1
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Kaur L, Mandal D. A density functional theory analysis of the C-H activation reactivity of iron(IV)-oxo complexes with an 'O' substituted tetramethylcyclam macrocycle. Dalton Trans 2024; 53:7527-7535. [PMID: 38597582 DOI: 10.1039/d4dt00063c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
In this article, we present a meticulous computational study to foresee the effect of an oxygen-rich macrocycle on the reactivity for C-H activation. For this study, a widely studied nonheme Fe(IV)O molecule with a TMC (1,4,8,11-tetramethyl 1,4,8,11-tetraazacyclotetradecane) macrocycle that is equatorially attached to four nitrogen atoms (designated as N4) and acetonitrile as an axial ligand has been taken into account. For the goal of hetero-substitution, step-by-step replacement of the N4 framework with O atoms, i.e., N4, N3O1, N2O2, N1O3, and O4 systems, has been considered, and dihydroanthracene (DHA) has been used as the substrate. In order to neutralise the system and prevent the self-interaction error in DFT, triflate counterions have also been included in the calculations. The study of the energetics of these C-H bond activation reactions and the potential energy surfaces mapped therefore reveal that the initial hydrogen abstraction, which is the rate-determining step, follows the two-state reactivity (TSR) pattern, which means that the originally excited quintet state falls lower in the transition state and the product. The reaction follows the hydrogen atom transfer (HAT) mechanism, as indicated by the spin density studies. The results revealed a fascinating reactivity order, in which the reactivity increases with the enrichment of the oxygen atom in the equatorial position, namely the order follows N4 < N3O1 < N2O2 < N1O3 < O4. The impacts of oxygen substitution on quantum mechanical tunneling and the H/D kinetic isotope effect have also been investigated. When analysing the causes of this reactivity pattern, a number of variables have been identified, including the reactant-like transition structure, spin density distribution, distortion energy, and energies of the electron acceptor orbital, i.e., the energy of the LUMO (σ*z2), which validate the obtained outcome. Our results also show very good agreement with earlier combined experimental and theoretical studies considering TMC and TMCO-type complexes. The DFT predictions reported here will undoubtedly encourage experimental research in this biomimetic field, as they provide an alternative with higher reactivity in which heteroatoms can be substituted for the traditional nitrogen atom.
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Affiliation(s)
- Lovleen Kaur
- Department of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Patiala-147004, Punjab, India.
| | - Debasish Mandal
- Department of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Patiala-147004, Punjab, India.
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2
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Satpathy JK, Yadav R, Bagha UK, Kumar D, Sastri CV, de Visser SP. Enhanced Reactivity through Equatorial Sulfur Coordination in Nonheme Iron(IV)-Oxo Complexes: Insights from Experiment and Theory. Inorg Chem 2024; 63:6752-6766. [PMID: 38551622 DOI: 10.1021/acs.inorgchem.4c00070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
Sulfur ligation in metalloenzymes often gives the active site unique properties, whether it is the axial cysteinate ligand in the cytochrome P450s or the equatorial sulfur/thiol ligation in nonheme iron enzymes. To understand sulfur ligation to iron complexes and how it affects the structural, spectroscopic, and intrinsic properties of the active species and the catalysis of substrates, we pursued a systematic study and compared sulfur with amine-ligated iron(IV)-oxo complexes. We synthesized and characterized a biomimetic N4S-ligated iron(IV)-oxo complex and compared the obtained results with an analogous N5-ligated iron(IV)-oxo complex. Our work shows that the amine for sulfur replacement in the equatorial ligand framework leads to a rate enhancement for oxygen atom and hydrogen atom transfer reactions. Moreover, the sulfur-ligated iron(IV)-oxo complex reacts through a different reaction mechanism as compared to the N5-ligated iron(IV)-oxo complex, where the former reacts through hydride transfer with the latter reacting via radical pathways. We show that the reactivity differences are caused by a dramatic change in redox potential between the two complexes. Our studies highlight the importance of implementing a sulfur ligand into the equatorial ligand framework of nonheme iron(IV)-oxo complexes and how it affects the physicochemical properties of the oxidant and its reactivity.
