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Nuutila A, Xiao X, van der Heul HU, van Wezel GP, Dinis P, Elsayed SS, Metsä-Ketelä M. Divergence of Classical and C-Ring-Cleaved Angucyclines: Elucidation of Early Tailoring Steps in Lugdunomycin and Thioangucycline Biosynthesis. ACS Chem Biol 2024; 19:1131-1141. [PMID: 38668630 PMCID: PMC11106748 DOI: 10.1021/acschembio.4c00082] [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: 02/02/2024] [Revised: 04/16/2024] [Accepted: 04/16/2024] [Indexed: 05/18/2024]
Abstract
Angucyclines are an important group of microbial natural products that display tremendous chemical diversity. Classical angucyclines are composed of a tetracyclic benz[a]anthracene scaffold with one ring attached at an angular orientation. However, in atypical angucyclines, the polyaromatic aglycone is cleaved at A-, B-, or C-rings, leading to structural rearrangements and enabling further chemical variety. Here, we have elucidated the branching points in angucycline biosynthesis leading toward cleavage of the C-ring in lugdunomycin and thioangucycline biosynthesis. We showed that 12-hydroxylation and 6-ketoreduction of UWM6 are shared steps in classical and C-ring-cleaved angucycline pathways, although the bifunctional 6-ketoreductase LugOIIred harbors additional unique 1-ketoreductase activity. We identified formation of the key intermediate 8-O-methyltetrangomycin by the LugN methyltransferase as the branching point toward C-ring-cleaved angucyclines. The final common step in lugdunomycin and thioangucycline biosynthesis is quinone reduction, catalyzed by the 7-ketoreductases LugG and TacO, respectively. In turn, the committing step toward thioangucyclines is 12-ketoreduction catalyzed by TacA, for which no orthologous protein exists on the lugdunomycin pathway. Our results confirm that quinone reductions are early tailoring steps and, therefore, may be mechanistically important for subsequent C-ring cleavage. Finally, many of the tailoring enzymes harbored broad substrate promiscuity, which we utilized in combinatorial enzymatic syntheses to generate the angucyclines SM 196 A and hydranthomycin. We propose that enzyme promiscuity and the competition of many of the enzymes for the same substrates lead to a branching biosynthetic network and formation of numerous shunt products typical for angucyclines rather than a canonical linear metabolic pathway.
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Affiliation(s)
- Aleksi Nuutila
- Department
of Life Technologies, University of Turku, FIN20014 Turku, Finland
| | - Xiansha Xiao
- Molecular
Biotechnology, Leiden University, PO Box 9505, 2300RA Leiden, The
Netherlands
| | - Helga U. van der Heul
- Molecular
Biotechnology, Leiden University, PO Box 9505, 2300RA Leiden, The
Netherlands
| | - Gilles P. van Wezel
- Molecular
Biotechnology, Leiden University, PO Box 9505, 2300RA Leiden, The
Netherlands
| | - Pedro Dinis
- Department
of Life Technologies, University of Turku, FIN20014 Turku, Finland
| | - Somayah S. Elsayed
- Molecular
Biotechnology, Leiden University, PO Box 9505, 2300RA Leiden, The
Netherlands
| | - Mikko Metsä-Ketelä
- Department
of Life Technologies, University of Turku, FIN20014 Turku, Finland
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Kudo K, Nishimura T, Izumikawa M, Kozone I, Hashimoto J, Fujie M, Suenaga H, Ikeda H, Satoh N, Shin-Ya K. Capability of a large bacterial artificial chromosome clone harboring multiple biosynthetic gene clusters for the production of diverse compounds. J Antibiot (Tokyo) 2024; 77:288-298. [PMID: 38438499 DOI: 10.1038/s41429-024-00711-9] [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: 10/30/2023] [Revised: 02/02/2024] [Accepted: 02/12/2024] [Indexed: 03/06/2024]
Abstract
The biosynthetic gene clusters (BGCs) for the macrocyclic lactone-based polyketide compounds are extremely large-sized because the polyketide synthases that generate the polyketide chains of the basic backbone are of very high molecular weight. In developing a heterologous expression system for the large BGCs amenable to the production of such natural products, we selected concanamycin as an appropriate target. We obtained a bacterial artificial chromosome (BAC) clone with a 211-kb insert harboring the entire BGC responsible for the biosynthesis of concanamycin. Heterologous expression of this clone in a host strain, Streptomyces avermitilis SUKA32, permitted the production of concanamycin, as well as that of two additional aromatic polyketides. Structural elucidation identified these additional products as ent-gephyromycin and a novel compound that was designated JBIR-157. We describe herein sequencing and expression studies performed on these BGCs, demonstrating the utility of large BAC clones for the heterologous expression of cryptic or near-silent loci.
