1
|
Li Q, Zhang S, Liu F, Su H, Sheng X. Quantum chemical modeling of enantioselective sulfoxidation and epoxidation reactions by indole monooxygenase VpIndA1. Phys Chem Chem Phys 2024; 26:16521-16528. [PMID: 38809594 DOI: 10.1039/d4cp00552j] [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: 05/30/2024]
Abstract
Indole monooxygenases (IMOs) are enzymes from the family of Group E monooxygenases, requiring flavin adenine dinucleotide (FAD) for their activities. IMOs play important roles in both sulfoxidation and epoxidation reactions. The broad substrate range and high selectivity of IMOs make them promising biocatalytic tools for synthesizing chiral compounds. In the present study, quantum chemical calculations using the cluster approach were performed to investigate the reaction mechanism and the enantioselectivity of the IMO from Variovorax paradoxus EPS (VpIndA1). The sulfoxidation of methyl phenyl sulfide (MPS) and the epoxidation of indene were chosen as the representative reactions. The calculations confirmed that the FADOOH intermediate is the catalytic species in the VpIndA1 reactions. The oxidation of MPS adopts a one-step mechanism involving the direct oxygen-transfer from FADOOH to the substrate and the proton transfer from the -OH group back to FAD, while the oxidation of indene follows a stepwise mechanism involving a carbocation intermediate. It was computationally predicted that VpIndA1 prefers the formation of (S)-product for the MPS sulfoxidation and (1S,2R)-product for the indene epoxidation, consistent with the experimental observations. Importantly, the factors controlling the stereo-preference of the two reactions are identified. The findings in the present study provide valuable insights into the VpIndA1-catalyzed reactions, which are essential for the rational design of this enzyme and other IMOs for industrial applications. It is also worth emphasizing that the quantum chemical cluster approach is again demonstrated to be powerful in studying the enantioselectivity of enzymatic reactions.
Collapse
Affiliation(s)
- Qinrou Li
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, P. R. China
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China.
| | - Shiqing Zhang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China.
- National Center of Technology Innovation for Synthetic Biology, National Engineering Research Center of Industrial Enzymes and Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin 300308, P. R. China
| | - Fufeng Liu
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, P. R. China
| | - Hao Su
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China.
- National Center of Technology Innovation for Synthetic Biology, National Engineering Research Center of Industrial Enzymes and Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin 300308, P. R. China
| | - Xiang Sheng
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China.
- National Center of Technology Innovation for Synthetic Biology, National Engineering Research Center of Industrial Enzymes and Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin 300308, P. R. China
| |
Collapse
|
2
|
Kratky J, Eggerichs D, Heine T, Hofmann S, Sowa P, Weiße RH, Tischler D, Sträter N. Structural and Mechanistic Studies on Substrate and Stereoselectivity of the Indole Monooxygenase VpIndA1: New Avenues for Biocatalytic Epoxidations and Sulfoxidations. Angew Chem Int Ed Engl 2023; 62:e202300657. [PMID: 36762980 DOI: 10.1002/anie.202300657] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/09/2023] [Accepted: 02/10/2023] [Indexed: 02/11/2023]
Abstract
Flavoprotein monooxygenases are a versatile group of enzymes for biocatalytic transformations. Among these, group E monooxygenases (GEMs) catalyze enantioselective epoxidation and sulfoxidation reactions. Here, we describe the crystal structure of an indole monooxygenase from the bacterium Variovorax paradoxus EPS, a GEM designated as VpIndA1. Complex structures with substrates reveal productive binding modes that, in conjunction with force-field calculations and rapid mixing kinetics, reveal the structural basis of substrate and stereoselectivity. Structure-based redesign of the substrate cavity yielded variants with new substrate selectivity (for sulfoxidation of benzyl phenyl sulfide) or with greatly enhanced stereoselectivity (from 35.1 % to 99.8 % ee for production of (1S,2R)-indene oxide). This first determination of the substrate binding mode of GEMs combined with structure-function relationships opens the door for structure-based design of these powerful biocatalysts.
Collapse
Affiliation(s)
- Julia Kratky
- Institute of Bioanalytical Chemistry, Leipzig University, Deutscher Platz 5, 04103, Leipzig, Germany
| | - Daniel Eggerichs
- Microbial Biotechnology, Ruhr-Universität Bochum, Universitätsstr. 150, 44780, Bochum, Germany
| | - Thomas Heine
- Environmental Microbiology, TU Bergakademie Freiberg, Leipziger Str. 29, 09599, Freiberg, Germany
| | - Sarah Hofmann
- Environmental Microbiology, TU Bergakademie Freiberg, Leipziger Str. 29, 09599, Freiberg, Germany
| | - Philipp Sowa
- Microbial Biotechnology, Ruhr-Universität Bochum, Universitätsstr. 150, 44780, Bochum, Germany
| | - Renato H Weiße
- Institute of Bioanalytical Chemistry, Leipzig University, Deutscher Platz 5, 04103, Leipzig, Germany
| | - Dirk Tischler
- Microbial Biotechnology, Ruhr-Universität Bochum, Universitätsstr. 150, 44780, Bochum, Germany.,Environmental Microbiology, TU Bergakademie Freiberg, Leipziger Str. 29, 09599, Freiberg, Germany
| | - Norbert Sträter
- Institute of Bioanalytical Chemistry, Leipzig University, Deutscher Platz 5, 04103, Leipzig, Germany
| |
Collapse
|
3
|
Ernst S, Mährlein A, Ritzmann NH, Drees SL, Fetzner S. A comparative study of
N
‐hydroxylating flavoprotein monooxygenases reveals differences in kinetics and cofactor binding. FEBS J 2022; 289:5637-5655. [DOI: 10.1111/febs.16444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 02/21/2022] [Accepted: 03/18/2022] [Indexed: 12/01/2022]
Affiliation(s)
- Simon Ernst
- Institute of Molecular Microbiology and Biotechnology University of Münster Germany
| | - Almuth Mährlein
- Institute of Molecular Microbiology and Biotechnology University of Münster Germany
| | - Niklas H. Ritzmann
- Institute of Molecular Microbiology and Biotechnology University of Münster Germany
| | - Steffen L. Drees
- Institute of Molecular Microbiology and Biotechnology University of Münster Germany
| | - Susanne Fetzner
- Institute of Molecular Microbiology and Biotechnology University of Münster Germany
| |
Collapse
|
4
|
Hall M. Enzymatic strategies for asymmetric synthesis. RSC Chem Biol 2021; 2:958-989. [PMID: 34458820 PMCID: PMC8341948 DOI: 10.1039/d1cb00080b] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 05/28/2021] [Indexed: 12/13/2022] Open
Abstract
Enzymes, at the turn of the 21st century, are gaining a momentum. Especially in the field of synthetic organic chemistry, a broad variety of biocatalysts are being applied in an increasing number of processes running at up to industrial scale. In addition to the advantages of employing enzymes under environmentally friendly reaction conditions, synthetic chemists are recognizing the value of enzymes connected to the exquisite selectivity of these natural (or engineered) catalysts. The use of hydrolases in enantioselective protocols paved the way to the application of enzymes in asymmetric synthesis, in particular in the context of biocatalytic (dynamic) kinetic resolutions. After two decades of impressive development, the field is now mature to propose a panel of catalytically diverse enzymes for (i) stereoselective reactions with prochiral compounds, such as double bond reduction and bond forming reactions, (ii) formal enantioselective replacement of one of two enantiotopic groups of prochiral substrates, as well as (iii) atroposelective reactions with noncentrally chiral compounds. In this review, the major enzymatic strategies broadly applicable in the asymmetric synthesis of optically pure chiral compounds are presented, with a focus on the reactions developed within the past decade.