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Affiliation(s)
- Jagnyesh K Satpathy
- Department of Chemistry, Indian Institute of Technology, Guwahati 781039, Assam, India
| | - Rolly Yadav
- Department of Chemistry, Indian Institute of Technology, Guwahati 781039, Assam, India
| | - Umesh K Bagha
- Department of Chemistry, Indian Institute of Technology, Guwahati 781039, Assam, India
| | - Devesh Kumar
- Department of Applied Physics, Babasaheb Bhimrao Ambedkar University, School for Physical Sciences, Vidya Vihar, Rae Bareilly Road, Lucknow 226025, UP, India
| | - Chivukula V Sastri
- Department of Chemistry, Indian Institute of Technology, Guwahati 781039, Assam, India
| | - Sam P de Visser
- Department of Chemistry, Indian Institute of Technology, Guwahati 781039, Assam, India
- The Manchester Institute of Biotechnology and Department of Chemical Engineering, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
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3
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Johnee Britto N, Jaccob M, Comba P, Anandababu K, Mayilmurugan R. DFT insights into the mechanism of O 2 activation catalyzed by a structural and functional model of cysteine dioxygenase with tris(2-pyridyl)methane-based ligand architecture. J Inorg Biochem 2023; 238:112066. [PMID: 36370503 DOI: 10.1016/j.jinorgbio.2022.112066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 10/26/2022] [Accepted: 11/03/2022] [Indexed: 11/07/2022]
Abstract
Cysteine dioxygenation is an important step in the metabolism of toxic L-cysteine (Cys) in the human body, carried out by cysteine dioxygenase enzyme (CDO). The disruption of this process is found to elicit neurological health issues. This work reports a computational investigation of mechanistic aspects of this reaction, using a recently reported tris(2-pyridyl)methane-based biomimetic model complex of CDO. The computed results indicate that, the initial SO2 bond formation process is the slowest step in the S-dioxygenation process, possessing an activation barrier of 12.7 kcal/mol. The remaining steps were found to be downhill requiring very small activation energies. The transition states were found to undergo spin crossover between triplet and quintet states, while the singlet surface remained unstable throughout the entire reaction. In essence, the mechanistic scheme and multistate reactivity pattern together with the relatively small computed rate-limiting activation barrier as well as the exothermic formation energy demonstrate that the model complex is an efficient biomimetic CDO model. In addition, the study also substantiates the involvement of Fe(IV)oxido intermediates in the mechanism of S-dioxygenation by the chosen model complex. The insights derived from the O2 activation process might pave way for development of more accurate CDO model catalysts that might be capable of even more efficiently mimicking the geometric, spectroscopic and functional features of the CDO enzyme.
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Affiliation(s)
- Neethinathan Johnee Britto
- Department of Chemistry & Computational Chemistry Laboratory, Loyola Institute of Frontier Energy (LIFE), Loyola College, University of Madras, Chennai 600 034, Tamil Nadu, India
| | - Madhavan Jaccob
- Department of Chemistry & Computational Chemistry Laboratory, Loyola Institute of Frontier Energy (LIFE), Loyola College, University of Madras, Chennai 600 034, Tamil Nadu, India.
| | - Peter Comba
- Heidelberg University, Anorganisch-Chemisches Institut and Interdisciplinary Center for Scientific Computing, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
| | - Karunanithi Anandababu
- Depatment of Chemistry, Indian Institute of Technology Bhilai, GEC Campus, Sejbahar, Raipur 492015, India
| | - Ramasamy Mayilmurugan
- Depatment of Chemistry, Indian Institute of Technology Bhilai, GEC Campus, Sejbahar, Raipur 492015, India
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4
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Kaur L, Mandal D. Role of "S" Substitution on C-H Activation Reactivity of Iron(IV)-Oxo Cyclam Complexes: a Computational Investigation. Inorg Chem 2022; 61:14582-14590. [PMID: 36069431 DOI: 10.1021/acs.inorgchem.2c01504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A comprehensive density functional theory (DFT) investigation has been presented in this article to address the role of equatorial sulfur ligation in C-H activation. A non-heme iron-oxo compound with four nitrogen atoms constituting the equatorially connected macrocyclic framework (represented as N4) [Fe(IV)═O(THC)(CH3CN)]2+(THC = 1,4,8,11-tetrahydro1,4,8,11-tetraazacyclotetradecane) has been considered as the base compound. Other complexes have been anticipated by the sequential replacement of this nitrogen by sulfur, that is, N4, N3S1, N2S2, N1S3, and S4. Counterions, as always, have been considered to avoid the self-interaction error in DFT. Generally, the anti-conformers (with respect to equatorial N-H and Fe═O) turned out to be the most stable. It was found that with the enrichment of the equatorial sulfur atom, reactivity increases successively, that is, we get the trend N4 < N3S1 < N2S2 < N1S3 < S4. Our investigations have also verified the available experimental results where it has been reported that N2S2 is more reactive than N4 in their mixed conformation. In search of insights into this typical pattern of reactivity, the interplay of several factors has been recognized, such as the distortion energy which decreases for the transition states with the addition of sulfur; the spin density on the oxygen atom which increases implying that the radical character of abstractor increases on sulfur ligation; the energy of the electron acceptor orbital (the lowest unoccupied molecular orbital (σz2*)) which decreases continuously with the sulfur substitution; and the triplet-quintet oxidant energy gap which decreases consistently with S enrichment in the equatorial position. The computational predictions reported here, if further validated by experiments, will definitely encourage the synthesis of sulfur-ligated bio-inspired complexes instead of the ones constituting nitrogen exclusively.
