1
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Xu H, Yuan Z, Yang S, Su Z, Hou XD, Deng Z, Zhang Y, Rao Y. Discovery of a Fungal P450 with an Unusual Two-Step Mechanism for Constructing a Bicyclo[3.2.2]nonane Skeleton. J Am Chem Soc 2024; 146:8716-8726. [PMID: 38484171 DOI: 10.1021/jacs.4c01284] [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: 03/28/2024]
Abstract
The successful biomimetic or chemoenzymatic synthesis of target natural products (NPs) and their derivatives relies on enzyme discovery. Herein, we discover a fungal P450 BTG5 that can catalyze the formation of a bicyclo[3.2.2]nonane structure through an unusual two-step mechanism of dimerization and cyclization in the biosynthesis of beticolin 1, whose bicyclo[3.2.2]nonane skeleton connects an anthraquinone moiety and a xanthone moiety. Further investigation reveals that BTG5-T318 not only determines the substrate selectivity but also alters the catalytic reactions, which allows the separation of the reaction to two individual steps, thereby understanding its catalytic mechanism. It reveals that the first heterodimerization undergoes the common oxidation process for P450s, while the second uncommon formal redox-neutral cyclization step is proved as a redox-mediated reaction, which has never been reported. Therefore, this work advances our understanding of P450-catalyzed reactions and paves the way for expansion of the diversity of this class of NPs through synthetic biology.
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Affiliation(s)
- Huibin Xu
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, P. R. China
| | - Zhenbo Yuan
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, P. R. China
| | - Sai Yang
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, P. R. China
| | - Zengping Su
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, P. R. China
| | - Xiao-Dong Hou
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, P. R. China
| | - Zhiwei Deng
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, P. R. China
| | - Yan Zhang
- School of Life Sciences and Health Engineering, Jiangnan University, Wuxi 214122, P. R. China
| | - Yijian Rao
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, P. R. China
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2
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Li S, Liu X, Tung CH, Liu L. Late-Stage Chemo- and Enantioselective Oxidation of Indoles to C3-Monosubstituted Oxindoles. J Am Chem Soc 2023. [PMID: 38038721 DOI: 10.1021/jacs.3c11742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
Catalytic asymmetric preparation of chiral 3-monosubstituted oxindoles represents a significant challenge in synthetic chemistry due to the ease of racemization of the tertiary stereocenter through enolization. Here, we describe a general titanium-catalyzed chemo- and enantioselective indole oxidation to produce a diverse set of chiral 3-monosubstituted oxindoles with up to 96% yield, 99% ee, and with a substrate/catalyst ratio of 10,000 by using the combination of a simple titanium(salan) catalyst with green and atom-economic terminal oxidant H2O2. The mild approach tolerates a broad range of functional groups, enabling late-stage asymmetric diversification of a series of commercial drugs and natural products together with late-stage asymmetric construction of a wide set of enzyme antagonists, all of which are difficult to achieve through existing methods.
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Affiliation(s)
- Song Li
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
| | - Xigong Liu
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
| | - Chen-Ho Tung
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
| | - Lei Liu
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
- Shenzhen Research Institute of Shandong University, Shenzhen 518057, China
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3
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Shi X, Zhao G, Li H, Zhao Z, Li W, Wu M, Du YL. Hydroxytryptophan biosynthesis by a family of heme-dependent enzymes in bacteria. Nat Chem Biol 2023; 19:1415-1422. [PMID: 37653171 DOI: 10.1038/s41589-023-01416-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Accepted: 08/03/2023] [Indexed: 09/02/2023]
Abstract
Hydroxytryptophan serves as a chemical precursor to a variety of bioactive specialized metabolites, including the human neurotransmitter serotonin and the hormone melatonin. Although the human and animal routes to hydroxytryptophan have been known for decades, how bacteria catalyze tryptophan indole hydroxylation remains a mystery. Here we report a class of tryptophan hydroxylases that are involved in various bacterial metabolic pathways. These enzymes utilize a histidine-ligated heme cofactor and molecular oxygen or hydrogen peroxide to catalyze regioselective hydroxylation on the tryptophan indole moiety, which is mechanistically distinct from their animal counterparts from the nonheme iron enzyme family. Through genome mining, we also identify members that can hydroxylate the tryptophan indole ring at alternative positions. Our results not only reveal a conserved way to synthesize hydroxytryptophans in bacteria but also provide a valuable enzyme toolbox for biocatalysis. As proof of concept, we assemble a highly efficient pathway for melatonin in a bacterial host.
