligand and
the hydroxo ligand. Modification of the ligand allowed the Fe(III)–hydroxide
complex to be isolated from NMO in the absence of Ca2+ ions,
and a C–H bond of an external substrate could be activated
during the reaction. This study highlights the importance of robust
ligand design in the development of synthetic catalysts that utilize
a high-valent iron center. Oxidation of an
Fe(II) complex supported by a sulfonamido tripodal ligand was explored
with dioxygen and an O-atom transfer reagent. While dioxygen gave
an Fe(III)−hydroxido complex, the O-atom transfer reagent resulted
in C−H activation of the ligand to form an Fe(III)−alkoxide
species. Modification of the ligand prevented this ligand oxidation
and allowed for activation of C−H bonds on an external substrate.
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Affiliation(s)
- Sarah A Cook
- Department of Chemistry, University of California-Irvine , 1102 Natural Sciences II, Irvine, California 92697, United States
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40
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Ray K, Pfaff FF, Wang B, Nam W. Status of Reactive Non-Heme Metal–Oxygen Intermediates in Chemical and Enzymatic Reactions. J Am Chem Soc 2014; 136:13942-58. [DOI: 10.1021/ja507807v] [Citation(s) in RCA: 351] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Kallol Ray
- Department
of Chemistry, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Florian Felix Pfaff
- Department
of Chemistry, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Bin Wang
- Department
of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Wonwoo Nam
- Department
of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
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41
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Cong Z, Kinemuchi H, Kurahashi T, Fujii H. Factors affecting hydrogen-tunneling contribution in hydroxylation reactions promoted by oxoiron(IV) porphyrin π-cation radical complexes. Inorg Chem 2014; 53:10632-41. [PMID: 25222493 DOI: 10.1021/ic501737j] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Hydrogen atom transfer with a tunneling effect (H-tunneling) has been proposed to be involved in aliphatic hydroxylation reactions catalyzed by cytochrome P450 and synthetic heme complexes as a result of the observation of large hydrogen/deuterium kinetic isotope effects (KIEs). In the present work, we investigate the factors controlling the H-tunneling contribution to the H-transfer process in hydroxylation reaction by examining the kinetics of hydroxylation reactions at the benzylic positions of xanthene and 1,2,3,4-tetrahydronaphthalene by oxoiron(IV) 5,10,15,20-tetramesitylporphyrin π-cation radical complexes ((TMP(+•))Fe(IV)O(L)) under single-turnover conditions. The Arrhenius plots for these hydroxylation reactions of H-isotopomers have upwardly concave profiles. The Arrhenius plots of D-isotopomers, clear isosbestic points, and product analysis rule out the participation of thermally dependent other reaction processes in the concave profiles. These results provide evidence for the involvement of H-tunneling in the rate-limiting H-transfer process. These profiles are simulated using an equation derived from Bell's tunneling model. The temperature dependence of the KIE values (k(H)/k(D)) determined for these reactions indicates that the KIE value increases as the reaction temperature becomes lower, the bond dissociation energy (BDE) of the C-H bond of a substrate becomes higher, and the reactivity of (TMP(+•))Fe(IV)O(L) decreases. In addition, we found correlation of the slope of the ln(k(H)/k(D)) - 1/T plot and the bond strengths of the Fe═O bond of (TMP(+•))Fe(IV)O(L) estimated from resonance Raman spectroscopy. These observations indicate that these factors modulate the extent of the H-tunneling contribution by modulating the ratio of the height and thickness of the reaction barrier.
