151
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Abstract
The S-oxygenation of cysteine with dioxygen to give cysteine sulfinic acid occurs at the non-heme iron active site of cysteine dioxygenase. Similar S-oxygenation events occur in other non-heme iron enzymes, including nitrile hydratase and isopenicillin N synthase, and these enzymes have inspired the development of a class of [N(x)S(y)]-Fe model complexes. Certain members of this class have provided some intriguing examples of S-oxygenation, and this article summarizes these results, focusing on the non-heme iron(II/III)-thiolate model complexes that are known to react with O(2) or other O-atom transfer oxidants to yield sulfur oxygenates. Key aspects of the synthesis, structure, and reactivity of these systems are presented, along with any mechanistic information available on the oxygenation reactions. A number of iron(III)-thiolate complexes react with O(2) to give S-oxygenates, and the degree to which the thiolate sulfur donors are oxidized varies among the different complexes, depending upon the nature of the ligand, metal geometry, and spin state. The first examples of iron(II)-thiolate complexes that react with O(2) to give selective S-oxygenation are just emerging. Mechanistic information on these transformations is limited, with isotope labeling studies providing much of the current mechanistic data. The many questions that remain unanswered for both models and enzymes provide strong motivation for future work in this area.
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Affiliation(s)
- Alison C. McQuilken
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - David P. Goldberg
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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152
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Liao RZ, Thiel W. Why Is the Oxidation State of Iron Crucial for the Activity of Heme-Dependent Aldoxime Dehydratase? A QM/MM Study. J Phys Chem B 2012; 116:9396-408. [DOI: 10.1021/jp305510c] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Rong-Zhen Liao
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470, Mülheim an der Ruhr, Germany
| | - Walter Thiel
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470, Mülheim an der Ruhr, Germany
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153
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Gonzalez-Ovalle LE, Quesne MG, Kumar D, Goldberg DP, de Visser SP. Axial and equatorial ligand effects on biomimetic cysteine dioxygenase model complexes. Org Biomol Chem 2012; 10:5401-9. [PMID: 22714822 PMCID: PMC3454459 DOI: 10.1039/c2ob25406a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Density functional theory (DFT) calculations are presented on biomimetic model complexes of cysteine dioxygenase and focus on the effect of axial and equatorial ligand placement. Recent studies by one of us [Y. M. Badiei, M. A. Siegler and D. P. Goldberg, J. Am. Chem. Soc. 2011, 133, 1274] gave evidence of a nonheme iron biomimetic model of cysteine dioxygenase using an i-propyl-bis(imino)pyridine, equatorial tridentate ligand. Addition of thiophenol, an anion - either chloride or triflate - and molecular oxygen, led to several possible stereoisomers of this cysteine dioxygenase biomimetic complex. Moreover, large differences in reactivity using chloride as compared to triflate as the binding anion were observed. Here we present a series of DFT calculations on the origin of these reactivity differences and show that it is caused by the preference of coordination site of anion versus thiophenol binding to the chemical system. Thus, stereochemical interactions of triflate and the bulky iso-propyl substituents of the ligand prevent binding of thiophenol in the trans position using triflate. By contrast, smaller anions, such as chloride, can bind in either cis or trans ligand positions and give isomers with similar stability. Our calculations help to explain the observance of thiophenol dioxygenation by this biomimetic system and gives details of the reactivity differences of ligated chloride versus triflate.
