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Uranga J, Rabe von Pappenheim F, Tittmann K, Mata RA. Dynamic Protonation States Underlie Carbene Formation in ThDP-Dependent Enzymes: A Theoretical Study. J Phys Chem B 2023; 127. [PMID: 37748048 PMCID: PMC10688766 DOI: 10.1021/acs.jpcb.3c03137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 09/09/2023] [Indexed: 09/27/2023]
Abstract
The activation mechanism of thiamine diphosphate (ThDP) in enzymes has long been the subject of intense research and controversial discussion. Particularly contentious is the formation of a carbene intermediate, the first one observed in an enzyme. For the formation of the carbene to take place, both intramolecular and intermolecular proton transfer pathways have been proposed. However, the physiologically relevant pH of ThDP-dependent enzymes around neutrality does not seem to be suitable for the formation of such reactive chemical species. Herein, we investigate the general mechanism of activation of the ThDP cofactor in human transketolase (TKT), by means of electronic structure methods. We show that in the case of the human TKT, the carbene species is accessible through a pKa shift induced by the electrostatics of a neighboring histidine residue (H110), whose protonation state change modulates the pKa of ThDP and suppresses the latter by more than 6 pH units. Our findings highlight that ThDP enzymes activate the cofactor beyond simple geometric constraints and the canonical glutamate. Such observations in nature can pave the way for the design of biomimetic carbene catalysts and the engineering of tailored enzymatic carbenes.
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Affiliation(s)
- Jon Uranga
- Institute
of Physical Chemistry, Georg-August Universität
Göttingen, Tammannstraße 6, 37077 Göttingen, Germany
| | - Fabian Rabe von Pappenheim
- Department
of Molecular Enzymology, Göttingen Center of Molecular Biosciences, Georg-August Universität Göttingen, Julia-Lermonotowa-Weg 3, D-37077 Göttingen, Germany
| | - Kai Tittmann
- Department
of Molecular Enzymology, Göttingen Center of Molecular Biosciences, Georg-August Universität Göttingen, Julia-Lermonotowa-Weg 3, D-37077 Göttingen, Germany
- Department
of Physical Biochemistry, Max-Planck-Institute
for Multidisciplinary Natural Sciences, Am Faßberg 11, D-37077 Göttingen, Germany
| | - Ricardo A. Mata
- Institute
of Physical Chemistry, Georg-August Universität
Göttingen, Tammannstraße 6, 37077 Göttingen, Germany
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2
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Solovjeva ON. New Role of Water in Transketolase Catalysis. Int J Mol Sci 2023; 24:ijms24032068. [PMID: 36768400 PMCID: PMC9917271 DOI: 10.3390/ijms24032068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Revised: 01/13/2023] [Accepted: 01/16/2023] [Indexed: 01/21/2023] Open
Abstract
Transketolase catalyzes the interconversion of keto and aldo sugars. Its coenzyme is thiamine diphosphate. The binding of keto sugar with thiamine diphosphate is possible only after C2 deprotonation of its thiazole ring. It is believed that deprotonation occurs due to the direct transfer of a proton to the amino group of its aminopyrimidine ring. Using mass spectrometry, it is shown that a water molecule is directly involved in the deprotonation process. After the binding of thiamine diphosphate with transketolase and its subsequent cleavage, a thiamine diphosphate molecule is formed with a mass increased by one oxygen molecule. After fragmentation, a thiamine diphosphate molecule is formed with a mass reduced by one and two hydrogen atoms, that is, HO and H2O are split off. Based on these data, it is assumed that after the formation of holotransketolase, water is covalently bound to thiamine diphosphate, and carbanion is formed as a result of its elimination. This may be a common mechanism for other thiamine enzymes. The participation of a water molecule in the catalysis of the one-substrate transketolase reaction and a possible reason for the effect of the acceptor substrate on the affinity of the donor substrate for active sites are also shown.
