1
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Peter M, Zhang ZX, Yang Y, Li SM. Biosynthesis of the Sesquiterpenoid Malfilanol D in Aspergillus ustus Implies Alkyl and Hydride Migrations during the Bicyclo[5.4.0]undecane Skeleton Formation. Org Lett 2024; 26:6670-6674. [PMID: 39073982 DOI: 10.1021/acs.orglett.4c02351] [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: 07/31/2024]
Abstract
The great variety and fascinating complexity of terpenoid skeletons are achieved through different cyclizations catalyzed by terpene cyclases. Here, we report a sesquiterpene cyclase (MfdS) from Aspergillus ustus for the formation of malfilanol D, a member of the group of biochemically less investigated sesquiterpenes with a bicyclo[5.4.0]undecane skeleton. Feeding 13C-labeled acetates in Aspergillus nidulans with the mfdS sequence provides evidence for a C-1 to C-10 cyclization with subsequent 1,2-alkyl and 1,2-hydride shifts in the formation of the 6/7-fused rings.
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Affiliation(s)
- Marlies Peter
- Institut für Pharmazeutische Biologie und Biotechnologie, Fachbereich Pharmazie, Philipps-Universität Marburg, Robert-Koch-Straße 4, Marburg 35037, Germany
| | - Zheng-Xi Zhang
- Institut für Pharmazeutische Biologie und Biotechnologie, Fachbereich Pharmazie, Philipps-Universität Marburg, Robert-Koch-Straße 4, Marburg 35037, Germany
| | - Yiling Yang
- Institut für Pharmazeutische Biologie und Biotechnologie, Fachbereich Pharmazie, Philipps-Universität Marburg, Robert-Koch-Straße 4, Marburg 35037, Germany
| | - Shu-Ming Li
- Institut für Pharmazeutische Biologie und Biotechnologie, Fachbereich Pharmazie, Philipps-Universität Marburg, Robert-Koch-Straße 4, Marburg 35037, Germany
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2
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González Requena V, Srivastava PL, Miller DJ, Allemann RK. Single Point Mutation Abolishes Water Capture in Germacradien-4-ol Synthase. Chembiochem 2024:e202400290. [PMID: 39031755 DOI: 10.1002/cbic.202400290] [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: 03/30/2024] [Revised: 06/13/2024] [Accepted: 06/21/2024] [Indexed: 07/22/2024]
Abstract
The high-fidelity sesquiterpene cyclase (-)-germacradien-4-ol synthase (GdolS) converts farnesyl diphosphate into the macrocyclic alcohol (-)-germacradien-4-ol. Site-directed mutagenesis was used to decipher the role of key residues in the water control mechanism. Replacement of Ala176, located in the G1/2 helix, with non-polar aliphatic residues of increasing size (valine, leucine, isoleucine and methionine) resulted in the accumulation of the non-hydroxylated products germacrene A and germacrene D. In contrast, hydroxylation was maintained when the polar residues threonine, glutamine or aspartate replaced Ala176. Additionally, although a contribution of His150 to the nucleophilic water addition could be ruled out, the imidazole ring of His150 appears to assist carbocation stabilisation. The results presented here shed light on how hydroxylating sesquiterpene synthases can be engineered to design modified sesquiterpene synthases to reduce the need for further steps in the biocatalytic production of oxygenated sesquiterpenoids.
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Affiliation(s)
- Víctor González Requena
- School of Chemistry, Main Building, Cardiff University, Park Place, Cardiff, CF10 3AT, United Kingdom
| | - Prabhakar L Srivastava
- School of Chemistry, Main Building, Cardiff University, Park Place, Cardiff, CF10 3AT, United Kingdom
| | - David J Miller
- School of Chemistry, Main Building, Cardiff University, Park Place, Cardiff, CF10 3AT, United Kingdom
| | - Rudolf K Allemann
- School of Chemistry, Main Building, Cardiff University, Park Place, Cardiff, CF10 3AT, United Kingdom
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3
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Matsuyama T, Togashi K, Nakano M, Sato H, Uchiyama M. Revision of the Peniroquesine Biosynthetic Pathway by Retro-Biosynthetic Theoretical Analysis: Ring Strain Controls the Unique Carbocation Rearrangement Cascade. JACS AU 2023; 3:1596-1603. [PMID: 37388688 PMCID: PMC10301677 DOI: 10.1021/jacsau.3c00039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 04/22/2023] [Accepted: 04/24/2023] [Indexed: 07/01/2023]
Abstract
Peniroquesine, a sesterterpenoid featuring a unique 5/6/5/6/5 fused pentacyclic ring system, has been known for a long time, but its biosynthetic pathway/mechanism remains elusive. Based on isotopic labeling experiments, a plausible biosynthetic pathway to peniroquesines A-C and their derivatives was recently proposed, in which the characteristic peniroquesine-type 5/6/5/6/5 pentacyclic skeleton is synthesized from geranyl-farnesyl pyrophosphate (GFPP) via a complex concerted A/B/C-ring formation, repeated reverse-Wagner-Meerwein alkyl shifts, three successive secondary (2°) carbocation intermediates, and a highly distorted trans-fused bicyclo[4.2.1]nonane intermediate. However, our density functional theory calculations do not support this mechanism. By applying a retro-biosynthetic theoretical analysis strategy, we were able to find a preferred pathway for peniroquesine biosynthesis, involving a multistep carbocation cascade including triple skeletal rearrangements, trans-cis isomerization, and 1,3-H shift. This pathway/mechanism is in good agreement with all of the reported isotope-labeling results.
