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Perkins SW, Hlaing MZ, Hicks KA, Rajakovich LJ, Snider MJ. Mechanism of the Multistep Catalytic Cycle of 6-Hydroxynicotinate 3-Monooxygenase Revealed by Global Kinetic Analysis. Biochemistry 2023; 62:1553-1567. [PMID: 37130364 DOI: 10.1021/acs.biochem.2c00514] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The class A flavoenzyme 6-hydroxynicotinate 3-monooxygenase (NicC) catalyzes a rare decarboxylative hydroxylation reaction in the degradation of nicotinate by aerobic bacteria. While the structure and critical residues involved in catalysis have been reported, the mechanism of this multistep enzyme has yet to be determined. A kinetic understanding of the NicC mechanism would enable comparison to other phenolic hydroxylases and illuminate its bioengineering potential for remediation of N-heterocyclic aromatic compounds. Toward these goals, transient state kinetic analyses by stopped-flow spectrophotometry were utilized to follow rapid changes in flavoenzyme absorbance spectra during all three stages of NicC catalysis: (1) 6-HNA binding; (2) NADH binding and FAD reduction; and (3) O2 binding with C4a-adduct formation, substrate hydroxylation, and FAD regeneration. Global kinetic simulations by numeric integration were used to supplement analytical fitting of time-resolved data and establish a kinetic mechanism. Results indicate that 6-HNA binding is a two-step process that substantially increases the affinity of NicC for NADH and enables the formation of a charge-transfer-complex intermediate to enhance the rate of flavin reduction. Singular value decomposition of the time-resolved spectra during the reaction of the substrate-bound, reduced enzyme with dioxygen provides evidence for the involvement of C4a-hydroperoxy-flavin and C4a-hydroxy-flavin intermediates in NicC catalysis. Global analysis of the full kinetic mechanism suggests that steady-state catalytic turnover is partially limited by substrate hydroxylation and C4a-hydroxy-flavin dehydration to regenerate the flavoenzyme. Insights gleaned from the kinetic model and determined microscopic rate constants provide a fundamental basis for understanding NicC's substrate specificity and reactivity.
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Affiliation(s)
- Scott W Perkins
- Department of Chemistry, The College of Wooster, Wooster, Ohio 44691, United States
| | - May Z Hlaing
- Department of Chemistry, The College of Wooster, Wooster, Ohio 44691, United States
| | - Katherine A Hicks
- Department of Chemistry, The State University of New York College at Cortland, Cortland, New York 13045, United States
| | - Lauren J Rajakovich
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Mark J Snider
- Department of Chemistry, The College of Wooster, Wooster, Ohio 44691, United States
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2
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Abstract
Many flavin-dependent phenolic hydroxylases (monooxygenases) have been extensively investigated. Their crystal structures and reaction mechanisms are well understood. These enzymes belong to groups A and D of the flavin-dependent monooxygenases and can be classified as single-component and two-component flavin-dependent monooxygenases. The insertion of molecular oxygen into the substrates catalyzed by these enzymes is beneficial for modifying the biological properties of phenolic compounds and their derivatives. This chapter provides an in-depth discussion of the structural features of single-component and two-component flavin-dependent phenolic hydroxylases. The reaction mechanisms of selected enzymes, including 3-hydroxy-benzoate 4-hydroxylase (PHBH) and 3-hydroxy-benzoate 6-hydroxylase as representatives of single-component enzymes and 3-hydroxyphenylacetate 4-hydroxylase (HPAH) as a representative of two-component enzymes, are discussed in detail. This chapter comprises the following four main parts: general reaction, structures, reaction mechanisms, and enzyme engineering for biocatalytic applications. Enzymes belonging to the same group catalyze similar reactions but have different unique structural features to control their reactivity to substrates and the formation and stabilization of C4a-hydroperoxyflavin. Protein engineering has been employed to improve the ability to use these enzymes to synthesize valuable compounds. A thorough understanding of the structural and mechanistic features controlling enzyme reactivity is useful for enzyme redesign and enzyme engineering for future biocatalytic applications.
