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Quan Z, Ohmiya Y, Liu YJ. Chemical Mechanism of Fireworm Bioluminescence - A Theoretical Proposition. J Phys Chem A 2023; 127:10851-10859. [PMID: 38103213 DOI: 10.1021/acs.jpca.3c07409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Odontosyllis undecimdonta is a marine worm, commonly known as a fireworm, that exhibits bluish-green bioluminescence (BL). The luciferin (L) and oxyluciferin (OL) during fireworm BL have been experimentally identified in vitro. The L and OL are the respective starting point and ending point of a series of complicated chemical reactions in the BL. However, the chemical mechanism of the fireworm BL remains largely unknown. Before the experiments provided strong evidence for the mechanism, based on our previously successful studies on several bioluminescent systems, we theoretically proposed the chemical mechanism of the fireworm BL in this article. By means of the spin-flip and time-dependent density functional calculations, we clearly described the complete process from L to OL: under the catalysis of luciferase, L undergoes deprotonation and reacts with 3O2 to form a dioxetanone anion via the single-electron transfer mechanism; the dioxetanone anion decomposes into the OL at the first singlet excited state (S1) by the gradually reversible charge-transfer-induced luminescence mechanism; and the S1-OL emits light and deexcites to OL in the ground state.
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Affiliation(s)
- Zhuo Quan
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Yoshihiro Ohmiya
- Osaka Institute of Technology (OIT), 5-16-1 Ohmiya, Asahi-ku, Osaka 535-8585, Japan
| | - Ya-Jun Liu
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
- Center for Advanced Materials Research, Beijing Normal University, Zhuhai 519087, China
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2
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Bui S, Gil-Guerrero S, van der Linden P, Carpentier P, Ceccarelli M, Jambrina PG, Steiner RA. Evolutionary adaptation from hydrolytic to oxygenolytic catalysis at the α/β-hydrolase fold. Chem Sci 2023; 14:10547-10560. [PMID: 37799987 PMCID: PMC10548524 DOI: 10.1039/d3sc03044j] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 08/31/2023] [Indexed: 10/07/2023] Open
Abstract
Protein fold adaptation to novel enzymatic reactions is a fundamental evolutionary process. Cofactor-independent oxygenases degrading N-heteroaromatic substrates belong to the α/β-hydrolase (ABH) fold superfamily that typically does not catalyze oxygenation reactions. Here, we have integrated crystallographic analyses under normoxic and hyperoxic conditions with molecular dynamics and quantum mechanical calculations to investigate its prototypic 1-H-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase (HOD) member. O2 localization to the "oxyanion hole", where catalysis occurs, is an unfavorable event and the direct competition between dioxygen and water for this site is modulated by the "nucleophilic elbow" residue. A hydrophobic pocket that overlaps with the organic substrate binding site can act as a proximal dioxygen reservoir. Freeze-trap pressurization allowed the structure of the ternary complex with a substrate analogue and O2 bound at the oxyanion hole to be determined. Theoretical calculations reveal that O2 orientation is coupled to the charge of the bound organic ligand. When 1-H-3-hydroxy-4-oxoquinaldine is uncharged, O2 binds with its molecular axis along the ligand's C2-C4 direction in full agreement with the crystal structure. Substrate activation triggered by deprotonation of its 3-OH group by the His-Asp dyad, rotates O2 by approximately 60°. This geometry maximizes the charge transfer between the substrate and O2, thus weakening the double bond of the latter. Electron density transfer to the O2(π*) orbital promotes the formation of the peroxide intermediate via intersystem crossing that is rate-determining. Our work provides a detailed picture of how evolution has repurposed the ABH-fold architecture and its simple catalytic machinery to accomplish metal-independent oxygenation.
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Affiliation(s)
- Soi Bui
- Randall Centre for Cell and Molecular Biophysics, King's College London London SE1 1UL UK
| | - Sara Gil-Guerrero
- Departamento de Química Física, University of Salamanca Salamanca 37008 Spain
| | - Peter van der Linden
- European Synchrotron Radiation Facility (ESRF), Partnership for Soft Condensed Matter (PSCM) 71 Avenue des Martyrs Grenoble 38000 France
| | - Philippe Carpentier
- European Synchrotron Radiation Facility (ESRF) 71 Avenue des Martyrs 38043 Grenoble France
- Université Grenoble Alpes, CNRS, CEA, Interdisciplinary Research Institute of Grenoble (IRIG), Laboratoire Chimie et Biologie des Métaux (LCBM) UMR 5249 17 Avenue des Martyrs 38054 Grenoble France
| | - Matteo Ceccarelli
- Department of Physics, University of Cagliari Monserrato 09042 Italy
- IOM-CNR Unità di Cagliari, Cittadella Universitaria Monserrato 09042 Italy
| | - Pablo G Jambrina
- Departamento de Química Física, University of Salamanca Salamanca 37008 Spain
| | - Roberto A Steiner
- Randall Centre for Cell and Molecular Biophysics, King's College London London SE1 1UL UK
- Department of Biomedical Sciences, University of Padova Italy
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3
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Zhang QY, Li X, Luo J, Li X, Song J, Wei D. Cofactor-Free Dioxygenases-Catalyzed Reaction Pathway via Proton-Coupled Electron Transfer. J Phys Chem B 2023; 127:95-103. [PMID: 36525303 DOI: 10.1021/acs.jpcb.2c03161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Understanding the general mechanism of the metal-free and cofactor-free oxidases and oxygenases catalyzed activation of triplet O2 is one of the most challenging questions in the field of enzymatic catalysis. Herein, we have performed Quantum Mechanics/Molecular Mechanics (QM/MM) multiscale simulations to reveal the detailed mechanism of the HOD catalyzed (i.e., 1-H-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase from Arthrobacter nitroguajacolicus Rü61a) decomposition of N-heteroaromatic compounds. The complete catalytic mechanism includes four steps: (1) proton transfer from 1-H-3-hydroxy-4-oxoquinaldine (QND) substrate to His251 residue coupled with an electron transfer from QND to triplet O2 (i.e., PCET), (2) formation of C-O bond via an open-shell singlet diradical recombination pathway, (3) ring-closure to form a bicyclic ring, and (4) dissociation of CO. The dissociation of CO is determined as the rate-limiting step, and its calculated energy barrier of 14.9 kcal/mol is consistent with the 15.5 kcal/mol barrier derived from experimental kinetic data. The mechanistic profile is not only valuable for understanding the fundamental pathway of cofactor-free oxidases and oxygenases-catalyzed reactions involving the triplet O2 activation but also discloses a new pathway that undergoes the processes of PCET and open-shell singlet transition state.