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Affiliation(s)
- Taro Matsuyama
- Graduate
School of Pharmaceutical Sciences, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Ko Togashi
- Graduate
School of Pharmaceutical Sciences, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Moe Nakano
- Interdisciplinary
Graduate School of Medicine and Engineering, University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi 400-8510, Japan
| | - Hajime Sato
- Interdisciplinary
Graduate School of Medicine and Engineering, University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi 400-8510, Japan
| | - Masanobu Uchiyama
- Graduate
School of Pharmaceutical Sciences, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
- Research
Initiative for Supra-Materials (RISM), Shinshu
University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
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4
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Larmore SP, Champagne PA. Cyclopropylcarbinyl-to-Homoallyl Carbocation Equilibria Influence the Stereospecificity in the Nucleophilic Substitution of Cyclopropylcarbinols. J Org Chem 2023. [PMID: 37141426 DOI: 10.1021/acs.joc.3c00257] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The synthesis of quaternary homoallylic halides and trichloroacetates from cyclopropylcarbinols, as reported by Marek (J. Am. Chem. Soc. 2020, 142, 5543-5548), is one of the few reported examples of stereospecific nucleophilic substitution involving chiral bridged carbocations. However, for the phenyl-substituted substrates, poor specificity is observed and mixtures of diastereomers are obtained. To understand the nature of the intermediates involved and explain the loss of specificity for certain substrates, we have performed a computational investigation of the reaction mechanism using ωB97X-D optimizations and DLPNO-CCSD(T) energy refinements. Our results indicate that cyclopropylcarbinyl cations are stable intermediates in this reaction, while bicyclobutonium structures are high-energy transition structures that are not involved. Instead, multiple rearrangement pathways of cyclopropylcarbinyl cations were located, including ring openings to homoallylic cations. The activation barriers required to reach such structures are correlated to the nature of the substituents; while direct nucleophilic attack on the chiral cyclopropylcarbinyl cations is kinetically favored for most systems, the rearrangements become competitive with nucleophilic attack for the phenyl-substituted systems, leading to a loss of specificity through rearranged carbocation intermediates. As such, stereospecific reactions of chiral cyclopropylcarbinyl cations depend on the energies required to access their corresponding homoallylic structures, from which selectivity is not guaranteed.
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Affiliation(s)
- Sean P Larmore
- Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102, United States
| | - Pier Alexandre Champagne
- Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102, United States
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5
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Zeng T, Hess BA, Zhang F, Wu R. Bio-inspired chemical space exploration of terpenoids. Brief Bioinform 2022; 23:6586263. [PMID: 35576010 DOI: 10.1093/bib/bbac197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 04/26/2022] [Accepted: 04/28/2022] [Indexed: 11/12/2022] Open
Abstract
Many computational methods are devoted to rapidly generating pseudo-natural products to expand the open-ended border of chemical spaces for natural products. However, the accessibility and chemical interpretation were often ignored or underestimated in conventional library/fragment-based or rule-based strategies, thus hampering experimental synthesis. Herein, a bio-inspired strategy (named TeroGen) is developed to mimic the two key biosynthetic stages (cyclization and decoration) of terpenoid natural products, by utilizing physically based simulations and deep learning models, respectively. The precision and efficiency are validated for different categories of terpenoids, and in practice, more than 30 000 sesterterpenoids (10 times as many as the known sesterterpenoids) are predicted to be linked in a reaction network, and their synthetic accessibility and chemical interpretation are estimated by thermodynamics and kinetics. Since it could not only greatly expand the chemical space of terpenoids but also numerate plausible biosynthetic routes, TeroGen is promising for accelerating heterologous biosynthesis, bio-mimic and chemical synthesis of complicated terpenoids and derivatives.
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Affiliation(s)
- Tao Zeng
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, P.R. China
| | | | - Fan Zhang
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, P.R. China
| | - Ruibo Wu
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, P.R. China
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6
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Sato H, Li BX, Takagi T, Wang C, Miyamoto K, Uchiyama M. DFT Study on the Biosynthesis of Verrucosane Diterpenoids and Mangicol Sesterterpenoids: Involvement of Secondary-Carbocation-Free Reaction Cascades. JACS AU 2021; 1:1231-1239. [PMID: 34467361 PMCID: PMC8397367 DOI: 10.1021/jacsau.1c00178] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Indexed: 05/03/2023]
Abstract
Some experimental observations indicate that a sequential formation of secondary (2°) carbocations might be involved in some biosynthetic pathways, including those of verrucosane-type diterpenoids and mangicol-type sesterterpenoids, but it remains controversial whether or not such 2° cations are viable intermediates. Here, we performed comprehensive density functional theory calculations of these biosynthetic pathways. The results do not support previously proposed pathways/mechanisms: in particular, we find that none of the putative 2° carbocation intermediates is involved in either of the biosynthetic pathways. In verrucosane biosynthesis, the proposed 2° carbocations (II and IV) in the early stage are bypassed by the formation of the adjacent 3° carbocations and by unusual skeletal rearrangement reactions, and in the later stage, the putative 2° carbocation intermediates (VI, VII, and VIII) are not present as the proposed forms but as nonclassical structures between homoallyl and cyclopropylcarbinyl cations. In the mangicol biosynthesis, one of the two proposed 2° carbocations (X) is bypassed by a C-C bond-breaking reaction to generate a 3° carbocation with a C=C bond, while the other (XI) is bypassed by a strong hyperconjugative interaction leading to a nonclassical carbocation. We propose new biosynthetic pathways/mechanisms for the verrucosane-type diterpenoids and mangicol-type sesterterpenoids. These pathways are in good agreement with the findings of previous biosynthetic studies, including isotope-labeling experiments and byproducts analysis, and moreover can account for the biosynthesis of related terpenes.