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Affiliation(s)
- Kei Kudo
- Department of Life Science and Biotechnology, National Institute of Advanced Industrial Science and Technology (AIST), 2-4-7 Aomi, Koto-ku, Tokyo, 135-0064, Japan
| | - Takehiro Nishimura
- Technology Research Association for Next Generation Natural Products Chemistry, 2-4-7 Aomi, Koto-ku, Tokyo, 135-0064, Japan
- Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato-ku, Tokyo, 105-8512, Japan
| | - Miho Izumikawa
- Japan Biological Informatics Consortium (JBIC), 2-4-32 Aomi, Koto-ku, Tokyo, 135-0064, Japan
| | - Ikuko Kozone
- Japan Biological Informatics Consortium (JBIC), 2-4-32 Aomi, Koto-ku, Tokyo, 135-0064, Japan
| | - Junko Hashimoto
- Japan Biological Informatics Consortium (JBIC), 2-4-32 Aomi, Koto-ku, Tokyo, 135-0064, Japan
| | - Manabu Fujie
- Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan
| | - Hikaru Suenaga
- Department of Life Science and Biotechnology, National Institute of Advanced Industrial Science and Technology (AIST), 2-4-7 Aomi, Koto-ku, Tokyo, 135-0064, Japan
| | - Haruo Ikeda
- Kitasato Institute for Life Sciences, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa, 252-0373, Japan
- Technology Research Association for Next Generation Natural Products Chemistry, 2-4-7 Aomi, Koto-ku, Tokyo, 135-0064, Japan
| | - Nori Satoh
- Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan
| | - Kazuo Shin-Ya
- Department of Life Science and Biotechnology, National Institute of Advanced Industrial Science and Technology (AIST), 2-4-7 Aomi, Koto-ku, Tokyo, 135-0064, Japan.
- Technology Research Association for Next Generation Natural Products Chemistry, 2-4-7 Aomi, Koto-ku, Tokyo, 135-0064, Japan.
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3
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Elsayed SS, van der Heul HU, Xiao X, Nuutila A, Baars LR, Wu C, Metsä-Ketelä M, van Wezel GP. Unravelling key enzymatic steps in C-ring cleavage during angucycline biosynthesis. Commun Chem 2023; 6:281. [PMID: 38110491 PMCID: PMC10728087 DOI: 10.1038/s42004-023-01059-1] [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: 06/30/2023] [Accepted: 11/08/2023] [Indexed: 12/20/2023] Open
Abstract
Angucyclines are type II polyketide natural products, often characterized by unusual structural rearrangements through B- or C-ring cleavage of their tetracyclic backbone. While the enzymes involved in B-ring cleavage have been extensively studied, little is known of the enzymes leading to C-ring cleavage. Here, we unravel the function of the oxygenases involved in the biosynthesis of lugdunomycin, a highly rearranged C-ring cleaved angucycline derivative. Targeted deletion of the oxygenase genes, in combination with molecular networking and structural elucidation, showed that LugOI is essential for C12 oxidation and maintaining a keto group at C6 that is reduced by LugOII, resulting in a key intermediate towards C-ring cleavage. An epoxide group is then inserted by LugOIII, and stabilized by the novel enzyme LugOV for the subsequent cleavage. Thus, for the first time we describe the oxidative enzymatic steps that form the basis for a wide range of rearranged angucycline natural products.
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Affiliation(s)
- Somayah S Elsayed
- Department of Molecular Biotechnology, Institute of Biology, Leiden University, Sylviusweg 72, 2333BE, Leiden, The Netherlands.
| | - Helga U van der Heul
- Department of Molecular Biotechnology, Institute of Biology, Leiden University, Sylviusweg 72, 2333BE, Leiden, The Netherlands
| | - Xiansha Xiao
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA
| | - Aleksi Nuutila
- Department of Life Technologies, University of Turku, Tykistökatu 6, FIN-20014, Turku, Finland
| | - Laura R Baars
- Department of Systems Pharmacology and Pharmacy, Leiden Academic Centre for Drug Research, Leiden University, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| | - Changsheng Wu
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, 266237, Qingdao, P.R. China
| | - Mikko Metsä-Ketelä
- Department of Life Technologies, University of Turku, Tykistökatu 6, FIN-20014, Turku, Finland
| | - Gilles P van Wezel
- Department of Molecular Biotechnology, Institute of Biology, Leiden University, Sylviusweg 72, 2333BE, Leiden, The Netherlands.
- Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708PB, Wageningen, The Netherlands.
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4
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Characterization of the Biosynthetic Gene Cluster and Shunt Products Yields Insights into the Biosynthesis of Balmoralmycin. Appl Environ Microbiol 2022; 88:e0120822. [PMID: 36350133 PMCID: PMC9746310 DOI: 10.1128/aem.01208-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Angucyclines are a family of structurally diverse, aromatic polyketides with some members that exhibit potent bioactivity. Angucyclines have also attracted considerable attention due to the intriguing biosynthetic origins that underlie their structural complexity and diversity. Balmoralmycin (compound 1) represents a unique group of angucyclines that contain an angular benz[α]anthracene tetracyclic system, a characteristic C-glycosidic bond-linked deoxy-sugar (d-olivose), and an unsaturated fatty acid chain. In this study, we identified a Streptomyces strain that produces balmoralmycin and seven biosynthetically related coproducts (compounds 2-8). Four of the coproducts (compounds 5-8) are novel compounds that feature a highly oxygenated or fragmented lactone ring, and three of them (compounds 3-5) exhibited cytotoxicity against the human pancreatic cancer cell line MIA PaCa-2 with IC50 values ranging from 0.9 to 1.2 μg/mL. Genome sequencing and CRISPR/dCas9-assisted gene knockdown led to the identification of the ~43 kb balmoralmycin biosynthetic gene cluster (bal BGC). The bal BGC encodes a type II polyketide synthase (PKS) system for assembling the angucycline aglycone, six enzymes for generating the deoxysugar d-olivose, and a hybrid type II/III PKS system for synthesizing the 2,4-decadienoic acid chain. Based on the genetic and chemical information, we propose a mechanism for the biosynthesis of balmoralmycin and the shunt products. The chemical and genetic studies yielded insights into the biosynthetic origin of the structural diversity of angucyclines. IMPORTANCE Angucyclines are structurally diverse aromatic polyketides that have attracted considerable attention due to their potent bioactivity and intriguing biosynthetic origin. Balmoralmycin is a representative of a small family of angucyclines with unique structural features and an unknown biosynthetic origin. We report a newly isolated Streptomyces strain that produces balmoralmycin in a high fermentation titer as well as several structurally related shunt products. Based on the chemical and genetic information, a biosynthetic pathway that involves a type II polyketide synthase (PKS) system, cyclases/aromatases, oxidoreductases, and other ancillary enzymes was established. The elucidation of the balmoralmycin pathway enriches our understanding of how structural diversity is generated in angucyclines and opens the door for the production of balmoralmycin derivatives via pathway engineering.