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Affiliation(s)
- Pirom Chenprakhon
- Institute for Innovative Learning, Mahidol University, Nakhon Pathom, Thailand.
| | - Panu Pimviriyakul
- Department of Biochemistry, Faculty of Science, Kasetsart University, Chatuchak, Bangkok, Thailand; Department of Biotechnology, Faculty of Engineering and Industrial Technology, Silpakorn University, Nakhon Pathom, Thailand
| | - Chanakan Tongsook
- Department of Chemistry, Faculty of Science, Silpakorn University, Nakhon Pathom, Thailand
| | - Pimchai Chaiyen
- School of Biomolecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Wangchan Valley, Rayong, Thailand
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3
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Di Cera E. Mechanisms of ligand binding. BIOPHYSICS REVIEWS 2020; 1:011303. [PMID: 33313600 PMCID: PMC7714259 DOI: 10.1063/5.0020997] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 09/09/2020] [Indexed: 12/25/2022]
Abstract
Many processes in chemistry and biology involve interactions of a ligand with its molecular target. Interest in the mechanism governing such interactions has dominated theoretical and experimental analysis for over a century. The interpretation of molecular recognition has evolved from a simple rigid body association of the ligand with its target to appreciation of the key role played by conformational transitions. Two conceptually distinct descriptions have had a profound impact on our understanding of mechanisms of ligand binding. The first description, referred to as induced fit, assumes that conformational changes follow the initial binding step to optimize the complex between the ligand and its target. The second description, referred to as conformational selection, assumes that the free target exists in multiple conformations in equilibrium and that the ligand selects the optimal one for binding. Both descriptions can be merged into more complex reaction schemes that better describe the functional repertoire of macromolecular systems. This review deals with basic mechanisms of ligand binding, with special emphasis on induced fit, conformational selection, and their mathematical foundations to provide rigorous context for the analysis and interpretation of experimental data. We show that conformational selection is a surprisingly versatile mechanism that includes induced fit as a mathematical special case and even captures kinetic properties of more complex reaction schemes. These features make conformational selection a dominant mechanism of molecular recognition in biology, consistent with the rich conformational landscape accessible to biological macromolecules being unraveled by structural biology.
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Affiliation(s)
- Enrico Di Cera
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA
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4
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Pitsawong W, Chenprakhon P, Dhammaraj T, Medhanavyn D, Sucharitakul J, Tongsook C, van Berkel WJH, Chaiyen P, Miller AF. Tuning of p Ka values activates substrates in flavin-dependent aromatic hydroxylases. J Biol Chem 2020; 295:3965-3981. [PMID: 32014994 DOI: 10.1074/jbc.ra119.011884] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 01/29/2020] [Indexed: 12/31/2022] Open
Abstract
Hydroxylation of substituted phenols by flavin-dependent monooxygenases is the first step of their biotransformation in various microorganisms. The reaction is thought to proceed via electrophilic aromatic substitution, catalyzed by enzymatic deprotonation of substrate, in single-component hydroxylases that use flavin as a cofactor (group A). However, two-component hydroxylases (group D), which use reduced flavin as a co-substrate, are less amenable to spectroscopic investigation. Herein, we employed 19F NMR in conjunction with fluorinated substrate analogs to directly measure pKa values and to monitor protein events in hydroxylase active sites. We found that the single-component monooxygenase 3-hydroxybenzoate 6-hydroxylase (3HB6H) depresses the pKa of the bound substrate analog 4-fluoro-3-hydroxybenzoate (4F3HB) by 1.6 pH units, consistent with previously proposed mechanisms. 19F NMR was applied anaerobically to the two-component monooxygenase 4-hydroxyphenylacetate 3-hydroxylase (HPAH), revealing depression of the pKa of 3-fluoro-4-hydroxyphenylacetate by 2.5 pH units upon binding to the C2 component of HPAH. 19F NMR also revealed a pKa of 8.7 ± 0.05 that we attributed to an active-site residue involved in deprotonating bound substrate, and assigned to His-120 based on studies of protein variants. Thus, in both types of hydroxylases, we confirmed that binding favors the phenolate form of substrate. The 9 and 14 kJ/mol magnitudes of the effects for 3HB6H and HPAH-C2, respectively, are consistent with pKa tuning by one or more H-bonding interactions. Our implementation of 19F NMR in anaerobic samples is applicable to other two-component flavin-dependent hydroxylases and promises to expand our understanding of their catalytic mechanisms.