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Affiliation(s)
- Hajime Sato
- Interdisciplinary
Graduate School of Medicine and Engineering, University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi 400-8510, Japan
- Graduate
School of Pharmaceutical Sciences, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Bi-Xiao Li
- Graduate
School of Pharmaceutical Sciences, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Taisei Takagi
- Graduate
School of Pharmaceutical Sciences, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Chao Wang
- Graduate
School of Pharmaceutical Sciences, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Kazunori Miyamoto
- Graduate
School of Pharmaceutical Sciences, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masanobu Uchiyama
- Graduate
School of Pharmaceutical Sciences, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
- Research
Initiative for Supra-Materials, Shinshu
University, 3-15-1 Tokida,
Ueda, Nagano 386-8567, Japan
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7
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Muangphrom P, Misaki M, Suzuki M, Shimomura M, Suzuki H, Seki H, Muranaka T. Identification and characterization of (+)-α-bisabolol and 7-epi-silphiperfol-5-ene synthases from Artemisia abrotanum. PHYTOCHEMISTRY 2019; 164:144-153. [PMID: 31151061 DOI: 10.1016/j.phytochem.2019.05.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 04/30/2019] [Accepted: 05/10/2019] [Indexed: 06/09/2023]
Abstract
Triquinane is a type of sesquiterpenoid with a unique structure that contains a fused tricyclopentane ring and exhibits a wide range of bioactivities. Like other sesquiterpenoids, the first committed step in triquinane-type sesquiterpenoid biosynthesis is the cyclization of farnesyl pyrophosphate (FPP), a common precursor of all sesquiterpenoids, catalyzed by sesquiterpene synthase. Artemisia abrotanum L. (Asteraceae), a common plant used in the culinary and cosmetics industries, has been reported to accumulate high levels of triquinane silphiperfol-5-en-3-one A. This compound is potentially biosynthesized from the cyclization of FPP into 7-epi-silphiperfol-5-ene followed by a multi-step oxidation to silphiperfol-5-en-3-one A. In this study, we aimed to identify the sesquiterpene synthase responsible for the synthesis of 7-epi-silphiperfol-5-ene. We performed RNA sequencing of A. abrotanum leaves and gene candidates were mined by homology searches using the triquinane α-isocomene synthase of chamomile (MrTPS2) as query. After gene cloning, we obtained five variants of putative sesquiterpene synthase showing greater than 85% amino acid identity to MrTPS2 and greater than 95% amino acid identity to each other. Heterologous expression of these variants in a FPP-high-producing yeast strain revealed the first four variants to be (+)-α-bisabolol synthases (AabrBOS1-4). However, the fifth candidate cyclized FPP into 7-epi-silphiperfol-5-ene and can therefore be defined as a 7-epi-silphiperfol-5-ene synthase (AabrSPS). These findings revealed the first committed enzyme involved in silphiperfol-5-en-3-one A and (+)-α-bisabolol biosyntheses in A. abrotanum. Furthermore, the results of this study will be useful for enhancing the production of these compounds for further applications.
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Affiliation(s)
- Paskorn Muangphrom
- Department of Biotechnology, Graduate School of Engineering, Osaka University 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Momoka Misaki
- Department of Biotechnology, Graduate School of Engineering, Osaka University 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Munenori Suzuki
- Department of Biotechnology, Graduate School of Engineering, Osaka University 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan; KNC Laboratories Co., Ltd., 3-2-34 Takatsukadai, Nishi-ku, Kobe, Hyogo, 651-2271, Japan; Kihara Institute for Biological Research, Yokohama City University 641-12 Maioka-cho, Totsuka-ku, Yokohama, Kanagawa, 244-0813, Japan
| | - Masaya Shimomura
- Kihara Institute for Biological Research, Yokohama City University 641-12 Maioka-cho, Totsuka-ku, Yokohama, Kanagawa, 244-0813, Japan
| | - Hideyuki Suzuki
- Department of Applied Genomics, Kazusa DNA Research Institute, 2-6-7 Kazusa-kamatari, Kisarazu, Chiba, 292-0818, Japan
| | - Hikaru Seki
- Department of Biotechnology, Graduate School of Engineering, Osaka University 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan; Kihara Institute for Biological Research, Yokohama City University 641-12 Maioka-cho, Totsuka-ku, Yokohama, Kanagawa, 244-0813, Japan.