Collapse
Affiliation(s)
- Mélanie Hall
- Institute of Chemistry, University of Graz Heinrichstrasse 28 8010 Graz Austria
- Field of Excellence BioHealth - University of Graz Austria
| |
Collapse
|
5
|
Martínez-Montero L, Tischler D, Süss P, Schallmey A, Franssen MCR, Hollmann F, Paul CE. Asymmetric azidohydroxylation of styrene derivatives mediated by a biomimetic styrene monooxygenase enzymatic cascade. Catal Sci Technol 2021; 11:5077-5085. [PMID: 34381590 PMCID: PMC8328376 DOI: 10.1039/d1cy00855b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 06/13/2021] [Indexed: 12/18/2022]
Abstract
Enantioenriched azido alcohols are precursors for valuable chiral aziridines and 1,2-amino alcohols, however their chiral substituted analogues are difficult to access. We established a cascade for the asymmetric azidohydroxylation of styrene derivatives leading to chiral substituted 1,2-azido alcohols via enzymatic asymmetric epoxidation, followed by regioselective azidolysis, affording the azido alcohols with up to two contiguous stereogenic centers. A newly isolated two-component flavoprotein styrene monooxygenase StyA proved to be highly selective for epoxidation with a nicotinamide coenzyme biomimetic as a practical reductant. Coupled with azide as a nucleophile for regioselective ring opening, this chemo-enzymatic cascade produced highly enantioenriched aromatic α-azido alcohols with up to >99% conversion. A bi-enzymatic counterpart with halohydrin dehalogenase-catalyzed azidolysis afforded the alternative β-azido alcohol isomers with up to 94% diastereomeric excess. We anticipate our biocatalytic cascade to be a starting point for more practical production of these chiral compounds with two-component flavoprotein monooxygenases.
Collapse
Affiliation(s)
- Lía Martínez-Montero
- Department of Biotechnology, Delft University of Technology Van der Maasweg 9 2629 HZ Delft The Netherlands
| | - Dirk Tischler
- Microbial Biotechnology, Ruhr-Universität Bochum Universitätsstr. 150 44780 Bochum Germany
| | - Philipp Süss
- Enzymicals AG Walther-Rathenau-Straße 49a 17489 Greifswald Germany
| | - Anett Schallmey
- Institute for Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig Spielmannstraße 7 38106 Braunschweig Germany
| | - Maurice C R Franssen
- Laboratory of Organic Chemistry, Wageningen University Stippeneng 4 6708 WE Wageningen The Netherlands
| | - Frank Hollmann
- Department of Biotechnology, Delft University of Technology Van der Maasweg 9 2629 HZ Delft The Netherlands
| | - Caroline E Paul
- Department of Biotechnology, Delft University of Technology Van der Maasweg 9 2629 HZ Delft The Netherlands
| |
Collapse
|
6
|
Panter F, Bader CD, Müller R. The Sandarazols are Cryptic and Structurally Unique Plasmid-Encoded Toxins from a Rare Myxobacterium*. Angew Chem Int Ed Engl 2021; 60:8081-8088. [PMID: 33534143 PMCID: PMC8048970 DOI: 10.1002/anie.202014671] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 01/12/2021] [Indexed: 11/20/2022]
Abstract
Herein, we describe a new plasmid found in Sandaracinus sp. MSr10575 named pSa001 spanning 209.7 kbp that harbors a cryptic secondary metabolite biosynthesis gene cluster (BGC). Activation of this BGC by homologous-recombination-mediated exchange of the native promoter sequence against a vanillate inducible system led to the production and subsequent isolation and structure elucidation of novel secondary metabolites, the sandarazols A-G. The sandarazols contain intriguing structural features and very reactive functional groups such as an α-chlorinated ketone, an epoxyketone, and a (2R)-2-amino-3-(N,N-dimethylamino)-propionic acid building block. In-depth investigation of the underlying biosynthetic machinery led to a concise biosynthetic model for the new compound family, including several uncommon biosynthetic steps. The chlorinated congener sandarazol C shows an IC50 value of 0.5 μm against HCT 116 cells and a MIC of 14 μm against Mycobacterium smegmatis, which points at the sandarazols' potential function as defensive secondary metabolites or toxins.