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Affiliation(s)
- Qiao-Yu Zhang
- Green Catalysis Center, and College of Chemistry, Zhengzhou University, 100 Science Avenue, Zhengzhou, Henan450001, China
| | - Xing Li
- Department of Traditional Chinese Medicine, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong510280, China
| | - Jing Luo
- Green Catalysis Center, and College of Chemistry, Zhengzhou University, 100 Science Avenue, Zhengzhou, Henan450001, China
| | - Xue Li
- Key Laboratory for Special Functional Materials of Ministry of Education, School of Materials and Engineering, Henan University, Kaifeng475001, China
| | - Jinshuai Song
- Green Catalysis Center, and College of Chemistry, Zhengzhou University, 100 Science Avenue, Zhengzhou, Henan450001, China
| | - Donghui Wei
- Green Catalysis Center, and College of Chemistry, Zhengzhou University, 100 Science Avenue, Zhengzhou, Henan450001, China
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4
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Wang MY, Liu YJ. Chemistry in Fungal Bioluminescence: A Theoretical Study from Luciferin to Light Emission. J Org Chem 2021; 86:1874-1881. [DOI: 10.1021/acs.joc.0c02788] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Ming-Yu Wang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ya-Jun Liu
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
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Ellis ES, MacHale LT, Szilagyi RK, DuBois JL. How Chemical Environment Activates Anthralin and Molecular Oxygen for Direct Reaction. J Org Chem 2020; 85:1315-1321. [PMID: 31830417 DOI: 10.1021/acs.joc.9b03133] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The role of the chemical environment in promoting anthralin/O2 reactions was discovered using neat solvents to model the amino acids of a cofactor-independent oxygenase. Experimental and computational results highlight the importance of the substrate-enolate, which is accessed via energetically small, escalating steps in which the ground-state keto-isomer is tautomerized to an enol and then ionized by solvent. The resulting ion-pair is poised for spontaneous electron transfer to O2. Similar activation may be exploited in biological/nonbiological oxidations involving O2.
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Affiliation(s)
- Emerald S Ellis
- Department of Chemistry and Biochemistry , Montana State University , P.O. Box 173400, Bozeman , Montana 59717 , United States
| | - Luke T MacHale
- Department of Chemistry and Biochemistry , Montana State University , P.O. Box 173400, Bozeman , Montana 59717 , United States
| | - Robert K Szilagyi
- Department of Chemistry and Biochemistry , Montana State University , P.O. Box 173400, Bozeman , Montana 59717 , United States
| | - Jennifer L DuBois
- Department of Chemistry and Biochemistry , Montana State University , P.O. Box 173400, Bozeman , Montana 59717 , United States
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6
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Minaev B. How cofactor-free oxygenases can overcome spin prohibition in substrates oxygenation by dioxygen. Chem Phys 2019. [DOI: 10.1016/j.chemphys.2019.01.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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7
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Quesne MG, Silveri F, de Leeuw NH, Catlow CRA. Advances in Sustainable Catalysis: A Computational Perspective. Front Chem 2019; 7:182. [PMID: 31032245 PMCID: PMC6473102 DOI: 10.3389/fchem.2019.00182] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 03/07/2019] [Indexed: 11/13/2022] Open
Abstract
The enormous challenge of moving our societies to a more sustainable future offers several exciting opportunities for computational chemists. The first principles approach to "catalysis by design" will enable new and much greener chemical routes to produce vital fuels and fine chemicals. This prospective outlines a wide variety of case studies to underscore how the use of theoretical techniques, from QM/MM to unrestricted DFT and periodic boundary conditions, can be applied to biocatalysis and to both homogeneous and heterogenous catalysts of all sizes and morphologies to provide invaluable insights into the reaction mechanisms they catalyze.