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Affiliation(s)
- Warintra Pitsawong
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055
| | - Pirom Chenprakhon
- Institute for Innovative Learning, Mahidol University, Nakhon Pathom 73170, Thailand
| | - Taweesak Dhammaraj
- Faculty of Pharmacy, Mahasarakham University, Maha Sarakham 44150, Thailand
| | - Dheeradhach Medhanavyn
- Department of Biochemistry and Center for Excellence in Protein and Enzyme Technology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Jeerus Sucharitakul
- Department of Biochemistry, Faculty of Dentistry, Chulalongkorn University, Bangkok 10300, Thailand
| | - Chanakan Tongsook
- Department of Chemistry, Faculty of Science, Silpakorn University, Nakhon Pathom 73000, Thailand
| | - Willem J H van Berkel
- Laboratory of Food Chemistry, Wageningen University and Research, Bornse Weilanden 9, 6708 WG, Wageningen, The Netherlands
| | - Pimchai Chaiyen
- School of Biomolecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Wangchan Valley, 555 Moo 1 Payupnai, Wangchan, Rayong 21210, Thailand
| | - Anne-Frances Miller
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055
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Guarneri A, Westphal AH, Leertouwer J, Lunsonga J, Franssen MCR, Opperman DJ, Hollmann F, Berkel WJH, Paul CE. Flavoenzyme‐mediated Regioselective Aromatic Hydroxylation with Coenzyme Biomimetics. ChemCatChem 2020. [DOI: 10.1002/cctc.201902044] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Alice Guarneri
- Laboratory of Organic ChemistryWageningen University Stippeneng 4 Wageningen 6708 WE The Netherlands
| | - Adrie H. Westphal
- Laboratory of BiochemistryWageningen University Stippeneng 4 Wageningen 6708 WE The Netherlands
| | - Jos Leertouwer
- Department of BiotechnologyDelft University of Technology Van der Maasweg 9 Delft 2629 HZ The Netherlands
| | - Joy Lunsonga
- Laboratory of Organic ChemistryWageningen University Stippeneng 4 Wageningen 6708 WE The Netherlands
| | - Maurice C. R. Franssen
- Laboratory of Organic ChemistryWageningen University Stippeneng 4 Wageningen 6708 WE The Netherlands
| | - Diederik J. Opperman
- Department of BiotechnologyUniversity of the Free State 205 Nelson Mandela Drive Bloemfontein 9300 South Africa
| | - Frank Hollmann
- Department of BiotechnologyDelft University of Technology Van der Maasweg 9 Delft 2629 HZ The Netherlands
| | - Willem J. H. Berkel
- Laboratory of Food ChemistryWageningen University Bornse Weilanden 9 Wageningen 6708 WG The Netherlands
| | - Caroline E. Paul
- Department of BiotechnologyDelft University of Technology Van der Maasweg 9 Delft 2629 HZ The Netherlands
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7
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A novel gene, encoding 3-aminobenzoate 6-monooxygenase, involved in 3-aminobenzoate degradation in Comamonas sp. strain QT12. Appl Microbiol Biotechnol 2018; 102:4843-4852. [DOI: 10.1007/s00253-018-9015-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 04/09/2018] [Accepted: 04/10/2018] [Indexed: 12/14/2022]
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8
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Montersino S, Te Poele E, Orru R, Westphal AH, Barendregt A, Heck AJR, van der Geize R, Dijkhuizen L, Mattevi A, van Berkel WJH. 3-Hydroxybenzoate 6-Hydroxylase from Rhodococcus jostii RHA1 Contains a Phosphatidylinositol Cofactor. Front Microbiol 2017; 8:1110. [PMID: 28670303 PMCID: PMC5472690 DOI: 10.3389/fmicb.2017.01110] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Accepted: 05/31/2017] [Indexed: 01/05/2023] Open
Abstract