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Affiliation(s)
- Luis E. Gonzalez-Ovalle
- Manchester Interdisciplinary Biocenter and School of Chemical Engineering and Analytical Science, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK. Fax: +44 161306 5201
| | - Matthew G. Quesne
- Manchester Interdisciplinary Biocenter and School of Chemical Engineering and Analytical Science, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK. Fax: +44 161306 5201
| | - Devesh Kumar
- Department of Applied Physics, School of Physical Sciences, Babasaheb, Bhimrao Ambedkar University, Vidya Vihar, Rae Bareilly Road, Lucknow 226-025, India
| | - David P. Goldberg
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, USA
| | - Sam P. de Visser
- Manchester Interdisciplinary Biocenter and School of Chemical Engineering and Analytical Science, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK. Fax: +44 161306 5201
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154
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Cho J, Woo J, Nam W. A Chromium(III)–Superoxo Complex in Oxygen Atom Transfer Reactions as a Chemical Model of Cysteine Dioxygenase. J Am Chem Soc 2012; 134:11112-5. [DOI: 10.1021/ja304357z] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Jaeheung Cho
- Department of Bioinspired
Science, Ewha Womans University, Seoul 120-750, Korea
| | - Jaeyoung Woo
- Department of Bioinspired
Science, Ewha Womans University, Seoul 120-750, Korea
| | - Wonwoo Nam
- Department of Bioinspired
Science, Ewha Womans University, Seoul 120-750, Korea
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155
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Leeladee P, Baglia RA, Prokop KA, Latifi R, de Visser SP, Goldberg DP. Valence tautomerism in a high-valent manganese-oxo porphyrinoid complex induced by a Lewis acid. J Am Chem Soc 2012; 134:10397-400. [PMID: 22667991 DOI: 10.1021/ja304609n] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Addition of the Lewis acid Zn(2+) to (TBP(8)Cz)Mn(V)(O) induces valence tautomerization, resulting in the formation of [(TBP(8)Cz(+•))Mn(IV)(O)-Zn(2+)]. This new species was characterized by UV-vis, EPR, the Evans method, and (1)H NMR and supported by DFT calculations. Removal of Zn(2+) quantitatively restores the starting material. Electron-transfer and hydrogen-atom-transfer reactions are strongly influenced by the presence of Zn(2+).
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Affiliation(s)
- Pannee Leeladee
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA
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156
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McQuilken AC, Jiang Y, Siegler MA, Goldberg DP. Addition of dioxygen to an N4S(thiolate) iron(II) cysteine dioxygenase model gives a structurally characterized sulfinato-iron(II) complex. J Am Chem Soc 2012; 134:8758-61. [PMID: 22578255 PMCID: PMC3403739 DOI: 10.1021/ja302112y] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The non-heme iron enzyme cysteine dioxygenase (CDO) catalyzes the S-oxygenation of cysteine by O(2) to give cysteine sulfinic acid. The synthesis of a new structural and functional model of the cysteine-bound CDO active site, [Fe(II)(N3PyS)(CH(3)CN)]BF(4) (1) is reported. This complex was prepared with a new facially chelating 4N/1S(thiolate) pentadentate ligand. The reaction of 1 with O(2) resulted in oxygenation of the thiolate donor to afford the doubly oxygenated sulfinate product [Fe(II)(N3PySO(2))(NCS)] (2), which was crystallographically characterized. The thiolate donor provided by the new N3PyS ligand has a dramatic influence on the redox potential and O(2) reactivity of this Fe(II) model complex.
