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Wenger ES, Martinie RJ, Ushimaru R, Pollock CJ, Sil D, Li A, Hoang N, Palowitch GM, Graham BP, Schaperdoth I, Burke EJ, Maggiolo AO, Chang WC, Allen BD, Krebs C, Silakov A, Boal AK, Bollinger JM. Optimized Substrate Positioning Enables Switches in the C-H Cleavage Site and Reaction Outcome in the Hydroxylation-Epoxidation Sequence Catalyzed by Hyoscyamine 6β-Hydroxylase. J Am Chem Soc 2024; 146:24271-24287. [PMID: 39172701 PMCID: PMC11374477 DOI: 10.1021/jacs.4c04406] [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] [Indexed: 08/24/2024]
Abstract
Hyoscyamine 6β-hydroxylase (H6H) is an iron(II)- and 2-oxoglutarate-dependent (Fe/2OG) oxygenase that produces the prolifically administered antinausea drug, scopolamine. After its namesake hydroxylation reaction, H6H then couples the newly installed C6 oxygen to C7 to produce the drug's epoxide functionality. Oxoiron(IV) (ferryl) intermediates initiate both reactions by cleaving C-H bonds, but it remains unclear how the enzyme switches the target site and promotes (C6)O-C7 coupling in preference to C7 hydroxylation in the second step. In one possible epoxidation mechanism, the C6 oxygen would─analogously to mechanisms proposed for the Fe/2OG halogenases and, in our more recent study, N-acetylnorloline synthase (LolO)─coordinate as alkoxide to the C7-H-cleaving ferryl intermediate to enable alkoxyl coupling to the ensuing C7 radical. Here, we provide structural and kinetic evidence that H6H does not employ substrate coordination or repositioning for the epoxidation step but instead exploits the distinct spatial dependencies of competitive C-H cleavage (C6 vs C7) and C-O-coupling (oxygen rebound vs cyclization) steps to promote the two-step sequence. Structural comparisons of ferryl-mimicking vanadyl complexes of wild-type H6H and a variant that preferentially 7-hydroxylates instead of epoxidizing 6β-hydroxyhyoscyamine suggest that a modest (∼10°) shift in the Fe-O-H(C7) approach angle is sufficient to change the outcome. The 7-hydroxylation:epoxidation partition ratios of both proteins increase more than 5-fold in 2H2O, reflecting an epoxidation-specific requirement for cleavage of the alcohol O-H bond, which, unlike in the LolO oxacyclization, is not accomplished by iron coordination in advance of C-H cleavage.
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Affiliation(s)
- Eliott S Wenger
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | | | - Richiro Ushimaru
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-8657, Japan
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2
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Ushimaru R. Three-membered ring formation catalyzed by α-ketoglutarate-dependent nonheme iron enzymes. J Nat Med 2024; 78:21-32. [PMID: 37980694 PMCID: PMC10764440 DOI: 10.1007/s11418-023-01760-4] [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: 10/16/2023] [Accepted: 10/25/2023] [Indexed: 11/21/2023]
Abstract
Epoxides, aziridines, and cyclopropanes are found in various medicinal natural products, including polyketides, terpenes, peptides, and alkaloids. Many classes of biosynthetic enzymes are involved in constructing these ring structures during their biosynthesis. This review summarizes our current knowledge regarding how α-ketoglutarate-dependent nonheme iron enzymes catalyze the formation of epoxides, aziridines, and cyclopropanes in nature, with a focus on enzyme mechanisms.
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Affiliation(s)
- Richiro Ushimaru
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan.
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo, 113-8657, Japan.
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3
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Li B, Wen W, Wen W, Guo H, Fu C, Zhang Y, Zhu L. Application of Chitosan/Poly(vinyl alcohol) Stabilized Copper Film Materials for the Borylation of α, β-Unsaturated Ketones, Morita-Baylis-Hillman Alcohols and Esters in Aqueous Phase. Molecules 2023; 28:5609. [PMID: 37513482 PMCID: PMC10386186 DOI: 10.3390/molecules28145609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 07/21/2023] [Accepted: 07/21/2023] [Indexed: 07/30/2023] Open
Abstract
A chitosan/poly(vinyl alcohol)-stabilized copper nanoparticle (CP@Cu NPs) was used as a heterogeneous catalyst for the borylation of α, β-unsaturated ketones, MBH alcohols, and MBH esters in mild conditions. This catalyst not only demonstrated remarkable efficiency in synthesizing organoboron compounds but also still maintained excellent reactivity and stability even after seven recycled uses of the catalyst. This methodology provides a gentle and efficient approach to synthesize the organoboron compounds by efficiently constructing carbon-boron bonds.
