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Hydrolysis Mechanism of Carbamate Methomyl by a Novel Esterase PestE: A QM/MM Approach. Int J Mol Sci 2022; 24:ijms24010433. [PMID: 36613879 PMCID: PMC9820155 DOI: 10.3390/ijms24010433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 12/20/2022] [Accepted: 12/23/2022] [Indexed: 12/28/2022] Open
Abstract
Methomyl is one of the most important carbamates that has caused potential hazardous effects on both human beings and the environment. Here, we systematically investigated the hydrolysis mechanism of methomyl catalyzed by esterase PestE using molecular dynamics simulations (MD) and quantum mechanics/molecular mechanics (QM/MM) calculations. The hydrolysis mechanism involves two elementary steps: (Ⅰ) serine-initiated nucleophilic attack and (Ⅱ) C-O bond cleavage. Our work elicits the atomic level details of the hydrolysis mechanism and free energy profiles along the reaction pathway. The Boltzmann-weighted average potential barriers are 19.1 kcal/mol and 7.5 kcal/mol for steps Ⅰ and Ⅱ, respectively. We identified serine-initiated nucleophilic attack as the rate determining-step. The deep learning-based kcat prediction model indicated that the barrier of the rate-determining step is 15.4 kcal/mol, which is in good agreement with the calculated results using Boltzmann-weighted average method. We have elucidated the importance of the protein-substrate interactions and the roles of the key active site residues during the hydrolysis process through noncovalent interactions analysis and electrostatic potential (ESP) analysis. The results provide practical value for achieving efficient degradation of carbamates by hydrolases.
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2
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Mai BK, Neris NM, Yang Y, Liu P. C-N Bond Forming Radical Rebound Is the Enantioselectivity-Determining Step in P411-Catalyzed Enantioselective C(sp 3)-H Amination: A Combined Computational and Experimental Investigation. J Am Chem Soc 2022; 144:11215-11225. [PMID: 35583461 DOI: 10.1021/jacs.2c02283] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Engineered metalloenzymes represent promising catalysts for stereoselective C-H functionalization reactions. Recently, P450 enzymes have been evolved to allow for new-to-nature intramolecular C(sp3)-H amination reactions via a nitrene transfer mechanism, giving rise to diamine derivatives with excellent enantiocontrol. To shed light on the origin of enantioselectivity, a combined computational and experimental study was carried out. Hybrid quantum mechanics/molecular mechanics calculations were performed to investigate the activation energies and enantioselectivities of both the hydrogen atom transfer (HAT) and the subsequent C-N bond forming radical rebound steps. Contrary to previously hypothesized enantioinduction mechanisms, our calculations show that the radical rebound step is enantioselectivity-determining, whereas the preceding HAT step is only moderately stereoselective. Furthermore, the selectivity in the initial HAT is ablated by rapid conformational change of the radical intermediate prior to C-N bond formation. This finding is corroborated by our experimental study using a set of enantiomerically pure, monodeuterated substrates. Furthermore, classical and ab initio molecular dynamics simulations were carried out to investigate the conformational flexibility of the carbon-centered radical intermediate. This key radical species undergoes a facile conformational change in the enzyme active site from the pro-(R) to the pro-(S) configuration, whereas the radical rebound is slower due to the spin-state change and ring strain of the cyclization process, thereby allowing stereoablative C-N bond formation. Together, these studies revealed an underappreciated enantioinduction mechanism in biocatalytic C(sp3)-H functionalizations involving radical intermediates, opening up new avenues for the development of other challenging asymmetric C(sp3)-H functionalizations.
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Affiliation(s)
- Binh Khanh Mai
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Natalia M Neris
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
| | - Yang Yang
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
- Biomolecular Science and Engineering (BMSE) Program, University of California, Santa Barbara, California 93106, United States
| | - Peng Liu
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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3
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Deng WH, Lu Y, Liao RZ. Revealing the Mechanism of Isethionate Sulfite-Lyase by QM/MM Calculations. J Chem Inf Model 2021; 61:5871-5882. [PMID: 34806370 DOI: 10.1021/acs.jcim.1c00978] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Isethionate sulfite-lyase (IseG) is a recently characterized glycyl radical enzyme (GRE) that catalyzes radical-mediated C-S bond cleavage of isethionate to produce acetaldehyde and sulfite. Herein, we use quantum mechanical/molecular mechanical (QM/MM) calculations to investigate the detailed catalytic reaction mechanism of IseG. Our calculations indicate that a previously proposed direct 1,2-elimination mechanism is disfavored. Instead, we suggest a new 1,2-migration mechanism for this enzymatic reaction: a key stepwise 1,2-SO3- radical migration occurs after the catalytically active cysteinyl radical grabs a hydrogen atom from isethionate, followed by hydrogen atom transfer from cysteine to a 1-hydroxylethane-1-sulfonate radical intermediate. Finally, the elimination of sulfite from 1-hydroxylethane-1-sulfonate to result in the final product is likely to occur outside the enzyme. Glu468 in the active site is found to help orient the substrate rather than grabbing a proton from the hydroxyl group of the substrate. Our findings help reveal the mechanisms of radical-mediated C-S bond cleavage of organosulfonates catalyzed by GREs and expand the understanding of radical-based enzymatic catalysis.