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Affiliation(s)
- Lovleen Kaur
- School of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Patiala 147004, Punjab, India
| | - Debasish Mandal
- School of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Patiala 147004, Punjab, India
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5
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Gordon JB, McGale JP, Siegler MA, Goldberg DP. Proton-Coupled Electron-Transfer Reactivity Controls Iron versus Sulfur Oxidation in Nonheme Iron-Thiolate Complexes. Inorg Chem 2021; 60:6255-6265. [PMID: 33872005 DOI: 10.1021/acs.inorgchem.0c03779] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reaction of the five-coordinate FeII(N4S) complexes, [FeII(iPr3TACN)(abtX)](OTf) (abt = aminobenzenethiolate, X = H, CF3), with a one-electron oxidant and an appropriate base leads to net H atom loss, generating new FeIII(iminobenzenethiolate) complexes that were characterized by single-crystal X-ray diffraction (XRD), as well as UV-vis, EPR, and Mössbauer spectroscopies. The spectroscopic data indicate that the iminobenzenethiolate complexes have S = 3/2 ground states. In the absence of a base, oxidation of the FeII(abt) complexes leads to disulfide formation instead of oxidation at the metal center. Bracketing studies with separated proton-coupled electron-transfer (PCET) reagents show that the FeII(aminobenzenethiolate) and FeIII(iminobenzenethiolate) forms are readily interconvertible by H+/e- transfer and provide a measure of the bond dissociation free energy (BDFE) for the coordinated N-H bond between 64 and 69 kcal mol-1. This work shows that coordination to the iron center causes a dramatic weakening of the N-H bond and that Fe- versus S-oxidation in a nonheme iron complex can be controlled by the protonation state of an ancillary amino donor.
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Affiliation(s)
- Jesse B Gordon
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Jeremy P McGale
- 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
| | - David P Goldberg
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
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6
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Müller L, Hoof S, Keck M, Herwig C, Limberg C. Enhancing Tris(pyrazolyl)borate-Based Models of Cysteine/Cysteamine Dioxygenases through Steric Effects: Increased Reactivities, Full Product Characterization and Hints to Initial Superoxide Formation. Chemistry 2020; 26:11851-11861. [PMID: 32432367 PMCID: PMC7540079 DOI: 10.1002/chem.202001818] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Indexed: 02/03/2023]
Abstract
The design of biomimetic model complexes for the cysteine dioxygenase (CDO) and cysteamine dioxygenase (ADO) is reported, where the 3-His coordination of the iron ion is simulated by three pyrazole donors of a trispyrazolyl borate ligand (Tp) and protected cysteine and cysteamine represent substrate ligands. It is found that the replacement of phenyl groups-attached at the 3-positions of the pyrazole units in a previous model-by mesityl residues has massive consequences, as the latter arrange to a more spacious reaction pocket. Thus, the reaction with O2 proceeds much faster and afterwards the first structural characterization of an iron(II) η2 -O,O-sulfinate product became possible. If one of the three Tp-mesityl groups is placed in the 5-position, an even larger reaction pocket results, which leads to yet faster rates and accumulation of a reaction intermediate at low temperatures, as shown by UV/Vis and Mössbauer spectroscopy. After comparison with the results of investigations on the cobalt analogues this intermediate is tentatively assigned to an iron(III) superoxide species.
