1
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Dereven'kov IA, Osokin VS, Khodov IA, Sobornova VV, Ershov NA, Makarov SV. meso-Bromination of cyano- and aquacobalamins facilitates their processing into Co(II)-species by glutathione. J Biol Inorg Chem 2023; 28:571-581. [PMID: 37479902 DOI: 10.1007/s00775-023-02009-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2023] [Accepted: 07/05/2023] [Indexed: 07/23/2023]
Abstract
Cyanocobalamin (CNCbl), a medicinal form of vitamin B12, is resistant to glutathione (GSH), and undergoes intracellular processing via reductive decyanation producing the Co(II)-form of Cbl (Cbl(II)) mediated by the CblC-protein. Alteration of the CblC-protein structure might inhibit CNCbl processing. Here, we showed that introducing a bromine atom to the C10-position of the CNCbl corrin ring facilitates its reaction with GSH leading to the formation of Cbl(II) and cyanide dissociation. In a neutral medium, the reaction between C10-Br-CNCbl and GSH proceeds via the complexation of the reactants further leading to dimethylbenzimidazole (DMBI) substitution and electron transfer from GSH to the Co(III)-ion. The reaction is accelerated upon the GSH thiol group deprotonation. The key factors explaining the higher reactivity of C10-Br-CNCbl compared with unmodified CNCbl towards GSH are increasing the electrode potential of CNCbl two-electron reduction upon meso-bromination and the substantial labilization of DMBI, which was shown by comparing their reactions with cyanide and the pKa values of DMBI protonation (pKa base-off). Aquacobalamin (H2OCbl) brominated at the C10-position of the corrin reacts with GSH to give Cbl(II) via GSH complexation and subsequent reaction of this complex with a second GSH molecule, whereas unmodified H2OCbl generates glutathionyl-Cbl, which is resistant to further reduction by GSH.
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Affiliation(s)
- Ilia A Dereven'kov
- Department of Food Chemistry, Ivanovo State University of Chemistry and Technology, Sheremetevskiy Str. 7, 153000, Ivanovo, Russia.
| | - Vladimir S Osokin
- Department of Food Chemistry, Ivanovo State University of Chemistry and Technology, Sheremetevskiy Str. 7, 153000, Ivanovo, Russia
| | - Ilya A Khodov
- G.A. Krestov Institute of Solution Chemistry, Russian Academy of Sciences, 153045, Ivanovo, Russia
| | - Valentina V Sobornova
- G.A. Krestov Institute of Solution Chemistry, Russian Academy of Sciences, 153045, Ivanovo, Russia
| | - Nikita A Ershov
- Department of Food Chemistry, Ivanovo State University of Chemistry and Technology, Sheremetevskiy Str. 7, 153000, Ivanovo, Russia
| | - Sergei V Makarov
- Department of Food Chemistry, Ivanovo State University of Chemistry and Technology, Sheremetevskiy Str. 7, 153000, Ivanovo, Russia
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2
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Elmendorf LD, Brunold TC. Vibronic Coupling in Vitamin B 12: A Combined Spectroscopic and Computational Study. Inorg Chem 2023; 62:12762-12772. [PMID: 37463115 DOI: 10.1021/acs.inorgchem.3c01305] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023]
Abstract
Understanding the diverse reactivities of vitamin B12 and its derivatives, collectively called cobalamins, requires detailed knowledge of their geometric and electronic structures. Electronic absorption (Abs) and resonance Raman (rR) spectroscopies have proven invaluable in this area, particularly when used in concert with computational techniques such as density functional theory (DFT). There remain, however, lingering uncertainties in the computational description of electronic excited states of cobalamins, particularly surrounding the vibronic coupling that impacts the Abs bandshapes and gives rise to rR enhancement of vibrational modes. Past computational analyses of the vibrational spectra of cobalamins have either neglected rR enhancement or calculated rR enhancement for only a small number of modes. In the present study, we used the recently developed ORCA_ASA computational tool in conjunction with the popular B3LYP and BP86 functionals to predict Abs bandshapes and rR spectra for vitamin B12. The ORCA_ASA/B3LYP-computed Abs envelope in the visible spectral region and rR spectra of vitamin B12 agree remarkably well with our experimental data, while BP86 fails to reproduce both. This finding represents a significant advance in our understanding of how these two commonly used density functionals differently model the electronic properties of cobalamins. Guided by the computed frequencies for the Co-C stretching and Co-C-N bending modes, we identified, for the first time, isotope-sensitive features in our rR spectra of 12CNCbl and 13CNCbl that can be assigned to these modes. A normal coordinate analysis of the experimentally determined Co-C stretching and Co-C-N bending frequencies indicates that the Co-C force constant for vitamin B12 is 2.67 mdyn/Å, considerably larger than the Co-C force constants reported for alkylcobalamins.