Collapse
Affiliation(s)
- Fabian Panter
- Department of Microbial Natural ProductsHelmholtz-Institute for Pharmaceutical Research Saarland (HIPS)Helmholtz Centre for Infection Research (HZI) and Department of PharmacySaarland University, Campus E8 166123SaarbrückenGermany
- German Centre for Infection Research (DZIF), Partner SiteHannover-BraunschweigGermany
- Helmholtz International Lab for Anti-Infectives, Campus E8 166123SaarbrückenGermany
| | - Chantal D. Bader
- Department of Microbial Natural ProductsHelmholtz-Institute for Pharmaceutical Research Saarland (HIPS)Helmholtz Centre for Infection Research (HZI) and Department of PharmacySaarland University, Campus E8 166123SaarbrückenGermany
- German Centre for Infection Research (DZIF), Partner SiteHannover-BraunschweigGermany
| | - Rolf Müller
- Department of Microbial Natural ProductsHelmholtz-Institute for Pharmaceutical Research Saarland (HIPS)Helmholtz Centre for Infection Research (HZI) and Department of PharmacySaarland University, Campus E8 166123SaarbrückenGermany
- German Centre for Infection Research (DZIF), Partner SiteHannover-BraunschweigGermany
- Helmholtz International Lab for Anti-Infectives, Campus E8 166123SaarbrückenGermany
| |
Collapse
|
7
|
Panter F, Bader CD, Müller R. Die Sandarazole sind kryptische und strukturell einzigartige, Plasmid‐codierte Toxine aus einem seltenen Myxobakterium**. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202014671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Fabian Panter
- Abteilung Mikrobielle Naturstoffe Helmholtz-Institut für Pharmazeutische Forschung Saarland (HIPS) Helmholtz Zentrum für Infektionsforschung (HZI) und Fachbereich Pharmazie Universität des Saarlandes, Campus E8 1 66123 Saarbrücken Deutschland
- Deutsches Zentrum für Infektionsforschung (DZIF), Partner Site Hannover-Braunschweig Deutschland
- Helmholtz International Lab for Anti-Infectives, Campus E8 1 66123 Saarbrücken Deutschland
| | - Chantal D. Bader
- Abteilung Mikrobielle Naturstoffe Helmholtz-Institut für Pharmazeutische Forschung Saarland (HIPS) Helmholtz Zentrum für Infektionsforschung (HZI) und Fachbereich Pharmazie Universität des Saarlandes, Campus E8 1 66123 Saarbrücken Deutschland
- Deutsches Zentrum für Infektionsforschung (DZIF), Partner Site Hannover-Braunschweig Deutschland
| | - Rolf Müller
- Abteilung Mikrobielle Naturstoffe Helmholtz-Institut für Pharmazeutische Forschung Saarland (HIPS) Helmholtz Zentrum für Infektionsforschung (HZI) und Fachbereich Pharmazie Universität des Saarlandes, Campus E8 1 66123 Saarbrücken Deutschland
- Deutsches Zentrum für Infektionsforschung (DZIF), Partner Site Hannover-Braunschweig Deutschland
- Helmholtz International Lab for Anti-Infectives, Campus E8 1 66123 Saarbrücken Deutschland
| |
Collapse
|
8
|
Walter A, Storch G. Synthetic C6-Functionalized Aminoflavin Catalysts Enable Aerobic Bromination of Oxidation-Prone Substrates. Angew Chem Int Ed Engl 2020; 59:22505-22509. [PMID: 32790228 PMCID: PMC7756793 DOI: 10.1002/anie.202009657] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 08/08/2020] [Indexed: 12/19/2022]
Abstract
Flavoenzymes catalyze oxidations via hydroperoxide intermediates that result from activation of molecular O2. These reactions—such as hydroxylation and halogenation—depend on the additional catalytic activity of functional groups in the peptide environment of the flavin cofactor. We report synthetic flavin catalysts that contain C6 amino modifications at the isoalloxazine core and are consequently capable of mediating halogenations outside the peptide surrounding. The catalysts are competent in the selective, biomimetic bromination of oxidation‐prone phenols, flavones, and flavanones using a halide salt in combination with 2,6‐lutidinium oxalate as a flavin reductant under visible‐light irradiation. Our studies show the beneficial effect of stacked bisflavins as well as the catalytic activity of the flavin modifications. The designed flavin catalysts outperform isolated natural (−)‐riboflavin and contribute to the continuing search for tailored flavins in oxidation reactions.
Collapse
Affiliation(s)
- Alexandra Walter
- Department ChemieTechnische Universität MünchenLichtenbergstr. 485747GarchingGermany
| | - Golo Storch
- Department ChemieTechnische Universität MünchenLichtenbergstr. 485747GarchingGermany
| |
Collapse
|
9
|
Walter A, Storch G. Synthetische, C6‐funktionalisierte Aminoflavinkatalysatoren ermöglichen die aerobe Bromierung oxidationsanfälliger Substrate. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202009657] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Alexandra Walter
- Department Chemie Technische Universität München Lichtenbergstr. 4 85747 Garching Deutschland
| | - Golo Storch
- Department Chemie Technische Universität München Lichtenbergstr. 4 85747 Garching Deutschland
| |
Collapse
|
10
|
Amongre R, Gassner G. Regenerable copper anode for the Cu(I)-mediated reduction of FAD in the electroenzymatic styrene epoxidation reaction. Bioelectrochemistry 2020; 137:107679. [PMID: 33120296 DOI: 10.1016/j.bioelechem.2020.107679] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 09/17/2020] [Accepted: 09/24/2020] [Indexed: 12/19/2022]
Abstract
Styrene monooxygenase (SMO) is a two-component flavoenzyme composed of NADH-dependent flavin reductase (SMOB) and FAD-specific styrene epoxidase (NSMOA) components. The enantioselective styrene epoxidation reaction catalyzed by this enzyme can be streamlined for chemosynthetic applications by substituting NADH and the reductase with an electrode to supply the epoxidase with reducing equivalents required for catalysis. Slow kinetics of adsorption and desorption of FAD from the electrode surface and unproductive side reactions of the reduced flavin with oxygen limit the efficiency of direct electroenzymatic catalysis. In the present work we develop a miniature spectroelectrochemical cell equipped with a copper electrode for the anodic synthesis of Cu(I) chelates of EDTA, glutamate, and citrate as FAD-reducing agents, and a platinum electrode for the electrolytic generation of oxygen. Copper oxidized in the flavin reduction reaction can be reclaimed subsequently as copper metal at the electrode surface. About 80% transformation of styrene is achieved in a single cell cycle of reduction and oxygenation at pH 7 and 25 °C in good agreement with that predicted by numerical simulation. When the cell is operated in two successive cycles, styrene oxide can be synthesized with an electroenzymatic epoxidation activity of 663U/g in 94% yield. This approach to electroenzymatic catalysis shows promise for the quantitative transformation of styrene to styrene oxide and may be applied more generally to other flavoprotein monooxygenases.