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Affiliation(s)
- Wen-Hao Deng
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica, Hubei Key Laboratory of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
| | - You Lu
- Scientific Computing Department, UKRI STFC Daresbury Laboratory, Sci-Tech Daresbury, Warrington WA4 4AD, United Kingdom
| | - Rong-Zhen Liao
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica, Hubei Key Laboratory of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
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4
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Zhang R, Li P, Zhang R, Shi X, Li Y, Zhang Q, Wang W. Computational study on the detoxifying mechanism of DDT metabolized by cytochrome P450 enzymes. JOURNAL OF HAZARDOUS MATERIALS 2021; 414:125457. [PMID: 33652222 DOI: 10.1016/j.jhazmat.2021.125457] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 02/06/2021] [Accepted: 02/15/2021] [Indexed: 06/12/2023]
Abstract
Predicting the detoxifying mechanism and potential toxic derivatives of xenobiotic substances is significant for risk assessment. The present study delineated the detoxifying mechanism of 1-chloro-4-[2,2,2-trichloro-1-(4-chlorophenyl)ethyl]benzene (DDT) metabolized by human P450 enzymes using a combination of molecular dynamic (MD), quantum mechanics/molecular mechanics (QM/MM) and density functional theory (DFT). This study highlights that DDT can be metabolized by P450 enzymes through the hydrogen abstraction and electrophilic addition mechanism, and the main derivatives are epoxides (2,3-oxide-DDT and 3,4-oxide-DDT), DDE and dicofol. The epoxides are unstable and the C-O bond cleavage easily occurs by the reaction with hydronium ion or hydroxyl radicals, yielding endocrine disruptor hydroxylated DDT. The eco-toxicity evaluation indicates that the derivatives of DDT are less toxic than DDT, and the solubility increase of the derivatives can accelerate their excretion from the body. The study can provide an understanding of the biotransformation of DDT by the P450 enzymes in human livers.
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Affiliation(s)
- Ruiming Zhang
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
| | - Pengfei Li
- Shandong Academy for Environmental Planning, Jinan 250014, PR China
| | - Ruiying Zhang
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
| | - Xiangli Shi
- College of Geography and Environment, Shandong Normal University, Jinan 250014, PR China
| | - Yanwei Li
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
| | - Qingzhu Zhang
- Environment Research Institute, Shandong University, Qingdao 266237, PR China.
| | - Wenxing Wang
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
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5
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Liu Y, Han L, Cheng Z, Liu Z, Zhou Z. Enzymatic Biosynthesis of l-2-Aminobutyric Acid by Glutamate Mutase Coupled with l-Aspartate-β-decarboxylase Using l-Glutamate as the Sole Substrate. ACS Catal 2020. [DOI: 10.1021/acscatal.0c04141] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yufeng Liu
- Key Laboratory of Industrial Biotechnology (Ministry of Education), School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Laichuang Han
- Key Laboratory of Industrial Biotechnology (Ministry of Education), School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Zhongyi Cheng
- Key Laboratory of Industrial Biotechnology (Ministry of Education), School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Zhongmei Liu
- Key Laboratory of Industrial Biotechnology (Ministry of Education), School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Zhemin Zhou
- Key Laboratory of Industrial Biotechnology (Ministry of Education), School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
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6
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Mamun AA, Toda MJ, Lodowski P, Jaworska M, Kozlowski PM. Mechanism of Light Induced Radical Pair Formation in Coenzyme B12-Dependent Ethanolamine Ammonia-Lyase. ACS Catal 2018. [DOI: 10.1021/acscatal.8b00120] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Abdullah Al Mamun
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, United States
| | - Megan J. Toda
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, United States
| | - Piotr Lodowski
- Department of Theoretical Chemistry, Institute of Chemistry, University of Silesia in Katowice, Szkolna 9, PL-40 006 Katowice, Poland
| | - Maria Jaworska
- Department of Theoretical Chemistry, Institute of Chemistry, University of Silesia in Katowice, Szkolna 9, PL-40 006 Katowice, Poland
| | - Pawel M. Kozlowski
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, United States
- Department of Food Sciences, Medical University of Gdansk, Al. Gen. J. Hallera 107, 80-416 Gdansk, Poland
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7
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Ryde U. How Many Conformations Need To Be Sampled To Obtain Converged QM/MM Energies? The Curse of Exponential Averaging. J Chem Theory Comput 2017; 13:5745-5752. [DOI: 10.1021/acs.jctc.7b00826] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Ulf Ryde
- Department of Theoretical
Chemistry, Lund University, Chemical Centre, P.O. Box 124, SE-221 00 Lund, Sweden
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8