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Ouchene R, Stien D, Segret J, Kecha M, Rodrigues AMS, Veckerlé C, Suzuki MT. Integrated Metabolomic, Molecular Networking, and Genome Mining Analyses Uncover Novel Angucyclines From Streptomyces sp. RO-S4 Strain Isolated From Bejaia Bay, Algeria. Front Microbiol 2022; 13:906161. [PMID: 35814649 PMCID: PMC9260717 DOI: 10.3389/fmicb.2022.906161] [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: 03/28/2022] [Accepted: 05/16/2022] [Indexed: 11/13/2022] Open
Abstract
Multi-omic approaches have recently made big strides toward the effective exploration of microorganisms, accelerating the discovery of new bioactive compounds. We combined metabolomic, molecular networking, and genomic-based approaches to investigate the metabolic potential of the Streptomyces sp. RO-S4 strain isolated from the polluted waters of Bejaia Bay in Algeria. Antagonistic assays against methicillin-resistant Staphylococcus aureus with RO-S4 organic extracts showed an inhibition zone of 20 mm by using the agar diffusion method, and its minimum inhibitory concentration was 16 μg/ml. A molecular network was created using GNPS and annotated through the comparison of MS/MS spectra against several databases. The predominant compounds in the RO-S4 extract belonged to the angucycline family. Three compounds were annotated as known metabolites, while all the others were putatively new to Science. Notably, all compounds had fridamycin-like aglycones, and several of them had a lactonized D ring analogous to that of urdamycin L. The whole genome of Streptomyces RO-S4 was sequenced to identify the biosynthetic gene cluster (BGC) linked to these angucyclines, which yielded a draft genome of 7,497,846 bp with 72.4% G+C content. Subsequently, a genome mining analysis revealed 19 putative biosynthetic gene clusters, including a grincamycin-like BGC with high similarity to that of Streptomyces sp. CZN-748, that was previously reported to also produce mostly open fridamycin-like aglycones. As the ring-opening process leading to these compounds is still not defined, we performed a comparative analysis with other angucycline BGCs and advanced some hypotheses to explain the ring-opening and lactonization, possibly linked to the uncoupling between the activity of GcnE and GcnM homologs in the RO-S4 strain. The combination of metabolomic and genomic approaches greatly improved the interpretation of the metabolic potential of the RO-S4 strain.
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Affiliation(s)
- Rima Ouchene
- Laboratoire de Microbiologie Appliquée (LMA), Faculté des Sciences de la Nature et de la Vie, Université de Bejaia, Bejaia, Algeria
- Sorbonne Université, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes, LBBM, F-66650, Banyuls-sur-mer, France
| | - Didier Stien
- Sorbonne Université, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes, LBBM, F-66650, Banyuls-sur-mer, France
- *Correspondence: Didier Stien
| | - Juliette Segret
- Sorbonne Université, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes, LBBM, F-66650, Banyuls-sur-mer, France
| | - Mouloud Kecha
- Laboratoire de Microbiologie Appliquée (LMA), Faculté des Sciences de la Nature et de la Vie, Université de Bejaia, Bejaia, Algeria
| | - Alice M. S. Rodrigues
- Sorbonne Université, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes, LBBM, F-66650, Banyuls-sur-mer, France
| | - Carole Veckerlé
- Sorbonne Université, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes, LBBM, F-66650, Banyuls-sur-mer, France
| | - Marcelino T. Suzuki
- Sorbonne Université, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes, LBBM, F-66650, Banyuls-sur-mer, France
- Marcelino T. Suzuki
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6
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Xiao X, Elsayed SS, Wu C, van der Heul HU, Metsä-Ketelä M, Du C, Prota AE, Chen CC, Liu W, Guo RT, Abrahams JP, van Wezel GP. Functional and Structural Insights into a Novel Promiscuous Ketoreductase of the Lugdunomycin Biosynthetic Pathway. ACS Chem Biol 2020; 15:2529-2538. [PMID: 32840360 PMCID: PMC7506943 DOI: 10.1021/acschembio.0c00564] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
![]()
Angucyclines are
a structurally diverse class of actinobacterial
natural products defined by their varied polycyclic ring systems,
which display a wide range of biological activities. We recently discovered
lugdunomycin (1), a highly rearranged polyketide antibiotic
derived from the angucycline backbone that is synthesized via several
yet unexplained enzymatic reactions. Here, we show via in
vivo, in vitro, and structural analysis
that the promiscuous reductase LugOII catalyzes both a C6 and an unprecedented
C1 ketoreduction. This then sets the stage for the subsequent C-ring
cleavage that is key to the rearranged scaffolds of 1. The 1.1 Å structures of LugOII in complex with either ligand
8-O-Methylrabelomycin (4) or 8-O-Methyltetrangomycin (5) and of apoenzyme
were resolved, which revealed a canonical Rossman fold and a remarkable
conformational change during substrate capture and release. Mutational
analysis uncovered key residues for substrate access, position, and
catalysis as well as specific determinants that control its dual functionality.