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Affiliation(s)
- Zhiqi Cong
- Department of Chemistry, Biology and Environmental Science, Faculty of Science, Nara Women's University , Kitauoyanishi, Nara 830-8506, Japan
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42
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Ergel B, Gill ML, Brown L, Yu B, Palmer AG, Hunt JF. Protein dynamics control the progression and efficiency of the catalytic reaction cycle of the Escherichia coli DNA-repair enzyme AlkB. J Biol Chem 2014; 289:29584-601. [PMID: 25043760 DOI: 10.1074/jbc.m114.575647] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A central goal of enzymology is to understand the physicochemical mechanisms that enable proteins to catalyze complex chemical reactions with high efficiency. Recent methodological advances enable the contribution of protein dynamics to enzyme efficiency to be explored more deeply. Here, we utilize enzymological and biophysical studies, including NMR measurements of conformational dynamics, to develop a quantitative mechanistic scheme for the DNA repair enzyme AlkB. Like other iron/2-oxoglutarate-dependent dioxygenases, AlkB employs a two-step mechanism in which oxidation of 2-oxoglutarate generates a highly reactive enzyme-bound oxyferryl intermediate that, in the case of AlkB, slowly hydroxylates an alkylated nucleobase. Our results demonstrate that a microsecond-to-millisecond time scale conformational transition facilitates the proper sequential order of substrate binding to AlkB. Mutations altering the dynamics of this transition allow generation of the oxyferryl intermediate but promote its premature quenching by solvent, which uncouples 2-oxoglutarate turnover from nucleobase oxidation. Therefore, efficient catalysis by AlkB depends upon the dynamics of a specific conformational transition, establishing another paradigm for the control of enzyme function by protein dynamics.
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Affiliation(s)
- Burçe Ergel
- From the Department of Biological Sciences, Columbia University, New York, New York 10027-6601 and
| | - Michelle L Gill
- the Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032-3702
| | - Lewis Brown
- From the Department of Biological Sciences, Columbia University, New York, New York 10027-6601 and
| | - Bomina Yu
- From the Department of Biological Sciences, Columbia University, New York, New York 10027-6601 and
| | - Arthur G Palmer
- the Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032-3702
| | - John F Hunt
- From the Department of Biological Sciences, Columbia University, New York, New York 10027-6601 and
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Company A, Sabenya G, González-Béjar M, Gómez L, Clémancey M, Blondin G, Jasniewski AJ, Puri M, Browne WR, Latour JM, Que L, Costas M, Pérez-Prieto J, Lloret-Fillol J. Triggering the generation of an iron(IV)-oxo compound and its reactivity toward sulfides by Ru(II) photocatalysis. J Am Chem Soc 2014; 136:4624-33. [PMID: 24568126 PMCID: PMC3985778 DOI: 10.1021/ja412059c] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
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The
preparation of [FeIV(O)(MePy2tacn)]2+ (2, MePy2tacn = N-methyl-N,N-bis(2-picolyl)-1,4,7-triazacyclononane)
by reaction of [FeII(MePy2tacn)(solvent)]2+ (1) and PhIO in CH3CN and its full
characterization are described. This compound can also be prepared
photochemically from its iron(II) precursor by irradiation at 447
nm in the presence of catalytic amounts of [RuII(bpy)3]2+ as photosensitizer and a sacrificial electron
acceptor (Na2S2O8). Remarkably, the
rate of the reaction of the photochemically prepared compound 2 toward sulfides increases 150-fold under irradiation, and 2 is partially regenerated after the sulfide has been consumed;
hence, the process can be repeated several times. The origin of this
rate enhancement has been established by studying the reaction of
chemically generated compound 2 with sulfides under different
conditions, which demonstrated that both light and [RuII(bpy)3]2+ are necessary for the observed increase
in the reaction rate. A combination of nanosecond time-resolved absorption
spectroscopy with laser pulse excitation and other mechanistic studies
has led to the conclusion that an electron transfer mechanism is the
most plausible explanation for the observed rate enhancement. According
to this mechanism, the in-situ-generated [RuIII(bpy)3]3+ oxidizes the sulfide to form the corresponding
radical cation, which is eventually oxidized by 2 to
the corresponding sulfoxide.