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Affiliation(s)
- Xinjie Shi
- The Fourth Affiliated Hospital and Department of Microbiology, School of Medicine, Zhejiang University, Hangzhou, China
| | - Guiyun Zhao
- The Fourth Affiliated Hospital and Department of Microbiology, School of Medicine, Zhejiang University, Hangzhou, China
- Department of Pharmacy, The Fourth Affiliated Hospital, School of Medicine, Zhejiang University, Yiwu, China
| | - Hu Li
- Polytechnic Institute, Zhejiang University, Hangzhou, China
| | - Zhijie Zhao
- The Fourth Affiliated Hospital and Department of Microbiology, School of Medicine, Zhejiang University, Hangzhou, China
| | - Wei Li
- The Fourth Affiliated Hospital and Department of Microbiology, School of Medicine, Zhejiang University, Hangzhou, China
| | - Miaolian Wu
- Department of Pharmacy, The Fourth Affiliated Hospital, School of Medicine, Zhejiang University, Yiwu, China
| | - Yi-Ling Du
- The Fourth Affiliated Hospital and Department of Microbiology, School of Medicine, Zhejiang University, Hangzhou, China.
- Department of Pharmacy, The Fourth Affiliated Hospital, School of Medicine, Zhejiang University, Yiwu, China.
- Jinan Microecological Biomedicine Shandong Laboratory, Jinan, China.
- Zhejiang Provincial Key Laboratory for Microbial Biochemistry and Metabolic Engineering, Hangzhou, China.
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4
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Ehinger FJ, Niehs SP, Dose B, Dell M, Krabbe J, Pidot SJ, Stinear TP, Scherlach K, Ross C, Lackner G, Hertweck C. Analysis of Rhizonin Biosynthesis Reveals Origin of Pharmacophoric Furylalanine Moieties in Diverse Cyclopeptides. Angew Chem Int Ed Engl 2023; 62:e202308540. [PMID: 37650335 DOI: 10.1002/anie.202308540] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 08/28/2023] [Accepted: 08/29/2023] [Indexed: 09/01/2023]
Abstract
Rhizonin A and B are hepatotoxic cyclopeptides produced by bacterial endosymbionts (Mycetohabitans endofungorum) of the fungus Rhizopus microsporus. Their toxicity critically depends on the presence of 3-furylalanine (Fua) residues, which also occur in pharmaceutically relevant cyclopeptides of the endolide and bingchamide families. The biosynthesis and incorporation of Fua by non-ribosomal peptide synthetases (NRPS), however, has remained elusive. By genome sequencing and gene inactivation we elucidated the gene cluster responsible for rhizonin biosynthesis. A suite of isotope labeling experiments identified tyrosine and l-DOPA as Fua precursors and provided the first mechanistic insight. Bioinformatics, mutational analysis and heterologous reconstitution identified dioxygenase RhzB as necessary and sufficient for Fua formation. RhzB is a novel type of heme-dependent aromatic oxygenases (HDAO) that enabled the discovery of the bingchamide biosynthesis gene cluster through genome mining.