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Zhao C, Dong L, Liu Y. A QM/MM study of the catalytic mechanism of SAM methyltransferase RlmN from Escherichia coli. Proteins 2017. [PMID: 28643349 DOI: 10.1002/prot.25337] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
RlmN is a radical S-adenosylmethionine (SAM) enzyme that catalyzes the C2 methylation of adenosine 2503 (A2503) in 23S rRNA and adenosine 37 (A37) in several Escherichia coli transfer RNAs (tRNA). The catalytic reaction of RlmN is distinctly different from that of typical SAM-dependent methyltransferases that employs an SN 2 mechanism, but follows a ping-pong mechanism which involves the intermediate methylation of a conserved cysteine residue. Recently, the x-ray structure of a key intermediate in the RlmN reaction has been reported, allowing us to perform combined quantum mechanics and molecular mechanics (QM/MM) calculations to delineate the reaction details of RlmN at atomic level. Starting from the Cross-Linked RlmN C118A-tRNA complex, the possible mechanisms for both the formation and the resolution of the cross-linked species (IM2) have been illuminated. On the basis of our calculations, IM2 is formed by the attack of the C355-based methylene radical on the sp2 -hybridized C2 of the adenosine ring, corresponding to energy barrier of 14.4 kcal/mol, and the resolution of IM2 is confirmed to follow a radical fragmentation mechanism. The cleavage of C'-S' bond of mC355-A37 cross-link is in concert with the deprotonation of C2 by C118 residue, which is the rate-limiting step with an energy barrier of 17.4 kcal/mol. Moreover, the cleavage of C'-S' bond of IM2 can occur independently, that is, it does not require the loss of an electron of IM2 and the formation of disulfide bond between C355 and C118 as precondition. These findings would deepen the understanding of the catalysis of RlmN.
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Affiliation(s)
- Chenxiao Zhao
- School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong, 250100, China
| | - Lihua Dong
- School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong, 250100, China.,School of Chemistry and Chemical Engineering, Qilu Normal University, Jinan, Shandong, 250013, China
| | - Yongjun Liu
- School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong, 250100, China
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9
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Wang X, Zhu W, Liu Y. Tryptophan lyase (NosL): mechanistic insights into amine dehydrogenation and carboxyl fragment migration by QM/MM calculations. Catal Sci Technol 2017. [DOI: 10.1039/c7cy00573c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
QM/MM calculations suggest two feasible pathways for the breaking of the C–C bond of the substrate. The breaking of the Cα–Cβ bond leads to the final product, whereas the cleavage of the Cα–C bond will terminate in the EPR-trapped radical intermediate.
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Affiliation(s)
- Xiya Wang
- School of Chemistry and Chemical Engineering
- Shandong University
- Jinan
- China
| | - Wenyou Zhu
- College of Chemistry and Chemical Engineering
- Xuzhou Institute of Technology
- Xuzhou
- China
| | - Yongjun Liu
- School of Chemistry and Chemical Engineering
- Shandong University
- Jinan
- China
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10
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Li Y, Zhang R, Du L, Zhang Q, Wang W. How Many Conformations of Enzymes Should Be Sampled for DFT/MM Calculations? A Case Study of Fluoroacetate Dehalogenase. Int J Mol Sci 2016; 17:E1372. [PMID: 27556449 PMCID: PMC5000767 DOI: 10.3390/ijms17081372] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 08/12/2016] [Accepted: 08/16/2016] [Indexed: 11/16/2022] Open
Abstract
The quantum mechanics/molecular mechanics (QM/MM) method (e.g., density functional theory (DFT)/MM) is important in elucidating enzymatic mechanisms. It is indispensable to study "multiple" conformations of enzymes to get unbiased energetic and structural results. One challenging problem, however, is to determine the minimum number of conformations for DFT/MM calculations. Here, we propose two convergence criteria, namely the Boltzmann-weighted average barrier and the disproportionate effect, to tentatively address this issue. The criteria were tested by defluorination reaction catalyzed by fluoroacetate dehalogenase. The results suggest that at least 20 conformations of enzymatic residues are required for convergence using DFT/MM calculations. We also tested the correlation of energy barriers between small QM regions and big QM regions. A roughly positive correlation was found. This kind of correlation has not been reported in the literature. The correlation inspires us to propose a protocol for more efficient sampling. This saves 50% of the computational cost in our current case.
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Affiliation(s)
- Yanwei Li
- Environment Research Institute, Shandong University, Jinan 250100, China.
| | - Ruiming Zhang
- Environment Research Institute, Shandong University, Jinan 250100, China.
| | - Likai Du
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan 430070, China..
| | - Qingzhu Zhang
- Environment Research Institute, Shandong University, Jinan 250100, China.
| | - Wenxing Wang
- Environment Research Institute, Shandong University, Jinan 250100, China.