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Affiliation(s)
- Matthew G Quesne
- School of Chemistry, Cardiff University, Cardiff, United Kingdom
| | - Fabrizio Silveri
- School of Chemistry, Cardiff University, Cardiff, United Kingdom
| | - Nora H de Leeuw
- School of Chemistry, Cardiff University, Cardiff, United Kingdom
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8
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Spin-orbit coupling effects in O(2) activation by cofactor-independent 2,4-dioxygenase. UKRAINIAN BIOCHEMICAL JOURNAL 2019. [DOI: 10.15407/ubj91.01.038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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9
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Cantú Reinhard FG, DuBois JL, de Visser SP. Catalytic Mechanism of Nogalamycin Monoxygenase: How Does Nature Synthesize Antibiotics without a Metal Cofactor? J Phys Chem B 2018; 122:10841-10854. [DOI: 10.1021/acs.jpcb.8b09648] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Fabián G. Cantú Reinhard
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
| | - Jennifer L. DuBois
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59715-3400, United States
| | - Sam P. de Visser
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
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10
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A Comparative Review on the Catalytic Mechanism of Nonheme Iron Hydroxylases and Halogenases. Catalysts 2018. [DOI: 10.3390/catal8080314] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Enzymatic halogenation and haloperoxidation are unusual processes in biology; however, a range of halogenases and haloperoxidases exist that are able to transfer an aliphatic or aromatic C–H bond into C–Cl/C–Br. Haloperoxidases utilize hydrogen peroxide, and in a reaction with halides (Cl−/Br−), they react to form hypohalides (OCl−/OBr−) that subsequently react with substrate by halide transfer. There are three types of haloperoxidases, namely the iron-heme, nonheme vanadium, and flavin-dependent haloperoxidases that are reviewed here. In addition, there are the nonheme iron halogenases that show structural and functional similarity to the nonheme iron hydroxylases and form an iron(IV)-oxo active species from a reaction of molecular oxygen with α-ketoglutarate on an iron(II) center. They subsequently transfer a halide (Cl−/Br−) to an aliphatic C–H bond. We review the mechanism and function of nonheme iron halogenases and hydroxylases and show recent computational modelling studies of our group on the hectochlorin biosynthesis enzyme and prolyl-4-hydroxylase as examples of nonheme iron halogenases and hydroxylases. These studies have established the catalytic mechanism of these enzymes and show the importance of substrate and oxidant positioning on the stereo-, chemo- and regioselectivity of the reaction that takes place.
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11
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Postils V, Saint-André M, Timmins A, Li XX, Wang Y, Luis JM, Solà M, de Visser SP. Quantum Mechanics/Molecular Mechanics Studies on the Relative Reactivities of Compound I and II in Cytochrome P450 Enzymes. Int J Mol Sci 2018; 19:E1974. [PMID: 29986417 PMCID: PMC6073316 DOI: 10.3390/ijms19071974] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 06/28/2018] [Accepted: 07/02/2018] [Indexed: 02/03/2023] Open
Abstract
The cytochromes P450 are drug metabolizing enzymes in the body that typically react with substrates through a monoxygenation reaction. During the catalytic cycle two reduction and protonation steps generate a high-valent iron (IV)-oxo heme cation radical species called Compound I. However, with sufficient reduction equivalents present, the catalytic cycle should be able to continue to the reduced species of Compound I, called Compound II, rather than a reaction of Compound I with substrate. In particular, since electron transfer is usually on faster timescales than atom transfer, we considered this process feasible and decided to investigate the reaction computationally. In this work we present a computational study using density functional theory methods on active site model complexes alongside quantum mechanics/molecular mechanics calculations on full enzyme structures of cytochrome P450 enzymes. Specifically, we focus on the relative reactivity of Compound I and II with a model substrate for O⁻H bond activation. We show that generally the barrier heights for hydrogen atom abstraction are higher in energy for Compound II than Compound I for O⁻H bond activation. Nevertheless, for the activation of such bonds, Compound II should still be an active oxidant under enzymatic conditions. As such, our computational modelling predicts that under high-reduction environments the cytochromes P450 can react with substrates via Compound II but the rates will be much slower.
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Affiliation(s)
- Verònica Postils
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Maria Aurèlia Capmany i Farnés, 69, 17003 Girona, Catalonia, Spain.
- Manchester Institute of Biotechnology, School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
| | - Maud Saint-André
- Manchester Institute of Biotechnology, School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
| | - Amy Timmins
- Manchester Institute of Biotechnology, School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
| | - Xiao-Xi Li
- State Key Laboratory for Oxo Synthesis and Selective Oxidation, Suzhou Research Institute of LICP, Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences, Lanzhou 730000, China.
| | - Yong Wang
- State Key Laboratory for Oxo Synthesis and Selective Oxidation, Suzhou Research Institute of LICP, Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences, Lanzhou 730000, China.
| | - Josep M Luis
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Maria Aurèlia Capmany i Farnés, 69, 17003 Girona, Catalonia, Spain.
| | - Miquel Solà
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Maria Aurèlia Capmany i Farnés, 69, 17003 Girona, Catalonia, Spain.