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Affiliation(s)
- Olga N Solovjeva
- Belozersky Institute of Physico-Chemical Biology, Moscow State University, 119234 Moscow, Russia
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3
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Nauton L, Hecquet L, Théry V. QM/MM Study of Human Transketolase: Thiamine Diphosphate Activation Mechanism and Complete Catalytic Cycle. J Chem Inf Model 2021; 61:3502-3515. [PMID: 34161071 DOI: 10.1021/acs.jcim.1c00190] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A computational model for human transketolase was proposed, showing that thiamine diphosphate activation was based on His110 in place of His481 reported in yeast transketolase. In addition, a complete catalytic reaction pathway was investigated using d-xylulose-5-phosphate and d-ribose-5-phosphate as substrates, showing at every step a perfect superimposition of our model with high-resolution crystallographic structures 3MOS, 4KXV, and 4KXX. This study shows that H2N4' of the active thiamine diphosphate "V form" no longer has a self-activating role but allows self-stabilization of the cofactor and of the Breslow intermediate. These advances in our knowledge of the human transketolase mechanism offer interesting prospects for the design of new drugs, this enzyme being involved in several diseases, and for a better understanding of the reactions catalyzed by transketolases from other sources.
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Affiliation(s)
- Lionel Nauton
- Université Clermont Auvergne, CNRS, Clermont Auvergne INP, ICCF, F-63000 Clermont-Ferrand, France
| | - Laurence Hecquet
- Université Clermont Auvergne, CNRS, Clermont Auvergne INP, ICCF, F-63000 Clermont-Ferrand, France
| | - Vincent Théry
- Université Clermont Auvergne, CNRS, Clermont Auvergne INP, ICCF, F-63000 Clermont-Ferrand, France
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4
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Medina FE, Prejanò M. Water Molecules Allow the Intramolecular Activation of the Thiamine Di-Phosphate Cofactor in Human Transketolase: Mechanistic Insights into a Famous Proposal. ACS Catal 2021. [DOI: 10.1021/acscatal.0c05414] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Fabiola E. Medina
- Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Universidad Andres Bello, Autopista Concepción-Talcahuano, Talcahuano 7100, Chile
| | - Mario Prejanò
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm SE-10691, Sweden
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Planas F, McLeish MJ, Himo F. Computational characterization of enzyme-bound thiamin diphosphate reveals a surprisingly stable tricyclic state: implications for catalysis. Beilstein J Org Chem 2019; 15:145-159. [PMID: 30745990 PMCID: PMC6350894 DOI: 10.3762/bjoc.15.15] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 12/10/2018] [Indexed: 12/05/2022] Open
Abstract
Thiamin diphosphate (ThDP)-dependent enzymes constitute a large class of enzymes that catalyze a diverse range of reactions. Many are involved in stereospecific carbon–carbon bond formation and, consequently, have found increasing interest and utility as chiral catalysts in various biocatalytic applications. All ThDP-catalyzed reactions require the reaction of the ThDP ylide (the activated state of the cofactor) with the substrate. Given that the cofactor can adopt up to seven states on an enzyme, identifying the factors affecting the stability of the pre-reactant states is important for the overall understanding of the kinetics and mechanism of the individual reactions. In this paper we use density functional theory calculations to systematically study the different cofactor states in terms of energies and geometries. Benzoylformate decarboxylase (BFDC), which is a well characterized chiral catalyst, serves as the prototypical ThDP-dependent enzyme. A model of the active site was constructed on the basis of available crystal structures, and the cofactor states were characterized in the presence of three different ligands (crystallographic water, benzoylformate as substrate, and (R)-mandelate as inhibitor). Overall, the calculations reveal that the relative stabilities of the cofactor states are greatly affected by the presence and identity of the bound ligands. A surprising finding is that benzoylformate binding, while favoring ylide formation, provided even greater stabilization to a catalytically inactive tricyclic state. Conversely, the inhibitor binding greatly destabilized the ylide formation. Together, these observations have significant implications for the reaction kinetics of the ThDP-dependent enzymes, and, potentially, for the use of unnatural substrates in such reactions.