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Affiliation(s)
- Friedrich J Ehinger
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstraße 11a, 07745, Jena, Germany
| | - Sarah P Niehs
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstraße 11a, 07745, Jena, Germany
| | - Benjamin Dose
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstraße 11a, 07745, Jena, Germany
| | - Maria Dell
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstraße 11a, 07745, Jena, Germany
| | - Jana Krabbe
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstraße 11a, 07745, Jena, Germany
| | - Sacha J Pidot
- Department of Microbiology and Immunology, Doherty Institute, 792 Elizabeth Street, Melbourne, 3000, Australia
| | - Timothy P Stinear
- Department of Microbiology and Immunology, Doherty Institute, 792 Elizabeth Street, Melbourne, 3000, Australia
| | - Kirstin Scherlach
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstraße 11a, 07745, Jena, Germany
| | - Claudia Ross
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstraße 11a, 07745, Jena, Germany
| | - Gerald Lackner
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstraße 11a, 07745, Jena, Germany
| | - Christian Hertweck
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstraße 11a, 07745, Jena, Germany
- Institute of Microbiology, Faculty of Biological Sciences, Friedrich Schiller University Jena, 07743, Jena, Germany
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5
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Gering HE, Li X, Tang H, Swartz PD, Chang WC, Makris TM. A Ferric-Superoxide Intermediate Initiates P450-Catalyzed Cyclic Dipeptide Dimerization. J Am Chem Soc 2023; 145:19256-19264. [PMID: 37611404 DOI: 10.1021/jacs.3c04542] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
The cytochrome P450 (CYP) AspB is involved in the biosynthesis of the diketopiperazine (DKP) aspergilazine A. Tryptophan-linked dimeric DKP alkaloids are a large family of natural products that are found in numerous species and exhibit broad and often potent bioactivity. The proposed mechanisms for C-N bond formation by AspB, and similar C-C bond formations by related CYPs, have invoked the use of a ferryl-intermediate as an oxidant to promote substrate dimerization. Here, the parallel application of steady-state and transient kinetic approaches reveals a very different mechanism that involves a ferric-superoxide species as a primary oxidant to initiate DKP-assembly. Single turnover kinetic isotope effects and a substrate analog suggest the probable nature and site for abstraction. The direct observation of CYP-superoxide reactivity rationalizes the atypical outcome of AspB and reveals a new reaction manifold in heme enzymes.
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Affiliation(s)
- Hannah E Gering
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Xiaojun Li
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Haoyu Tang
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Paul D Swartz
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Wei-Chen Chang
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Thomas M Makris
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
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6
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Nguyen RC, Stagliano C, Liu A. Structural insights into the half-of-sites reactivity in homodimeric and homotetrameric metalloenzymes. Curr Opin Chem Biol 2023; 75:102332. [PMID: 37269676 PMCID: PMC10528533 DOI: 10.1016/j.cbpa.2023.102332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 04/24/2023] [Accepted: 04/29/2023] [Indexed: 06/05/2023]
Abstract
Half-of-sites reactivity in many homodimeric and homotetrameric metalloenzymes has been known for half a century, yet its benefit remains poorly understood. A recently reported cryo-electron microscopy structure has given some clues on the less optimized reactivity of Escherichia coli ribonucleotide reductase with an asymmetric association of α2β2 subunits during catalysis. Moreover, nonequivalence of enzyme active sites has been reported in many other enzymes, possibly as a means of regulation. They are often induced by substrate binding or caused by a critical component introduced from a neighboring subunit in response to substrate loadings, such as in prostaglandin endoperoxide H synthase, cytidine triphosphate synthase, glyoxalase, tryptophan dioxygenase, and several decarboxylases or dehydrogenases. Overall, half-of-sites reactivity is likely not an act of wasting resources but rather a method devised in nature to accommodate catalytic or regulatory needs.
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Affiliation(s)
- Romie C Nguyen
- Department of Chemistry, University of Texas, San Antonio, TX, 78249, USA
| | - Cassadee Stagliano
- Department of Chemistry, University of Texas, San Antonio, TX, 78249, USA
| | - Aimin Liu
- Department of Chemistry, University of Texas, San Antonio, TX, 78249, USA.