The insights obtained in this work hold promise for the discovery
and engineering of other promiscuous reductases that may be harnessed
for the generation of novel biocatalysts for chemoenzymatic applications.
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Affiliation(s)
- Xiansha Xiao
- Molecular Biotechnology, Leiden University, PO Box 9505, 2300RA Leiden, The Netherlands
| | - Somayah S. Elsayed
- Molecular Biotechnology, Leiden University, PO Box 9505, 2300RA Leiden, The Netherlands
| | - Changsheng Wu
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, Shandong 266237, P. R. China
| | - Helga U. van der Heul
- Molecular Biotechnology, Leiden University, PO Box 9505, 2300RA Leiden, The Netherlands
| | - Mikko Metsä-Ketelä
- Department of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland
| | - Chao Du
- Molecular Biotechnology, Leiden University, PO Box 9505, 2300RA Leiden, The Netherlands
| | - Andrea E. Prota
- Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
| | - Chun-Chi Chen
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, Hubei 43420, P. R. China
| | - Weidong Liu
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, Hubei 43420, P. R. China
| | - Rey-Ting Guo
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, Hubei 43420, P. R. China
| | - Jan Pieter Abrahams
- Molecular Biotechnology, Leiden University, PO Box 9505, 2300RA Leiden, The Netherlands
- Bio-nano diffraction Biozentrum, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
- Biozentrum, University of Basel, Mattenstrasse 26, CH-4058 Basel, Switzerland
| | - Gilles P. van Wezel
- Molecular Biotechnology, Leiden University, PO Box 9505, 2300RA Leiden, The Netherlands
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Fewer DP, Metsä‐Ketelä M. A pharmaceutical model for the molecular evolution of microbial natural products. FEBS J 2019; 287:1429-1449. [DOI: 10.1111/febs.15129] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 10/11/2019] [Accepted: 11/05/2019] [Indexed: 12/20/2022]
Affiliation(s)
- David P. Fewer
- Department of Microbiology University of Helsinki Finland
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8
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Mo J, Ye J, Chen H, Hou B, Wu H, Zhang H. Cloning and identification of the Frigocyclinone biosynthetic gene cluster from Streptomyces griseus strain NTK 97. Biosci Biotechnol Biochem 2019; 83:2082-2089. [PMID: 31303144 DOI: 10.1080/09168451.2019.1638755] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
Frigocyclinone is a novel antibiotic with antibacterial and anticancer activities. It is produced by both Antarctica-derived Streptomyces griseus NTK 97 and marine sponge-associated Streptomyces sp. M7_15. Here, we first report the biosynthetic gene cluster of frigocyclinone in the S. griseus NTK 97. The frigocyclinone gene cluster spans a DNA region of 33-kb which consists of 30 open reading frames (ORFs), encoding minimal type II polyketide synthase, aromatase and cyclase, redox tailoring enzymes, sugar biosynthesis-related enzymes, C-glycosyltransferase, a resistance protein, and three regulatory proteins. Based on the bioinformatic analysis, a biosynthetic pathway for frigocyclinone was proposed. Second, to verify the cloned gene cluster, CRISPR-Cpf1 mediated gene disruption was conducted. Mutant with the disruption of beta-ketoacyl synthase encoding gene frig20 fully loses the ability of producing frigocyclinone, while inactivating the glycosyltransferase gene frig1 leads to the production of key intermediate of anti-MRSA anthraquinone tetrangomycin.