Collapse
Affiliation(s)
- Robert Amongre
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, CA, United States
| | - George Gassner
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, CA, United States.
| |
Collapse
|
11
|
Abstract
Flavoenzymes are broadly employed as biocatalysts for a large variety of reactions, owing to the chemical versatility of the flavin cofactor. Oxidases set aside, many flavoenzymes require a source of electrons in form of the biological reductant nicotinamide NAD(P)H in order to initiate catalysis via the reduced flavin. Chemists can take advantage of the reactivity of reduced flavins with oxygen to carry out monooxygenation reactions, while the reduced flavin can also be used for formal hydrogenation reactions. The main advantage of these reactions compared to chemical approaches is the frequent regio-, chemo- and stereo-selectivity of the biocatalysts, which allows the synthesis of chiral molecules in optically active form. This chapter provides an overview of the variety of biocatalytic processes that have been developed with flavoenzymes, with a particular focus on nicotinamide-dependent enzymes. The diversity of molecules obtained is highlighted and in several cases, strategies that allow control of the stereochemical outcome of the reactions are reviewed.
Collapse
Affiliation(s)
- Mélanie Hall
- Department of Chemistry, University of Graz, Graz, Austria.
| |
Collapse
|
12
|
Tischler D, Kumpf A, Eggerichs D, Heine T. Styrene monooxygenases, indole monooxygenases and related flavoproteins applied in bioremediation and biocatalysis. FLAVIN-DEPENDENT ENZYMES: MECHANISMS, STRUCTURES AND APPLICATIONS 2020; 47:399-425. [DOI: 10.1016/bs.enz.2020.05.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
|
13
|
Abstract
Styrene monooxygenases are soluble two-component flavoproteins that catalyze the NADH and FAD-dependent enantioselective epoxidation of styrene to styrene oxide in the aqueous phase. These enzymes present interesting mechanistic features and potential as catalysts in biotechnological applications ranging from green chemical synthesis to bioremediation. This chapter presents approaches for the expression of the reductase (SMOB, StyB) and epoxidase (SMOA, StyA) components of SMO from pET-vectors as native or N-terminally histidine-tagged proteins in commercial strains of E. coli. The two-component structure of SMO and hydrophobic nature of styrene substrate requires some special consideration in evaluating the mechanism of this enzyme. The modular composition of the enzyme allows the flavin-reduction reaction of SMOB and styrene epoxidation reaction of SMOA to be evaluated both independently and as a composite catalytic system. The freedom to independently study the reductase and epoxidase components of SMO significantly simplifies studies of equilibrium-binding and the coupling of the free energy of ligand binding to the electrochemical potential of bound FAD. In this chapter, methods of steady-state and pre-steady-state kinetic assay, experimental approaches to equilibrium-binding reactions of flavin and substrate, and determination of the electrochemical midpoint potential of FAD bound to the reductase and epoxidase components of SMO are presented. This presentation focuses on approaches that have been successfully used in the study of the wild-type styrene monooxygenase system recovered from Pseudomonas putida (S12), but similar approaches may be effective in the characterization of related two-component enzyme systems.
Collapse
Affiliation(s)
- George T Gassner
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, CA, United States.
| |
Collapse
|
14
|
van Schie MMCH, Paul CE, Arends IWCE, Hollmann F. Photoenzymatic epoxidation of styrenes. Chem Commun (Camb) 2019; 55:1790-1792. [DOI: 10.1039/c8cc08149b] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photochemical reduction of flavin adenine dinucleotide (FAD) enables the direct, non-enzymatic regeneration of styrene monooxygenase for enantiospecific epoxidation reactions.
Collapse
Affiliation(s)
| | - Caroline E. Paul
- Laboratory of Organic Chemistry, Wageningen University & Research
- 6708WE Wageningen
- The Netherlands
| | | | - Frank Hollmann
- Department of Biotechnology, Delft University of Technology
- 2629 HZ Delft
- The Netherlands
| |
Collapse
|
15
|
Heine T, van Berkel WJH, Gassner G, van Pée KH, Tischler D. Two-Component FAD-Dependent Monooxygenases: Current Knowledge and Biotechnological Opportunities. BIOLOGY 2018; 7:biology7030042. [PMID: 30072664 PMCID: PMC6165268 DOI: 10.3390/biology7030042] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 07/31/2018] [Accepted: 08/01/2018] [Indexed: 12/11/2022]
Abstract
Flavoprotein monooxygenases create valuable compounds that are of high interest for the chemical, pharmaceutical, and agrochemical industries, among others. Monooxygenases that use flavin as cofactor are either single- or two-component systems. Here we summarize the current knowledge about two-component flavin adenine dinucleotide (FAD)-dependent monooxygenases and describe their biotechnological relevance. Two-component FAD-dependent monooxygenases catalyze hydroxylation, epoxidation, and halogenation reactions and are physiologically involved in amino acid metabolism, mineralization of aromatic compounds, and biosynthesis of secondary metabolites. The monooxygenase component of these enzymes is strictly dependent on reduced FAD, which is supplied by the reductase component. More and more representatives of two-component FAD-dependent monooxygenases have been discovered and characterized in recent years, which has resulted in the identification of novel physiological roles, functional properties, and a variety of biocatalytic opportunities.
Collapse
Affiliation(s)
- Thomas Heine
- Institute of Biosciences, Environmental Microbiology, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany.
| | - Willem J H van Berkel
- Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
| | - George Gassner
- Department of Chemistry and Biochemistry, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA.
| | - Karl-Heinz van Pée
- Allgemeine Biochemie, Technische Universität Dresden, 01062 Dresden, Germany.
| | - Dirk Tischler
- Institute of Biosciences, Environmental Microbiology, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany.