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Affiliation(s)
- Lars Müller
- Institut für ChemieHumboldt-Universität zu BerlinBrook-Taylor-Straße 212489BerlinGermany
| | - Santina Hoof
- Institut für ChemieHumboldt-Universität zu BerlinBrook-Taylor-Straße 212489BerlinGermany
| | - Matthias Keck
- Institut für ChemieHumboldt-Universität zu BerlinBrook-Taylor-Straße 212489BerlinGermany
| | - Christian Herwig
- Institut für ChemieHumboldt-Universität zu BerlinBrook-Taylor-Straße 212489BerlinGermany
| | - Christian Limberg
- Institut für ChemieHumboldt-Universität zu BerlinBrook-Taylor-Straße 212489BerlinGermany
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7
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Wang L, Gennari M, Cantú Reinhard FG, Gutiérrez J, Morozan A, Philouze C, Demeshko S, Artero V, Meyer F, de Visser SP, Duboc C. A Non-Heme Diiron Complex for (Electro)catalytic Reduction of Dioxygen: Tuning the Selectivity through Electron Delivery. J Am Chem Soc 2019; 141:8244-8253. [DOI: 10.1021/jacs.9b02011] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Lianke Wang
- Université Grenoble Alpes, CNRS UMR 5250, DCM, F-38000 Grenoble, France
| | - Marcello Gennari
- Université Grenoble Alpes, CNRS UMR 5250, DCM, F-38000 Grenoble, France
| | - Fabián G. Cantú Reinhard
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Javier Gutiérrez
- Université Grenoble Alpes, CNRS UMR 5250, DCM, F-38000 Grenoble, France
| | - Adina Morozan
- Université Grenoble Alpes, CNRS, CEA, Laboratoire de Chimie et
Biologie des Métaux, F-38000 Grenoble, France
| | | | - Serhiy Demeshko
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
| | - Vincent Artero
- Université Grenoble Alpes, CNRS, CEA, Laboratoire de Chimie et
Biologie des Métaux, F-38000 Grenoble, France
| | - Franc Meyer
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
| | - 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
| | - Carole Duboc
- Université Grenoble Alpes, CNRS UMR 5250, DCM, F-38000 Grenoble, France
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8
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Fischer AA, Lindeman SV, Fiedler AT. A synthetic model of the nonheme iron-superoxo intermediate of cysteine dioxygenase. Chem Commun (Camb) 2018; 54:11344-11347. [PMID: 30246208 PMCID: PMC6201693 DOI: 10.1039/c8cc06247a] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A nonheme Fe(ii) complex (1) that models substrate-bound cysteine dioxygenase (CDO) reacts with O2 at -80 °C to yield a purple intermediate (2). Analysis with spectroscopic and computational methods determined that 2 features a thiolate-ligated Fe(iii) center bound to a superoxide radical, mimicking the putative structure of a key CDO intermediate.
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Affiliation(s)
- Anne A Fischer
- Department of Chemistry, Marquette University, 1414 W. Clybourn St., Milwaukee, WI 53233, USA.
| | - Sergey V Lindeman
- Department of Chemistry, Marquette University, 1414 W. Clybourn St., Milwaukee, WI 53233, USA.
| | - Adam T Fiedler
- Department of Chemistry, Marquette University, 1414 W. Clybourn St., Milwaukee, WI 53233, USA.
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9
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A Comparative Review on the Catalytic Mechanism of Nonheme Iron Hydroxylases and Halogenases. Catalysts 2018. [DOI: 10.3390/catal8080314] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Enzymatic halogenation and haloperoxidation are unusual processes in biology; however, a range of halogenases and haloperoxidases exist that are able to transfer an aliphatic or aromatic C–H bond into C–Cl/C–Br. Haloperoxidases utilize hydrogen peroxide, and in a reaction with halides (Cl−/Br−), they react to form hypohalides (OCl−/OBr−) that subsequently react with substrate by halide transfer. There are three types of haloperoxidases, namely the iron-heme, nonheme vanadium, and flavin-dependent haloperoxidases that are reviewed here. In addition, there are the nonheme iron halogenases that show structural and functional similarity to the nonheme iron hydroxylases and form an iron(IV)-oxo active species from a reaction of molecular oxygen with α-ketoglutarate on an iron(II) center. They subsequently transfer a halide (Cl−/Br−) to an aliphatic C–H bond. We review the mechanism and function of nonheme iron halogenases and hydroxylases and show recent computational modelling studies of our group on the hectochlorin biosynthesis enzyme and prolyl-4-hydroxylase as examples of nonheme iron halogenases and hydroxylases. These studies have established the catalytic mechanism of these enzymes and show the importance of substrate and oxidant positioning on the stereo-, chemo- and regioselectivity of the reaction that takes place.