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Affiliation(s)
- Laura D Elmendorf
- Department of Chemistry, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States
| | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States
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3
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Marques HM. The inorganic chemistry of the cobalt corrinoids - an update. J Inorg Biochem 2023; 242:112154. [PMID: 36871417 DOI: 10.1016/j.jinorgbio.2023.112154] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 01/23/2023] [Accepted: 01/26/2023] [Indexed: 02/05/2023]
Abstract
The inorganic chemistry of the cobalt corrinoids, derivatives of vitamin B12, is reviewed, with particular emphasis on equilibrium constants for, and kinetics of, their axial ligand substitution reactions. The role the corrin ligand plays in controlling and modifying the properties of the metal ion is emphasised. Other aspects of the chemistry of these compounds, including their structure, corrinoid complexes with metals other than cobalt, the redox chemistry of the cobalt corrinoids and their chemical redox reactions, and their photochemistry are discussed. Their role as catalysts in non-biological reactions and aspects of their organometallic chemistry are briefly mentioned. Particular mention is made of the role that computational methods - and especially DFT calculations - have played in developing our understanding of the inorganic chemistry of these compounds. A brief overview of the biological chemistry of the B12-dependent enzymes is also given for the reader's convenience.
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Affiliation(s)
- Helder M Marques
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa.
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4
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Dereven'kov IA, Osokin VS, Hannibal L, Makarov SV, Khodov IA, Koifman OI. Mechanism of cyanocobalamin chlorination by hypochlorous acid. J Biol Inorg Chem 2021; 26:427-434. [PMID: 33914169 DOI: 10.1007/s00775-021-01869-5] [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: 12/08/2020] [Accepted: 04/22/2021] [Indexed: 11/29/2022]
Abstract
Hypochlorous acid (HOCl) is a strong oxidant produced by myeloperoxidase. Previous work suggested that HOCl modifies the corrin ring of cobalamins to yield chlorinated species via mechanisms that are incompletely understood. Herein, we report a mechanistic study on the reaction between cyanocobalamin (CNCbl, vitamin B12) and HOCl. Under weakly acidic, neutral and weakly alkaline conditions, the reaction produces the c-lactone derivative of CNCbl chlorinated at the C10-position of corrin ring (C10-Cl-CNCbl-c-lactone). Formation of C10-Cl-CNCbl-c-lactone was not observed at pH ≥ 9.9. The chlorination of CNCbl by HOCl proceeds via two pathways involving one and two HOCl molecules: the reaction is initiated by the very fast formation of a complex between CNCbl and HOCl, which either undergoes slow transformation to chlorinated species, or rapidly reacts with a second HOCl molecule to produce C10-Cl-CNCbl. Subsequent reaction of C10-Cl-CNCbl with HOCl proceeds rapidly toward lactone ring formation by H-atom abstraction at position C8. This work uncovered mechanisms and products of the reaction of a biologically active and therapeutically used cobalamin, CNCbl and the endogenous oxidant HOCl. Binding and reactivity studies of C10-Cl-CNCbl and C10-Cl-CNCbl-c-lactone with relevant proteins of the cobalamin pathway and with cultured cells are necessary to elucidate the potential physiological effects of these species.