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Affiliation(s)
- Jian Mo
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology , Shanghai , China.,Department of Applied Biology, East China University of Science and Technology , Shanghai , China
| | - Jiang Ye
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology , Shanghai , China.,Department of Applied Biology, East China University of Science and Technology , Shanghai , China
| | - Haozhe Chen
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology , Shanghai , China.,Department of Applied Biology, East China University of Science and Technology , Shanghai , China
| | - Bingbing Hou
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology , Shanghai , China.,Department of Applied Biology, East China University of Science and Technology , Shanghai , China
| | - Haizhen Wu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology , Shanghai , China.,Department of Applied Biology, East China University of Science and Technology , Shanghai , China
| | - Huizhan Zhang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology , Shanghai , China.,Department of Applied Biology, East China University of Science and Technology , Shanghai , China
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Fan K, Zhang Q. The functional differentiation of the post-PKS tailoring oxygenases contributed to the chemical diversities of atypical angucyclines. Synth Syst Biotechnol 2018; 3:275-282. [PMID: 30533539 PMCID: PMC6260466 DOI: 10.1016/j.synbio.2018.11.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 10/05/2018] [Accepted: 11/06/2018] [Indexed: 12/31/2022] Open
Abstract
Angucyclines are one of the largest families of aromatic polyketides with various chemical structures and bioactivities. Decades of studies have made it easy for us to depict the picture of their early biosynthetic pathways. Two families of oxygenases, the FAD-dependent oxygenases and the ring opening oxygenases, contribute to the formation of some unique skeletons of atypical angucyclines. The FAD-dependent oxygenases involved in the biosynthetic gene clusters of typical angucyclines catalyze two hydroxylation reactions at C-12 and C-12b of prejadomycin, while their homolog JadH in jadomycin gene cluster catalyze the C-12 hydroxylation and 4a,12b-dehydration reactions of prejadomycin, which leads to the production of dehydrorabelomycin, a common intermediate during the biosynthesis of atypical angucyclines. Ring opening oxygenases of a unique family of oxygenases catalyze the oxidative C—C bond cleavage reaction of dehydrorabelomycin, followed by different rearrangement reactions, resulting in the formation of the various chemical skeletons of atypical angucyclines. These results suggested that the functional differentiation of these oxygenases could apparently enrich the sources of aromatic polyketides with greater structure diversities.
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Affiliation(s)
- Keqiang Fan
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, People's Republic of China
| | - Qian Zhang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, People's Republic of China.,University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
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10
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Metsä-Ketelä M. Evolution inspired engineering of antibiotic biosynthesis enzymes. Org Biomol Chem 2017; 15:4036-4041. [DOI: 10.1039/c7ob00189d] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Chimeragenesis is an effective tool to probe the structure/function relationships of proteins without high-throughput screening systems. Here the proof-of-principle is presented with three pairs of proteins.
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11
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Ozeir M, Pelosi L, Ismail A, Mellot-Draznieks C, Fontecave M, Pierrel F. Coq6 is responsible for the C4-deamination reaction in coenzyme Q biosynthesis in Saccharomyces cerevisiae. J Biol Chem 2015; 290:24140-51. [PMID: 26260787 DOI: 10.1074/jbc.m115.675744] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Indexed: 11/06/2022] Open
Abstract
The yeast Saccharomyces cerevisiae is able to use para-aminobenzoic acid (pABA) in addition to 4-hydroxybenzoic acid as a precursor of coenzyme Q, a redox lipid essential to the function of the mitochondrial respiratory chain. The biosynthesis of coenzyme Q from pABA requires a deamination reaction at position C4 of the benzene ring to substitute the amino group with an hydroxyl group. We show here that the FAD-dependent monooxygenase Coq6, which is known to hydroxylate position C5, also deaminates position C4 in a reaction implicating molecular oxygen, as demonstrated with labeling experiments. We identify mutations in Coq6 that abrogate the C4-deamination activity, whereas preserving the C5-hydroxylation activity. Several results support that the deletion of Coq9 impacts Coq6, thus explaining the C4-deamination defect observed in Δcoq9 cells. The vast majority of flavin monooxygenases catalyze hydroxylation reactions on a single position of their substrate. Coq6 is thus a rare example of a flavin monooxygenase that is able to act on two different carbon atoms of its C4-aminated substrate, allowing its deamination and ultimately its conversion into coenzyme Q by the other proteins constituting the coenzyme Q biosynthetic pathway.
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Affiliation(s)
- Mohammad Ozeir
- From the University of Grenoble Alpes, LCBM, UMR5249, F-38000 Grenoble, France
| | - Ludovic Pelosi
- the University of Grenoble Alpes, LAPM, F-38000 Grenoble, France, the CNRS, LAPM, F-38000 Grenoble, France
| | - Alexandre Ismail
- the Laboratoire de Chimie des Processus Biologiques, UMR 8229 CNRS, UPMC, Collège de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France, and the Sup'Biotech, IONIS Education Group, 66 rue Guy-Moquet, F-94800 Villejuif, France
| | - Caroline Mellot-Draznieks
- the Laboratoire de Chimie des Processus Biologiques, UMR 8229 CNRS, UPMC, Collège de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France, and
| | - Marc Fontecave
- the Laboratoire de Chimie des Processus Biologiques, UMR 8229 CNRS, UPMC, Collège de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France, and
| | - Fabien Pierrel
- the University of Grenoble Alpes, LAPM, F-38000 Grenoble, France, the CNRS, LAPM, F-38000 Grenoble, France,
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12
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Wang B, Ren J, Li L, Guo F, Pan G, Ai G, Aigle B, Fan K, Yang K. Kinamycin biosynthesis employs a conserved pair of oxidases for B-ring contraction. Chem Commun (Camb) 2015; 51:8845-8. [DOI: 10.1039/c5cc01986a] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A conserved pair of oxidases is characterized as nature's machinery for benzofluorenone formation.