3-Hydroxybenzoate 6-hydroxylase (3HB6H, EC 1.13.14.26) is a FAD-dependent monooxygenase involved in the catabolism of aromatic compounds in soil microorganisms. 3HB6H is unique among flavoprotein hydroxylases in that it harbors a phospholipid ligand. The purified protein obtained from expressing the gene encoding 3HB6H from Rhodococcus jostii RHA1 in the host Escherichia coli contains a mixture of phosphatidylglycerol and phosphatidylethanolamine, which are the major constituents of E. coli's cytoplasmic membrane. Here, we purified 3HB6H (RjHB6H) produced in the host R. jostii RHA#2 by employing a newly developed actinomycete expression system. Biochemical and biophysical analysis revealed that Rj3HB6H possesses similar catalytic and structural features as 3HB6H, but now contains phosphatidylinositol, which is a specific constituent of actinomycete membranes. Native mass spectrometry suggests that the lipid cofactor stabilizes monomer-monomer contact. Lipid analysis of 3HB6H from Pseudomonas alcaligenes NCIMB 9867 (Pa3HB6H) produced in E. coli supports the conclusion that 3HB6H enzymes have an intrinsic ability to bind phospholipids with different specificity, reflecting the membrane composition of their bacterial host.
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Affiliation(s)
- Stefania Montersino
- Laboratory of Biochemistry, Wageningen University and ResearchWageningen, Netherlands
| | - Evelien Te Poele
- Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of GroningenGroningen, Netherlands
| | - Roberto Orru
- Department of Biology and Biotechnology, University of PaviaPavia, Italy
| | - Adrie H Westphal
- Laboratory of Biochemistry, Wageningen University and ResearchWageningen, Netherlands
| | - Arjan Barendregt
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Research, Utrecht UniversityUtrecht, Netherlands
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Research, Utrecht UniversityUtrecht, Netherlands
| | - Robert van der Geize
- Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of GroningenGroningen, Netherlands
| | - Lubbert Dijkhuizen
- Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of GroningenGroningen, Netherlands
| | - Andrea Mattevi
- Department of Biology and Biotechnology, University of PaviaPavia, Italy
| | - Willem J H van Berkel
- Laboratory of Biochemistry, Wageningen University and ResearchWageningen, Netherlands
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9
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Sucharitakul J, Medhanavyn D, Pakotiprapha D, van Berkel WJH, Chaiyen P. Tyr217 and His213 are important for substrate binding and hydroxylation of 3-hydroxybenzoate 6-hydroxylase fromRhodococcus jostiiRHA1. FEBS J 2016; 283:860-81. [DOI: 10.1111/febs.13636] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 11/03/2015] [Accepted: 12/21/2015] [Indexed: 01/28/2023]
Affiliation(s)
- Jeerus Sucharitakul
- Department of Biochemistry; Faculty of Dentistry; Chulalongkorn University; Bangkok Thailand
| | - Dheeradhach Medhanavyn
- Department of Biochemistry and Center for Excellence in Proteins and Enzyme Technology; Faculty of Science; Mahidol University; Bangkok Thailand
| | - Danaya Pakotiprapha
- Department of Biochemistry and Center for Excellence in Proteins and Enzyme Technology; Faculty of Science; Mahidol University; Bangkok Thailand
| | | | - Pimchai Chaiyen
- Department of Biochemistry and Center for Excellence in Proteins and Enzyme Technology; Faculty of Science; Mahidol University; Bangkok Thailand
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10
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Graf MMH, Sucharitakul J, Bren U, Chu DB, Koellensperger G, Hann S, Furtmüller PG, Obinger C, Peterbauer CK, Oostenbrink C, Chaiyen P, Haltrich D. Reaction of pyranose dehydrogenase from Agaricus meleagris with its carbohydrate substrates. FEBS J 2015; 282:4218-41. [PMID: 26284701 PMCID: PMC4950071 DOI: 10.1111/febs.13417] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 08/04/2015] [Accepted: 08/13/2015] [Indexed: 01/25/2023]
Abstract
Monomeric Agaricus meleagris pyranose dehydrogenase (AmPDH) belongs to the glucose-methanol-choline family of oxidoreductases. An FAD cofactor is covalently tethered to His103 of the enzyme. AmPDH can double oxidize various mono- and oligosaccharides at different positions (C1 to C4). To study the structure/function relationship of selected active-site residues of AmPDH pertaining to substrate (carbohydrate) turnover in more detail, several active-site variants were generated, heterologously expressed in Pichia pastoris, and characterized by biochemical, biophysical and computational means. The crystal structure of AmPDH shows two active-site histidines, both of which could take on the role as the catalytic base in the reductive half-reaction. Steady-state