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Affiliation(s)
- Ilia A Dereven'kov
- Ivanovo State University of Chemistry and Technology, Sheremetevskiy Str. 7, 153000, Ivanovo, Russian Federation.
| | - Vladimir S Osokin
- Ivanovo State University of Chemistry and Technology, Sheremetevskiy Str. 7, 153000, Ivanovo, Russian Federation
| | - Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center-University of Freiburg, 79106, Freiburg, Germany
| | - Sergei V Makarov
- Ivanovo State University of Chemistry and Technology, Sheremetevskiy Str. 7, 153000, Ivanovo, Russian Federation
| | - Ilya A Khodov
- G.A. Krestov Institute of Solution Chemistry, Russian Academy of Sciences, Akademicheskaya Str. 1, 153045, Ivanovo, Russian Federation
| | - Oskar I Koifman
- Ivanovo State University of Chemistry and Technology, Sheremetevskiy Str. 7, 153000, Ivanovo, Russian Federation
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5
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Use of 13C and 1H NMR to determine the structure of the diastereomeric cobalt corrinoids aquacyanocobinamide and aquacyanocobester. Polyhedron 2020. [DOI: 10.1016/j.poly.2019.114203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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6
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Nowakowska M, Chemaly SM, Rousseau AL, Govender PP, Varadwaj PR, Varadwaj A, Yamashita K, Marques HM. Probing the nature of the Co(III) ion in corrins: The reactions of aquacyano-5-seco-cobyrinic acid heptamethyl ester with anionic ligands. Inorganica Chim Acta 2019. [DOI: 10.1016/j.ica.2018.09.073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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7
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Wierzba AJ, Wincenciuk A, Karczewski M, Vullev VI, Gryko D. meso
‐Modified Cobalamins: Synthesis, Structure, and Properties. Chemistry 2018; 24:10344-10356. [DOI: 10.1002/chem.201801807] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Indexed: 11/06/2022]
Affiliation(s)
- Aleksandra J. Wierzba
- Institute of Organic Chemistry Polish Academy of Sciences Kasprzaka 44/52 01-224 Warsaw Poland
| | - Aleksandra Wincenciuk
- Institute of Organic Chemistry Polish Academy of Sciences Kasprzaka 44/52 01-224 Warsaw Poland
- Department of Chemistry University of Warsaw Pasteura 1 02-093 Warsaw Poland
| | - Maksymilian Karczewski
- Institute of Organic Chemistry Polish Academy of Sciences Kasprzaka 44/52 01-224 Warsaw Poland
| | - Valentine I. Vullev
- Bioengineering, Chemistry, Biochemistry, and Materials Science and Engineering University of California, Riverside Materials Science and Engineering Building, Room 235 Riverside CA 92521 USA
| | - Dorota Gryko
- Institute of Organic Chemistry Polish Academy of Sciences Kasprzaka 44/52 01-224 Warsaw Poland
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8
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Rudshteyn B, Vibbert HB, May R, Wasserman E, Warnke I, Hopkins MD, Batista VS. Thermodynamic and Structural Factors That Influence the Redox Potentials of Tungsten–Alkylidyne Complexes. ACS Catal 2017. [DOI: 10.1021/acscatal.7b01636] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Benjamin Rudshteyn
- Department
of Chemistry and Energy Sciences Institute, Yale University, New Haven, Connecticut 06520, United States
| | - Hunter B. Vibbert
- Department
of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Richard May
- Department
of Chemistry and Energy Sciences Institute, Yale University, New Haven, Connecticut 06520, United States
| | - Eric Wasserman
- Department
of Chemistry and Energy Sciences Institute, Yale University, New Haven, Connecticut 06520, United States
| | - Ingolf Warnke
- Department
of Chemistry and Energy Sciences Institute, Yale University, New Haven, Connecticut 06520, United States
| | - Michael D. Hopkins
- Department
of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Victor S. Batista
- Department
of Chemistry and Energy Sciences Institute, Yale University, New Haven, Connecticut 06520, United States
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9
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Karczewski M, Ociepa M, Pluta K, ó Proinsias K, Gryko D. Vitamin B12
Catalysis: Probing the Structure/Efficacy Relationship. Chemistry 2017; 23:7024-7030. [DOI: 10.1002/chem.201606059] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Indexed: 11/06/2022]
Affiliation(s)
- Maksymilian Karczewski
- Institute of Organic Chemistry; Polish Academy of Sciences; Kasprzaka 44/52 01-224 Warsaw Poland
| | - Michał Ociepa
- Institute of Organic Chemistry; Polish Academy of Sciences; Kasprzaka 44/52 01-224 Warsaw Poland
| | - Katarzyna Pluta
- Institute of Organic Chemistry; Polish Academy of Sciences; Kasprzaka 44/52 01-224 Warsaw Poland
| | - Keith ó Proinsias