| | - Sam P de Visser
- Manchester Institute of Biotechnology, School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
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de Visser SP. Mechanistic Insight on the Activity and Substrate Selectivity of Nonheme Iron Dioxygenases. CHEM REC 2018; 18:1501-1516. [PMID: 29878456 DOI: 10.1002/tcr.201800033] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Accepted: 05/18/2018] [Indexed: 01/05/2023]
Abstract
Nonheme iron dioxygenases catalyze vital reactions for human health particularly related to aging processes. They are involved in the biosynthesis of amino acids, but also the biodegradation of toxic compounds. Typically they react with their substrate(s) through oxygen atom transfer, although often with the assistance of a co-substrate like α-ketoglutarate that is converted to succinate and CO2 . Many reaction processes catalyzed by the nonheme iron dioxygenases are stereoselective or regiospecific and hence understanding the mechanism and protein involvement in the selectivity is important for the design of biotechnological applications of these enzymes. To this end, I will review recent work of our group on nonheme iron dioxygenases and include background information on their general structure and catalytic cycle. Examples of stereoselective and regiospecific reaction mechanisms we elucidated are for the AlkB repair enzyme, prolyl-4-hydroxylase and the ergothioneine biosynthesis enzyme. Finally, I cover an example where we bioengineered S-p-hydroxymandelate synthase into the R-p-hydroxymandelate synthase.
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Affiliation(s)
- Sam P de Visser
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
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13
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Timmins A, de Visser SP. How Are Substrate Binding and Catalysis Affected by Mutating Glu 127 and Arg 161 in Prolyl-4-hydroxylase? A QM/MM and MD Study. Front Chem 2017; 5:94. [PMID: 29170737 PMCID: PMC5684110 DOI: 10.3389/fchem.2017.00094] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 10/24/2017] [Indexed: 11/13/2022] Open
Abstract
Prolyl-4-hydroxylase is a vital enzyme for human physiology involved in the biosynthesis of 4-hydroxyproline, an essential component for collagen formation. The enzyme performs a unique stereo- and regioselective hydroxylation at the C4 position of proline despite the fact that the C5 hydrogen atoms should be thermodynamically easier to abstract. To gain insight into the mechanism and find the origin of this regioselectivity, we have done a quantum mechanics/molecular mechanics (QM/MM) study on wildtype and mutant structures. In a previous study (Timmins et al., 2017) we identified several active site residues critical for substrate binding and positioning. In particular, the Glu127 and Arg161 were shown to form multiple hydrogen bonding and ion-dipole interactions with substrate and could thereby affect the regio- and stereoselectivity of the reaction. In this work, we decided to test that hypothesis and report a QM/MM and molecular dynamics (MD) study on prolyl-4-hydroxylase and several active site mutants where Glu127 or Arg161 are mutated for Asp, Gln, or Lys. Thus, the R161D and R161Q mutants give very high barriers for hydrogen atom abstraction from any proline C-H bond and therefore will be inactive. The R161K mutant, by contrast, sees the regio- and stereoselectivity of the reaction change but still is expected to hydroxylate proline at room temperature. By contrast, the Glu127 mutants E127D and E127Q show possible changes in regioselectivity with the former being more probable to react compared to the latter.
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Affiliation(s)
| | - Sam P. de Visser
- School of Chemical Engineering and Analytical Science, Manchester Institute of Biotechnology, The University of Manchester, Manchester, United Kingdom
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14
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Timmins A, Saint-André M, de Visser SP. Understanding How Prolyl-4-hydroxylase Structure Steers a Ferryl Oxidant toward Scission of a Strong C-H Bond. J Am Chem Soc 2017; 139:9855-9866. [PMID: 28657747 DOI: 10.1021/jacs.7b02839] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Prolyl-4-hydroxylase (P4H) is a non-heme iron hydroxylase that regio- and stereospecifically hydroxylates proline residues in a peptide chain into R-4-hydroxyproline, which is essential for collagen cross-linking purposes in the human body. Surprisingly, in P4H, a strong aliphatic C-H bond is activated, while thermodynamically much weaker aliphatic C-H groups, that is, at the C3 and C5 positions, are untouched. Little is known on the origins of the high regio- and stereoselectivity of P4H and many non-heme and heme enzymes in general, and insight into this matter may be relevant to Biotechnology as well as Drug Development. The active site of the protein contains two aromatic residues (Tyr140 and Trp243) that we expected to be crucial for guiding the regioselectivity of the reaction. We performed a detailed quantum mechanics/molecular mechanics (QM/MM) and molecular dynamics (MD) study on wild-type and mutant structures. The work shows that Trp243 is involved in key protein loop-loop interactions that affect the shape and size of the substrate binding pocket and its mutation has major long-range effects. By contrast, the Tyr140 residue is shown to guide the regio- and stereoselectivity by holding the substrate and ferryl oxidant in a specific orientation through hydrogen bonding and π-stacking interactions. Compelling evidence is found that the Tyr140 residue is involved in expelling the product from the binding pocket after the reaction is complete. It is shown that mutations where the hydrogen bonding network that involves the Tyr140 and Trp243 residues is disrupted lead to major changes in folding of the protein and the size and shape of the substrate binding pocket. Specifically, the Trp243 residue positions the amino acid side chains of Arg161 and Glu127 in specific orientations with substrate. As such, the P4H enzyme is a carefully designed protein with a subtle and rigid secondary structure that enables the binding of substrate, guides the regioselectivity, and expels product efficiently.