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Affiliation(s)
- Alison C. McQuilken
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland, 21218, United States
| | - Yunbo Jiang
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland, 21218, United States
| | - Maxime A. Siegler
- 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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157
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Che X, Gao J, Zhang D, Liu C. How Do the Thiolate Ligand and Its Relative Position Control the Oxygen Activation in the Cysteine Dioxygenase Model? J Phys Chem A 2012; 116:5510-7. [DOI: 10.1021/jp3001515] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xin Che
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Institute of Theoretical Chemistry, School of Chemistry & Chemical Engineering, Shandong University, Jinan 250100, P. R. China
| | - Jun Gao
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Institute of Theoretical Chemistry, School of Chemistry & Chemical Engineering, Shandong University, Jinan 250100, P. R. China
| | - Dongju Zhang
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Institute of Theoretical Chemistry, School of Chemistry & Chemical Engineering, Shandong University, Jinan 250100, P. R. China
| | - Chengbu Liu
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Institute of Theoretical Chemistry, School of Chemistry & Chemical Engineering, Shandong University, Jinan 250100, P. R. China
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158
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Ye S, Riplinger C, Hansen A, Krebs C, Bollinger JM, Neese F. Electronic structure analysis of the oxygen-activation mechanism by Fe(II)- and α-ketoglutarate (αKG)-dependent dioxygenases. Chemistry 2012; 18:6555-67. [PMID: 22511515 PMCID: PMC3955955 DOI: 10.1002/chem.201102829] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Indexed: 11/09/2022]
Abstract
α-Ketoglutarate (αKG)-dependent nonheme iron enzymes utilize a high-spin (HS) ferrous center to couple the activation of oxygen to the decarboxylation of the cosubstrate αKG to yield succinate and CO(2), and to generate a high-valent ferryl species that then acts as an oxidant to functionalize the target C-H bond. Herein a detailed analysis of the electronic-structure changes that occur in the oxygen activation by this enzyme was performed. The rate-limiting step, which is identical on the septet and quintet surfaces, is the nucleophilic attack of the distal O atom of the O(2) adduct on the carbonyl group in αKG through a bicyclic transition state ((5, 7) TS1). Due to the different electronic structures in (5, 7) TS1, the decay of (7)TS1 leads to a ferric oxyl species, which undergoes a rapid intersystem crossing to form the ferryl intermediate. By contrast, a HS ferrous center ligated by a peroxosuccinate is obtained on the quintet surface following (5)TS1. Thus, additional two single-electron transfer steps are required to afford the same Fe(IV)-oxo species. However, the triplet reaction channel is catalytically irrelevant. The biological role of αKG played in the oxygen-activation reaction is dual. The αKG LUMO (C=O π*) serves as an electron acceptor for the nucleophilic attack of the superoxide monoanion. On the other hand, the αKG HOMO (C1-C2 σ) provides the second and third electrons for the further reduction of the superoxide. In addition to density functional theory, high-level ab initio calculations have been used to calculate the accurate energies of the critical points on the alternative potential-energy surfaces. Overall, the results delivered by the ab initio calculations are largely parallel to those obtained with the B3LYP density functional, thus lending credence to our conclusions.
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Affiliation(s)
- Shengfa Ye
- Max-Plank Institute for Bioinorganic Chemistry Stiftstrasse 34–36 45470 Mülheim an der Ruhr (Germany)
| | - Christoph Riplinger
- Max-Plank Institute for Bioinorganic Chemistry Stiftstrasse 34–36 45470 Mülheim an der Ruhr (Germany)
| | - Andreas Hansen
- Max-Plank Institute for Bioinorganic Chemistry Stiftstrasse 34–36 45470 Mülheim an der Ruhr (Germany)
| | - Carsten Krebs
- Department of Chemistry Department of Biochemistry and Molecular Biology The Pennsylvania State University University Park, Pennsylvania 16802 (USA)
| | - J. Martin Bollinger
- Department of Chemistry Department of Biochemistry and Molecular Biology The Pennsylvania State University University Park, Pennsylvania 16802 (USA)
| | - Frank Neese
- Max-Plank Institute for Bioinorganic Chemistry Stiftstrasse 34–36 45470 Mülheim an der Ruhr (Germany)
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159
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Regioselectivity of substrate hydroxylation versus halogenation by a nonheme iron(IV)–oxo complex: possibility of rearrangement pathways. J Biol Inorg Chem 2012; 17:841-52. [DOI: 10.1007/s00775-012-0901-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 04/24/2012] [Indexed: 10/28/2022]
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160
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Liao RZ, Thiel W. Comparison of QM-Only and QM/MM Models for the Mechanism of Tungsten-Dependent Acetylene Hydratase. J Chem Theory Comput 2012; 8:3793-803. [DOI: 10.1021/ct3000684] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rong-Zhen Liao
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470, Mülheim an der Ruhr, Germany
| | - Walter Thiel
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470, Mülheim an der Ruhr, Germany
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161
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Latifi R, Valentine JS, Nam W, de Visser SP. Predictive studies of H-atom abstraction reactions by an iron(IV)-oxo corrole cation radical oxidant. Chem Commun (Camb) 2012; 48:3491-3. [PMID: 22377754 DOI: 10.1039/c2cc30365e] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Density functional theory calculations compare the reactivity of iron(IV)-oxo porphyrin and corrole cation radical species in H-atom abstraction reactions.