| | - Toshiya Muranaka
- Department of Biotechnology, Graduate School of Engineering, Osaka University 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan; Kihara Institute for Biological Research, Yokohama City University 641-12 Maioka-cho, Totsuka-ku, Yokohama, Kanagawa, 244-0813, Japan
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8
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Rinkel J, Dickschat JS. Mechanistic investigations on multiproduct β-himachalene synthase from Cryptosporangium arvum. Beilstein J Org Chem 2019; 15:1008-1019. [PMID: 31164939 PMCID: PMC6541374 DOI: 10.3762/bjoc.15.99] [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: 03/12/2019] [Accepted: 04/26/2019] [Indexed: 12/30/2022] Open
Abstract
A bacterial terpene synthase from Cryptosporangium arvum was characterised as a multiproduct β-himachalene synthase. In vitro studies showed not only a high promiscuity with respect to its numerous sesquiterpene products, including the structurally demanding terpenes longicyclene, longifolene and α-longipinene, but also to its substrates, as additional activity was observed with geranyl- and geranylgeranyl diphosphate. In-depth mechanistic investigations using isotopically labelled precursors regarding the stereochemical course of both 1,11-cyclisation and 1,3-hydride shift furnished a detailed catalytic model suggesting the molecular basis of the observed low product selectivity. The enzyme’s synthetic potential was also exploited in the preparation of sesquiterpene isotopomers, which provided insights into their EIMS fragmentation mechanisms.
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Affiliation(s)
- Jan Rinkel
- Kekulé-Institute for Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
| | - Jeroen S Dickschat
- Kekulé-Institute for Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
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9
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Abstract
Plants produce a diverse portfolio of sesquiterpenes that are important in their response to herbivores and the interaction with other plants. Their biosynthesis from farnesyl diphosphate depends on the sesquiterpene synthases that admit different cyclizations and rearrangements to yield a blend of sesquiterpenes. Here, we investigate to what extent sesquiterpene biosynthesis metabolic pathways can be reconstructed just from the knowledge of the final product and the reaction mechanisms catalyzed by sesquiterpene synthases. We use the software package MedØlDatschgerl (MØD) to generate chemical networks and to elucidate pathways contained in them. As examples, we successfully consider the reachability of the important plant sesquiterpenes β -caryophyllene, α -humulene, and β -farnesene. We also introduce a graph database to integrate the simulation results with experimental biological evidence for the selected predicted sesquiterpenes biosynthesis.
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10
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Lee CW, Taylor BLH, Petrova GP, Patel A, Morokuma K, Houk KN, Stoltz BM. An Unexpected Ireland–Claisen Rearrangement Cascade During the Synthesis of the Tricyclic Core of Curcusone C: Mechanistic Elucidation by Trial-and-Error and Automatic Artificial Force-Induced Reaction (AFIR) Computations. J Am Chem Soc 2019; 141:6995-7004. [PMID: 30907087 DOI: 10.1021/jacs.9b01146] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Chung Whan Lee
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Buck L. H. Taylor
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Galina P. Petrova
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan
| | - Ashay Patel
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Keiji Morokuma
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan
| | - K. N. Houk
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Brian M. Stoltz
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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11
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Castiñeira Reis M, López CS, Nieto Faza O, Tantillo DJ. Pushing the limits of concertedness. A waltz of wandering carbocations. Chem Sci 2019; 10:2159-2170. [PMID: 30881640 PMCID: PMC6385557 DOI: 10.1039/c8sc03567a] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 12/10/2018] [Indexed: 12/21/2022] Open
Abstract
Among the array of complex terpene-forming carbocation cyclization/rearrangement reactions, the so-called "triple shift" reactions are among the most unexpected. Such reactions involve the asynchronous combination of three 1,n-shifts into a concerted process, e.g., a 1,2-alkyl shift followed by a 1,3-hydride shift followed by a second 1,2-alkyl shift. This type of reaction so far has been proposed to occur during the biosynthesis of diterpenes and the sidechains of sterols. Here we describe efforts to push the limits of concertedness in this type of carbocation reaction by designing, and characterizing with quantum chemical computations, systems that could couple additional 1,n-shift events to a triple shift leading, in principle to quadruple, pentuple, etc. shifts. While our designs did not lead to clear-cut examples of quadruple, etc. shifts, they did lead to reactions with surprisingly flat energy surfaces where more than five chemical events connect reactants and plausible products. Ab initio molecular dynamics simulations demonstrate that the formal minima on these surfaces interchange on short timescales, both with each other and with additional unexpected structures, allowing us a glimpse into a very complex manifold that allows ready access to great structural diversity.
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Affiliation(s)
- Marta Castiñeira Reis
- Departamento de Química Orgánica , Universidade de Vigo , Lagoas-Marcosende , 36310 , Vigo , Spain
| | - Carlos Silva López
- Departamento de Química Orgánica , Universidade de Vigo , Lagoas-Marcosende , 36310 , Vigo , Spain
| | - Olalla Nieto Faza
- Departamento de Química Orgánica , Universidade de Vigo , As Lagoas , 32004 , Ourense , Spain .
| | - Dean J Tantillo
- Department of Chemistry , University of California , One Shields Ave , Davis , CA 95616 , USA .