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10
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Timmins A, Saint-André M, de Visser SP. Understanding How Prolyl-4-hydroxylase Structure Steers a Ferryl Oxidant toward Scission of a Strong C-H Bond. J Am Chem Soc 2017; 139:9855-9866. [PMID: 28657747 DOI: 10.1021/jacs.7b02839] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Prolyl-4-hydroxylase (P4H) is a non-heme iron hydroxylase that regio- and stereospecifically hydroxylates proline residues in a peptide chain into R-4-hydroxyproline, which is essential for collagen cross-linking purposes in the human body. Surprisingly, in P4H, a strong aliphatic C-H bond is activated, while thermodynamically much weaker aliphatic C-H groups, that is, at the C3 and C5 positions, are untouched. Little is known on the origins of the high regio- and stereoselectivity of P4H and many non-heme and heme enzymes in general, and insight into this matter may be relevant to Biotechnology as well as Drug Development. The active site of the protein contains two aromatic residues (Tyr140 and Trp243) that we expected to be crucial for guiding the regioselectivity of the reaction. We performed a detailed quantum mechanics/molecular mechanics (QM/MM) and molecular dynamics (MD) study on wild-type and mutant structures. The work shows that Trp243 is involved in key protein loop-loop interactions that affect the shape and size of the substrate binding pocket and its mutation has major long-range effects. By contrast, the Tyr140 residue is shown to guide the regio- and stereoselectivity by holding the substrate and ferryl oxidant in a specific orientation through hydrogen bonding and π-stacking interactions. Compelling evidence is found that the Tyr140 residue is involved in expelling the product from the binding pocket after the reaction is complete. It is shown that mutations where the hydrogen bonding network that involves the Tyr140 and Trp243 residues is disrupted lead to major changes in folding of the protein and the size and shape of the substrate binding pocket. Specifically, the Trp243 residue positions the amino acid side chains of Arg161 and Glu127 in specific orientations with substrate. As such, the P4H enzyme is a carefully designed protein with a subtle and rigid secondary structure that enables the binding of substrate, guides the regioselectivity, and expels product efficiently.
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Affiliation(s)
- Amy Timmins
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester , 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Maud Saint-André
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester , 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - 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
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11
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Faponle AS, Seebeck FP, de Visser SP. Sulfoxide Synthase versus Cysteine Dioxygenase Reactivity in a Nonheme Iron Enzyme. J Am Chem Soc 2017; 139:9259-9270. [PMID: 28602090 DOI: 10.1021/jacs.7b04251] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The sulfoxide synthase EgtB represents a unique family of nonheme iron enzymes that catalyze the formation of a C-S bond between N-α-trimethyl histidine and γ-glutamyl cysteine, which is the key step in the biosynthesis of ergothioneine, an important amino acid related to aging. A controversy has arisen regarding its catalytic mechanism related to the function of the active-site Tyr377 residue. The biosynthesis of ergothioneine in EgtB shows structural similarities to cysteine dioxygenase which transfers two oxygen atoms to the thiolate group of cysteine. The question, therefore, is how do EgtB enzymes catalyze the C-S bond-formation reaction, while also preventing a dioxygenation of its cysteinate substrate? In this work we present a quantum mechanics/molecular mechanics study into the mechanism of sulfoxide synthase enzymes as compared to cysteine dioxygenase enzymes and present pathways for both reaction channels in EgtB. We show that EgtB contains a conserved tyrosine residue that reacts via proton-coupled electron transfer with the iron(III)-superoxo species and creates an iron(III)-hydroperoxo intermediate, thereby preventing the possible thiolate dioxygenation side reaction. The nucleophilic C-S bond-formation step happens subsequently concomitant to relay of the proton of the iron(II)-hydroperoxo back to Tyr377. This is the rate-determining step in the reaction cycle and is followed by hydrogen-atom transfer from the CE1-H group of trimethyl histidine substrate to iron(II)-superoxo. In the final step, a quick and almost barrierless sulfoxidation leads to the sulfoxide product complexes. The work highlights a unique machinery and active-site setup of the enzyme that drives the sulfoxide synthase reaction.
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Affiliation(s)
- Abayomi S Faponle
- The Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester , 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Florian P Seebeck
- Department for Chemistry, University of Basel , St. Johanns-Ring 19, Basel 4056, Switzerland
| | - Sam P de Visser
- The Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester , 131 Princess Street, Manchester M1 7DN, United Kingdom
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12
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Hong S, Lee YM, Ray K, Nam W. Dioxygen activation chemistry by synthetic mononuclear nonheme iron, copper and chromium complexes. Coord Chem Rev 2017. [DOI: 10.1016/j.ccr.2016.07.006] [Citation(s) in RCA: 114] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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13
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Fischer AA, Lindeman SV, Fiedler AT. Spectroscopic and computational studies of reversible O2 binding by a cobalt complex of relevance to cysteine dioxygenase. Dalton Trans 2017; 46:13229-13241. [DOI: 10.1039/c7dt01600j] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Spectroscopic and computational studies of reversible O2 binding by a cobalt active-site mimic shed light on the catalytic mechanism of cysteine dioxygenases.