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Affiliation(s)
- Reza Latifi
- Department of Chemistry and Nano Science, Department of Bioinspired Science, Centre for Biomimetic Systems, Ewha Womans University, Seoul 120-750, Korea
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162
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Chen H, Cho KB, Lai W, Nam W, Shaik S. Dioxygen Activation by a Non-Heme Iron(II) Complex: Theoretical Study toward Understanding Ferric–Superoxo Complexes. J Chem Theory Comput 2012; 8:915-26. [DOI: 10.1021/ct300015y] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Hui Chen
- Beijing National Laboratory for Molecular
Sciences (BNLMS), CAS Key Laboratory of Photochemistry, Institute
of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- Institute of Chemistry and the Lise Meitner-Minerva Center for Computational
Quantum Chemistry, The Hebrew University of Jerusalem, Givat Ram Campus, 91904 Jerusalem, Israel
| | - Kyung-Bin Cho
- Department of Bioinspired Science, Department of Chemistry
and Nano Science, Ewha Womans University, Seoul, 120-750, Korea
| | - Wenzhen Lai
- Institute of Chemistry and the Lise Meitner-Minerva Center for Computational
Quantum Chemistry, The Hebrew University of Jerusalem, Givat Ram Campus, 91904 Jerusalem, Israel
- Department of Chemistry, Renmin University of China, Beijing, 100872, China
| | - Wonwoo Nam
- Department of Bioinspired Science, Department of Chemistry
and Nano Science, Ewha Womans University, Seoul, 120-750, Korea
| | - Sason Shaik
- Institute of Chemistry and the Lise Meitner-Minerva Center for Computational
Quantum Chemistry, The Hebrew University of Jerusalem, Givat Ram Campus, 91904 Jerusalem, Israel
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163
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Sallmann M, Siewert I, Fohlmeister L, Limberg C, Knispel C. Ein Trispyrazolylborato-Eisen-Cysteinato-Komplex als funktionelles Modell für die Cystein-Dioxygenase. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201107345] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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164
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Sallmann M, Siewert I, Fohlmeister L, Limberg C, Knispel C. A trispyrazolylborato iron cysteinato complex as a functional model for the cysteine dioxygenase. Angew Chem Int Ed Engl 2012; 51:2234-7. [PMID: 22287034 DOI: 10.1002/anie.201107345] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Indexed: 11/07/2022]
Affiliation(s)
- Madleen Sallmann
- Humboldt-Universität zu Berlin, Institut für Chemie, Berlin, Germany
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165
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Latifi R, Tahsini L, Nam W, de Visser SP. Regioselectivity of aliphatic versus aromatic hydroxylation by a nonheme iron(ii)-superoxo complex. Phys Chem Chem Phys 2012; 14:2518-24. [DOI: 10.1039/c2cp23352e] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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166
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Du L, Gao J, Liu Y, Zhang D, Liu C. The reaction mechanism of hydroxyethylphosphonate dioxygenase: a QM/MM study. Org Biomol Chem 2012; 10:1014-24. [DOI: 10.1039/c1ob06221b] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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167
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Kumar D, Sastry GN, de Visser SP. Axial Ligand Effect On The Rate Constant of Aromatic Hydroxylation By Iron(IV)–Oxo Complexes Mimicking Cytochrome P450 Enzymes. J Phys Chem B 2011; 116:718-30. [DOI: 10.1021/jp2113522] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Devesh Kumar
- Department of Applied Physics, School for Physical Sciences, Babasaheb Bhimrao Ambedkar University, Vidya Vihar, Rae Bareilly Road, Lucknow 226 025, India
- Molecular Modelling Group, Indian Institute of Chemical Technology, Hyderabad 500-607, India
| | - G. Narahari Sastry
- Molecular Modelling Group, Indian Institute of Chemical Technology, Hyderabad 500-607, India
| | - Sam P. de Visser