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12
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Karunanithi PS, Zerbe P. Terpene Synthases as Metabolic Gatekeepers in the Evolution of Plant Terpenoid Chemical Diversity. FRONTIERS IN PLANT SCIENCE 2019; 10:1166. [PMID: 31632418 PMCID: PMC6779861 DOI: 10.3389/fpls.2019.01166] [Citation(s) in RCA: 133] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 08/26/2019] [Indexed: 05/18/2023]
Abstract
Terpenoids comprise tens of thousands of small molecule natural products that are widely distributed across all domains of life. Plants produce by far the largest array of terpenoids with various roles in development and chemical ecology. Driven by selective pressure to adapt to their specific ecological niche, individual species form only a fraction of the myriad plant terpenoids, typically representing unique metabolite blends. Terpene synthase (TPS) enzymes are the gatekeepers in generating terpenoid diversity by catalyzing complex carbocation-driven cyclization, rearrangement, and elimination reactions that enable the transformation of a few acyclic prenyl diphosphate substrates into a vast chemical library of hydrocarbon and, for a few enzymes, oxygenated terpene scaffolds. The seven currently defined clades (a-h) forming the plant TPS family evolved from ancestral triterpene synthase- and prenyl transferase-type enzymes through repeated events of gene duplication and subsequent loss, gain, or fusion of protein domains and further functional diversification. Lineage-specific expansion of these TPS clades led to variable family sizes that may range from a single TPS gene to families of more than 100 members that may further function as part of modular metabolic networks to maximize the number of possible products. Accompanying gene family expansion, the TPS family shows a profound functional plasticity, where minor active site alterations can dramatically impact product outcome, thus enabling the emergence of new functions with minimal investment in evolving new enzymes. This article reviews current knowledge on the functional diversity and molecular evolution of the plant TPS family that underlies the chemical diversity of bioactive terpenoids across the plant kingdom.
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Affiliation(s)
- Prema S Karunanithi
- Department of Plant Biology, University of California Davis, Davis, CA, United States
| | - Philipp Zerbe
- Department of Plant Biology, University of California Davis, Davis, CA, United States
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13
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Blank PN, Pemberton TA, Chow JY, Poulter CD, Christianson DW. Crystal Structure of Cucumene Synthase, a Terpenoid Cyclase That Generates a Linear Triquinane Sesquiterpene. Biochemistry 2018; 57:6326-6335. [PMID: 30346736 DOI: 10.1021/acs.biochem.8b00899] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Linear triquinanes are sesquiterpene natural products with hydrocarbon skeletons consisting of three fused five-membered rings. Importantly, several of these compounds exhibit useful anticancer, anti-inflammatory, and antibiotic properties. However, linear triquinanes pose significant challenges to organic synthesis because of the structural and stereochemical complexity of their hydrocarbon skeletons. To illuminate nature's solution to the generation of linear triquinanes, we now describe the crystal structure of Streptomyces clavuligerus cucumene synthase. This sesquiterpene cyclase catalyzes the stereospecific cyclization of farnesyl diphosphate to form a linear triquinane product, (5 S,7 S,10 R,11 S)-cucumene. Specifically, we report the structure of the wild-type enzyme at 3.05 Å resolution and the structure of the T181N variant at 1.96 Å resolution, both in the open active site conformations without any bound ligands. The high-resolution structure of T181N cucumene synthase enables inspection of the active site contour, which adopts a three-dimensional shape complementary to a linear triquinane. Several aromatic residues outline the active site contour and are believed to facilitate cation-π interactions that would stabilize carbocation intermediates in catalysis. Thus, aromatic residues in the active site not only define the template for catalysis but also play a role in reducing activation barriers in the multistep cyclization cascade.
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Affiliation(s)
- Patrick N Blank
- Roy and Diana Vagelos Laboratories, Department of Chemistry , University of Pennsylvania , 231 South 34th Street , Philadelphia , Pennsylvania 19104-6323 , United States
| | - Travis A Pemberton
- Roy and Diana Vagelos Laboratories, Department of Chemistry , University of Pennsylvania , 231 South 34th Street , Philadelphia , Pennsylvania 19104-6323 , United States
| | - Jeng-Yeong Chow
- Department of Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112 , United States
| | - C Dale Poulter
- Department of Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112 , United States
| | - David W Christianson
- Roy and Diana Vagelos Laboratories, Department of Chemistry , University of Pennsylvania , 231 South 34th Street , Philadelphia , Pennsylvania 19104-6323 , United States
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14
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Isegawa M, Sharma AK, Ogo S, Morokuma K. DFT Study on Fe(IV)-Peroxo Formation and H Atom Transfer Triggered O2 Activation by NiFe Complex. Organometallics 2018. [DOI: 10.1021/acs.organomet.8b00098] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Miho Isegawa
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University 744 Moto-oka, Nishi-ku, Fukuoka 819-0385, Japan
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan
| | - Akhilesh K. Sharma
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan
| | - Seiji Ogo
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University 744 Moto-oka, Nishi-ku, Fukuoka 819-0385, Japan
| | - Keiji Morokuma
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan
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15
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Zhang F, Wang YH, Tang X, Wu R. Catalytic promiscuity of the non-native FPP substrate in the TEAS enzyme: non-negligible flexibility of the carbocation intermediate. Phys Chem Chem Phys 2018; 20:15061-15073. [DOI: 10.1039/c8cp02262c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
By QM(DFT)/MM MD simulations, it has been revealed that the non-native substrate catalytic promiscuity of TEAS (one of the sesquiterpene cyclases) is mostly attributable to its notable conformational flexibility of the branching intermediate bisabolyl cation.