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Affiliation(s)
- Bojie Li
- School of Chemistry and Materials Science, Hubei Key Laboratory of Quality Control of Characteristic Fruits and Vegetables, Hubei Engineering University, Xiaogan 432000, China
| | - Wu Wen
- School of Chemistry and Materials Science, Hubei Key Laboratory of Quality Control of Characteristic Fruits and Vegetables, Hubei Engineering University, Xiaogan 432000, China
- School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
| | - Wei Wen
- School of Chemistry and Materials Science, Hubei Key Laboratory of Quality Control of Characteristic Fruits and Vegetables, Hubei Engineering University, Xiaogan 432000, China
- School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
| | - Haifeng Guo
- School of Chemistry and Materials Science, Hubei Key Laboratory of Quality Control of Characteristic Fruits and Vegetables, Hubei Engineering University, Xiaogan 432000, China
- School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
| | - Chengpeng Fu
- School of Chemistry and Materials Science, Hubei Key Laboratory of Quality Control of Characteristic Fruits and Vegetables, Hubei Engineering University, Xiaogan 432000, China
- School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
| | - Yaoyao Zhang
- School of Chemistry and Materials Science, Hubei Key Laboratory of Quality Control of Characteristic Fruits and Vegetables, Hubei Engineering University, Xiaogan 432000, China
| | - Lei Zhu
- School of Chemistry and Materials Science, Hubei Key Laboratory of Quality Control of Characteristic Fruits and Vegetables, Hubei Engineering University, Xiaogan 432000, China
- School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
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4
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Ushimaru R, Abe I. Unusual Dioxygen-Dependent Reactions Catalyzed by Nonheme Iron Enzymes in Natural Product Biosynthesis. ACS Catal 2022. [DOI: 10.1021/acscatal.2c05247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Richiro Ushimaru
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
- ACT-X, Japan Science and Technology Agency (JST), Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Ikuro Abe
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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5
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Tao H, Ushimaru R, Awakawa T, Mori T, Uchiyama M, Abe I. Stereoselectivity and Substrate Specificity of the Fe(II)/α-Ketoglutarate-Dependent Oxygenase TqaL. J Am Chem Soc 2022; 144:21512-21520. [DOI: 10.1021/jacs.2c08116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Hui Tao
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Richiro Ushimaru
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo 113-0033, Japan
- ACT-X, Japan Science and Technology Agency (JST), Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Takayoshi Awakawa
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo 113-0033, Japan
- RIKEN Center for Sustainable Resource Science, Wako, Saitama 351-0198, Japan
| | - Takahiro Mori
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo 113-0033, Japan
- PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
| | - Masanobu Uchiyama
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
- Research Initiative for Supra-Materials (RISM), Shinshu University, Ueda 386-8567, Japan
| | - Ikuro Abe
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo 113-0033, Japan
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6
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Maldonado-Domínguez M, Srnec M. H-Atom Abstraction Reactivity through the Lens of Asynchronicity and Frustration with Their Counteracting Effects on Barriers. Inorg Chem 2022; 61:18811-18822. [DOI: 10.1021/acs.inorgchem.2c03269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Mauricio Maldonado-Domínguez
- J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8 18223, Czech Republic
| | - Martin Srnec
- J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8 18223, Czech Republic
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7
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Wojdyla Z, Borowski T. Properties of the Reactants and Their Interactions within and with the Enzyme Binding Cavity Determine Reaction Selectivities. The Case of Fe(II)/2-Oxoglutarate Dependent Enzymes. Chemistry 2022; 28:e202104106. [PMID: 34986268 DOI: 10.1002/chem.202104106] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Indexed: 12/12/2022]
Abstract
Fe(II)/2-oxoglutarate dependent dioxygenases (ODDs) share a double stranded beta helix (DSBH) fold and utilise a common reactive intermediate, ferryl species, to catalyse oxidative transformations of substrates. Despite the structural similarities, ODDs accept a variety of substrates and facilitate a wide range of reactions, that is hydroxylations, desaturations, (oxa)cyclisations and ring rearrangements. In this review we present and discuss the factors contributing to the observed (regio)selectivities of ODDs. They span from inherent properties of the reactants, that is, substrate molecule and iron cofactor, to the interactions between the substrate and the enzyme's binding cavity; the latter can counterbalance the effect of the former. Based on results of both experimental and computational studies dedicated to ODDs, we also line out the properties of the reactants which promote reaction outcomes other than the "default" hydroxylation. It turns out that the reaction selectivity depends on a delicate balance of interactions between the components of the investigated system.