kinetics revealed that His512 is the only catalytic base because H512A showed a reduction in (kcat /KM )glucose by a factor of 10(5) , whereas this catalytic efficiency was reduced by two or three orders of magnitude for His556 variants (H556A, H556N). This was further corroborated by transient-state kinetics, where a comparable decrease in the reductive rate constant was observed for H556A, whereas the rate constant for the oxidative half-reaction (using benzoquinone as substrate) was increased for H556A compared to recombinant wild-type AmPDH. Steady-state kinetics furthermore indicated that Gln392, Tyr510, Val511 and His556 are important for the catalytic efficiency of PDH. Molecular dynamics (MD) simulations and free energy calculations were used to predict d-glucose oxidation sites, which were validated by GC-MS measurements. These simulations also suggest that van der Waals interactions are the main driving force for substrate recognition and binding.
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Affiliation(s)
- Michael M H Graf
- Food Biotechnology Laboratory, Department of Food Science and Technology, University of Natural Resources and Life Sciences Vienna (BOKU), Austria
| | - Jeerus Sucharitakul
- Department of Biochemistry, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand
| | - Urban Bren
- Institute of Molecular Modeling and Simulation, University of Natural Resources and Life Sciences Vienna (BOKU), Austria
- Laboratory for Physical Chemistry and Chemical Thermodynamics, Faculty of Chemistry and Chemical Technology, University of Maribor, Slovenia
| | - Dinh Binh Chu
- Division of Analytical Chemistry, Department of Chemistry, University of Natural Resources and Life Sciences Vienna (BOKU), Austria
- School of Chemical Engineering, Department of Analytical Chemistry, Hanoi University of Science and Technology, Hanoi, Vietnam
| | - Gunda Koellensperger
- Institute of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Austria
| | - Stephan Hann
- Division of Analytical Chemistry, Department of Chemistry, University of Natural Resources and Life Sciences Vienna (BOKU), Austria
| | - Paul G Furtmüller
- Division of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences Vienna (BOKU), Austria
| | - Christian Obinger
- Division of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences Vienna (BOKU), Austria
| | - Clemens K Peterbauer
- Food Biotechnology Laboratory, Department of Food Science and Technology, University of Natural Resources and Life Sciences Vienna (BOKU), Austria
| | - Chris Oostenbrink
- Institute of Molecular Modeling and Simulation, University of Natural Resources and Life Sciences Vienna (BOKU), Austria
| | - Pimchai Chaiyen
- Department of Biochemistry and Center of Excellence in Protein Structure and Function, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Dietmar Haltrich
- Food Biotechnology Laboratory, Department of Food Science and Technology, University of Natural Resources and Life Sciences Vienna (BOKU), Austria
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11
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Immobilization of 3-hydroxybenzoate 6-hydroxylase onto functionalized electrospun polycaprolactone ultrafine fibers: A novel heterogeneous catalyst. REACT FUNCT POLYM 2014. [DOI: 10.1016/j.reactfunctpolym.2014.05.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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12
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Pinthong C, Maenpuen S, Amornwatcharapong W, Yuthavong Y, Leartsakulpanich U, Chaiyen P. Distinct biochemical properties of human serine hydroxymethyltransferase compared with thePlasmodiumenzyme: implications for selective inhibition. FEBS J 2014; 281:2570-83. [DOI: 10.1111/febs.12803] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 03/25/2014] [Accepted: 03/31/2014] [Indexed: 11/28/2022]
Affiliation(s)
- Chatchadaporn Pinthong
- Department of Biochemistry and Center of Excellence in Protein Structure and Function; Mahidol University; Bangkok Thailand
| | | | - Watcharee Amornwatcharapong
- Department of Biochemistry and Center of Excellence in Protein Structure and Function; Mahidol University; Bangkok Thailand