- Manchester Interdisciplinary Biocenter and School of Chemical Engineering and Analytical Science, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
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168
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Kumar D, Sastry GN, Goldberg DP, de Visser SP. Mechanism of S-oxygenation by a cysteine dioxygenase model complex. J Phys Chem A 2011; 116:582-91. [PMID: 22091701 DOI: 10.1021/jp208230g] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In this work, we present the first computational study on a biomimetic cysteine dioxygenase model complex, [Fe(II)(LN(3)S)](+), in which LN(3)S is a tetradentate ligand with a bis(imino)pyridyl scaffold and a pendant arylthiolate group. The reaction mechanism of sulfur dioxygenation with O(2) was examined by density functional theory (DFT) methods and compared with results obtained for cysteine dioxygenase. The reaction proceeds via multistate reactivity patterns on competing singlet, triplet, and quintet spin state surfaces. The reaction mechanism is analogous to that found for cysteine dioxygenase enzymes (Kumar, D.; Thiel, W.; de Visser, S. P. J. Am. Chem. Soc. 2011, 133, 3869-3882); hence, the computations indicate that this complex can closely mimic the enzymatic process. The catalytic mechanism starts from an iron(III)-superoxo complex and the attack of the terminal oxygen atom of the superoxo group on the sulfur atom of the ligand. Subsequently, the dioxygen bond breaks to form an iron(IV)-oxo complex with a bound sulfenato group. After reorganization, the second oxygen atom is transferred to the substrate to give a sulfinic acid product. An alternative mechanism involving the direct attack of dioxygen on the sulfur, without involving any iron-oxygen intermediates, was also examined. Importantly, a significant energetic preference for dioxygen coordinating to the iron center prior to attack at sulfur was discovered and serves to elucidate the function of the metal ion in the reaction process. The computational results are in good agreement with experimental observations, and the differences and similarities of the biomimetic complex and the enzymatic cysteine dioxygenase center are highlighted.
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Affiliation(s)
- Devesh Kumar
- Molecular Modelling Group, Indian Institute of Chemical Technology, Hyderabad 500-607, India.
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169
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Tchesnokov EP, Wilbanks SM, Jameson GNL. A Strongly Bound High-Spin Iron(II) Coordinates Cysteine and Homocysteine in Cysteine Dioxygenase. Biochemistry 2011; 51:257-64. [DOI: 10.1021/bi201597w] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Egor P. Tchesnokov
- Department of Chemistry & MacDiarmid Institute for Advanced Materials and Nanotechnology and ‡Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Sigurd M. Wilbanks
- Department of Chemistry & MacDiarmid Institute for Advanced Materials and Nanotechnology and ‡Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Guy N. L. Jameson
- Department of Chemistry & MacDiarmid Institute for Advanced Materials and Nanotechnology and ‡Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand
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170
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Crawford JA, Li W, Pierce BS. Single turnover of substrate-bound ferric cysteine dioxygenase with superoxide anion: enzymatic reactivation, product formation, and a transient intermediate. Biochemistry 2011; 50:10241-53. [PMID: 21992268 DOI: 10.1021/bi2011724] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cysteine dioxygenase (CDO) is a non-heme mononuclear iron enzyme that catalyzes the O(2)-dependent oxidation of L-cysteine (Cys) to produce cysteine sulfinic acid (CSA). In this study we demonstrate that the catalytic cycle of CDO can be "primed" by one electron through chemical oxidation to produce CDO with ferric iron in the active site (Fe(III)-CDO, termed 2). While catalytically inactive, the substrate-bound form of Fe(III)-CDO (2a) is more amenable to interrogation by UV-vis and EPR spectroscopy than the 'as-isolated' Fe(II)-CDO enzyme (1). Chemical-rescue experiments