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14
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Faponle AS, de Visser SP. The Role of Nonheme Transition Metal-Oxo, -Peroxo, and -Superoxo Intermediates in Enzyme Catalysis and Reactions of Bioinspired Complexes. ADVANCES IN INORGANIC CHEMISTRY 2017. [DOI: 10.1016/bs.adioch.2017.01.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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15
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Fischer AA, Stracey N, Lindeman SV, Brunold TC, Fiedler AT. Synthesis, X-ray Structures, Electronic Properties, and O 2/NO Reactivities of Thiol Dioxygenase Active-Site Models. Inorg Chem 2016; 55:11839-11853. [PMID: 27801576 DOI: 10.1021/acs.inorgchem.6b01931] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Mononuclear non-heme iron complexes that serve as structural and functional mimics of the thiol dioxygenases (TDOs), cysteine dioxygenase (CDO) and cysteamine dioxygenase (ADO), have been prepared and characterized with crystallographic, spectroscopic, kinetic, and computational methods. The high-spin Fe(II) complexes feature the facially coordinating tris(4,5-diphenyl-1-methylimidazol-2-yl)phosphine (Ph2TIP) ligand that replicates the three histidine (3His) triad of the TDO active sites. Further coordination with bidentate l-cysteine ethyl ester (CysOEt) or cysteamine (CysAm) anions yielded five-coordinate (5C) complexes that resemble the substrate-bound forms of CDO and ADO, respectively. Detailed electronic-structure descriptions of the [Fe(Ph2TIP)(LS,N)]BPh4 complexes, where LS,N = CysOEt (1) or CysAm (2), were generated through a combination of spectroscopic techniques [electronic absorption, magnetic circular dichroism (MCD)] and density functional theory (DFT). Complexes 1 and 2 decompose in the presence of O2 to yield the corresponding sulfinic acid (RSO2H) products, thereby emulating the reactivity of the TDO enzymes and related complexes. Rate constants and activation parameters for the dioxygenation reactions were measured and interpreted with the aid of DFT calculations for O2-bound intermediates. Treatment of the TDO models with nitric oxide (NO)-a well-established surrogate of O2-led to a mixture of high-spin and low-spin {FeNO}7 species at low temperature (-70 °C), as indicated by electron paramagnetic resonance (EPR) spectroscopy. At room temperature, these Fe/NO adducts convert to a common species with EPR and infrared (IR) features typical of cationic dinitrosyl iron complexes (DNICs). To complement these results, parallel spectroscopic, computational, and O2/NO reactivity studies were carried out using previously reported TDO models that feature an anionic hydrotris(3-phenyl-5-methyl-pyrazolyl)borate (Ph,MeTp-) ligand. Though the O2 reactivities of the Ph2TIP- and Ph,MeTp-based complexes are quite similar, the supporting ligand perturbs the energies of Fe 3d-based molecular orbitals and modulates Fe-S bond covalency, suggesting possible rationales for the presence of neutral 3His coordination in CDO and ADO.
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Affiliation(s)
- Anne A Fischer
- Department of Chemistry, Marquette University , Milwaukee, Wisconsin 53201, United States
| | - Nuru Stracey
- Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Sergey V Lindeman
- Department of Chemistry, Marquette University , Milwaukee, Wisconsin 53201, United States
| | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Adam T Fiedler
- Department of Chemistry, Marquette University , Milwaukee, Wisconsin 53201, United States
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Yang T, Quesne MG, Neu HM, Cantú Reinhard FG, Goldberg DP, de Visser SP. Singlet versus Triplet Reactivity in an Mn(V)-Oxo Species: Testing Theoretical Predictions Against Experimental Evidence. J Am Chem Soc 2016; 138:12375-86. [PMID: 27545752 PMCID: PMC5228574 DOI: 10.1021/jacs.6b05027] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Discerning the factors that control the reactivity of high-valent metal-oxo species is critical to both an understanding of metalloenzyme reactivity and related transition metal catalysts. Computational studies have suggested that an excited higher spin state in a number of metal-oxo species can provide a lower energy barrier for oxidation reactions, leading to the conclusion that this unobserved higher spin state complex should be considered as the active oxidant. However, testing these computational predictions by experiment is difficult and has rarely been accomplished. Herein, we describe a detailed computational study on the role of spin state in the reactivity of a high-valent manganese(V)-oxo complex with para-Z-substituted thioanisoles and utilize experimental evidence to distinguish between the theoretical results. The calculations show an unusual change in mechanism occurs for the dominant singlet spin state that correlates with the electron-donating property of the para-Z substituent, while this change is not observed on the triplet spin state. Minimum energy crossing point calculations predict small spin-orbit coupling constants making the spin state change from low spin to high spin unlikely. The trends in reactivity for the para-Z-substituted thioanisole derivatives provide an experimental measure for the spin state reactivity in manganese-oxo corrolazine complexes. Hence, the calculations show that the V-shaped Hammett plot is reproduced by the singlet surface but not by the triplet state trend. The substituent effect is explained with valence bond models, which confirm a change from an electrophilic to a nucleophilic mechanism through a change of substituent.