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Affiliation(s)
- Fan Zhang
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
| | - Yong-Heng Wang
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
| | - Xiaowen Tang
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
| | - Ruibo Wu
- School of Pharmaceutical Sciences
- Sun Yat-sen University
- Guangzhou 510006
- China
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16
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Sameera WMC, Kumar Sharma A, Maeda S, Morokuma K. Artificial Force Induced Reaction Method for Systematic Determination of Complex Reaction Mechanisms. CHEM REC 2016; 16:2349-2363. [PMID: 27492586 DOI: 10.1002/tcr.201600052] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Indexed: 01/07/2023]
Abstract
Nowadays, computational studies are very important for the elucidation of reaction mechanisms and selectivity of complex reactions. However, traditional computational methods usually require an estimated reaction path, mainly driven by limited experimental implications, intuition, and assumptions of stationary points. However, the artificial force induced reaction (AFIR) method in the global reaction route mapping (GRRM) strategy can be used for unbiased and automatic reaction path searches for complex reactions. In this account, we highlight applications of the AFIR method to a variety of reactions (organic, organometallic, enzymatic, and photochemical) of complex molecular systems. In addition, the AFIR method has been successfully used to rationalise the origin of stereo- and regioselectivity. The AFIR method can be applied from small to large molecular systems, and will be a very useful tool for the study of complex molecular problems in many areas of chemistry, biology, and material sciences.
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Affiliation(s)
- W M C Sameera
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto, 606-8103, Japan
| | | | - Satoshi Maeda
- Department of Chemistry, Hokkaido University, Sapporo, 060-0810, Japan
| | - Keiji Morokuma
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto, 606-8103, Japan.
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17
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Tian B, Poulter CD, Jacobson MP. Defining the Product Chemical Space of Monoterpenoid Synthases. PLoS Comput Biol 2016; 12:e1005053. [PMID: 27517297 PMCID: PMC4982680 DOI: 10.1371/journal.pcbi.1005053] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 07/09/2016] [Indexed: 11/18/2022] Open
Abstract
Terpenoid synthases create diverse carbon skeletons by catalyzing complex carbocation rearrangements, making them particularly challenging for enzyme function prediction. To begin to address this challenge, we have developed a computational approach for the systematic enumeration of terpenoid carbocations. Application of this approach allows us to systematically define a nearly complete chemical space for the potential carbon skeletons of products from monoterpenoid synthases. Specifically, 18758 carbocations were generated, which we cluster into 74 cyclic skeletons. Five of the 74 skeletons are found in known natural products; some of the others are plausible for new functions, either in nature or engineered. This work systematizes the description of function for this class of enzymes, and provides a basis for predicting functions of uncharacterized enzymes. To our knowledge, this is the first computational study to explore the complete product chemical space of this important class of enzymes. Terpenoids, as one of the largest classes of natural products, provide complex carbocycle structures for many drugs (e.g. taxol) and prodrugs. The diverse carbocycle structures arise from complex carbocation rearrangements catalyzed by terpenoid synthases. Many putative terpene synthase enzymes identified in genome sequencing efforts remain functionally uncharacterized, and some of these will undoubtedly have novel products, potentially including previously undiscovered carbocycles. In this work, we present a computational approach that systematically enumerates all plausible carbocations of monoterpenoid synthases in order to define and organize the potentially large product chemical space of this important class of enzymes.
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Affiliation(s)
- Boxue Tian
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, San Francisco, California, United States of America
- California Institute for Quantitative Biomedical Research, University of California, San Francisco, San Francisco, California, United States of America
| | - C. Dale Poulter
- Department of Chemistry, University of Utah, Salt Lake City, Utah, United States of America
| | - Matthew P. Jacobson
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, San Francisco, California, United States of America
- California Institute for Quantitative Biomedical Research, University of California, San Francisco, San Francisco, California, United States of America
- * E-mail:
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18
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Maeda S, Harabuchi Y, Takagi M, Taketsugu T, Morokuma K. Artificial Force Induced Reaction (AFIR) Method for Exploring Quantum Chemical Potential Energy Surfaces. CHEM REC 2016; 16:2232-2248. [DOI: 10.1002/tcr.201600043] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Indexed: 12/25/2022]
Affiliation(s)
- Satoshi Maeda
- Department of Chemistry, Faculty of Science; Hokkaido University; Sapporo 060-0810 Japan
| | - Yu Harabuchi
- Department of Chemistry, Faculty of Science; Hokkaido University; Sapporo 060-0810 Japan
| | - Makito Takagi
- Graduate School of Chemical Sciences and Engineering; Hokkaido University; Sapporo 060-8628 Japan
| | - Tetsuya Taketsugu
- Department of Chemistry, Faculty of Science; Hokkaido University; Sapporo 060-0810 Japan
| | - Keiji Morokuma
- Fukui Institute for Fundamental Chemistry, Kyoto University; Kyoto 606-8103 Japan
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19