were performed in which superoxide (O(2)(•-)) anions were introduced to 2a to explore the possibility that a Fe(III)-superoxide species represents the first intermediate within the catalytic pathway of CDO. In principle, O(2)(•-) can serve as a suitable acceptor for the remaining 3-electrons necessary for CSA formation and regeneration of the active Fe(II)-CDO enzyme (1). Indeed, addition of O(2)(•-) to 2a resulted in the rapid formation of a transient species (termed 3a) observable at 565 nm by UV-vis spectroscopy. The subsequent decay of 3a is kinetically matched to CSA formation. Moreover, a signal attributed to 3a was also identified using parallel mode X-band EPR spectroscopy (g ~ 11). Spectroscopic simulations, observed temperature dependence, and the microwave power saturation behavior of 3a are consistent with a ground state S = 3 from a ferromagnetically coupled (J ~ -8 cm(-1)) high-spin ferric iron (S(A) = 5/2) with a bound radical (S(B) = 1/2), presumably O(2)(•-). Following treatment with O(2)(•-), the specific activity of recovered CDO increased to ~60% relative to untreated enzyme.
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Affiliation(s)
- Joshua A Crawford
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington, Arlington, Texas 76019, United States
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171
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Hirao H, Morokuma K. ONIOM(DFT:MM) Study of 2-Hydroxyethylphosphonate Dioxygenase: What Determines the Destinies of Different Substrates? J Am Chem Soc 2011; 133:14550-3. [DOI: 10.1021/ja206222f] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hajime Hirao
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Keiji Morokuma
- Fukui Institute for Fundamental Chemistry, Kyoto University, 34-4 Takano Nishihiraki-cho, Sakyo, Kyoto 606-8103, Japan
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172
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Siakkou E, Rutledge MT, Wilbanks SM, Jameson GNL. Correlating crosslink formation with enzymatic activity in cysteine dioxygenase. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:2003-9. [PMID: 21839860 DOI: 10.1016/j.bbapap.2011.07.019] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 07/15/2011] [Accepted: 07/21/2011] [Indexed: 10/17/2022]
Abstract
Cysteine dioxygenase (CDO) from rat and other mammals exhibits a covalent post-translational modification between the residues C93 and Y157 that is in close proximity to the active site, and whose presence enhances the enzyme's activity. Protein with and without C93-Y157 crosslink migrates as distinct bands in SDS-PAGE, allowing quantification of the relative ratios between the two forms by densitometry of the respective bands. Expression of recombinant rat wild type CDO in Escherichia coli typically produces 40-50% with the C93-Y157 crosslink. A strategy was developed to increase the ratio of the non-crosslinked form in an enzyme preparation of reasonable quantity and purity, allowing direct assessment of the activity of non-crosslinked CDO and mechanism of formation of the crosslink. The presence of ferrous iron and oxygen is a prerequisite for C93-Y157 crosslink formation. Absence of oxygen during protein expression increased the fraction of non-crosslinked CDO, while presence of the metal chelator EDTA had little effect. Metal affinity chromatography was used to enrich non-crosslinked content. Both the enzymatic rate of cysteine oxidation and the amount of cross-linking between C93 and Y157 increased significantly upon exposure of CDO to air/oxygen and substrate cysteine in the presence of iron in a hitherto unreported two-phase process. The instantaneous activity was proportional to the amount of crosslinked enzyme present, demonstrating that the non-crosslinked form has negligible enzymatic activity. The biphasic kinetics suggest the existence of an as yet uncharacterised intermediate in crosslink formation and enzyme activation.
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Affiliation(s)
- Eleni Siakkou
- Department of Chemistry, University of Otago, Dunedin, New Zealand
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