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Affiliation(s)
- Ferran Planas
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden
| | - Michael J McLeish
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, Indianapolis IN 46202, USA
| | - Fahmi Himo
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden
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Thiamine Deficiency and Neurodegeneration: the Interplay Among Oxidative Stress, Endoplasmic Reticulum Stress, and Autophagy. Mol Neurobiol 2016; 54:5440-5448. [PMID: 27596507 DOI: 10.1007/s12035-016-0079-9] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 08/23/2016] [Indexed: 12/12/2022]
Abstract
Thiamine (vitamin B1) is an essential nutrient and indispensable for normal growth and development of the organism due to its multilateral participation in key biochemical and physiological processes. Humans must obtain thiamine from their diet since it is synthesized only in bacteria, fungi, and plants. Thiamine deficiency (TD) can result from inadequate intake, increased requirement, excessive deletion, and chronic alcohol consumption. TD affects multiple organ systems, including the cardiovascular, muscular, gastrointestinal, and central and peripheral nervous systems. In the brain, TD causes a cascade of events including mild impairment of oxidative metabolism, neuroinflammation, and neurodegeneration, which are commonly observed in neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). Thiamine metabolites may serve as promising biomarkers for neurodegenerative diseases, and thiamine supplementations exhibit therapeutic potential for patients of some neurodegenerative diseases. Experimental TD has been used to model aging-related neurodegenerative diseases. However, to date, the cellular and molecular mechanisms underlying TD-induced neurodegeneration are not clear. Recent research evidence indicates that TD causes oxidative stress, endoplasmic reticulum (ER) stress, and autophagy in the brain, which are known to contribute to the pathogenesis of various neurodegenerative diseases. In this review, we discuss the role of oxidative stress, ER stress, and autophagy in TD-mediated neurodegeneration. We propose that it is the interplay of oxidative stress, ER stress, and autophagy that contributes to TD-mediated neurodegeneration.
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Nauton L, Hélaine V, Théry V, Hecquet L. Insights into the Thiamine Diphosphate Enzyme Activation Mechanism: Computational Model for Transketolase Using a Quantum Mechanical/Molecular Mechanical Method. Biochemistry 2016; 55:2144-52. [PMID: 26998737 DOI: 10.1021/acs.biochem.5b00787] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We propose the first computational model for transketolase (TK), a thiamine diphosphate (ThDP)-dependent enzyme, using a quantum mechanical/molecular mechanical method on the basis of crystallographic TK structures from yeast and Escherichia coli, together with experimental kinetic data reported in the literature with wild-type and mutant TK. This model allowed us to define a new route for ThDP activation in the enzyme environment. We evidenced a strong interaction between ThDP and Glu418B of the TK active site, itself stabilized by Glu162A. The crucial point highlighted here is that deprotonation of ThDP C2 is not performed by ThDP N4' as reported in the literature, but by His481B, involving a HOH688A molecule bridge. Thus, ThDP N4' is converted from an amino form to an iminium form, ensuring the stabilization of the C2 carbanion or carbene. Finally, ThDP activation proceeds via an intermolecular process and not by an intramolecular one as reported in the literature. More generally, this proposed ThDP activation mechanism can be applied to some other ThDP-dependent enzymes and used to define the entire TK mechanism with donor and acceptor substrates more accurately.
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Affiliation(s)
- Lionel Nauton
- Université Clermont Auvergne, Université Blaise-Pascal , Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand, France.,CNRS , UMR 6296, ICCF, F-63178 Aubiere, France
| | - Virgil Hélaine
- Université Clermont Auvergne, Université Blaise-Pascal , Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand, France.,CNRS , UMR 6296, ICCF, F-63178 Aubiere, France
| | - Vincent Théry
- Université Clermont Auvergne, Université Blaise-Pascal , Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand, France.,CNRS , UMR 6296, ICCF, F-63178 Aubiere, France
| | - Laurence Hecquet
- Université Clermont Auvergne, Université Blaise-Pascal , Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand, France.,CNRS , UMR 6296, ICCF, F-63178 Aubiere, France
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8
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Electron density reactivity indexes of the tautomeric/ionization forms of thiamin diphosphate. J Mol Model 2013; 19:3799-803. [PMID: 23793740 DOI: 10.1007/s00894-013-1908-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 06/03/2013] [Indexed: 10/26/2022]
Abstract
The generation of the highly reactive ylide in thiamin diphosphate catalysis is analyzed in terms of the nucleophilicity of key atoms, by means of density functional calculations at X3LYP/6-31++G(d,p) level of theory. The Fukui functions of all tautomeric/ionization forms are calculated in order to assess their reactivity. The results allow to conclude that the highly conserved glutamic residue does not protonate the N1' atom of the pyrimidyl ring, but it participates in a strong hydrogen bonding, stabilizing the eventual negative charge on the nitrogen, in all forms involved in the ylide generation. This condition provides the necessary reactivity on key atoms, N4' and C2, to carry out the formation of the ylide required to initiate the catalytic cycle of ThDP-dependent enzymes. This study represents a new approach for the ylide formation in ThDP catalysis.