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Zhang F, Chen N, Wu R. Molecular Dynamics Simulations Elucidate Conformational Dynamics Responsible for the Cyclization Reaction in TEAS. J Chem Inf Model 2016; 56:877-85. [PMID: 27082764 DOI: 10.1021/acs.jcim.6b00091] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The Mg-dependent 5-epi-aristolochene synthase from Nicotiana tabacum (called TEAS) could catalyze the linear farnesyl pyrophosphate (FPP) substrate to form bicyclic hydrocarbon 5-epi-aristolochene. The cyclization reaction mechanism of TEAS was proposed based on static crystal structures and quantum chemistry calculations in a few previous studies, but substrate FPP binding kinetics and protein conformational dynamics responsible for the enzymatic catalysis are still unclear. Herein, by elaborative and extensive molecular dynamics simulations, the loop conformation change and several crucial residues promoting the cyclization reaction in TEAS are elucidated. It is found that the unusual noncatalytic NH2-terminal domain is essential to stabilize Helix-K and the adjoining J-K loop of the catalytic COOH-terminal domain. It is also illuminated that the induce-fit J-K/A-C loop dynamics is triggered by Y527 and the optimum substrate binding mode in a "U-shape" conformation. The U-shaped ligand binding pose is maintained well with the cooperative interaction of the three Mg(2+)-containing coordination shell and conserved residue W273. Furthermore, the conserved Arg residue pair R264/R266 and aromatic residue pair Y527/W273, whose spatial orientations are also crucial to promote the closure of the active site to a hydrophobic pocket, as well as to form π-stacking interactions with the ligand, would facilitate the carbocation migration and electrophilic attack involving the catalytic reaction. Our investigation more convincingly proves the greater roles of the protein local conformational dynamics than do hints from the static crystal structure observations. Thus, these findings can act as a guide to new protein engineering strategies on diversifying the sesquiterpene products for drug discovery.
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Affiliation(s)
- Fan Zhang
- School of Pharmaceutical Sciences, Sun Yat-sen University , Guangzhou 510006, Guangdong, P.R. China
| | - Nanhao Chen
- School of Pharmaceutical Sciences, Sun Yat-sen University , Guangzhou 510006, Guangdong, P.R. China
| | - Ruibo Wu
- School of Pharmaceutical Sciences, Sun Yat-sen University , Guangzhou 510006, Guangdong, P.R. China
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20
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Computational-guided discovery and characterization of a sesquiterpene synthase from Streptomyces clavuligerus. Proc Natl Acad Sci U S A 2015; 112:5661-6. [PMID: 25901324 DOI: 10.1073/pnas.1505127112] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Terpenoids are a large structurally diverse group of natural products with an array of functions in their hosts. The large amount of genomic information from recent sequencing efforts provides opportunities and challenges for the functional assignment of terpene synthases that construct the carbon skeletons of these compounds. Inferring function from the sequence and/or structure of these enzymes is not trivial because of the large number of possible reaction channels and products. We tackle this problem by developing an algorithm to enumerate possible carbocations derived from the farnesyl cation, the first reactive intermediate of the substrate, and evaluating their steric and electrostatic compatibility with the active site. The homology model of a putative pentalenene synthase (Uniprot: B5GLM7) from Streptomyces clavuligerus was used in an automated computational workflow for product prediction. Surprisingly, the workflow predicted a linear triquinane scaffold as the top product skeleton for B5GLM7. Biochemical characterization of B5GLM7 reveals the major product as (5S,7S,10R,11S)-cucumene, a sesquiterpene with a linear triquinane scaffold. To our knowledge, this is the first documentation of a terpene synthase involved in the synthesis of a linear triquinane. The success of our prediction for B5GLM7 suggests that this approach can be used to facilitate the functional assignment of novel terpene synthases.
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21
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Hamlin TA, Hamann CS, Tantillo DJ. Delocalization of Charge and Electron Density in the Humulyl Cation—Implications for Terpene Biosynthesis. J Org Chem 2015; 80:4046-53. [DOI: 10.1021/acs.joc.5b00381] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Trevor A. Hamlin
- Department
of Chemistry and Biochemistry, Albright College, 13th and Bern
Streets, Reading, Pennsylvania 19604, United States
| | - Christian S. Hamann
- Department
of Chemistry and Biochemistry, Albright College, 13th and Bern
Streets, Reading, Pennsylvania 19604, United States
| | - Dean J. Tantillo
- Department
of Chemistry, University of California—Davis, 1 Shields Avenue, Davis, California 95616, United States
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22
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Pemberton RP, Ho KC, Tantillo DJ. Modulation of inherent dynamical tendencies of the bisabolyl cation via preorganization in epi-isozizaene synthase. Chem Sci 2015; 6:2347-2353. [PMID: 29308148 PMCID: PMC5645776 DOI: 10.1039/c4sc03782k] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2014] [Accepted: 01/30/2015] [Indexed: 01/09/2023] Open
Abstract
The relative importance of preorganization, selective transition state stabilization and inherent reactivity are assessed through quantum chemical and docking calculations for a sesquiterpene synthase (epi-isozizaene synthase, EIZS). Inherent reactivity of the bisabolyl cation, both static and dynamic, appears to determine the pathway to product, although preorganization and selective binding of the final transition state structure in the multi-step carbocation cascade that forms epi-isozizaene appear to play important roles.