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7
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Nolan K, Wang Y. Combined spectroscopic and structural approaches to explore the mechanism of histidine-ligated heme-dependent aromatic oxygenases. Methods Enzymol 2023; 685:405-432. [PMID: 37245909 PMCID: PMC11057917 DOI: 10.1016/bs.mie.2023.03.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The emergence of histidine-ligated heme-dependent aromatic oxygenases (HDAOs) has greatly enriched heme chemistry, and more studies are required to appreciate the diversity found in His-ligated heme proteins. This chapter describes recent methods in probing the HDAO mechanisms in detail, along with the discussion on how they can benefit structure-function studies of other heme systems. The experimental details are centered on studies of TyrHs, followed by explanation of how the results obtained would advance the understanding of the specific enzyme and also HDAOs. Spectroscopic methods, namely, electronic absorption and EPR spectroscopies, and X-ray crystallography are valuable techniques commonly used to characterize the properties of the heme center and the nature of heme-based intermediate. Herein, we show that the combination of these tools are extremely powerful, not only because one can acquire electronic, magnetic, and conformational information from different phases, but also because of the advantages brought by spectroscopic characterization on crystal samples.
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Affiliation(s)
- Katie Nolan
- Department of Chemistry, University of Georgia, Athens, GA, United States
| | - Yifan Wang
- Department of Chemistry, University of Georgia, Athens, GA, United States.
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8
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Knox HL, Allen KN. Expanding the viewpoint: Leveraging sequence information in enzymology. Curr Opin Chem Biol 2023; 72:102246. [PMID: 36599282 PMCID: PMC10251232 DOI: 10.1016/j.cbpa.2022.102246] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 10/31/2022] [Accepted: 11/21/2022] [Indexed: 01/04/2023]
Abstract
The use of protein sequence to inform enzymology in terms of structure, mechanism, and function has burgeoned over the past two decades. Referred to as genomic enzymology, the utilization of bioinformatic tools such as sequence similarity networks and phylogenetic analyses has allowed the identification of new substrates and metabolites, novel pathways, and unexpected reaction mechanisms. The holistic examination of superfamilies can yield insight into the origins and paths of evolution of enzymes and the range of their substrates and mechanisms. Herein, we highlight advances in the use of genomic enzymology to address problems which the in-depth analyses of a single enzyme alone could not enable.
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Affiliation(s)
- Hayley L Knox
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA, 02215-2521, USA
| | - Karen N Allen
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA, 02215-2521, USA.
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9
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Peng W, Yan S, Zhang X, Liao L, Zhang J, Shaik S, Wang B. How Do Preorganized Electric Fields Function in Catalytic Cycles? The Case of the Enzyme Tyrosine Hydroxylase. J Am Chem Soc 2022; 144:20484-20494. [DOI: 10.1021/jacs.2c09263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Wei Peng
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Shengheng Yan
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Xuan Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Langxing Liao
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Jinyan Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem, 9190407 Jerusalem, Israel
| | - Binju Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
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10
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Lučić M, Wilson MT, Tosha T, Sugimoto H, Shilova A, Axford D, Owen RL, Hough MA, Worrall JAR. Serial Femtosecond Crystallography Reveals the Role of Water in the One- or Two-Electron Redox Chemistry of Compound I in the Catalytic Cycle of the B-Type Dye-Decolorizing Peroxidase DtpB. ACS Catal 2022; 12:13349-13359. [PMID: 36366763 PMCID: PMC9638988 DOI: 10.1021/acscatal.2c03754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 10/05/2022] [Indexed: 11/30/2022]
Abstract
![]()
Controlling the reactivity
of high-valent Fe(IV)–O
catalytic
intermediates, Compounds I and II, generated in heme enzymes upon
reaction with dioxygen or hydrogen peroxide, is important for function.