- Institute of Organic Chemistry; Polish Academy of Sciences; Kasprzaka 44/52 01-224 Warsaw Poland
| | - Dorota Gryko
- Institute of Organic Chemistry; Polish Academy of Sciences; Kasprzaka 44/52 01-224 Warsaw Poland
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10
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Jiajun D, Maza JR, Xu Y, Xu T, Momen R, Kirk SR, Jenkins S. A stress tensor and QTAIM perspective on the substituent effects of biphenyl subjected to torsion. J Comput Chem 2016; 37:2508-17. [PMID: 27546220 DOI: 10.1002/jcc.24476] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 06/26/2016] [Accepted: 08/06/2016] [Indexed: 11/11/2022]
Abstract
The Quantum Theory of Atoms in Molecules (QTAIM) defines quantities in 3D space that can be easily obtained from routine quantum chemical calculations. The present investigation shows that local properties can be related quantitatively to measures traditionally connected to experimental data, such as Hammett constants. We consider the specific case of substituted biphenyl to quantify the effects of a torsion φ, 0.0° ≤ φ ≤ 180.0°, of the C-C bond linking the two phenyl rings for C12 H9 -x, where x = N(CH3 )2 , NH2 , CH3 , CHO, CN, NO2, on the entire molecule. QTAIM interpreted Hammett constants, aΔH(rb ) are introduced and constructed using the difference between the H(rb ) value of C12 H9 -x and the C12 H9 -H, biphenyl which is the reference molecule, with a constant of proportionality a. This investigation unexpectedly yields very good or good agreement for the x groups with the Hammett para-, meta-, and ortho-substituent constants and is checked against para-substituted benzene. We then proceed to present the interpreted substituent constants of seven new biphenyl substituent groups, where tabulated Hammett substituent constant values are not available; y = SiH3 , ZnCl, COOCH3 , SO2 NH2 , SO2 OH, COCl, CB3 . Consistency is found for the QTAIM interpreted biphenyl substituent constants of the seven new groups y independently using the stress tensor polarizability Pσ . In addition, a selection of future applications is discussed that highlight the usefulness of this approach. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- D Jiajun
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha Hunan, 410081, China
| | - J R Maza
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha Hunan, 410081, China
| | - Y Xu
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha Hunan, 410081, China
| | - T Xu
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha Hunan, 410081, China
| | - R Momen
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha Hunan, 410081, China
| | - S R Kirk
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha Hunan, 410081, China
| | - S Jenkins
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha Hunan, 410081, China
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11
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Probing the nature of the Co(III) ion in cobalamins: The ligand substitution reactions of aquacyanocobester, aquacyano(10-nitro)cobester and aquacyano(10-amino)cobester. Inorganica Chim Acta 2016. [DOI: 10.1016/j.ica.2016.06.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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12
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Morita Y, Oohora K, Mizohata E, Sawada A, Kamachi T, Yoshizawa K, Inoue T, Hayashi T. Crystal Structures and Coordination Behavior of Aqua- and Cyano-Co(III) Tetradehydrocorrins in the Heme Pocket of Myoglobin. Inorg Chem 2016; 55:1287-95. [DOI: 10.1021/acs.inorgchem.5b02598] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yoshitsugu Morita
- Department of Applied Chemistry, Graduate
School of Engineering, Osaka University, Suita 565-0871, Japan
| | - Koji Oohora
- Department of Applied Chemistry, Graduate
School of Engineering, Osaka University, Suita 565-0871, Japan
- Frontier Research Base for Global Young
Researchers, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan
| | - Eiichi Mizohata
- Department of Applied Chemistry, Graduate
School of Engineering, Osaka University, Suita 565-0871, Japan
| | - Akiyoshi Sawada
- Institute
for Materials Chemistry and Engineering and International Research
Center for Molecular Systems, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
| | - Takashi Kamachi
- Institute
for Materials Chemistry and Engineering and International Research
Center for Molecular Systems, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
| | - Kazunari Yoshizawa
- Institute
for Materials Chemistry and Engineering and International Research
Center for Molecular Systems, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
- Elements
Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Nishikyo-ku, Kyoto 615-8520, Japan
| | - Tsuyoshi Inoue
- Department of Applied Chemistry, Graduate
School of Engineering, Osaka University, Suita 565-0871, Japan