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Affiliation(s)
- Tzuhsiung Yang
- Department of Chemistry, The Johns Hopkins University, 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
| | - Heather M. Neu
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Fabián G. Cantú Reinhard
- 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, Baltimore, Maryland 21218, United States
| | - 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
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Sallmann M, Limberg C. Utilizing the Trispyrazolyl Borate Ligand for the Mimicking of O2-Activating Mononuclear Nonheme Iron Enzymes. Acc Chem Res 2015; 48:2734-43. [PMID: 26305516 DOI: 10.1021/acs.accounts.5b00148] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mononuclear, O2-activating nonheme iron enzymes are a fascinating class of metalloproteines, capable of realizing the most different reactions, ranging from C-H activation, via O atom transfer to C-C bond cleavage, in the course of O2 activation. They can lead us the way to achieve similar reactions with comparable efficiency and selectivity in chemical laboratories, which would be highly desirable aiming at accessing value-added products or to achieve degradation of unwanted compounds. Hence, these enyzmes motivate attempts to construct artificial low-molecular weight analogues, mimicking structural or functional characteristics. Such models can, for instance, provide insights about which of the features inherent to an active site are essential and guarantee the enzyme function, and from this kind of information the minimal requirements for a biomimetic or bioinspired complex that may be applied in catalysis can be derived. On the other hand, they can contribute to an understanding of the enzyme functioning. In order to create such replicates, it is important to faithfully mimic the surroundings of the iron centers in their active sites. Most of them feature two histidine residues and one carboxylate donor, while a few exhibit a deceptively simple (His)3Fe active site. For the simulation of these, the trispyrazolyl borate ligand (Tp) particularly offers itself, as the facial arrangement of three pyrazole donors is reminiscent of the three histidine-derived imidazole donors. The focus of this Account will be on bioinorganic/biomimetic research from our laboratory utilizing Tp ligands to develop molecular models for (i) two representatives of the (His)3Fe-enzyme family, namely, the cysteine dioxygenase (CDO) and acetyl acetone dioxygenase (Dke1), (ii) a related but less well-explored variant of the CDO-the 2-aminoethanethiol dioxygenase-as well as (iii) the 2-His-1-carboxylate representative 1-aminocyclopropane-1-carboxylic acid oxidase (ACCO). The CDO catalyzes the dioxygenation of cysteine with O2 to give cysteine sulfinic acid, which could be mimicked at TpFe units in a realistic manner. Furthermore, the successful dioxygenation of 2-aminoethanethiol at the same complex metal fragments lends further support to the hypothesis that the active sites of CDO and the one of 2-aminoethanethiol dioxygenase, whose structure is unknown, are quite similar. Dke1 is capable of cleaving diketones and ketoesters to give the corresponding carboxylic acids and α-keto aldehydes, and Tp-based models have achieved comparable C-C bond cleavage reactions. The ACCO develops ethylene from ACC in the course of oxidation, and recently this has been achieved the first time for a TpFe model, too.