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Affiliation(s)
- Bin Wang
- State Key Laboratory of Microbial Resources
- Institute of Microbiology
- Chinese Academy of Sciences
- 100101 Beijing
- China
| | - Jinwei Ren
- State Key Laboratory of Mycology
- Institute of Microbiology
- Chinese Academy of Sciences
- 100101 Beijing
- China
| | - Liyuan Li
- State Key Laboratory of Microbial Resources
- Institute of Microbiology
- Chinese Academy of Sciences
- 100101 Beijing
- China
| | - Fang Guo
- State Key Laboratory of Microbial Resources
- Institute of Microbiology
- Chinese Academy of Sciences
- 100101 Beijing
- China
| | - Guohui Pan
- State Key Laboratory of Microbial Resources
- Institute of Microbiology
- Chinese Academy of Sciences
- 100101 Beijing
- China
| | - Guomin Ai
- State Key Laboratory of Microbial Resources
- Institute of Microbiology
- Chinese Academy of Sciences
- 100101 Beijing
- China
| | - Bertrand Aigle
- Université de Lorraine
- Dynamique des Génomes et Adaptation Microbienne
- Vandœuvre-lès-Nancy
- France
- INRA
| | - Keqiang Fan
- State Key Laboratory of Microbial Resources
- Institute of Microbiology
- Chinese Academy of Sciences
- 100101 Beijing
- China
| | - Keqian Yang
- State Key Laboratory of Microbial Resources
- Institute of Microbiology
- Chinese Academy of Sciences
- 100101 Beijing
- China
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13
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Guo F, Xiang S, Li L, Wang B, Rajasärkkä J, Gröndahl-Yli-Hannuksela K, Ai G, Metsä-Ketelä M, Yang K. Targeted activation of silent natural product biosynthesis pathways by reporter-guided mutant selection. Metab Eng 2014; 28:134-142. [PMID: 25554073 DOI: 10.1016/j.ymben.2014.12.006] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 12/12/2014] [Accepted: 12/18/2014] [Indexed: 11/27/2022]
Abstract
The continuously increasing genome sequencing data has revealed numerous cryptic pathways, which might encode novel secondary metabolites with interesting biological activities. However, utilization of this hidden potential has been hindered by the observation that many of these gene clusters remain silent (or poorly expressed) under laboratory conditions. Here we present reporter-guided mutant selection (RGMS) as an effective and widely applicable method for targeted activation of silent gene clusters in the native producers. The strategy takes advantage of genome-scale random mutagenesis for generation of genetic diversity and a reporter-guided selection system for the identification of the desired target-activated mutants. It was first validated in the re-activation of jadomycin biosynthesis in Streptomyces venezuelae ISP5230, where high efficiency of activation was achieved. The same strategy was then applied to a hitherto unactivable pga gene cluster in Streptomyces sp. PGA64 leading to the identification of two new anthraquinone aminoglycosides, gaudimycin D and E.
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Affiliation(s)
- Fang Guo
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, No. 1 West Beichen Road, Chaoyang District, Beijing 100101, People׳s Republic of China; University of Chinese Academy of Sciences, Beijing 100049, People׳s Republic of China
| | - Sihai Xiang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, No. 1 West Beichen Road, Chaoyang District, Beijing 100101, People׳s Republic of China
| | - Liyuan Li
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, No. 1 West Beichen Road, Chaoyang District, Beijing 100101, People׳s Republic of China
| | - Bin Wang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, No. 1 West Beichen Road, Chaoyang District, Beijing 100101, People׳s Republic of China; University of Chinese Academy of Sciences, Beijing 100049, People׳s Republic of China
| | - Johanna Rajasärkkä
- Department of Biochemistry, University of Turku, Vatselankatu 2, FIN-20014 Turku, Finland
| | | | - Guomin Ai
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, No. 1 West Beichen Road, Chaoyang District, Beijing 100101, People׳s Republic of China
| | - Mikko Metsä-Ketelä
- Department of Biochemistry, University of Turku, Vatselankatu 2, FIN-20014 Turku, Finland
| | - Keqian Yang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, No. 1 West Beichen Road, Chaoyang District, Beijing 100101, People׳s Republic of China.
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14
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Patrikainen P, Niiranen L, Thapa K, Paananen P, Tähtinen P, Mäntsälä P, Niemi J, Metsä-Ketelä M. Structure-Based Engineering of Angucyclinone 6-Ketoreductases. ACTA ACUST UNITED AC 2014; 21:1381-1391. [DOI: 10.1016/j.chembiol.2014.07.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 07/24/2014] [Accepted: 07/25/2014] [Indexed: 11/27/2022]
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15
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Huijbers MME, Montersino S, Westphal AH, Tischler D, van Berkel WJH. Flavin dependent monooxygenases. Arch Biochem Biophys 2013; 544:2-17. [PMID: 24361254 DOI: 10.1016/j.abb.2013.12.005] [Citation(s) in RCA: 359] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 12/06/2013] [Accepted: 12/09/2013] [Indexed: 11/29/2022]
Abstract
Flavin-dependent monooxygenases catalyze a wide variety of chemo-, regio- and enantioselective oxygenation reactions. As such, they are involved in key biological processes ranging from catabolism, detoxification and biosynthesis, to light emission and axon guidance. Based on fold and function, flavin-dependent monooxygenases can be distributed into eight groups. Groups A and B comprise enzymes that rely on NAD(P)H as external electron donor. Groups C-F are two-protein systems, composed of a monooxygenase and a flavin reductase. Groups G and H comprise internal monooxygenases that reduce the flavin cofactor through substrate oxidation. Recently, many new flavin-dependent monooxygenases have been discovered. In addition to posing basic enzymological questions, these proteins attract attention of pharmaceutical and fine-chemical industries, given their importance as regio- and enantioselective biocatalysts. In this review we present an update of the classification of flavin-dependent monooxygenases and summarize the latest advances in our understanding of their catalytic and structural properties.