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Affiliation(s)
- Amy Timmins
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester , 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Maud Saint-André
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester , 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Sam P de Visser
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester , 131 Princess Street, Manchester M1 7DN, United Kingdom
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15
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Faponle AS, Seebeck FP, de Visser SP. Sulfoxide Synthase versus Cysteine Dioxygenase Reactivity in a Nonheme Iron Enzyme. J Am Chem Soc 2017; 139:9259-9270. [PMID: 28602090 DOI: 10.1021/jacs.7b04251] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The sulfoxide synthase EgtB represents a unique family of nonheme iron enzymes that catalyze the formation of a C-S bond between N-α-trimethyl histidine and γ-glutamyl cysteine, which is the key step in the biosynthesis of ergothioneine, an important amino acid related to aging. A controversy has arisen regarding its catalytic mechanism related to the function of the active-site Tyr377 residue. The biosynthesis of ergothioneine in EgtB shows structural similarities to cysteine dioxygenase which transfers two oxygen atoms to the thiolate group of cysteine. The question, therefore, is how do EgtB enzymes catalyze the C-S bond-formation reaction, while also preventing a dioxygenation of its cysteinate substrate? In this work we present a quantum mechanics/molecular mechanics study into the mechanism of sulfoxide synthase enzymes as compared to cysteine dioxygenase enzymes and present pathways for both reaction channels in EgtB. We show that EgtB contains a conserved tyrosine residue that reacts via proton-coupled electron transfer with the iron(III)-superoxo species and creates an iron(III)-hydroperoxo intermediate, thereby preventing the possible thiolate dioxygenation side reaction. The nucleophilic C-S bond-formation step happens subsequently concomitant to relay of the proton of the iron(II)-hydroperoxo back to Tyr377. This is the rate-determining step in the reaction cycle and is followed by hydrogen-atom transfer from the CE1-H group of trimethyl histidine substrate to iron(II)-superoxo. In the final step, a quick and almost barrierless sulfoxidation leads to the sulfoxide product complexes. The work highlights a unique machinery and active-site setup of the enzyme that drives the sulfoxide synthase reaction.
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Affiliation(s)
- Abayomi S Faponle
- The Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester , 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Florian P Seebeck
- Department for Chemistry, University of Basel , St. Johanns-Ring 19, Basel 4056, Switzerland
| | - Sam P de Visser
- The Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester , 131 Princess Street, Manchester M1 7DN, United Kingdom
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16
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Faponle AS, de Visser SP. The Role of Nonheme Transition Metal-Oxo, -Peroxo, and -Superoxo Intermediates in Enzyme Catalysis and Reactions of Bioinspired Complexes. ADVANCES IN INORGANIC CHEMISTRY 2017. [DOI: 10.1016/bs.adioch.2017.01.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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17
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Silva PJ. Refining the reaction mechanism of O 2 towards its co-substrate in cofactor-free dioxygenases. PeerJ 2016; 4:e2805. [PMID: 28028471 PMCID: PMC5178339 DOI: 10.7717/peerj.2805] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 11/19/2016] [Indexed: 11/21/2022] Open
Abstract
Cofactor-less oxygenases perform challenging catalytic reactions between singlet co-substrates and triplet oxygen, in spite of apparently violating the spin-conservation rule. In 1-H-3-hydroxy-4-oxoquinaldine-2,4-dioxygenase, the active site has been suggested by quantum chemical computations to fine tune triplet oxygen reactivity, allowing it to interact rapidly with its singlet substrate without the need for spin inversion, and in urate oxidase the reaction is thought to proceed through electron transfer from the deprotonated substrate to an aminoacid sidechain, which then feeds the electron to the oxygen molecule. In this work, we perform additional quantum chemical computations on these two systems to elucidate several intriguing features unaddressed by previous workers. These computations establish that in both enzymes the reaction proceeds through direct electron transfer from co-substrate to O2 followed by radical recombination, instead of minimum-energy crossing points between singlet and triplet potential energy surfaces without formal electron transfer. The active site does not affect the reactivity of oxygen directly but is crucial for the generation of the deprotonated form of the co-substrates, which have redox potentials far below those of their protonated forms and therefore may transfer electrons to oxygen without sizeable thermodynamic barriers. This mechanism seems to be shared by most cofactor-less oxidases studied so far.