| | - Takashi Hayashi
- Department of Applied Chemistry, Graduate
School of Engineering, Osaka University, Suita 565-0871, Japan
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13
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Kepp KP. Co-C dissociation of adenosylcobalamin (coenzyme B12): role of dispersion, induction effects, solvent polarity, and relativistic and thermal corrections. J Phys Chem A 2014; 118:7104-17. [PMID: 25116644 DOI: 10.1021/jp503607k] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Quantum-chemical cluster modeling is challenged in the limit of large, soft systems by the effects of dispersion and solvent, and well as other physical interactions. Adenosylcobalamin (AdoCbl, coenzyme B12), as one of the most complex cofactors in life, constitutes such a challenge. The cleavage of its unique organometallic Co-C bond has inspired multiple studies of this cofactor. This paper reports the fully relaxed potential energy surface of Co-C cleavage of AdoCbl, including for the first time all side-chain interactions with the dissociating Ado group. Various methods and corrections for dispersion, relativistic effects, solvent polarity, basis set superposition error, and thermal and vibrational effects were investigated, totaling more than 550 single-point energies for the large model. The results show immense variability depending on method, including solvation, functional type, and dispersion, challenging the conceived accuracy of methods used for such systems. In particular, B3LYP-D3 seems to severely underestimate the Co-C bond strength, consistent with previous results, and BP86 remains accurate for cobalamins when dispersion interactions are accounted for.
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Affiliation(s)
- Kasper P Kepp
- DTU Chemistry, Technical University of Denmark , Building 206, Kgs. Lyngby, DK-2800, Denmark
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14
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Zipp CF, Michael JP, Fernandes MA, Mathura S, Perry CB, Navizet I, Govender PP, Marques HM. The Synthesis of a Corrole Analogue of Aquacobalamin (Vitamin B12a) and Its Ligand Substitution Reactions. Inorg Chem 2014; 53:4418-29. [DOI: 10.1021/ic5000793] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Caitlin F. Zipp
- Molecular
Sciences Institute, School of Chemistry, University of the Witwatersrand, P.O. Wits, Johannesburg, 2050 South Africa
| | - Joseph P. Michael
- Molecular
Sciences Institute, School of Chemistry, University of the Witwatersrand, P.O. Wits, Johannesburg, 2050 South Africa
| | - Manuel A. Fernandes
- Molecular
Sciences Institute, School of Chemistry, University of the Witwatersrand, P.O. Wits, Johannesburg, 2050 South Africa
| | - Sadhna Mathura
- Molecular
Sciences Institute, School of Chemistry, University of the Witwatersrand, P.O. Wits, Johannesburg, 2050 South Africa
| | - Christopher B. Perry
- Molecular
Sciences Institute, School of Chemistry, University of the Witwatersrand, P.O. Wits, Johannesburg, 2050 South Africa
| | - Isabelle Navizet
- Molecular
Sciences Institute, School of Chemistry, University of the Witwatersrand, P.O. Wits, Johannesburg, 2050 South Africa
| | - Penny P. Govender
- Department
of Applied Chemistry, University of Johannesburg, P.O. Box 17011, Doornfontein, Johannesburg, 2028 South Africa
| | - Helder M. Marques
- Molecular
Sciences Institute, School of Chemistry, University of the Witwatersrand, P.O. Wits, Johannesburg, 2050 South Africa
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15
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Zhou J, Riccardi D, Beste A, Smith JC, Parks JM. Mercury methylation by HgcA: theory supports carbanion transfer to Hg(II). Inorg Chem 2013; 53:772-7. [PMID: 24377658 DOI: 10.1021/ic401992y] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Many proteins use corrinoid cofactors to facilitate methyl transfer reactions. Recently, a corrinoid protein, HgcA, has been shown to be required for the production of the neurotoxin methylmercury by anaerobic bacteria. A strictly conserved Cys residue in HgcA was predicted to be a lower-axial ligand to Co(III), which has never been observed in a corrinoid protein. Here, we use density functional theory to study homolytic and heterolytic Co-C bond dissociation and methyl transfer to Hg(II) substrates with model methylcobalamin complexes containing a lower-axial Cys or His ligand to cobalt, the latter of which is commonly found in other corrinoid proteins. We find that Cys thiolate coordination to Co facilitates both methyl radical and methyl carbanion transfer to Hg(II) substrates, but carbanion transfer is more favorable overall in the condensed phase. Thus, our findings are consistent with HgcA representing a new class of corrinoid protein capable of transferring methyl groups to electrophilic substrates.