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Affiliation(s)
- Madleen Sallmann
- Humboldt-Universität zu Berlin, Department of Chemistry, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Christian Limberg
- Humboldt-Universität zu Berlin, Department of Chemistry, Brook-Taylor-Str. 2, 12489 Berlin, Germany
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18
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Alkyl Chain Growth on a Transition Metal Center: How Does Iron Compare to Ruthenium and Osmium? Int J Mol Sci 2015; 16:23369-81. [PMID: 26426009 PMCID: PMC4632703 DOI: 10.3390/ijms161023369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 09/22/2015] [Accepted: 09/23/2015] [Indexed: 11/17/2022] Open
Abstract
Industrial Fischer-Tropsch processes involve the synthesis of hydrocarbons usually on metal surface catalysts. On the other hand, very few homogeneous catalysts are known to perform a Fischer-Tropsch style of reaction. In recent work, we established the catalytic properties of a diruthenium-platinum carbene complex, [(CpRu)2(μ2-H)(μ2-NHCH3)(μ3-C)PtCH3(P(CH3)3)2](CO)n+ with n = 0, 2 and Cp = η5-C5(CH3)5, and showed it to react efficiently by initial hydrogen atom transfer followed by methyl transfer to form an alkyl chain on the Ru-center. In particular, the catalytic efficiency was shown to increase after the addition of two CO molecules. As such, this system could be viewed as a potential homogeneous Fischer-Tropsch catalyst. Herein, we have engineered the catalytic center of the catalyst and investigated the reactivity of trimetal carbene complexes of the same type using iron, ruthenium and osmium at the central metal scaffold. The work shows that the reactivity should increase from diosmium to diruthenium to diiron; however, a non-linear trend is observed due to multiple factors contributing to the individual barrier heights. We identified all individual components of these reaction steps in detail and established the difference in reactivity of the various complexes.
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Sallmann M, Oldenburg F, Braun B, Réglier M, Simaan AJ, Limberg C. Ein funktionelles Strukturmodell für die 1-Aminocyclopropan- 1-carbonsäure-Oxidase. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201502529] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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20
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Sallmann M, Oldenburg F, Braun B, Réglier M, Simaan AJ, Limberg C. A structural and functional model for the 1-aminocyclopropane-1-carboxylic acid oxidase. Angew Chem Int Ed Engl 2015; 54:12325-8. [PMID: 26190407 DOI: 10.1002/anie.201502529] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 05/22/2015] [Indexed: 11/06/2022]
Abstract
The hitherto most realistic low-molecular-weight analogue for the 1-aminocyclopropane-1-carboxylic acid oxidase (ACCO) is reported. The ACCOs 2-His-1-carboxylate iron(II) active site was mimicked by a TpFe moiety, to which the natural substrate ACC could be bound. The resulting complex [Tp(Me,Ph) FeACC] (1), according to X-ray diffraction analysis performed for the nickel analogue, represents an excellent structural model, featuring ACC coordinated in a bidentate fashion-as proposed for the enzymatic substrate complex-as well as a vacant coordination site that forms the basis for the first successful replication also of the ACCO function: 1 is the first known ACC complex that reacts with O2 to produce ethylene. As a FeOOH species had been suggested as intermediate in the catalytic cycle, H2 O2 was tested as the oxidant, too, and indeed evolution of ethylene proceeded even more rapidly to give 65 % yield.
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Affiliation(s)
- Madleen Sallmann
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Strasse 2, 12489 Berlin (Germany) http://www.chemie.hu-berlin.de/aglimberg
| | - Fabio Oldenburg
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Strasse 2, 12489 Berlin (Germany) http://www.chemie.hu-berlin.de/aglimberg
| | - Beatrice Braun
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Strasse 2, 12489 Berlin (Germany) http://www.chemie.hu-berlin.de/aglimberg
| | - Marius Réglier
- Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397, Marseille, (France) http://ism2.univ-amu.fr/pages-bleues/index2.htm
| | - A Jalila Simaan
- Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397, Marseille, (France) http://ism2.univ-amu.fr/pages-bleues/index2.htm.
| | - Christian Limberg
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Strasse 2, 12489 Berlin (Germany) http://www.chemie.hu-berlin.de/aglimberg.
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Sainna MA, Singh D, Kumar D, de Visser SP. A Trimetal Carbene with Reactivity Reminiscent of Fischer–Tropsch Catalysis. Organometallics 2015. [DOI: 10.1021/acs.organomet.5b00305] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mala A. Sainna
- Manchester
Institute of Biotechnology and School of Chemical Engineering and
Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Devendra Singh
- Department
of Applied Physics, School for Physical Sciences, Babasaheb Bhimrao Ambedkar University, Vidya Vihar, Rae Bareilly Road, Lucknow (U. P.) 226 025, India
| | - Devesh Kumar
- Department
of Applied Physics, School for Physical Sciences, Babasaheb Bhimrao Ambedkar University, Vidya Vihar, Rae Bareilly Road, Lucknow (U. P.) 226 025, India
| | - 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
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