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Affiliation(s)
- Zuzanna Wojdyla
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Kraków, Niezapominajek 8, 30239 Krakow, Poland
| | - Tomasz Borowski
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Kraków, Niezapominajek 8, 30239 Krakow, Poland
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8
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Tassano E, Moore C, Dussauge S, Vargas A, Snajdrova R. Discovery of New Fe(II)/α-Ketoglutarate-Dependent Dioxygenases for Oxidation of l-Proline. Org Process Res Dev 2022. [DOI: 10.1021/acs.oprd.1c00405] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Erika Tassano
- Global Discovery Chemistry, Novartis Institute for Biomedical Research, 4056 Basel, Switzerland
| | - Charles Moore
- Global Discovery Chemistry, Novartis Institute for Biomedical Research, 4056 Basel, Switzerland
| | - Solene Dussauge
- Global Discovery Chemistry, Novartis Institute for Biomedical Research, 4056 Basel, Switzerland
| | - Alexandra Vargas
- Global Discovery Chemistry, Novartis Institute for Biomedical Research, 4056 Basel, Switzerland
| | - Radka Snajdrova
- Global Discovery Chemistry, Novartis Institute for Biomedical Research, 4056 Basel, Switzerland
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9
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Huang JP, Wang YJ, Tian T, Wang L, Yan Y, Huang SX. Tropane alkaloid biosynthesis: a centennial review. Nat Prod Rep 2021; 38:1634-1658. [PMID: 33533391 DOI: 10.1039/d0np00076k] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Covering: 1917 to 2020Tropane alkaloids (TAs) are a remarkable class of plant secondary metabolites, which are characterized by an 8-azabicyclo[3.2.1]octane (nortropane) ring. Members of this class, such as hyoscyamine, scopolamine, and cocaine, are well known for their long history as poisons, hallucinogens, and anaesthetic agents. Since the structure of the tropane ring system was first elucidated in 1901, organic chemists and biochemists have been interested in how these mysterious tropane alkaloids are assembled in vitro and in vivo. However, it was only in 2020 that the complete biosynthetic route of hyoscyamine and scopolamine was clarified, and their de novo production in yeast was also achieved. The aim of this review is to present the innovative ideas and results in exploring the story of tropane alkaloid biosynthesis in plants from 1917 to 2020. This review also highlights that Robinson's classic synthesis of tropinone, which is one hundred years old, is biomimetic, and underscores the importance of total synthesis in the study of natural product biosynthesis.
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Affiliation(s)
- Jian-Ping Huang
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China. and State Key Laboratory of Southwestern Chinese Medicine Resources, Innovative Institute of Chinese Medicine and Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137, China
| | - Yong-Jiang Wang
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China.
| | - Tian Tian
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China. and School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China
| | - Li Wang
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China.
| | - Yijun Yan
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China.
| | - Sheng-Xiong Huang
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China. and State Key Laboratory of Southwestern Chinese Medicine Resources, Innovative Institute of Chinese Medicine and Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137, China and School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China
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10
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Copeland RA, Davis KM, Shoda TKC, Blaesi EJ, Boal AK, Krebs C, Bollinger JM. An Iron(IV)-Oxo Intermediate Initiating l-Arginine Oxidation but Not Ethylene Production by the 2-Oxoglutarate-Dependent Oxygenase, Ethylene-Forming Enzyme. J Am Chem Soc 2021; 143:2293-2303. [PMID: 33522811 DOI: 10.1021/jacs.0c10923] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Ethylene-forming enzyme (EFE) is an ambifunctional iron(II)- and 2-oxoglutarate-dependent (Fe/2OG) oxygenase. In its major (EF) reaction, it converts carbons 1, 2, and 5 of 2OG to CO2 and carbons 3 and 4 to ethylene, a four-electron oxidation drastically different from the simpler decarboxylation of 2OG to succinate mediated by all other Fe/2OG enzymes. EFE also catalyzes a minor reaction, in which the normal decarboxylation is coupled to oxidation of l-arginine (a required activator for the EF pathway), resulting in its conversion to l-glutamate semialdehyde and guanidine. Here we show that, consistent with precedent, the l-Arg-oxidation (RO) pathway proceeds via an iron(IV)-oxo (ferryl) intermediate. Use of 5,5-[2H2]-l-Arg slows decay of the ferryl complex by >16-fold, implying that RO is initiated by hydrogen-atom transfer (HAT) from C5. That this large substrate deuterium kinetic isotope effect has no impact on the EF:RO partition ratio implies that the same ferryl intermediate cannot be on the EF pathway; the pathways must diverge earlier. Consistent with this conclusion, the variant enzyme bearing the Asp191Glu ligand substitution accumulates ∼4 times as much of the ferryl complex as the wild-type enzyme and exhibits a ∼40-fold diminished EF:RO partition ratio. The selective detriment of this nearly conservative substitution to the EF pathway implies that it has unusually stringent stereoelectronic requirements. An active-site, like-charge guanidinium pair, which involves the l-Arg substrate/activator and is unique to EFE among four crystallographically characterized l-Arg-modifying Fe/2OG oxygenases, may serve to selectively stabilize the transition state leading to the unique EF branch.