- Microbial Biotechnology, Ruhr University Bochum, Universitätsstr. 150, 44780 Bochum, Germany.
| |
Collapse
|
16
|
Tischler D, Schwabe R, Siegel L, Joffroy K, Kaschabek SR, Scholtissek A, Heine T. VpStyA1/VpStyA2B of Variovorax paradoxus EPS: An Aryl Alkyl Sulfoxidase Rather than a Styrene Epoxidizing Monooxygenase. Molecules 2018; 23:E809. [PMID: 29614810 PMCID: PMC6017014 DOI: 10.3390/molecules23040809] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 03/27/2018] [Accepted: 04/01/2018] [Indexed: 02/08/2023] Open
Abstract
Herein we describe the first representative of an E2-type two-component styrene monooxygenase of proteobacteria. It comprises a single epoxidase protein (VpStyA1) and a two domain protein (VpStyA2B) harboring an epoxidase (A2) and a FAD-reductase (B) domain. It was annotated as VpStyA1/VpStyA2B of Variovorax paradoxus EPS. VpStyA2B serves mainly as NADH:FAD-oxidoreductase. A Km of 33.6 ± 4.0 µM for FAD and a kcat of 22.3 ± 1.1 s-1 were determined and resulted in a catalytic efficiency (kcatKm-1) of 0.64 s-1 μM-1. To investigate its NADH:FAD-oxidoreductase function the linker between A2- and B-domain (AREAV) was mutated. One mutant (AAAAA) showed 18.7-fold higher affinity for FAD (kcatKm-1 of 5.21 s-1 μM-1) while keeping wildtype NADH-affinity and -oxidation activity. Both components, VpStyA2B and VpStyA1, showed monooxygenase activity on styrene of 0.14 U mg-1 and 0.46 U mg-1, as well as on benzyl methyl sulfide of 1.62 U mg-1 and 3.11 U mg-1, respectively. The high sulfoxidase activity was the reason to test several thioanisole-like substrates in biotransformations. VpStyA1 showed high substrate conversions (up to 95% in 2 h) and produced dominantly (S)-enantiomeric sulfoxides of all tested substrates. The AAAAA-mutant showed a 1.6-fold increased monooxygenase activity. In comparison, the GQWCSQY-mutant did neither show monooxygenase nor efficient FAD-reductase activity. Hence, the linker between the two domains of VpStyA2B has effects on the reductase as well as on the monooxygenase performance. Overall, this monooxygenase represents a promising candidate for biocatalyst development and studying natural fusion proteins.
Collapse
Affiliation(s)
- Dirk Tischler
- Institute of Biosciences, Environmental Microbiology, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany.
- Microbial Biotechnology, Ruhr University Bochum, Universitätsstr. 150, 44780 Bochum, Germany.
| | - Ringo Schwabe
- Institute of Biosciences, Environmental Microbiology, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany.
| | - Lucas Siegel
- Institute of Biosciences, Environmental Microbiology, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany.
| | - Kristin Joffroy
- Institute of Biosciences, Environmental Microbiology, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany.
| | - Stefan R Kaschabek
- Institute of Biosciences, Environmental Microbiology, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany.
| | - Anika Scholtissek
- Institute of Biosciences, Environmental Microbiology, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany.
| | - Thomas Heine
- Institute of Biosciences, Environmental Microbiology, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany.
| |
Collapse
|
17
|
Oelschlägel M, Zimmerling J, Tischler D. A Review: The Styrene Metabolizing Cascade of Side-Chain Oxygenation as Biotechnological Basis to Gain Various Valuable Compounds. Front Microbiol 2018; 9:490. [PMID: 29623070 PMCID: PMC5874493 DOI: 10.3389/fmicb.2018.00490] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 03/02/2018] [Indexed: 11/16/2022] Open
Abstract
Styrene is one of the most produced and processed chemicals worldwide and is released into the environment during widespread processing. But, it is also produced from plants and microorganisms. The natural occurrence of styrene led to several microbiological strategies to form and also to degrade styrene. One pathway designated as side-chain oxygenation has been reported as a specific route for the styrene degradation among microorganisms. It comprises the following enzymes: styrene monooxygenase (SMO; NADH-consuming and FAD-dependent, two-component system), styrene oxide isomerase (SOI; cofactor independent, membrane-bound protein) and phenylacetaldehyde dehydrogenase (PAD; NAD+-consuming) and allows an intrinsic cofactor regeneration. This specific way harbors a high potential for biotechnological use. Based on the enzymatic steps involved in this degradation route, important reactions can be realized from a large number of substrates which gain access to different interesting precursors for further applications. Furthermore, stereochemical transformations are possible, offering chiral products at high enantiomeric excess. This review provides an actual view on the microbiological styrene degradation followed by a detailed discussion on the enzymes of the side-chain oxygenation. Furthermore, the potential of the single enzyme reactions as well as the respective multi-step syntheses using the complete enzyme cascade are discussed in order to gain styrene oxides, phenylacetaldehydes, or phenylacetic acids (e.g., ibuprofen). Altered routes combining these putative biocatalysts with other enzymes are additionally described. Thus, the substrates spectrum can be enhanced and additional products as phenylethanols or phenylethylamines are reachable. Finally, additional enzymes with similar activities toward styrene and its metabolic intermediates are shown in order to modify the cascade described above or to use these enzyme independently for biotechnological application.