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11
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Zhu W, Liu Y. Ring Contraction Catalyzed by the Metal-Dependent Radical SAM Enzyme: 7-Carboxy-7-deazaguanine Synthase from B. multivorans. Theoretical Insights into the Reaction Mechanism and the Influence of Metal Ions. ACS Catal 2015. [DOI: 10.1021/acscatal.5b00156] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Wenyou Zhu
- Key
Laboratory of Colloid and Interface Chemistry, Ministry of Education,
School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China
| | - Yongjun Liu
- Key
Laboratory of Colloid and Interface Chemistry, Ministry of Education,
School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China
- Key
Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau
Biology, Chinese Academy of Sciences, Xining, Qinghai 810001, China
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12
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Zenn RK, Abad E, Kästner J. Influence of the Environment on the Oxidative Deamination of p-Substituted Benzylamines in Monoamine Oxidase. J Phys Chem B 2015; 119:3678-86. [DOI: 10.1021/jp512470a] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Roland K. Zenn
- Institute of Theoretical
Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Enrique Abad
- Institute of Theoretical
Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Johannes Kästner
- Institute of Theoretical
Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
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13
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Menon BRK, Menon N, Fisher K, Rigby SEJ, Leys D, Scrutton NS. Glutamate 338 is an electrostatic facilitator of C-Co bond breakage in a dynamic/electrostatic model of catalysis by ornithine aminomutase. FEBS J 2015; 282:1242-55. [PMID: 25627283 PMCID: PMC4413051 DOI: 10.1111/febs.13215] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 01/16/2015] [Accepted: 01/23/2015] [Indexed: 01/04/2023]
Abstract
How cobalamin-dependent enzymes promote C–Co homolysis to initiate radical catalysis has been debated extensively. For the pyridoxal 5′-phosphate and cobalamin-dependent enzymes lysine 5,6-aminomutase and ornithine 4,5-aminomutase (OAM), large-scale re-orientation of the cobalamin-binding domain linked to C–Co bond breakage has been proposed. In these models, substrate binding triggers dynamic sampling of the B12-binding Rossmann domain to achieve a catalytically competent ‘closed’ conformational state. In ‘closed’ conformations of OAM, Glu338 is thought to facilitate C–Co bond breakage by close association with the cobalamin adenosyl group. We investigated this using stopped-flow continuous-wave photolysis, viscosity dependence kinetic measurements, and electron paramagnetic resonance spectroscopy of a series of Glu338 variants. We found that substrate-induced C–Co bond homolysis is compromised in Glu388 variant forms of OAM, although photolysis of the C–Co bond is not affected by the identity of residue 338. Electrostatic interactions of Glu338 with the 5′-deoxyadenosyl group of B12 potentiate C–Co bond homolysis in ‘closed’ conformations only; these conformations are unlocked by substrate binding. Our studies extend earlier models that identified a requirement for large-scale motion of the cobalamin domain. Our findings indicate that large-scale motion is required to pre-organize the active site by enabling transient formation of ‘closed’ conformations of OAM. In ‘closed’ conformations, Glu338 interacts with the 5′-deoxyadenosyl group of cobalamin. This interaction is required to potentiate C–Co homolysis, and is a crucial component of the approximately 1012 rate enhancement achieved by cobalamin-dependent enzymes for C–Co bond homolysis.
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Affiliation(s)
- Binuraj R K Menon
- Biotechnology and Biological Sciences Research Council/Engineering and Physical Sciences Research Council Centre for Synthetic Biology of Fine and Speciality Chemicals, Manchester Institute of Biotechnology, Faculty of Life Sciences, The University of Manchester, UK
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14
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Ma G, Cheng N, Su H, Liu Y. Exploring the substrate-assisted acetylation mechanism by UDP-linked sugar N-acetyltransferase from QM/MM calculations: the role of residue Asn84 and the effects of starting geometries. RSC Adv 2015. [DOI: 10.1039/c4ra13278e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Based on the QM/MM calculation, we revised the proposed mechanism ofN-acetyltransferase and explore the role of Asn84 and the effects of starting geometries.