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9
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Karton A, O’Reilly RJ, Radom L. Assessment of Theoretical Procedures for Calculating Barrier Heights for a Diverse Set of Water-Catalyzed Proton-Transfer Reactions. J Phys Chem A 2012; 116:4211-21. [DOI: 10.1021/jp301499y] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Amir Karton
- School of
Chemistry and ARC Centre of Excellence for
Free Radical Chemistry and Biotechnology, University of Sydney, Sydney, NSW 2006, Australia
| | - Robert J. O’Reilly
- School of
Chemistry and ARC Centre of Excellence for
Free Radical Chemistry and Biotechnology, University of Sydney, Sydney, NSW 2006, Australia
| | - Leo Radom
- School of
Chemistry and ARC Centre of Excellence for
Free Radical Chemistry and Biotechnology, University of Sydney, Sydney, NSW 2006, Australia
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10
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Delgado EJ, Alderete JB, Jaña GA. Density-functional study on the equilibria in the ThDP activation. J Mol Model 2011; 17:2735-9. [DOI: 10.1007/s00894-011-1076-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Accepted: 03/28/2011] [Indexed: 10/18/2022]
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11
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Jaña G, Jiménez V, Villà-Freixa J, Prat-Resina X, Delgado E, Alderete J. Computational study on the carboligation reaction of acetohidroxyacid synthase: new approach on the role of the HEThDP- intermediate. Proteins 2010; 78:1774-88. [PMID: 20225259 DOI: 10.1002/prot.22693] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Acetohydroxyacid synthase (AHAS) is a thiamin diphosphate dependent enzyme that catalyses the decarboxylation of pyruvate to yield the hydroxyethyl-thiamin diphosphate (ThDP) anion/enamine intermediate (HEThDP(-)). This intermediate reacts with a second ketoacid to form acetolactate or acetohydroxybutyrate as products. Whereas the mechanism involved in the formation of HEThDP(-) from pyruvate is well understood, the role of the enzyme in controlling the carboligation reaction of HEThDP(-) has not been determined yet. In this work, molecular dynamics (MD) simulations were employed to identify the aminoacids involved in the carboligation stage. These MD studies were carried out over the catalytic subunit of yeast AHAS containing the reaction intermediate (HEThDP(-)) and a second pyruvate molecule. Our results suggest that additional acid-base ionizable groups are not required to promote the catalytic cycle, in contrast with earlier proposals. This finding leads us to postulate that the formation of acetolactate relies on the acid-base properties of the HEThDP(-) intermediate itself. PM3 semiempirical calculations were employed to obtain the energy profile of the proposed mechanism on a reduced model of the active site. These calculations confirm the role of HEThDP(-) intermediate as the ionizable group that promotes the carboligation and product formation steps of the catalytic cycle.
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Affiliation(s)
- Gonzalo Jaña
- Grupo de Química Teórica y Computacional, Facultad de Ciencias Químicas, Universidad de Concepción, Casilla 160-C, Concepción, Chile
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12
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Jaramillo P, Coutinho K, Canuto S. Solvent Effects in Chemical Processes. Water-Assisted Proton Transfer Reaction of Pterin in Aqueous Environment. J Phys Chem A 2009; 113:12485-95. [DOI: 10.1021/jp903638n] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Paula Jaramillo
- Instituto de Física, Universidade de São Paulo, CP 66318, 05314-970, São Paulo, SP, Brazil
| | - Kaline Coutinho
- Instituto de Física, Universidade de São Paulo, CP 66318, 05314-970, São Paulo, SP, Brazil
| | - Sylvio Canuto
- Instituto de Física, Universidade de São Paulo, CP 66318, 05314-970, São Paulo, SP, Brazil
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