Collapse
Affiliation(s)
- Michel Oelschlägel
- Environmental Microbiology Group, Institute of Biosciences, Technische Universität Bergakademie Freiberg, Freiberg, Germany
| | - Juliane Zimmerling
- Environmental Microbiology Group, Institute of Biosciences, Technische Universität Bergakademie Freiberg, Freiberg, Germany
| | - Dirk Tischler
- Environmental Microbiology Group, Institute of Biosciences, Technische Universität Bergakademie Freiberg, Freiberg, Germany
- Microbial Biotechnology, Ruhr University Bochum, Bochum, Germany
| |
Collapse
|
18
|
Heine T, Scholtissek A, Westphal AH, van Berkel WJH, Tischler D. N-terminus determines activity and specificity of styrene monooxygenase reductases. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1865:1770-1780. [PMID: 28888693 DOI: 10.1016/j.bbapap.2017.09.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 08/10/2017] [Accepted: 09/05/2017] [Indexed: 10/18/2022]
Abstract
Styrene monooxygenases (SMOs) are two-enzyme systems that catalyze the enantioselective epoxidation of styrene to (S)-styrene oxide. The FADH2 co-substrate of the epoxidase component (StyA) is supplied by an NADH-dependent flavin reductase (StyB). The genome of Rhodococcus opacus 1CP encodes two SMO systems. One system, which we define as E1-type, displays homology to the SMO from Pseudomonas taiwanensis VLB120. The other system, originally reported as a fused system (RoStyA2B), is defined as E2-type. Here we found that E1-type RoStyB is inhibited by FMN, while RoStyA2B is known to be active with FMN. To rationalize the observed specificity of RoStyB for FAD, we generated an artificial reductase, designated as RoStyBart, in which the first 22 amino acid residues of RoStyB were joined to the reductase part of RoStyA2B, while the oxygenase part (A2) was removed. RoStyBart mainly purified as apo-protein and mimicked RoStyB in being inhibited by FMN. Pre-incubation with FAD yielded a turnover number at 30°C of 133.9±3.5s-1, one of the highest rates observed for StyB reductases. RoStyBart holo-enzyme switches to a ping-pong mechanism and fluorescence analysis indicated for unproductive binding of FMN to the second (co-substrate) binding site. In summary, it is shown for the first time that optimization of the N-termini of StyB reductases allows the evolution of their activity and specificity.
Collapse
Affiliation(s)
- Thomas Heine
- Environmental Microbiology, Interdisciplinary Ecological Center, TU Bergakadmie Freiberg, Leipziger Straße 29, 09599 Freiberg, Germany; Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
| | - Anika Scholtissek
- Environmental Microbiology, Interdisciplinary Ecological Center, TU Bergakadmie Freiberg, Leipziger Straße 29, 09599 Freiberg, Germany; Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Adrie H Westphal
- Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Willem J H van Berkel
- Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Dirk Tischler
- Environmental Microbiology, Interdisciplinary Ecological Center, TU Bergakadmie Freiberg, Leipziger Straße 29, 09599 Freiberg, Germany.
| |
Collapse
|
19
|
Heine T, Tucker K, Okonkwo N, Assefa B, Conrad C, Scholtissek A, Schlömann M, Gassner G, Tischler D. Engineering Styrene Monooxygenase for Biocatalysis: Reductase-Epoxidase Fusion Proteins. Appl Biochem Biotechnol 2016; 181:1590-1610. [PMID: 27830466 DOI: 10.1007/s12010-016-2304-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 10/24/2016] [Indexed: 11/25/2022]
Abstract
The enantioselective epoxidation of styrene and related compounds by two-component styrene monooxygenases (SMOs) has targeted these enzymes for development as biocatalysts. In the present work, we prepare genetically engineered fusion proteins that join the C-terminus of the epoxidase (StyA) to the N-terminus of the reductase (StyB) through a linker peptide and demonstrate their utility as biocatalysts in the synthesis of Tyrain purple and other indigoid dyes. A single-vector expression system offers a simplified platform for transformation and expansion of the catalytic function of styrene monooxygenases, and the resulting fusion proteins are self-regulated and couple efficiently NADH oxidation to styrene epoxidation. We find that the reductase domain proceeds through a sequential ternary-complex mechanism at low FAD concentration and a double-displacement mechanism at higher concentrations of FAD. Single-turnover studies indicate an observed rate constant for FAD-to-FAD hydride transfer of ~8 s-1. This step is rate limiting in the styrene epoxidation reaction and helps to ensure that flavin reduction and styrene epoxidation reactions proceed without wasteful side reactions. Comparison of the reductase activity of the fusion proteins with the naturally occurring reductase, SMOB, and N-terminally histidine-tagged reductase, NSMOB, suggests that the observed changes in catalytic mechanism are due in part to an increase in flavin-binding affinity associated with the N-terminal extension of the reductase.
Collapse
Affiliation(s)
| | | | - Nonye Okonkwo
- San Francisco State University, San Francisco, CA, USA
| | | | | | | | | | | | - Dirk Tischler
- TU Bergakademie Freiberg, Freiberg, Germany.
- San Francisco State University, San Francisco, CA, USA.
| |
Collapse
|
20
|
Riedel A, Heine T, Westphal AH, Conrad C, Rathsack P, van Berkel WJH, Tischler D. Catalytic and hydrodynamic properties of styrene monooxygenases from Rhodococcus opacus 1CP are modulated by cofactor binding. AMB Express 2015; 5:112. [PMID: 26054733 PMCID: PMC4460183 DOI: 10.1186/s13568-015-0112-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 04/15/2015] [Indexed: 12/13/2022] Open
Abstract
Styrene monooxygenases (SMOs) are flavoenzymes catalyzing the epoxidation of styrene into styrene oxide. SMOs are composed of a monooxygenase (StyA) and a reductase (StyB). The latter delivers reduced FAD to StyA on the expense of NADH. We identified Rhodococcus opacus 1CP as the first microorganism to possess three different StyA isoforms occurring in two systems StyA1/StyA2B and StyA/StyB, respectively. The hydrodynamic properties of StyA isozymes were found to be modulated by the binding of the (reduced) FAD cofactor. StyA1 and SyA2B mainly occur as dimers in their active forms while StyA is a monomer. StyA1 showed the highest epoxidation activity and excellent enantioselectivity in aromatic sulfoxidation. The hydrodynamic and biocatalytic properties of SMOs from strain 1CP are of relevance for investigation of possible industrial applications.