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Affiliation(s)
- Guangcai Ma
- School of Chemistry and Chemical Engineering
- Shandong University
- Jinan
- China
| | - Na Cheng
- School of Chemistry and Chemical Engineering
- Shandong University
- Jinan
- China
| | - Hao Su
- School of Chemistry and Chemical Engineering
- Shandong University
- Jinan
- China
| | - Yongjun Liu
- School of Chemistry and Chemical Engineering
- Shandong University
- Jinan
- China
- Key Laboratory of Tibetan Medicine Research
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15
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Cooper AM, Kästner J. Averaging Techniques for Reaction Barriers in QM/MM Simulations. Chemphyschem 2014; 15:3264-9. [DOI: 10.1002/cphc.201402382] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 07/29/2014] [Indexed: 12/28/2022]
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16
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Silva PJ. With or without light: comparing the reaction mechanism of dark-operative protochlorophyllide oxidoreductase with the energetic requirements of the light-dependent protochlorophyllide oxidoreductase. PeerJ 2014; 2:e551. [PMID: 25237602 PMCID: PMC4157233 DOI: 10.7717/peerj.551] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 08/09/2014] [Indexed: 11/20/2022] Open
Abstract
The addition of two electrons and two protons to the C17=C18 bond in protochlorophyllide is catalyzed by a light-dependent enzyme relying on NADPH as electron donor, and by a light-independent enzyme bearing a (Cys)3Asp-ligated [4Fe–4S] cluster which is reduced by cytoplasmic electron donors in an ATP-dependent manner and then functions as electron donor to protochlorophyllide. The precise sequence of events occurring at the C17=C18 bond has not, however, been determined experimentally in the dark-operating enzyme. In this paper, we present the computational investigation of the reaction mechanism of this enzyme at the B3LYP/6-311+G(d,p)//B3LYP/6-31G(d) level of theory. The reaction mechanism begins with single-electron reduction of the substrate by the (Cys)3Asp-ligated [4Fe–4S], yielding a negatively-charged intermediate. Depending on the rate of Fe–S cluster re-reduction, the reaction either proceeds through double protonation of the single-electron-reduced substrate, or by alternating proton/electron transfer. The computed reaction barriers suggest that Fe–S cluster re-reduction should be the rate-limiting stage of the process. Poisson–Boltzmann computations on the full enzyme–substrate complex, followed by Monte Carlo simulations of redox and protonation titrations revealed a hitherto unsuspected pH-dependence of the reaction potential of the Fe–S cluster. Furthermore, the computed distributions of protonation states of the His, Asp and Glu residues were used in conjuntion with single-point ONIOM computations to obtain, for the first time, the influence of all protonation states of an enzyme on the reaction it catalyzes. Despite exaggerating the ease of reduction of the substrate, these computations confirmed the broad features of the reaction mechanism obtained with the medium-sized models, and afforded valuable insights on the influence of the titratable amino acids on each reaction step. Additional comparisons of the energetic features of the reaction intermediates with those of common biochemical redox intermediates suggest a surprisingly simple explanation for the mechanistic differences between the dark-catalyzed and light-dependent enzyme reaction mechanisms.
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Affiliation(s)
- Pedro J Silva
- REQUIMTE, Faculdade de Ciências da Saúde, Universidade Fernando Pessoa , Rua Carlos da Maia, Porto , Portugal
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17
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Li Y, Shi X, Zhang Q, Hu J, Chen J, Wang W. Computational evidence for the detoxifying mechanism of epsilon class glutathione transferase toward the insecticide DDT. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:5008-5016. [PMID: 24678828 DOI: 10.1021/es405230j] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A combined quantum mechanics/molecular mechanics (QM/MM) computation of the detoxifying mechanism of an epsilon class glutathione transferases (GSTs) toward organochlorine insecticide DDT, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane, has been carried out. The exponential average barrier of the proton transfer mechanism is 15.2 kcal/mol, which is 27.6 kcal/mol lower than that of the GS-DDT conjugant mechanism. It suggests that the detoxifying reaction proceeds via a proton transfer mechanism where GSH acts as a cofactor rather than a conjugate. The study reveals that the protein environment has a strong effect on the reaction barrier. The experimentally proposed residues Arg112, Glu116 and Phe120 were found to have a strong influence on the detoxifying reaction. The influence of residues Pro13, Cys15, His53, Ile55, Glu67, Ser68, Phe115, and Leu119 was detected as well. It is worth noticing that Ile55 facilitates the detoxifying reaction most. On the basis of the structure of DDT, structure 2, (BrC6H4)2CHCCl3, is the best candidate among all the tested structures in resisting the detoxification of enzyme agGSTe2.
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Affiliation(s)
- Yanwei Li
- Environment Research Institute, Shandong University , Jinan 250100, P. R. China
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18
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Abad E, Rommel JB, Kästner J. Reaction mechanism of the bicopper enzyme peptidylglycine α-hydroxylating monooxygenase. J Biol Chem 2014; 289:13726-38. [PMID: 24668808 DOI: 10.1074/jbc.m114.558494] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Peptidylglycine α-hydroxylating monooxygenase is a noninteracting bicopper enzyme that stereospecifically hydroxylates the terminal glycine of small peptides for its later amidation. Neuroendocrine messengers, such as oxytocin, rely on the biological activity of this enzyme. Each catalytic turnover requires one oxygen molecule, two protons from the solvent, and two electrons. Despite this enzyme having been widely studied, a consensus on the reaction mechanism has not yet been found. Experiments and theoretical studies favor a pro-S abstraction of a hydrogen atom followed by the rebinding of an OH group. However, several hydrogen-abstracting species have been postulated; because two protons are consumed during the reaction, several protonation states are available. An electron transfer between the copper atoms could play a crucial role for the catalysis as well. This leads to six possible abstracting species. In this study, we compare them on equal footing. We perform quantum mechanics/molecular mechanics calculations, considering the glycine hydrogen abstraction. Our results suggest that the most likely mechanism is a protonation of the abstracting species before the hydrogen abstraction and another protonation as well as a reduction before OH rebinding.