| | - Yongyuth Yuthavong
- National Center for Genetic Engineering and Biotechnology; National Science and Technology Development Agency; Pathumthani Thailand
| | - Ubolsree Leartsakulpanich
- National Center for Genetic Engineering and Biotechnology; National Science and Technology Development Agency; Pathumthani Thailand
| | - Pimchai Chaiyen
- Department of Biochemistry and Center of Excellence in Protein Structure and Function; Mahidol University; Bangkok Thailand
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13
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Huijbers MME, Montersino S, Westphal AH, Tischler D, van Berkel WJH. Flavin dependent monooxygenases. Arch Biochem Biophys 2013; 544:2-17. [PMID: 24361254 DOI: 10.1016/j.abb.2013.12.005] [Citation(s) in RCA: 359] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 12/06/2013] [Accepted: 12/09/2013] [Indexed: 11/29/2022]
Abstract
Flavin-dependent monooxygenases catalyze a wide variety of chemo-, regio- and enantioselective oxygenation reactions. As such, they are involved in key biological processes ranging from catabolism, detoxification and biosynthesis, to light emission and axon guidance. Based on fold and function, flavin-dependent monooxygenases can be distributed into eight groups. Groups A and B comprise enzymes that rely on NAD(P)H as external electron donor. Groups C-F are two-protein systems, composed of a monooxygenase and a flavin reductase. Groups G and H comprise internal monooxygenases that reduce the flavin cofactor through substrate oxidation. Recently, many new flavin-dependent monooxygenases have been discovered. In addition to posing basic enzymological questions, these proteins attract attention of pharmaceutical and fine-chemical industries, given their importance as regio- and enantioselective biocatalysts. In this review we present an update of the classification of flavin-dependent monooxygenases and summarize the latest advances in our understanding of their catalytic and structural properties.
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Affiliation(s)
- Mieke M E Huijbers
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands
| | - Stefania Montersino
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands
| | - Adrie H Westphal
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands
| | - Dirk Tischler
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands; Interdisciplinary Ecological Center, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany
| | - Willem J H van Berkel
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands.
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14
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Sucharitakul J, Tongsook C, Pakotiprapha D, van Berkel WJH, Chaiyen P. The reaction kinetics of 3-hydroxybenzoate 6-hydroxylase from Rhodococcus jostii RHA1 provide an understanding of the para-hydroxylation enzyme catalytic cycle. J Biol Chem 2013; 288:35210-21. [PMID: 24129570 DOI: 10.1074/jbc.m113.515205] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
3-Hydroxybenzoate 6-hydroxylase (3HB6H) from Rhodococcus jostii RHA1 is an NADH-specific flavoprotein monooxygenase that catalyzes the para-hydroxylation of 3-hydroxybenzoate (3HB) to form 2,5-dihydroxybenzoate (2,5-DHB). Based on results from stopped-flow spectrophotometry, the reduced enzyme-3HB complex reacts with oxygen to form a C4a-peroxy flavin with a rate constant of 1.13 ± 0.01 × 10(6) m(-1) s(-1) (pH 8.0, 4 °C). This intermediate is subsequently protonated to form a C4a-hydroperoxyflavin with a rate constant of 96 ± 3 s(-1). This step shows a solvent kinetic isotope effect of 1.7. Based on rapid-quench measurements, the hydroxylation occurs with a rate constant of 36 ± 2 s(-1). 3HB6H does not exhibit substrate inhibition on the flavin oxidation step, a common characteristic found in most ortho-hydroxylation enzymes. The apparent kcat at saturating concentrations of 3HB, NADH, and oxygen is 6.49 ± 0.02 s(-1). Pre-steady state and steady-state kinetic data were used to construct the catalytic cycle of the reaction. The data indicate that the steps of product release (11.7 s(-1)) and hydroxylation (36 ± 2 s(-1)) partially control the overall turnover.