Collapse
|
21
|
Badieyan S, Bach RD, Sobrado P. Mechanism of N-Hydroxylation Catalyzed by Flavin-Dependent Monooxygenases. J Org Chem 2015; 80:2139-47. [DOI: 10.1021/jo502651v] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Somayesadat Badieyan
- Department
of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Robert D. Bach
- Departments
of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Pablo Sobrado
- Department
of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
- Virginia
Tech Center for Drug Discovery, Virginia Tech, Blacksburg, Virginia 24061, United States
| |
Collapse
|
22
|
Marchi-Delapierre C, Rondot L, Cavazza C, Ménage S. Oxidation Catalysis by Rationally Designed Artificial Metalloenzymes. Isr J Chem 2014. [DOI: 10.1002/ijch.201400110] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
|
23
|
A mechanistic study on SMOB-ADP1: an NADH:flavin oxidoreductase of the two-component styrene monooxygenase of Acinetobacter baylyi ADP1. Arch Microbiol 2014; 196:829-45. [PMID: 25116410 DOI: 10.1007/s00203-014-1022-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 07/23/2014] [Accepted: 07/28/2014] [Indexed: 10/24/2022]
Abstract
Two styrene monooxygenase types, StyA/StyB and StyA1/StyA2B, have been described each consisting of an epoxidase and a reductase. A gene fusion which led to the chimeric reductase StyA2B and the occurrence in different phyla are major differences. Identification of SMOA/SMOB-ADP1 of Acinetobacter baylyi ADP1 may enlighten the gene fusion event since phylogenetic analysis indicated both proteins to be more related to StyA2B than to StyA/StyB. SMOB-ADP1 is classified like StyB and StyA2B as HpaC-like reductase. Substrate affinity and turnover number of the homo-dimer SMOB-ADP1 were determined for NADH (24 µM, 64 s(-1)) and FAD (4.4 µM, 56 s(-1)). SMOB-ADP1 catalysis follows a random sequential mechanism, and FAD fluorescence is quenched upon binding to SMOB-ADP1 (K d = 1.8 µM), which clearly distinguishes that reductase from StyB of Pseudomonas. In summary, this study confirmes made assumptions and provides phylogenetic and biochemical data for the differentiation of styrene monooxygenase-related flavin reductases.
Collapse
|
24
|
Sucharitakul J, Tinikul R, Chaiyen P. Mechanisms of reduced flavin transfer in the two-component flavin-dependent monooxygenases. Arch Biochem Biophys 2014; 555-556:33-46. [DOI: 10.1016/j.abb.2014.05.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 05/10/2014] [Accepted: 05/12/2014] [Indexed: 10/25/2022]
|
25
|
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.
Collapse
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.
| |
Collapse
|
26
|
Tischler D, Schlömann M, van Berkel WJH, Gassner GT. FAD C(4a)-hydroxide stabilized in a naturally fused styrene monooxygenase. FEBS Lett 2013; 587:3848-52. [PMID: 24157359 DOI: 10.1016/j.febslet.2013.10.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 10/08/2013] [Accepted: 10/09/2013] [Indexed: 10/26/2022]
Abstract
StyA2B represents a new class of styrene monooxygenases that integrates flavin-reductase and styrene-epoxidase activities into a single polypeptide. This naturally-occurring fusion protein offers new avenues for studying and engineering biotechnologically relevant enantioselective biochemical epoxidation reactions. Stopped-flow kinetic studies of StyA2B reported here identify reaction intermediates similar to those reported for the separate reductase and epoxidase components of related two-component systems. Our studies identify substrate epoxidation and elimination of water from the FAD C(4a)-hydroxide as rate-limiting steps in the styrene epoxidation reaction. Efforts directed at accelerating these reaction steps are expected to greatly increase catalytic efficiency and the value of StyA2B as biocatalyst.
Collapse
Affiliation(s)
- Dirk Tischler
- Interdisciplinary Ecological Center, TU Bergakadmie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany; Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands; Department of Chemistry and Biochemistry, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, United States.
| | | | | | | |
Collapse
|
27
|
Morrison E, Kantz A, Gassner GT, Sazinsky MH. Structure and mechanism of styrene monooxygenase reductase: new insight into the FAD-transfer reaction. Biochemistry 2013; 52:6063-75. [PMID: 23909369 DOI: 10.1021/bi400763h] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The two-component flavoprotein styrene monooxygenase (SMO) from Pseudomonas putida S12 catalyzes the NADH- and FAD-dependent epoxidation of styrene to styrene oxide. In this study, we investigate the mechanism of flavin reduction and transfer from the reductase (SMOB) to the epoxidase (NSMOA) component and report our findings in light of the 2.2 Å crystal structure of SMOB. Upon rapidly mixing with NADH, SMOB forms an NADH → FADox charge-transfer intermediate and catalyzes a hydride-transfer reaction from NADH to FAD, with a rate constant of 49.1 ± 1.4 s(-1), in a step that is coupled to the rapid dissociation of NAD(+). Electrochemical and equilibrium-binding studies indicate that NSMOA binds FADhq ∼13-times more tightly than SMOB, which supports a vectoral transfer of FADhq from the reductase to the epoxidase. After binding to NSMOA, FADhq rapidly reacts with molecular oxygen to form a stable C(4a)-hydroperoxide intermediate. The half-life of apoSMOB generated in the FAD-transfer reaction is increased ∼21-fold, supporting a protein-protein interaction between apoSMOB and the peroxide intermediate of NSMOA. The mechanisms of FAD dissociation and transport from SMOB to NSMOA were probed by monitoring the competitive reduction of cytochrome c in the presence and absence of pyridine nucleotides. On the basis of these studies, we propose a model in which reduced FAD binds to SMOB in equilibrium between an unreactive, sequestered state (S state) and more reactive, transfer state (T state). The dissociation of NAD(+) after the hydride-transfer reaction transiently populates the T state, promoting the transfer of FADhq to NSMOA. The binding of pyridine nucleotides to SMOB-FADhq shifts the FADhq-binding equilibrium from the T state to the S state. Additionally, the 2.2 Å crystal structure of SMOB-FADox reported in this work is discussed in light of the pyridine nucleotide-gated flavin-transfer and electron-transfer reactions.