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Affiliation(s)
- Jing Zhou
- Graduate School of Genome Science and Technology, University of Tennessee , Knoxville, Tennessee 37996, United States
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16
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Mathura S, Sannasy D, de Sousa AS, Perry CB, Navizet I, Marques HM. The preparation of N-acetyl-Co(III)-microperoxidase-8 (NAcCoMP8) and its ligand substitution reactions: A comparison with aquacobalamin (vitamin B12a). J Inorg Biochem 2013; 123:66-79. [DOI: 10.1016/j.jinorgbio.2013.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 03/01/2013] [Accepted: 03/04/2013] [Indexed: 12/01/2022]
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17
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DFT Studies of Trans and Cis Influences in the Homolysis of the Co–C Bond in Models of the Alkylcobalamins. J Phys Chem A 2013; 117:3057-68. [DOI: 10.1021/jp311788t] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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18
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Chemaly SM, Kendall L, Nowakowska M, Pon D, Perry CB, Marques HM. Probing the nature of the Co(III) ion in corrins: comparison of reactions of aquacyanocobyrinic acid heptamethyl ester and aquacyano-stable yellow cobyrinic acid hexamethyl ester with neutral N-donor ligands. Inorg Chem 2013; 52:1077-83. [PMID: 23268626 DOI: 10.1021/ic302386u] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Equilibrium constants (log K) for substitution of coordinated H(2)O in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, ACCbs) and aquacyano-stable yellow cobyrinic acid hexamethyl ester (aquacyano-stable yellow cobester, ACSYCbs), in which oxidation of the C5 carbon of the corrin interrupts the normal delocalized system of corrins, by neutral N-donor ligands (ammonia, ethanolamine, 2-methoxyethylamine, N-methylimidazole, and 4-methylpyridine) have been determined spectrophotometrically as a function of temperature. Log K values increase with the basicity of the ligand, but a strong compensation effect between ΔH and ΔS values causes a leveling effect. The aliphatic amines with a harder donor atom produce ΔH values that are more negative in their reactions with ACSYCbs than with ACCbs, while the softer, aromatic N donors produce more negative ΔH values with ACCbs than with ACSYCbs. Molecular modeling (DFT, M06L/SVP, and a quantum theory of atoms in molecules analysis of the electron density) shows that complexes of the aliphatic amines with SYCbs produce shorter and stronger Co-N bonds with less ionic character than the Co-N bonds of these ligands with the cobester. Conversely, the Co-N bond to the aromatic N donors is shorter, stronger, and somewhat less ionic in the complexes of the cobester than in those of the SYCbs. Therefore, the distinction between the harder Co(III) in ACSYCbs and softer Co(III) in ACCbs, reported previously for anionic ligands, is maintained for neutral N-donor ligands.
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Affiliation(s)
- Susan M Chemaly
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, PO Wits, Johannesburg, 2050 South Africa.
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