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Affiliation(s)
- Enrique Abad
- From the Computational Biochemistry Group, Institute of Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Judith B Rommel
- From the Computational Biochemistry Group, Institute of Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Johannes Kästner
- From the Computational Biochemistry Group, Institute of Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
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19
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Román-Meléndez GD, von Glehn P, Harvey JN, Mulholland AJ, Marsh ENG. Role of active site residues in promoting cobalt-carbon bond homolysis in adenosylcobalamin-dependent mutases revealed through experiment and computation. Biochemistry 2014; 53:169-77. [PMID: 24341954 PMCID: PMC3928028 DOI: 10.1021/bi4012644] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Adenosylcobalamin (AdoCbl) serves as a source of reactive free radicals that are generated by homolytic scission of the coenzyme's cobalt-carbon bond. AdoCbl-dependent enzymes accelerate AdoCbl homolysis by ∼10(12)-fold, but the mechanism by which this is accomplished remains unclear. We have combined experimental and computational approaches to gain molecular-level insight into this process for glutamate mutase. Two residues, glutamate 330 and lysine 326, form hydrogen bonds with the adenosyl group of the coenzyme. A series of mutations that impair the enzyme's ability to catalyze coenzyme homolysis and tritium exchange with the substrate by 2-4 orders of magnitude were introduced at these positions. These mutations, together with the wild-type enzyme, were also characterized in silico by molecular dynamics simulations of the enzyme-AdoCbl-substrate complex with AdoCbl modeled in the associated (Co-C bond formed) or dissociated [adenosyl radical with cob(II)alamin] state. The simulations reveal that the number of hydrogen bonds between the adenosyl group and the protein side chains increases in the homolytically dissociated state, with respect to the associated state, for both the wild-type and mutant enzymes. The mutations also cause a progressive increase in the mean distance between the 5'-carbon of the adenosyl radical and the abstractable hydrogen of the substrate. Interestingly, the distance between the 5'-carbon and substrate hydrogen, determined computationally, was found to inversely correlate with the log k for tritium exchange (r = 0.93) determined experimentally. Taken together, these results point to a dual role for these residues: they both stabilize the homolytic state through electrostatic interactions between the protein and the dissociated coenzyme and correctly position the adenosyl radical to facilitate the abstraction of hydrogen from the substrate.
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Affiliation(s)
| | - Patrick von Glehn
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK
| | - Jeremy N. Harvey
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK
| | - Adrian J. Mulholland
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK
| | - E. Neil G. Marsh
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
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20
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Abad E, Zenn RK, Kästner J. Reaction Mechanism of Monoamine Oxidase from QM/MM Calculations. J Phys Chem B 2013; 117:14238-46. [DOI: 10.1021/jp4061522] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Enrique Abad
- Computational Biochemistry
Group, Institute of Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Roland K. Zenn
- Computational Biochemistry
Group, Institute of Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Johannes Kästner
- Computational Biochemistry
Group, Institute of Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
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21
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Zhu W, Liu Y, Zhang R. QM/MM study of the conversion mechanism of lysine to methylornithine catalyzed by methylornithine synthase (PylB). Theor Chem Acc 2013. [DOI: 10.1007/s00214-013-1385-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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22
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Dowling DP, Croft AK, Drennan CL. Radical use of Rossmann and TIM barrel architectures for controlling coenzyme B12 chemistry. Annu Rev Biophys 2013; 41:403-27. [PMID: 22577824 DOI: 10.1146/annurev-biophys-050511-102225] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The ability of enzymes to harness free-radical chemistry allows for some of the most amazing transformations in nature, including reduction of ribonucleotides and carbon skeleton rearrangements. Enzyme cofactors involved in this chemistry can be large and complex, such as adenosylcobalamin (coenzyme B(12)), simpler, such as S-adenosylmethionine and an iron-sulfur cluster (i.e., poor man's B(12)), or very small, such as one nonheme iron atom coordinated by protein ligands. Although the chemistry catalyzed by these enzyme-bound cofactors is unparalleled, it does come at a price. The enzyme must be able to control these radical reactions, preventing unwanted chemistry and protecting the enzyme active site from damage. Here, we consider a set of radical folds: the (β/α)(8) or TIM barrel, combined with a Rossmann domain for coenzyme B(12)-dependent chemistry. Using specific enzyme examples, we consider how nature employs the common TIM barrel fold and its Rossmann domain partner for radical-based chemistry.