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11
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Kluza A, Wojdyla Z, Mrugala B, Kurpiewska K, Porebski PJ, Niedzialkowska E, Minor W, Weiss MS, Borowski T. Regioselectivity of hyoscyamine 6β-hydroxylase-catalysed hydroxylation as revealed by high-resolution structural information and QM/MM calculations. Dalton Trans 2020; 49:4454-4469. [PMID: 32182320 DOI: 10.1039/d0dt00302f] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Hyoscyamine 6β-hydroxylase (H6H) is a bifunctional non-heme 2-oxoglutarate/Fe2+-dependent dioxygenase that catalyzes the two final steps in the biosynthesis of scopolamine. Based on high resolution crystal structures of H6H from Datura metel, detailed information on substrate binding was obtained that provided insights into the onset of the enzymatic process. In particular, the role of two prominent residues was revealed - Glu-116 that interacts with the tertiary amine located on the hyoscyamine tropane moiety and Tyr-326 that forms CH-π hydrogen bonds with the hyoscyamine phenyl ring. The structures were used as the basis for QM/MM calculations that provided an explanation for the regioselectivity of the hydroxylation reaction on the hyoscyamine tropane moiety (C6 vs. C7) and quantified contributions of active site residues to respective barrier heights.
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Affiliation(s)
- Anna Kluza
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, PL-30239 Krakow, Poland.
| | - Zuzanna Wojdyla
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, PL-30239 Krakow, Poland.
| | - Beata Mrugala
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, PL-30239 Krakow, Poland.
| | - Katarzyna Kurpiewska
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, PL-30239 Krakow, Poland. and Department of Crystal Chemistry and Crystal Physics, Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, PL-30387 Krakow, Poland
| | - Przemyslaw J Porebski
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, PL-30239 Krakow, Poland. and Department of Molecular Physiology and Biological Physics, University of Virginia, 1340 Jefferson Park Avenue Pinn Hall, Charlottesville, VA 22908, USA
| | - Ewa Niedzialkowska
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, PL-30239 Krakow, Poland. and Department of Molecular Physiology and Biological Physics, University of Virginia, 1340 Jefferson Park Avenue Pinn Hall, Charlottesville, VA 22908, USA
| | - Wladek Minor
- Department of Molecular Physiology and Biological Physics, University of Virginia, 1340 Jefferson Park Avenue Pinn Hall, Charlottesville, VA 22908, USA
| | - Manfred S Weiss
- Macromolecular Crystallography, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, D-12489, Berlin, Germany
| | - Tomasz Borowski
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, PL-30239 Krakow, Poland.
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12
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Dunham NP, Arnold FH. Nature's Machinery, Repurposed: Expanding the Repertoire of Iron-Dependent Oxygenases. ACS Catal 2020; 10:12239-12255. [PMID: 33282461 PMCID: PMC7710332 DOI: 10.1021/acscatal.0c03606] [Citation(s) in RCA: 78] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Iron is an especially important redox-active cofactor in biology because of its ability to mediate reactions with atmospheric O2. Iron-dependent oxygenases exploit this earth-abundant transition metal for the insertion of oxygen atoms into organic compounds. Throughout the astounding diversity of transformations catalyzed by these enzymes, the protein framework directs reactive intermediates toward the precise formation of products, which, in many cases, necessitates the cleavage of strong C-H bonds. In recent years, members of several iron-dependent oxygenase families have been engineered for new-to-nature transformations that offer advantages over conventional synthetic methods. In this Perspective, we first explore what is known about the reactivity of heme-dependent cytochrome P450 oxygenases and nonheme iron-dependent oxygenases bearing the 2-His-1-carboxylate facial triad by reviewing mechanistic studies with an emphasis on how the protein scaffold maximizes the catalytic potential of the iron-heme and iron cofactors. We then review how these cofactors have been repurposed for abiological transformations by engineering the protein frameworks of these enzymes. Finally, we discuss contemporary challenges associated with engineering these platforms and comment on their roles in biocatalysis moving forward.