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Affiliation(s)
- Pedro J Silva
- FP-ENAS/Fac. de Ciências da Saúde, Universidade Fernando Pessoa , Porto , Portugal
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18
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New insight into cofactor-free oxygenation from combined experimental and computational approaches. Curr Opin Struct Biol 2016; 41:109-118. [DOI: 10.1016/j.sbi.2016.06.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Accepted: 06/22/2016] [Indexed: 01/07/2023]
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19
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Machovina MM, Usselman RJ, DuBois JL. Monooxygenase Substrates Mimic Flavin to Catalyze Cofactorless Oxygenations. J Biol Chem 2016; 291:17816-28. [PMID: 27307041 DOI: 10.1074/jbc.m116.730051] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Indexed: 01/16/2023] Open
Abstract
Members of the antibiotic biosynthesis monooxygenase family catalyze O2-dependent oxidations and oxygenations in the absence of any metallo- or organic cofactor. How these enzymes surmount the kinetic barrier to reactions between singlet substrates and triplet O2 is unclear, but the reactions have been proposed to occur via a flavin-like mechanism, where the substrate acts in lieu of a flavin cofactor. To test this model, we monitored the uncatalyzed and enzymatic reactions of dithranol, a substrate for the nogalamycin monooxygenase (NMO) from Streptomyces nogalater As with flavin, dithranol oxidation was faster at a higher pH, although the reaction did not appear to be base-catalyzed. Rather, conserved asparagines contributed to suppression of the substrate pKa The same residues were critical for enzymatic catalysis that, consistent with the flavoenzyme model, occurred via an O2-dependent slow step. Evidence for a superoxide/substrate radical pair intermediate came from detection of enzyme-bound superoxide during turnover. Small molecule and enzymatic superoxide traps suppressed formation of the oxygenation product under uncatalyzed conditions, whereas only the small molecule trap had an effect in the presence of NMO. This suggested that NMO both accelerated the formation and directed the recombination of a superoxide/dithranyl radical pair. These catalytic strategies are in some ways flavin-like and stand in contrast to the mechanisms of urate oxidase and (1H)-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase, both cofactor-independent enzymes that surmount the barriers to direct substrate/O2 reactivity via markedly different means.
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Affiliation(s)
- Melodie M Machovina
- From the Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59715-3400
| | - Robert J Usselman
- From the Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59715-3400
| | - Jennifer L DuBois
- From the Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59715-3400
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20
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Quesne MG, Borowski T, de Visser SP. Quantum Mechanics/Molecular Mechanics Modeling of Enzymatic Processes: Caveats and Breakthroughs. Chemistry 2015; 22:2562-81. [PMID: 26696271 DOI: 10.1002/chem.201503802] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Indexed: 11/08/2022]
Abstract
Nature has developed large groups of enzymatic catalysts with the aim to transfer substrates into useful products, which enables biosystems to perform all their natural functions. As such, all biochemical processes in our body (we drink, we eat, we breath, we sleep, etc.) are governed by enzymes. One of the problems associated with research on biocatalysts is that they react so fast that details of their reaction mechanisms cannot be obtained with experimental work. In recent years, major advances in computational hardware and software have been made and now large (bio)chemical systems can be studied using accurate computational techniques. One such technique is the quantum mechanics/molecular mechanics (QM/MM) technique, which has gained major momentum in recent years. Unfortunately, it is not a black-box method that is easily applied, but requires careful set-up procedures. In this work we give an overview on the technical difficulties and caveats of QM/MM and discuss work-protocols developed in our groups for running successful QM/MM calculations.
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Affiliation(s)
- Matthew G Quesne
- Jerzy Haber Institute of Catalysis and Surface Chemistry of the, Polish Academy of Sciences, Niezapominajek 8, 30-239, Krakow, Poland. .,Manchester Institute of Biotechnology and, School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK.
| | - Tomasz Borowski
- Jerzy Haber Institute of Catalysis and Surface Chemistry of the, Polish Academy of Sciences, Niezapominajek 8, 30-239, Krakow, Poland.
| | - Sam P de Visser
- Manchester Institute of Biotechnology and, School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK.
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21
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Rauwerdink A, Kazlauskas RJ. How the Same Core Catalytic Machinery Catalyzes 17 Different Reactions: the Serine-Histidine-Aspartate Catalytic Triad of α/β-Hydrolase Fold Enzymes. ACS Catal 2015; 5:6153-6176. [PMID: 28580193 DOI: 10.1021/acscatal.5b01539] [Citation(s) in RCA: 177] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Enzymes within a family often catalyze different reactions. In some cases, this variety stems from different catalytic machinery, but in other cases the machinery is identical; nevertheless, the enzymes catalyze different reactions. In this review, we examine the subset of α/β-hydrolase fold enzymes that contain the serine-histidine-aspartate catalytic triad. In spite of having the same protein fold and the same core catalytic machinery, these enzymes catalyze seventeen different reaction mechanisms. The most common reactions are hydrolysis of C-O, C-N and C-C bonds (Enzyme Classification (EC) group 3), but other enzymes are oxidoreductases (EC group 1), acyl transferases (EC group 2), lyases (EC group 4) or isomerases (EC group 5). Hydrolysis reactions often follow the canonical esterase mechanism, but eight variations occur where either the formation or cleavage of the acyl enzyme intermediate differs. The remaining eight mechanisms are lyase-type elimination reactions, which do not have an acyl enzyme intermediate and, in four cases, do not even require the catalytic serine. This diversity of mechanisms from the same catalytic triad stems from the ability of the enzymes to bind different substrates, from the requirements for different chemical steps imposed by these new substrates and, only in about half of the cases, from additional hydrogen bond partners or additional general acids/bases in the active site. This detailed analysis shows that binding differences and non-catalytic residues create new mechanisms and are essential for understanding and designing efficient enzymes.