It has been hypothesized that the presence (wet) or absence (dry)
of distal heme pocket water molecules can influence whether Compound
I undergoes sequential one-electron additions or a concerted two-electron
reduction. To test this hypothesis, we investigate the role of water
in the heme distal pocket of a dye-decolorizing peroxidase utilizing
a combination of serial femtosecond crystallography and rapid kinetic
studies. In a dry distal heme site, Compound I reduction proceeds
through a mechanism in which Compound II concentration is low. This
reaction shows a strong deuterium isotope effect, indicating that
reduction is coupled to proton uptake. The resulting protonated Compound
II (Fe(IV)–OH) rapidly reduces to the ferric state, giving
the appearance of a two-electron transfer process. In a wet site,
reduction of Compound I is faster, has no deuterium effect, and yields
highly populated Compound II, which is subsequently reduced to the
ferric form. This work provides a definitive experimental test of
the hypothesis advanced in the literature that relates sequential
or concerted electron transfer to Compound I in wet or dry distal
heme sites.
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Affiliation(s)
- Marina Lučić
- School of Life Sciences, University of Essex, Wivenhoe Park,
Essex, ColchesterCO4 3SQ, U.K
| | - Michael T. Wilson
- School of Life Sciences, University of Essex, Wivenhoe Park,
Essex, ColchesterCO4 3SQ, U.K
| | - Takehiko Tosha
- RIKEN, Spring-8 Center, 1-1-1 Kouto, Sayo, Hyogo679-5148Japan
| | | | - Anastasya Shilova
- Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire, DidcotOX11 0DE, U.K
| | - Danny Axford
- Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire, DidcotOX11 0DE, U.K
| | - Robin L. Owen
- Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire, DidcotOX11 0DE, U.K
| | - Michael A. Hough
- School of Life Sciences, University of Essex, Wivenhoe Park,
Essex, ColchesterCO4 3SQ, U.K
- Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire, DidcotOX11 0DE, U.K
| | - Jonathan A. R. Worrall
- School of Life Sciences, University of Essex, Wivenhoe Park,
Essex, ColchesterCO4 3SQ, U.K
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11
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Mondal P, Rajapakse S, Wijeratne GB. Following Nature's Footprint: Mimicking the High-Valent Heme-Oxo Mediated Indole Monooxygenation Reaction Landscape of Heme Enzymes. J Am Chem Soc 2022; 144:3843-3854. [PMID: 35112858 DOI: 10.1021/jacs.1c11068] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pathways for direct conversion of indoles to oxindoles have accumulated considerable interest in recent years due to their significance in the clear comprehension of various pathogenic processes in humans and the multipotent therapeutic value of oxindole pharmacophores. Heme enzymes are predominantly responsible for this conversion in biology and are thought to proceed with a compound-I active oxidant. These heme-enzyme-mediated indole monooxygenation pathways are rapidly emerging therapeutic targets; however, a clear mechanistic understanding is still lacking. Additionally, such knowledge holds promise in the rational design of highly specific indole monooxygenation synthetic protocols that are also cost-effective and environmentally benign. We herein report the first examples of synthetic compound-I and activated compound-II species that can effectively monooxygenate a diverse array of indoles with varied electronic and steric properties to exclusively produce the corresponding 2-oxindole products in good to excellent yields. Rigorous kinetic, thermodynamic, and mechanistic interrogations clearly illustrate an initial rate-limiting epoxidation step that takes place between the heme oxidant and indole substrate, and the resulting indole epoxide intermediate undergoes rearrangement driven by a 2,3-hydride shift on indole ring to ultimately produce 2-oxindole. The complete elucidation of the indole monooxygenation mechanism of these synthetic heme models will help reveal crucial insights into analogous biological systems, directly reinforcing drug design attempts targeting those heme enzymes. Moreover, these bioinspired model compounds are promising candidates for the future development of better synthetic protocols for the selective, efficient, and sustainable generation of 2-oxindole motifs, which are already known for a plethora of pharmacological benefits.
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Affiliation(s)
- Pritam Mondal
- Department of Chemistry and O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, Alabama 35205, United States
| | - Shanuk Rajapakse
- Department of Chemistry and O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, Alabama 35205, United States
| | - Gayan B Wijeratne
- Department of Chemistry and O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, Alabama 35205, United States
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