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Affiliation(s)
- Mieke M E Huijbers
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands
| | - Stefania Montersino
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands
| | - Adrie H Westphal
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands
| | - Dirk Tischler
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands; Interdisciplinary Ecological Center, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany
| | - Willem J H van Berkel
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands.
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16
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Sucharitakul J, Tongsook C, Pakotiprapha D, van Berkel WJH, Chaiyen P. The reaction kinetics of 3-hydroxybenzoate 6-hydroxylase from Rhodococcus jostii RHA1 provide an understanding of the para-hydroxylation enzyme catalytic cycle. J Biol Chem 2013; 288:35210-21. [PMID: 24129570 DOI: 10.1074/jbc.m113.515205] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
3-Hydroxybenzoate 6-hydroxylase (3HB6H) from Rhodococcus jostii RHA1 is an NADH-specific flavoprotein monooxygenase that catalyzes the para-hydroxylation of 3-hydroxybenzoate (3HB) to form 2,5-dihydroxybenzoate (2,5-DHB). Based on results from stopped-flow spectrophotometry, the reduced enzyme-3HB complex reacts with oxygen to form a C4a-peroxy flavin with a rate constant of 1.13 ± 0.01 × 10(6) m(-1) s(-1) (pH 8.0, 4 °C). This intermediate is subsequently protonated to form a C4a-hydroperoxyflavin with a rate constant of 96 ± 3 s(-1). This step shows a solvent kinetic isotope effect of 1.7. Based on rapid-quench measurements, the hydroxylation occurs with a rate constant of 36 ± 2 s(-1). 3HB6H does not exhibit substrate inhibition on the flavin oxidation step, a common characteristic found in most ortho-hydroxylation enzymes. The apparent kcat at saturating concentrations of 3HB, NADH, and oxygen is 6.49 ± 0.02 s(-1). Pre-steady state and steady-state kinetic data were used to construct the catalytic cycle of the reaction. The data indicate that the steps of product release (11.7 s(-1)) and hydroxylation (36 ± 2 s(-1)) partially control the overall turnover.
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Affiliation(s)
- Jeerus Sucharitakul
- From the Department of Biochemistry, Faculty of Dentistry, Chulalongkorn University, Henri Dunant Road, Patumwan, Bangkok 10330, Thailand
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17
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Paananen P, Patrikainen P, Kallio P, Mäntsälä P, Niemi J, Niiranen L, Metsä-Ketelä M. Structural and Functional Analysis of Angucycline C-6 Ketoreductase LanV Involved in Landomycin Biosynthesis. Biochemistry 2013; 52:5304-14. [DOI: 10.1021/bi400712q] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Pasi Paananen
- Department
of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland
| | - Pekka Patrikainen
- Department
of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland
| | - Pauli Kallio
- Department
of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland
| | - Pekka Mäntsälä
- Department
of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland
| | - Jarmo Niemi
- Department
of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland
| | - Laila Niiranen
- Department
of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland
| | - Mikko Metsä-Ketelä
- Department
of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland
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18
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Kallio P, Patrikainen P, Belogurov GA, Mäntsälä P, Yang K, Niemi J, Metsä-Ketelä M. Tracing the evolution of angucyclinone monooxygenases: structural determinants for C-12b hydroxylation and substrate inhibition in PgaE. Biochemistry 2013; 52:4507-16. [PMID: 23731237 DOI: 10.1021/bi400381s] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Two functionally distinct homologous flavoprotein hydroxylases, PgaE and JadH, have been identified as branching points in the biosynthesis of the polyketide antibiotics gaudimycin C and jadomycin A, respectively. These evolutionarily related enzymes are both bifunctional and able to catalyze the same initial reaction, C-12 hydroxylation of the common angucyclinone intermediate prejadomycin. The enzymes diverge in their secondary activities, which include hydroxylation at C-12b by PgaE and dehydration at C-4a/C-12b by JadH. A further difference is that the C-12 hydroxylation is subject to substrate inhibition only in PgaE. Here we have identified regions associated with the C-12b hydroxylation in PgaE by extensive chimeragenesis, focusing on regions surrounding the active site. The results highlight the importance of a hairpin-β motif near the dimer interface, with two nonconserved residues, P78 and I79 (corresponding to Q89 and F90, respectively, in JadH), and invariant residue H73 playing key roles. Kinetic characterization of PgaE variants demonstrates that the secondary C-12b hydroxylation and substrate inhibition by prejadomycin are likely to be interlinked. The crystal structure of the PgaE P78Q/I79F variant at 2.4 Å resolution confirms that the changes do not alter the conformation of the β-strand secondary structure and that the side chains of these residues in effect point away from the active site toward the dimer interface. The results support a catalytic model for PgaE containing two binding modes for C-12 and C-12b hydroxylations, where binding of prejadomycin in the orientation for C-12b hydroxylation leads to substrate inhibition. The presence of an allosteric network is evident based on enzyme kinetics.