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Affiliation(s)
- Alissa Rauwerdink
- Department of Biochemistry, Molecular Biology & Biophysics and The Biotechnology Institute, University of Minnesota, Saint Paul, Minnesota 55108, United States
| | - Romas J. Kazlauskas
- Department of Biochemistry, Molecular Biology & Biophysics and The Biotechnology Institute, University of Minnesota, Saint Paul, Minnesota 55108, United States
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22
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Hernández-Ortega A, Quesne MG, Bui S, Heyes DJ, Steiner RA, Scrutton NS, de Visser SP. Catalytic Mechanism of Cofactor-Free Dioxygenases and How They Circumvent Spin-Forbidden Oxygenation of Their Substrates. J Am Chem Soc 2015; 137:7474-87. [DOI: 10.1021/jacs.5b03836] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Aitor Hernández-Ortega
- Manchester
Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Matthew G. Quesne
- Manchester
Institute of Biotechnology and School of Chemical Engineering and
Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Soi Bui
- Randall
Division of Cell and Molecular Biophysics, King’s College London, London SE1 1UL, United Kingdom
| | - Derren J. Heyes
- Manchester
Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Roberto A. Steiner
- Randall
Division of Cell and Molecular Biophysics, King’s College London, London SE1 1UL, United Kingdom
| | - Nigel S. Scrutton
- Manchester
Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Sam P. de Visser
- Manchester
Institute of Biotechnology and School of Chemical Engineering and
Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
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23
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Saito T, Kawakami T, Yamanaka S, Okumura M. Computational Study of Catalytic Reaction of Quercetin 2,4-Dioxygenase. J Phys Chem B 2015; 119:6952-62. [PMID: 25990020 DOI: 10.1021/acs.jpcb.5b03564] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We present a quantum mechanics/molecular mechanics (QM/MM) and QM-only study on the oxidative ring-cleaving reaction of quercetin catalyzed by quercetin 2,4-dioxygenase (2,4-QD). 2,4-QD has a mononuclear type 2 copper center and incorporates two oxygen atoms at C2 and C4 positions of the substrate. It has not been clear whether dioxygen reacts with a copper ion or a substrate radical as the first step. We have found that dioxygen is more likely to bind to a Cu(2+) ion, involving the dissociation of the substrate from the copper ion. Then a Cu(2+)-alkylperoxo complex can be generated. Comparison of geometry and stability between QM-only and QM/MM results strongly indicates that steric effects of the protein environment contribute to maintain the orientation of the substrate dissociated from the copper center. The present QM/MM results also highlight that a prior rearrangement of the Cu(2+)-alkylperoxo complex and a subsequent hydrogen bond switching assisted by the movement of Glu73 can facilitate formation of an endoperoxide intermediate selectively.
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Affiliation(s)
- Toru Saito
- †Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.,‡Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology (JST) Agency, Kawaguchi, Saitama 332-0012, Japan
| | - Takashi Kawakami
- †Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Shusuke Yamanaka
- †Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.,‡Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology (JST) Agency, Kawaguchi, Saitama 332-0012, Japan
| | - Mitsutaka Okumura
- †Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.,‡Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology (JST) Agency, Kawaguchi, Saitama 332-0012, Japan
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24
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Sallmann M, Kumar S, Chernev P, Nehrkorn J, Schnegg A, Kumar D, Dau H, Limberg C, de Visser SP. Structure and Mechanism Leading to Formation of the Cysteine Sulfinate Product Complex of a Biomimetic Cysteine Dioxygenase Model. Chemistry 2015; 21:7470-9. [DOI: 10.1002/chem.201500644] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Indexed: 01/10/2023]
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25
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Luanloet T, Sucharitakul J, Chaiyen P. Selectivity of substrate binding and ionization of 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase. FEBS J 2015; 282:3107-25. [PMID: 25639849 DOI: 10.1111/febs.13220] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 01/21/2015] [Accepted: 01/28/2015] [Indexed: 11/30/2022]
Abstract
2-Methyl-3-hydroxypyridine-5-carboxylic acid (MHPC) oxygenase (EC 1.14.12.4) from Pseudomonas sp. MA-1 is a flavin-dependent monooxygenase that catalyzes a hydroxylation and aromatic ring cleavage reaction. The functional roles of two residues, Tyr223 and Tyr82, located ~ 5 Å away from MHPC, were characterized using site-directed mutagenesis, along with ligand binding, product analysis and transient kinetic experiments. Mutation of Tyr223 resulted in enzyme variants that were impaired in their hydroxylation activity and had Kd values for substrate binding 5-10-fold greater than the wild-type enzyme. Because this residue is adjacent to the water molecule that is located next to the 3-hydroxy group of MHPC, the results indicate that the interaction between Tyr223, H2 O and the 3-hydroxyl group of MHPC are important for substrate binding and hydroxylation. By contrast, the Kd for substrate binding of Tyr82His and Tyr82Phe variants were similar to that of the wild-type enzyme. However, only ~ 40-50% of the substrate was hydroxylated in the reactions of both variants, whereas most of the substrate was hydroxylated in the wild-type enzyme reaction. In free solution, MHPC or 5-hydroxynicotinic acid exists in a mixture of monoanionic and tripolar ionic forms, whereas only the tripolar ionic form binds to the wild-type enzyme. The binding of tripolar ionic MHPC would allow efficient hydroxylation through an electrophilic aromatic substitution mechanism. For the Tyr82His and Tyr82Phe variants, both forms of substrates can bind to the enzymes, indicating that the mutation at Tyr82 abolished the selectivity of the enzyme towards the tripolar ionic form. Transient kinetic studies indicated that the hydroxylation rate constants of both Tyr82 variants are approximately two- to 2.5-fold higher than that of the wild-type enzyme. Altogether, our findings suggest that Tyr82 is important for the binding selectivity of MHPC oxygenase towards the tripolar ionic species, whereas the interaction between Tyr223 and the substrate is important for ensuring hydroxylation. These results highlight how the active site of a flavoenzyme is able to deal with the presence of multiple forms of a substrate in solution and ensure efficient hydroxylation.