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Affiliation(s)
- Daniel P Dowling
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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23
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Jones AR, Levy C, Hay S, Scrutton NS. Relating localized protein motions to the reaction coordinate in coenzyme B12-dependent enzymes. FEBS J 2013; 280:2997-3008. [DOI: 10.1111/febs.12223] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Revised: 02/27/2013] [Accepted: 02/27/2013] [Indexed: 01/27/2023]
Affiliation(s)
| | - Colin Levy
- Manchester Institute of Biotechnology and Faculty of Life Sciences; The University of Manchester; Manchester; UK
| | - Sam Hay
- Manchester Institute of Biotechnology and Faculty of Life Sciences; The University of Manchester; Manchester; UK
| | - Nigel S. Scrutton
- Manchester Institute of Biotechnology and Faculty of Life Sciences; The University of Manchester; Manchester; UK
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24
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Grebner C, Kästner J, Thiel W, Engels B. A New Tabu-Search-Based Algorithm for Solvation of Proteins. J Chem Theory Comput 2012; 9:814-21. [DOI: 10.1021/ct300898d] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Christoph Grebner
- Julius-Maximilians-Universität
Würzburg, Institut für Physikalische und
Theoretische Chemie, Emil-Fischer-Straße 42, D-97074 Würzburg,
Germany
| | - Johannes Kästner
- Universität
Stuttgart,
Institut für Theoretische Chemie, Pfaffenwaldring 55, D-70569
Stuttgart, Germany
| | - Walter Thiel
- Max-Planck-Institut
für
Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an
der Ruhr, Germany
| | - Bernd Engels
- Julius-Maximilians-Universität
Würzburg, Institut für Physikalische und
Theoretische Chemie, Emil-Fischer-Straße 42, D-97074 Würzburg,
Germany
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25
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Rommel JB, Liu Y, Werner HJ, Kästner J. Role of tunneling in the enzyme glutamate mutase. J Phys Chem B 2012; 116:13682-9. [PMID: 23127187 DOI: 10.1021/jp308526t] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The role of quantum mechanical atom tunneling during the conversion of glutamate to methylaspartate catalyzed by glutamate mutase is investigated by quantum mechanical/molecular mechanical (QM/MM) simulations based on coupled cluster and density functional calculations. The use of instanton theory allows us to calculate the tunneling contributions of up to 78 atoms in the active site. We calculate kinetic isotope effects (KIEs) and compare them to experimental data. The simulations lead to deuterium KIEs of 10 for the hydrogen abstraction from glutamate substrate and 16 for the hydrogen abstraction from methylaspartate substrate, which are consistent with the experimental results. The hydrogen abstraction from methylaspartate has higher primary deuterium and tritium (46.1) KIEs than the abstraction from glutamate. The tunneling effect increases the reaction rate by a factor of 12.3 for the hydrogen abstraction from methylaspartate at 0. Tunneling is supported by the environment by preparing the enzyme through classical motions. Consideraton of the tunneling contributions of more and more atoms around the active center shows that the motions at the ribose ring play a central role during the tunneling enhancement of the hydrogen transfers. Our simulations give new insight into the catalytic process in glutamate mutase and the way enzymes use tunneling effects for a successful catalysis.
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Affiliation(s)
- Judith B Rommel
- Institute of Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
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26
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Friedrich P, Baisch U, Harrington RW, Lyatuu F, Zhou K, Zelder F, McFarlane W, Buckel W, Golding BT. Experimental study of hydrogen bonding potentially stabilizing the 5'-deoxyadenosyl radical from coenzyme B12. Chemistry 2012; 18:16114-22. [PMID: 23080006 DOI: 10.1002/chem.201201840] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Revised: 08/21/2012] [Indexed: 01/28/2023]
Abstract
Coenzyme B(12) can assist radical enzymes that accomplish the vicinal interchange of a hydrogen atom with a functional group. It has been proposed that the Co-C bond homolysis of coenzyme B(12) to cob(II)alamin and the 5'-deoxyadenosyl radical is aided by hydrogen bonding of the corrin C19-H to the 3'-O of the ribose moiety of the incipient 5'-deoxyadenosyl radical, which is stabilized by 30 kJ mol(-1) (B. Durbeej et al., Chem. Eur. J. 2009, 15, 8578-8585). The diastereoisomers (R)- and (S)-2,3-dihydroxypropylcobalamin were used as models for coenzyme B(12). A downfield shift of the NMR signal for the C19-H proton was observed for the (R)-isomer (δ=4.45 versus 4.01 ppm for the (S)-isomer) and can be ascribed to an intramolecular hydrogen bond between the C19-H and the oxygen of CHOH. Crystal structures of (R)- and (S)-2,3-dihydroxypropylcobalamin showed C19-H⋅⋅⋅O distances of 3.214(7) Å (R-isomer) and 3.281(11) Å (S-isomer), which suggest weak hydrogen-bond interactions (-ΔG<6 kJ mol(-1)) between the CHOH of the dihydroxypropyl ligand and the C19-H. Exchange of the C19-H, which is dependent on the cobalt redox state, was investigated with cob(I)alamin, cob(II)alamin, and cob(III)alamin by using NMR spectroscopy to monitor the uptake of deuterium from deuterated water in the pH range 3-11. No exchange was found for any of the cobalt oxidation states. 3',5'-Dideoxyadenosylcobalamin, but not the 2',5'-isomer, was found to act as a coenzyme for glutamate mutase, with a 15-fold lower k(cat)/K(M) than 5'-deoxyadenosylcobalamin. This indicates that stabilization of the 5'-deoxyadenosyl radical by a hydrogen bond that involves the C19-H and the 3'-OH group of the cofactor is, at most, 7 kJ mol(-1) (-ΔG). Examination of the crystal structure of glutamate mutase revealed additional stabilizing factors: hydrogen bonds between both the 2'-OH and 3'-OH groups and glutamate 330. The actual strength of a hydrogen bond between the C19-H and the 3'-O of the ribose moiety of the 5'-deoxyadenosyl group is concluded not to exceed 6 kJ mol(-1) (-ΔG).