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Affiliation(s)
- Pauli Kallio
- Department of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland
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Taguchi T, Yabe M, Odaki H, Shinozaki M, Metsä-Ketelä M, Arai T, Okamoto S, Ichinose K. Biosynthetic Conclusions from the Functional Dissection of Oxygenases for Biosynthesis of Actinorhodin and Related Streptomyces Antibiotics. ACTA ACUST UNITED AC 2013; 20:510-20. [DOI: 10.1016/j.chembiol.2013.03.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 02/25/2013] [Accepted: 03/06/2013] [Indexed: 11/28/2022]
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20
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Abstract
Riboflavin-based coenzymes, tightly bound to enzymes catalyzing substrate oxidations and reductions, enable an enormous range of chemical transformations in biosynthetic pathways. Flavoenzymes catalyze substrate oxidations involving amine and alcohol oxidations and desaturations to olefins, the latter setting up Diels-Alder cyclizations in lovastatin and solanapyrone biosyntheses. Both C(4a) and N(5) of the flavin coenzymes are sites for covalent adduct formation. For example, the reactivity of dihydroflavins with molecular oxygen leads to flavin-4a-OOH adducts which then carry out a diverse range of oxygen transfers, including Baeyer-Villiger type ring expansions, olefin epoxidations, halogenations via transient HOCl generation, and an oxidative Favorskii rerrangement during enterocin assembly.
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Affiliation(s)
- Christopher T Walsh
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Ave., Boston, MA 02115, USA.
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21
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Roduner E, Kaim W, Sarkar B, Urlacher VB, Pleiss J, Gläser R, Einicke WD, Sprenger GA, Beifuß U, Klemm E, Liebner C, Hieronymus H, Hsu SF, Plietker B, Laschat S. Selective Catalytic Oxidation of CH Bonds with Molecular Oxygen. ChemCatChem 2012. [DOI: 10.1002/cctc.201200266] [Citation(s) in RCA: 211] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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22
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Patrikainen P, Kallio P, Fan K, Klika KD, Shaaban KA, Mäntsälä P, Rohr J, Yang K, Niemi J, Metsä-Ketelä M. Tailoring enzymes involved in the biosynthesis of angucyclines contain latent context-dependent catalytic activities. ACTA ACUST UNITED AC 2012; 19:647-55. [PMID: 22633416 DOI: 10.1016/j.chembiol.2012.04.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 03/07/2012] [Accepted: 04/04/2012] [Indexed: 10/28/2022]
Abstract
Comparison of homologous angucycline modification enzymes from five closely related Streptomyces pathways (pga, cab, jad, urd, lan) allowed us to deduce the biosynthetic steps responsible for the three alternative outcomes: gaudimycin C, dehydrorabelomycin, and 11-deoxylandomycinone. The C-12b-hydroxylated urdamycin and gaudimycin metabolites appear to be the ancestral representatives from which landomycins and jadomysins have evolved as a result of functional divergence of the ketoreductase LanV and hydroxylase JadH, respectively. Specifically, LanV has acquired affinity for an earlier biosynthetic intermediate resulting in a switch in biosynthetic order and lack of hydroxyls at C-4a and C-12b, whereas in JadH, C-4a/C-12b dehydration has evolved into an independent secondary function replacing C-12b hydroxylation. Importantly, the study reveals that many of the modification enzymes carry several alternative, hidden, or ancestral catalytic functions, which are strictly dependent on the biosynthetic context.
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Affiliation(s)
- Pekka Patrikainen
- Department of Biochemistry and Food Chemistry, University of Turku, 20014 Turku, Finland
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Characterization of the two-component monooxygenase system AlnT/AlnH reveals early timing of quinone formation in alnumycin biosynthesis. J Bacteriol 2012; 194:2829-36. [PMID: 22467789 DOI: 10.1128/jb.00228-12] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alnumycin A is an aromatic polyketide with a strong resemblance to related benzoisochromanequinone (BIQ) antibiotics, such as the model antibiotic actinorhodin. One intriguing difference between these metabolites is that the positions of the benzene and quinone rings are reversed in alnumycin A in comparison to the BIQ polyketides. In this paper we demonstrate that inactivation of either the monooxygenase alnT gene or the flavin reductase alnH gene results in the accumulation of a novel nonquinoid metabolite, thalnumycin A (ThA), in the culture medium. Additionally, two other previously characterized metabolites, K1115 A and 1,6-dihydroxy-8-propylanthraquinone (DHPA), were identified, which had oxidized into quinones putatively nonenzymatically at the incorrect position in the central ring. None of the compounds isolated contained correctly formed pyran rings, which suggests that on the alnumycin pathway quinone biosynthesis occurs prior to third ring cyclization. The regiochemistry of the two-component monooxygenase system AlnT/AlnH was finally confirmed in vitro by using ThA, FMN, and NADH in enzymatic synthesis, where the reaction product, thalnumycin B (ThB), was verified to contain the expected p-hydroquinone structure in the lateral ring.
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