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Affiliation(s)
- Thikumporn Luanloet
- Department of Biochemistry and Center of Excellence in Protein Structure & Function, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Jeerus Sucharitakul
- Department of Biochemistry, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand
| | - Pimchai Chaiyen
- Department of Biochemistry and Center of Excellence in Protein Structure & Function, Faculty of Science, Mahidol University, Bangkok, Thailand
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26
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Jastrzebski R, Quesne MG, Weckhuysen BM, de Visser SP, Bruijnincx PCA. Experimental and computational evidence for the mechanism of intradiol catechol dioxygenation by non-heme iron(III) complexes. Chemistry 2014; 20:15686-91. [PMID: 25322920 PMCID: PMC4497327 DOI: 10.1002/chem.201404988] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Indexed: 11/15/2022]
Abstract
Catechol intradiol dioxygenation is a unique reaction catalyzed by iron-dependent enzymes and non-heme iron(III) complexes. The mechanism by which these systems activate dioxygen in this important metabolic process remains controversial. Using a combination of kinetic measurements and computational modelling of multiple iron(III) catecholato complexes, we have elucidated the catechol cleavage mechanism and show that oxygen binds the iron center by partial dissociation of the substrate from the iron complex. The iron(III) superoxide complex that is formed subsequently attacks the carbon atom of the substrate by a rate-determining C-O bond formation step.
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Affiliation(s)
- Robin Jastrzebski
- Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht UniversityUniversiteitsweg 99, 3584 CG Utrecht (The Netherlands)
- The Manchester Institute for Biotechnology and the School of Chemical Engineering and Analytical Science, The University of Manchester131 Princess Street, Manchester, M1 7DN (UK)
| | - Matthew G Quesne
- The Manchester Institute for Biotechnology and the School of Chemical Engineering and Analytical Science, The University of Manchester131 Princess Street, Manchester, M1 7DN (UK)
| | - Bert M Weckhuysen
- Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht UniversityUniversiteitsweg 99, 3584 CG Utrecht (The Netherlands)
| | - Sam P de Visser
- The Manchester Institute for Biotechnology and the School of Chemical Engineering and Analytical Science, The University of Manchester131 Princess Street, Manchester, M1 7DN (UK)
| | - Pieter C A Bruijnincx
- Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht UniversityUniversiteitsweg 99, 3584 CG Utrecht (The Netherlands)
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27
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Rubber oxygenase and latex clearing protein cleave rubber to different products and use different cleavage mechanisms. Appl Environ Microbiol 2014; 80:5012-20. [PMID: 24907333 DOI: 10.1128/aem.01271-14] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Two types of enzyme for oxidative cleavage of poly(cis-1,4-isoprene) are known. One is rubber oxygenase (RoxA) that is secreted by Xanthomonas sp. strain 35Y and a few other Gram-negative rubber-degrading bacteria during growth on polyisoprene. RoxA was studied in the past, and the recently solved structure showed a structural relationship to bacterial cytochrome c peroxidases (J. Seidel et al., Proc. Natl. Acad. Sci. U. S. A. 110:13833-13838, 2013, http://dx.doi.org/10.1073/pnas.1305560110). The other enzyme is latex-clearing protein (Lcp) that is secreted by rubber-degrading actinomycetes, but Lcp has not yet been purified. Here, we expressed Lcp of Streptomyces sp. strain K30 in a ΔroxA background of Xanthomonas sp. strain 35Y and purified native (untagged) Lcp. The specific activities of Lcp and RoxA were 0.70 and 0.48 U/mg, respectively. Lcp differed from RoxA in the absence of heme groups and other characteristics. Notably, Lcp degraded polyisoprene via endo-type cleavage to tetra-C20 and higher oligo-isoprenoids with aldehyde and keto end groups, whereas RoxA used an exo-type cleavage mechanism to give the main end product 12-oxo-4,8-dimethyltrideca-4,8-diene-1-al (ODTD). RoxA was able to cleave isolated Lcp-derived oligo-isoprenoid molecules to ODTD. Inhibitor studies, spectroscopic investigations and metal analysis gave no indication for the presence of iron, other metals, or cofactors in Lcp. Our results suggest that Lcp could be a member of the growing group of cofactor-independent oxygenases and differs in the cleavage mechanism from heme-dependent RoxA. In conclusion, RoxA and Lcp represent two different answers to the same biochemical problem, the cleavage of polyisoprene, a polymer that has carbon-carbon double bonds as the only functional groups for enzymatic attack.
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