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Affiliation(s)
- Anna Company
- Grup de Química Bioinorgànica i Supramolecular (QBIS), Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi , E17071 Girona, Catalonia, Spain
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Pabis A, Geronimo I, Paneth P. A DFT study of the cis-dihydroxylation of nitroaromatic compounds catalyzed by nitrobenzene dioxygenase. J Phys Chem B 2014; 118:3245-56. [PMID: 24624972 PMCID: PMC3970850 DOI: 10.1021/jp4076299] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
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The
mechanism of cis-dihydroxylation of nitrobenzene
and 2-nitrotoluene catalyzed by nitrobenzene 1,2-dioxygenase (NBDO),
a member of the naphthalene family of Rieske non-heme iron dioxygenases,
was studied by means of the density functional theory method using
four models of the enzyme active site. Different possible reaction
pathways for the substrate dioxygenation initiated either by the FeIII–OOH or HO–FeV=O attack
on the aromatic ring were considered and the computed activation barriers
compared with the Gibbs free energy of activation for the oxygen–oxygen
cleavage leading to the formation of the iron(V)–oxo species
from its ferric hydroperoxo precursor. The mechanism of the substrate cis-dihydroxylation leading to the formation of a cis-dihydrodiol was then investigated, and the most feasible
mechanism was found to be starting with the attack of the high-valent
iron–oxo species on the substrate ring yielding a radical intermediate,
which further evolves toward the final product.
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Affiliation(s)
- Anna Pabis
- Institute of Applied Radiation Chemistry, Lodz University of Technology , Zeromskiego 116, 90-924 Lodz, Poland
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Paria S, Chatterjee S, Paine TK. Reactivity of an Iron–Oxygen Oxidant Generated upon Oxidative Decarboxylation of Biomimetic Iron(II) α-Hydroxy Acid Complexes. Inorg Chem 2014; 53:2810-21. [DOI: 10.1021/ic402443r] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sayantan Paria
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science (IACS), 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Sayanti Chatterjee
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science (IACS), 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Tapan Kanti Paine
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science (IACS), 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
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England J, Bigelow JO, Van Heuvelen KM, Farquhar ER, Martinho M, Meier KK, Frisch JR, Münck E, Que L. An Ultra-Stable Oxoiron(IV) Complex and Its Blue Conjugate Base. Chem Sci 2014; 5:1204-1215. [PMID: 24660055 PMCID: PMC3956701 DOI: 10.1039/c3sc52755g] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Treatment of [FeII(L)](OTf)2 (4), (where L = 1,4,8-Me3cyclam-11-CH2C(O)NMe2) with iodosylbenzene yielded the corresponding S = 1 oxoiron(IV) complex [FeIV(O(L)](OTf)2 (5) in nearly quantitative yield. The remarkably high stability of 5 (t1/2 ≈ 5 days at 25 °C) facilitated its characterization by X-ray crystallography and a raft of spectroscopic techniques. Treatment of 5 with strong base was found to generate a distinct, significantly less stable S = 1 oxoiron(IV) complex, 6 (t1/2 ~ 1.5 hrs. at 0 °C), which could be converted back to 5 by addition of a strong acid; these observations indicate that 5 and 6 represent a conjugate acid-base pair. That 6 can be formulated as [FeIV(O)(L-H)](OTf) was further supported by ESI mass spectrometry, spectroscopic and electrochemical studies, and DFT calculations. The close structural similarity of 5 and 6 provided a unique opportunity to probe the influence of the donor trans to the FeIV=O unit upon its reactivity in H-atom transfer (HAT) and O-atom transfer (OAT), and 5 was found to display greater reactivity than 6 in both OAT and HAT. While the greater OAT reactivity of 5 is expected on the basis of its higher redox potential, its higher HAT reactivity does not follow the anti-electrophilic trend reported for a series of [FeIV(O)(TMC)(X)] complexes (TMC = tetramethylcyclam) and thus appears to be inconsistent with the Two-State Reactivity rationale that is the prevailing explanation for the relative facility of oxoiron(IV) complexes to undergo HAT.