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Affiliation(s)
- Ryan P Pemberton
- Department of Chemistry , University of California, Davis , One Shields Avenue , Davis , CA 95616 , USA .
| | - Krystina C Ho
- Department of Chemistry , University of California, Davis , One Shields Avenue , Davis , CA 95616 , USA .
| | - Dean J Tantillo
- Department of Chemistry , University of California, Davis , One Shields Avenue , Davis , CA 95616 , USA .
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23
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Huang AC, Sefton MA, Sumby CJ, Tiekink ERT, Taylor DK. Mechanistic studies on the autoxidation of α-guaiene: structural diversity of the sesquiterpenoid downstream products. JOURNAL OF NATURAL PRODUCTS 2015; 78:131-45. [PMID: 25581486 DOI: 10.1021/np500819f] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Two unstable hydroperoxides, 6b and 10a, and 13 downstream sesquiterpenoids have been isolated from the autoxidation mixture of the bicyclic sesquiterpene α-guaiene (1) on cellulose filter paper. One of the significant natural products isolated was rotundone (2), which is the only known impact odorant displaying a peppery aroma. Other products included corymbolone (4a) and its C-6 epimer 4b, the (2R)- and (2S)-rotundols (7a/b), and several hitherto unknown epimers of natural chabrolidione A, namely, 7-epi-chabrolidione A (3a) and 1,7-epi-chabrolidione A (3b). Two 4-hydroxyrotundones (8a/b) and a range of epoxides (9a/b and 5a/b) were also formed in significant amounts after autoxidation. Their structures were elucidated on the basis of spectroscopic data and X-ray crystallography, and a number of them were confirmed through total synthesis. The mechanisms of formation of the majority of the products may be accounted for by initial formation of the 2- and 4-hydroperoxyguaienes (6a/b and 10a/b) followed by various fragmentation or degradation pathways. Given that α-guaiene (1) is well known to exist in the essential oils of numerous plants, coupled with the fact that aerial oxidation to form this myriad of downstream oxidation products occurs readily at ambient temperature, suggests that many of them have been overlooked during previous isolation studies from natural sources.
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Affiliation(s)
- An-Cheng Huang
- School of Agriculture, Food and Wine, The University of Adelaide , Waite Campus, 5064, Adelaide, South Australia, Australia
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24
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Abstract
In this article strategies for the design and synthesis of natural product analogues are summarized and illustrated with some selected examples.
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Affiliation(s)
- Martin E. Maier
- Institut für Organische Chemie
- Eberhard Karls Universität Tübingen
- 72076 Tübingen
- Germany
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25
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Tian BX, Wallrapp FH, Holiday GL, Chow JY, Babbitt PC, Poulter CD, Jacobson MP. Predicting the functions and specificity of triterpenoid synthases: a mechanism-based multi-intermediate docking approach. PLoS Comput Biol 2014; 10:e1003874. [PMID: 25299649 PMCID: PMC4191879 DOI: 10.1371/journal.pcbi.1003874] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 08/25/2014] [Indexed: 11/18/2022] Open
Abstract
Terpenoid synthases construct the carbon skeletons of tens of thousands of natural products. To predict functions and specificity of triterpenoid synthases, a mechanism-based, multi-intermediate docking approach is proposed. In addition to enzyme function prediction, other potential applications of the current approach, such as enzyme mechanistic studies and enzyme redesign by mutagenesis, are discussed. The rapid growth in the number of protein sequences presents challenges for enzyme function assignment. Computational methods, such as bioinformatics, homology modeling and docking, are becoming increasingly important for predicting of enzyme functions from protein sequences. Terpenoids are one of largest classes of natural products, and many drugs (e.g. taxol) consist of terpenoids or terpenoid derivatives. Understanding the biosynthesis of the terpenoids is of great interest. Terpenoid synthases catalyze the key cyclization steps of the biosynthesis of terpenoids via carbocation rearrangements, generating numerous multiple-ring carbon skeletons. Triterpenoid synthases, as an important class of terpenoid synthases, catalyze the cyclization of either squalene or oxido-squalene into cyclized products such as sterols (e.g. lanosterol). In this work, we propose a computational approach that can be used to predict product specificity of the triterpenoid synthases. Our approach provides insight into the ‘design principles’ of these fascinating enzymes, and may become a practical approach for function prediction and enzyme engineering.
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Affiliation(s)
- Bo-Xue Tian
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, San Francisco, California, United States of America
- California Institute for Quantitative Biomedical Research, University of California, San Francisco, San Francisco, California, United States of America
| | - Frank H. Wallrapp
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, San Francisco, California, United States of America
- California Institute for Quantitative Biomedical Research, University of California, San Francisco, San Francisco, California, United States of America
| | - Gemma L. Holiday
- California Institute for Quantitative Biomedical Research, University of California, San Francisco, San Francisco, California, United States of America
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, United States of America
| | - Jeng-Yeong Chow
- Department of Chemistry, University of Utah, Salt Lake City, Utah, United States of America
| | - Patricia C. Babbitt
- California Institute for Quantitative Biomedical Research, University of California, San Francisco, San Francisco, California, United States of America
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, United States of America
| | - C. Dale Poulter
- Department of Chemistry, University of Utah, Salt Lake City, Utah, United States of America
| | - Matthew P. Jacobson
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, San Francisco, California, United States of America
- California Institute for Quantitative Biomedical Research, University of California, San Francisco, San Francisco, California, United States of America
- * E-mail:
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