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Affiliation(s)
- Noah P. Dunham
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, MC 210-41, Pasadena, California 91125, United States
| | - Frances H. Arnold
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, MC 210-41, Pasadena, California 91125, United States
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13
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Pan J, Wenger ES, Matthews ML, Pollock CJ, Bhardwaj M, Kim AJ, Allen BD, Grossman RB, Krebs C, Bollinger JM. Evidence for Modulation of Oxygen Rebound Rate in Control of Outcome by Iron(II)- and 2-Oxoglutarate-Dependent Oxygenases. J Am Chem Soc 2019; 141:15153-15165. [PMID: 31475820 DOI: 10.1021/jacs.9b06689] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Iron(II)- and 2-oxoglutarate-dependent (Fe/2OG) oxygenases generate iron(IV)-oxo (ferryl) intermediates that can abstract hydrogen from aliphatic carbons (R-H). Hydroxylation proceeds by coupling of the resultant substrate radical (R•) and oxygen of the Fe(III)-OH complex ("oxygen rebound"). Nonhydroxylation outcomes result from different fates of the Fe(III)-OH/R• state; for example, halogenation results from R• coupling to a halogen ligand cis to the hydroxide. We previously suggested that halogenases control substrate-cofactor disposition to disfavor oxygen rebound and permit halogen coupling to prevail. Here, we explored the general implication that, when a ferryl intermediate can ambiguously target two substrate carbons for different outcomes, rebound to the site capable of the alternative outcome should be slower than to the adjacent, solely hydroxylated site. We evaluated this prediction for (i) the halogenase SyrB2, which exclusively hydroxylates C5 of norvaline appended to its carrier protein but can either chlorinate or hydroxylate C4 and (ii) two bifunctional enzymes that normally hydroxylate one carbon before coupling that oxygen to a second carbon (producing an oxacycle) but can, upon encountering deuterium at the first site, hydroxylate the second site instead. In all three cases, substrate hydroxylation incorporates a greater fraction of solvent-derived oxygen at the site that can also undergo the alternative outcome than at the other site, most likely reflecting an increased exchange of the initially O2-derived oxygen ligand in the longer-lived Fe(III)-OH/R• states. Suppression of rebound may thus be generally important for nonhydroxylation outcomes by these enzymes.
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Affiliation(s)
| | | | | | | | - Minakshi Bhardwaj
- Department of Chemistry , University of Kentucky , Lexington , Kentucky 40546-0312 , United States
| | | | | | - Robert B Grossman
- Department of Chemistry , University of Kentucky , Lexington , Kentucky 40546-0312 , United States
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Effects of Water Availability in the Soil on Tropane Alkaloid Production in Cultivated Datura stramonium. Metabolites 2019; 9:metabo9070131. [PMID: 31277288 PMCID: PMC6680536 DOI: 10.3390/metabo9070131] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 06/26/2019] [Accepted: 06/28/2019] [Indexed: 12/14/2022] Open
Abstract
Background: different Solanaceae and Erythroxylaceae species produce tropane alkaloids. These alkaloids are the starting material in the production of different pharmaceuticals. The commercial demand for tropane alkaloids is covered by extracting them from cultivated plants. Datura stramonium is cultivated under greenhouse conditions as a source of tropane alkaloids. Here we investigate the effect of different levels of water availability in the soil on the production of tropane alkaloids by D. stramonium. Methods: We tested four irrigation levels on the accumulation of tropane alkaloids. We analyzed the profile of tropane alkaloids using an untargeted liquid chromatography/mass spectrometry method. Results: Using a combination of informatics and manual interpretation of mass spectra, we generated several structure hypotheses for signals in D. stramonium extracts that we assign as putative tropane alkaloids. Quantitation of mass spectrometry signals for our structure hypotheses across different anatomical organs allowed us to identify patterns of tropane alkaloids associated with different levels of irrigation. Furthermore, we identified anatomic partitioning of tropane alkaloid isomers with pharmaceutical applications. Conclusions: Our results show that soil water availability is an effective method for maximizing the production of specific tropane alkaloids for industrial applications.
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