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Affiliation(s)
- Jason England
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
| | - Jennifer O. Bigelow
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
| | - Katherine M. Van Heuvelen
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
| | - Erik R. Farquhar
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
| | - Marléne Martinho
- Department of Chemistry, Carnegie Mellon University, 4400 5Ave., Pittsburgh, PA 15213, USA
| | - Katlyn K. Meier
- Department of Chemistry, Carnegie Mellon University, 4400 5Ave., Pittsburgh, PA 15213, USA
| | - Jonathan R. Frisch
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
| | - Eckard Münck
- Department of Chemistry, Carnegie Mellon University, 4400 5Ave., Pittsburgh, PA 15213, USA
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
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Rat S, Ménage S, Thomas F, Nivière V. Non-heme iron hydroperoxo species in superoxide reductase as a catalyst for oxidation reactions. Chem Commun (Camb) 2014; 50:14213-6. [DOI: 10.1039/c4cc06114d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The non-heme high-spin ferric iron hydroperoxo species formed in superoxide reductase can act both as a nucleophile and as an electrophile to catalyze oxidation reactions.
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Affiliation(s)
- S. Rat
- Univ. Grenoble Alpes
- iRTSV-LCBM
- F-38000 Grenoble, France
- CNRS
- iRTSV-LCBM
| | - S. Ménage
- Univ. Grenoble Alpes
- iRTSV-LCBM
- F-38000 Grenoble, France
- CNRS
- iRTSV-LCBM
| | - F. Thomas
- Département de Chimie Moléculaire – Chimie Inorganique Redox Biomimétique (CIRE) – UMR CNRS 5250
- Univ. Grenoble Alpes
- 38041 Grenoble cedex 9, France
| | - V. Nivière
- Univ. Grenoble Alpes
- iRTSV-LCBM
- F-38000 Grenoble, France
- CNRS
- iRTSV-LCBM
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Geronimo I, Paneth P. A DFT and ONIOM study of C–H hydroxylation catalyzed by nitrobenzene 1,2-dioxygenase. Phys Chem Chem Phys 2014; 16:13889-99. [DOI: 10.1039/c4cp01030b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The DFT and ONIOM calculations show that C–H hydroxylation by nitrobenzene 1,2-dioxygenase proceeds through a HO–FeVO intermediate.
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Affiliation(s)
- Inacrist Geronimo
- Institute of Applied Radiation Chemistry
- Lodz University of Technology
- 90-924 Łódź, Poland
| | - Piotr Paneth
- Institute of Applied Radiation Chemistry
- Lodz University of Technology
- 90-924 Łódź, Poland
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Elucidation of the Fe(IV)=O intermediate in the catalytic cycle of the halogenase SyrB2. Nature 2013; 499:320-3. [PMID: 23868262 PMCID: PMC4123442 DOI: 10.1038/nature12304] [Citation(s) in RCA: 161] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 05/16/2013] [Indexed: 01/15/2023]
Abstract
Mononuclear non-haem iron (NHFe) enzymes catalyse a wide variety of oxidative reactions including halogenation, hydroxylation, ring closure, desaturation, and aromatic ring cleavage. These are highly important for mammalian somatic processes such as phenylalanine metabolism, production of neurotransmitters, hypoxic response, and the biosynthesis of natural products.1–3 The key reactive intermediate in the catalytic cycles of these enzymes is an S = 2 FeIV=O species, which has been trapped for a number of NHFe enzymes4–8 including the halogenase SyrB2, the subject of this study. Computational studies to understand the reactivity of the enzymatic NHFe FeIV=O intermediate9–13 are limited in applicability due to the paucity of experimental knowledge regarding its geometric and electronic structures, which determine its reactivity. Synchrotron-based nuclear resonance vibrational spectroscopy (NRVS) is a sensitive and effective method that defines the dependence of the vibrational modes of Fe on the nature of the FeIV=O active site.14–16 Here we present the first NRVS structural characterisation of the reactive FeIV=O intermediate of a NHFe enzyme. This FeIV=O intermediate reacts via an initial H-atom abstraction step, with its subsquent halogenation (native) or hydroxylation (non-native) rebound reactivity being dependent on the substrate.17 A correlation of the experimental NRVS data to electronic structure calculations indicates that the substrate is able to direct the orientation of the FeIV=O intermediate, presenting specific frontier molecular orbitals (FMOs) which can activate the selective halogenation versus hydroxylation reactivity.
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