Collapse
Affiliation(s)
- Eliot Morrison
- Department of Chemistry and Biochemistry, San Francisco State University , San Francisco, California, United States
| | | | | | | |
Collapse
|
28
|
Form follows function: structural and catalytic variation in the class a flavoprotein monooxygenases. Int J Mol Sci 2012; 13:15601-39. [PMID: 23443084 PMCID: PMC3546652 DOI: 10.3390/ijms131215601] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 11/08/2012] [Accepted: 11/09/2012] [Indexed: 12/02/2022] Open
Abstract
Flavoprotein monooxygenases (FPMOs) exhibit an array of mechanistic solutions to a common chemical objective; the monooxygenation of a target substrate. Each FPMO efficiently couples reduction of a flavin cofactor by NAD(P)H to oxygenation of the target substrate via a (hydro)peroxyflavin intermediate. This purpose of this review is to describe in detail the Class A flavoprotein hydroxylases (FPMO) in the context of the other FPMO classes (B–F). Both one and two component FPMOs are found in nature. Two-component enzymes require, in addition to the monooxygenase, the involvement of a reductase that first catalyzes the reduction of the flavin by NAD(P)H. The Class A and B FPMOs are single-component and manage to orchestrate the same net reaction within a single peptide. The Class A enzymes have, by some considerable margin, the most complete research record. These enzymes use choreographed movements of the flavin ring that facilitate access of the organic substrates to the active site, provide a means for interaction of NADPH with the flavin, offer a mechanism to sequester the dioxygen reduction chemistry from solvent and a means to release the product. The majority of the discrete catalytic events of the catalytic cycle can be observed directly in exquisite detail using spectrophotometric kinetic methods and many of the key mechanistic conclusions are further supported by structural data. This review attempts to compile each of the key observations made for both paradigm and newly discovered examples of Class A FPMOs into a complete catalytic description of one enzymatic turnover.
Collapse
|
29
|
Chaiyen P, Fraaije MW, Mattevi A. The enigmatic reaction of flavins with oxygen. Trends Biochem Sci 2012; 37:373-80. [DOI: 10.1016/j.tibs.2012.06.005] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 06/19/2012] [Accepted: 06/28/2012] [Indexed: 10/28/2022]
|
30
|
Mutations at the putative active cavity of styrene monooxygenase: enhanced activity and reversed enantioselectivity. J Biotechnol 2012; 161:235-41. [PMID: 22796094 DOI: 10.1016/j.jbiotec.2012.06.028] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Revised: 06/05/2012] [Accepted: 06/08/2012] [Indexed: 11/23/2022]
Abstract
Styrene monooxygenase (SMO) catalyzes the first step of styrene degradation, and also serves as an important enzyme for the synthesis of enantiopure epoxides. To enhance its activity, molecular docking of styrene was performed based on the X-ray crystal structure of the oxygenase subunit of SMO to identify three amino acid residues (Tyr73, His76 and Ser96) being adjacent to the phenyl ring of styrene. Variants at those positions were constructed and their enzymatic activities were analyzed. Three mutants (Y73V, Y73F, and S96A) were found to exhibit higher enzymatic activities than the wild-type in the epoxidation of styrene, while retaining excellent stereoselectivity. The specific epoxidation activity of the most active mutant S96A toward styrene and trans-β-methyl styrene were 2.6 and 2.3-fold of the wild-type, respectively. In addition, the Y73V mutant showed an unexpected reversal of enantiomeric preference toward 1-phenylcyclohexene.
Collapse
|
31
|
Thibodeaux CJ, Chang WC, Liu HW. Enzymatic chemistry of cyclopropane, epoxide, and aziridine biosynthesis. Chem Rev 2012; 112:1681-709. [PMID: 22017381 PMCID: PMC3288687 DOI: 10.1021/cr200073d] [Citation(s) in RCA: 202] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Wei-chen Chang
- College of Pharmacy and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
| | - Hung-wen Liu
- Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712
- College of Pharmacy and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
| |
Collapse
|
32
|
Tongsook C, Sucharitakul J, Thotsaporn K, Chaiyen P. Interactions with the substrate phenolic group are essential for hydroxylation by the oxygenase component of p-hydroxyphenylacetate 3-hydroxylase. J Biol Chem 2011; 286:44491-502. [PMID: 22052902 DOI: 10.1074/jbc.m111.284463] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
p-Hydroxyphenylacetate (HPA) 3-hydroxylase is a two-component flavoprotein monooxygenase that catalyzes the hydroxylation of p-hydroxyphenylacetate to form 3,4-dihydroxyphenylacetate. Based on structures of the oxygenase component (C(2)), both His-120 and Ser-146 are located ~2.8 Å from the hydroxyl group of HPA. The variants H120N, H120Q, H120Y, H120D, and H120E can form C4a-hydroperoxy-FMN (a reactive intermediate necessary for hydroxylation) but cannot hydroxylate HPA. The impairment of H120N is not due to substrate binding because the variant can still bind HPA. In contrast, the H120K variant catalyzes hydroxylation with efficiency comparable with that of the wild-type enzyme; the hydroxylation rate constant for H120K is 5.7 ± 0.6 s(-1), and the product conversion ratio is 75%, compared with values of 16 s(-1) and 90% for the wild-type enzyme. H120R can also catalyze hydroxylation, suggesting that a positive charge on residue 120 can substitute for the hydroxylation function of His-120. Because the hydroxylation reaction of wild-type C(2) is pH-independent between pH 6 and 10, the protonation status of key components required for hydroxylation likely remains unchanged in this pH range. His-120 may be positively charged for selective binding to the phenolate form of HPA, i.e. to form the His(δ+)·HPA(δ-) complex, which in turn promotes oxygen atom transfer via an electrophilic aromatic substitution mechanism. Analysis of Ser-146 variants revealed that this residue is necessary for but not directly engaged in hydroxylation. Product formation in S146A is pH-independent and constant at ~70% over a pH range of 6-10, whereas product formation for S146C decreased from ~65% at pH 6.0 to 27% at pH 10.0. These data indicate that the ionization of Cys-146 in the S146C variant has an adverse effect on hydroxylation, possibly by perturbing formation of the His(δ+)·HPA(δ-) complex needed for hydroxylation.
Collapse
Affiliation(s)
- Chanakan Tongsook
- Department of Biochemistry and Center of Excellence in Protein Structure and Function, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand
| | | | | | | |
Collapse
|
33
|
Lin H, Liu JY, Wang HB, Ahmed AAQ, Wu ZL. Biocatalysis as an alternative for the production of chiral epoxides: A comparative review. ACTA ACUST UNITED AC 2011. [DOI: 10.1016/j.molcatb.2011.07.012] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
34
|
Montersino S, Tischler D, Gassner GT, van Berkel WJH. Catalytic and Structural Features of Flavoprotein Hydroxylases and Epoxidases. Adv Synth Catal 2011. [DOI: 10.1002/adsc.201100384] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|