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Affiliation(s)
- Jeerus Sucharitakul
- From the Department of Biochemistry, Faculty of Dentistry, Chulalongkorn University, Henri Dunant Road, Patumwan, Bangkok 10330, Thailand
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15
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Vogt AD, Pozzi N, Chen Z, Di Cera E. Essential role of conformational selection in ligand binding. Biophys Chem 2013; 186:13-21. [PMID: 24113284 DOI: 10.1016/j.bpc.2013.09.003] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 09/17/2013] [Accepted: 09/17/2013] [Indexed: 11/26/2022]
Abstract
Two competing and mutually exclusive mechanisms of ligand recognition - conformational selection and induced fit - have dominated our interpretation of ligand binding in biological macromolecules for almost six decades. Conformational selection posits the pre-existence of multiple conformations of the macromolecule from which the ligand selects the optimal one. Induced fit, on the other hand, postulates the existence of conformational rearrangements of the original conformation into an optimal one that are induced by binding of the ligand. In the former case, conformational transitions precede the binding event; in the latter, conformational changes follow the binding step. Kineticists have used a facile criterion to distinguish between the two mechanisms based on the dependence of the rate of relaxation to equilibrium, kobs, on the ligand concentration, [L]. A value of kobs decreasing hyperbolically with [L] has been seen as diagnostic of conformational selection, while a value of kobs increasing hyperbolically with [L] has been considered diagnostic of induced fit. However, this simple conclusion is only valid under the rather unrealistic assumption of conformational transitions being much slower than binding and dissociation events. In general, induced fit only produces values of kobs that increase with [L] but conformational selection is more versatile and is associated with values of kobs that increase with, decrease with or are independent of [L]. The richer repertoire of kinetic properties of conformational selection applies to kinetic mechanisms with single or multiple saturable relaxations and explains the behavior of nearly all experimental systems reported in the literature thus far. Conformational selection is always sufficient and often necessary to account for the relaxation kinetics of ligand binding to a biological macromolecule and is therefore an essential component of any binding mechanism. On the other hand, induced fit is never necessary and only sufficient in a few cases. Therefore, the long assumed importance and preponderance of induced fit as a mechanism of ligand binding should be reconsidered.
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Affiliation(s)
- Austin D Vogt
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, United States
| | - Nicola Pozzi
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, United States
| | - Zhiwei Chen
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, United States
| | - Enrico Di Cera
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, United States.
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Vogt AD, Di Cera E. Conformational selection is a dominant mechanism of ligand binding. Biochemistry 2013; 52:5723-9. [PMID: 23947609 DOI: 10.1021/bi400929b] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Molecular recognition in biological macromolecules is achieved by binding interactions coupled to conformational transitions that precede or follow the binding step, two limiting mechanisms known as conformational selection and induced fit, respectively. Sorting out the contribution of these mechanisms to any binding interaction remains a challenging task of general interest in biochemistry. Here we show that conformational selection is associated with a vast repertoire of kinetic behaviors, can never be disproved a priori as a mechanism of ligand binding, and is sufficient to explain the relaxation kinetics documented experimentally for a large number of systems. On the other hand, induced fit features a narrow spectrum of kinetic behaviors and can be disproved in many cases in which conformational selection offers the only possible explanation. This conclusion offers a paradigm shift in the analysis of relaxation kinetics, with conformational selection acquiring preeminence as a mechanism of ligand binding. The dominant role of conformational selection supports the emerging structural view of the macromolecule as a conformational ensemble from which the ligand selects the initial optimal fit to produce a biological response.
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Affiliation(s)
- Austin D Vogt
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Missouri 63104, United States
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