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Affiliation(s)
- Peter Friedrich
- School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
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27
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Adenosylcobalamin enzymes: theory and experiment begin to converge. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1824:1154-64. [PMID: 22516318 DOI: 10.1016/j.bbapap.2012.03.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 02/04/2012] [Accepted: 03/27/2012] [Indexed: 11/21/2022]
Abstract
Adenosylcobalamin (coenzyme B(12)) serves as the cofactor for a group of enzymes that catalyze unusual rearrangement or elimination reactions. The role of the cofactor as the initiator of reactive free radicals needed for these reactions is well established. Less clear is how these enzymes activate the coenzyme towards homolysis and control the radicals once generated. The availability of high resolution X-ray structures combined with detailed kinetic and spectroscopic analyses have allowed several adenosylcobalamin enzymes to be computationally modeled in some detail. Computer simulations have generally obtained good agreement with experimental data and provided valuable insight into the mechanisms of these unusual reactions. Importantly, atomistic modeling of the enzymes has allowed the role of specific interactions between protein, substrate and coenzyme to be explored, leading to mechanistic predictions that can now be tested experimentally. This article is part of a Special Issue entitled: Radical SAM enzymes and Radical Enzymology.
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28
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Reig AJ, Conrad KS, Brunold TC. Combined spectroscopic/computational studies of vitamin B12 precursors: geometric and electronic structures of cobinamides. Inorg Chem 2012; 51:2867-79. [PMID: 22332807 DOI: 10.1021/ic202052g] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Vitamin B(12) (cyanocobalamin) and its biologically active derivatives, methylcobalamin and adenosylcobalamin, are members of the family of corrinoids, which also includes cobinamides. As biological precursors to cobalamins, cobinamides possess the same structural core, consisting of a low-spin Co(3+) ion that is ligated equatorially by the four nitrogens of a highly substituted tetrapyrrole macrocycle (the corrin ring), but differ with respect to the lower axial ligation. Specifically, cobinamides possess a water molecule instead of the nucleotide loop that coordinates axially to Co(3+)cobalamins via its dimethylbenzimidazole (DMB) base. Compared to the cobalamin species, cobinamides have proven much more difficult to study experimentally, thus far eluding characterization by X-ray crystallography. In this study, we have utilized combined quantum mechanics/molecular mechanics (QM/MM) computations to generate complete structural models of a representative set of cobinamide species with varying upper axial ligands. To validate the use of this approach, analogous QM/MM geometry optimizations were carried out on entire models of the cobalamin counterparts for which high-resolution X-ray structural data are available. The accuracy of the cobinamide structures was assessed further by comparing electronic absorption spectra computed using time-dependent density functional theory to those obtained experimentally. Collectively, the results obtained in this study indicate that the DMB → H(2)O lower axial ligand switch primarily affects the energies of the Co 3d(z(2))-based molecular orbital (MO) and, to a lesser extent, the other Co 3d-based MOs as well as the corrin π-based highest energy MO. Thus, while the energy of the lowest-energy electronic transition of cobalamins changes considerably as a function of the upper axial ligand, it is nearly invariant for the cobinamides.
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Affiliation(s)
- Amanda J Reig
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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29
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Quitterer F, List A, Eisenreich W, Bacher A, Groll M. Kristallstruktur der Methylornithin-Synthase (PylB): Einblicke in die Biosynthese von Pyrrolysin. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201106765] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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30
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Quitterer F, List A, Eisenreich W, Bacher A, Groll M. Crystal structure of methylornithine synthase (PylB): insights into the pyrrolysine biosynthesis. Angew Chem Int Ed Engl 2011; 51:1339-42. [PMID: 22095926 DOI: 10.1002/anie.201106765] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Indexed: 11/08/2022]
Affiliation(s)
- Felix Quitterer
- Center for Integrated Protein Science at the Department Chemie, Lehrstuhl für Biochemie, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
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