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Liu ZC, Wang ZQ, Zhang X, Yin L. Copper(I)-catalyzed asymmetric alkylation of α-imino-esters. Nat Commun 2023; 14:2187. [PMID: 37069200 PMCID: PMC10110621 DOI: 10.1038/s41467-023-37967-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 04/04/2023] [Indexed: 04/19/2023] Open
Abstract
Asymmetric alkylation of enolates is one of the most direct and important reactions to prepare α-chiral carbonyl compounds. Except for the classical methods that rely on the use of chiral auxiliaries, asymmetric catalysis emerged as a powerful tool, especially asymmetric phase-transfer catalysis. However, in the field of transition metal catalysis, only limited success with asymmetric alkylation of enolates was achieved. Hereby, we disclose a copper(I)-catalyzed asymmetric alkylation of α-imino-esters with various alkyl halides, including allyl bromides, propargyl bromide, benzyl bromides, α-bromo carbonyl compounds, and alkyl iodides. Both linear and cyclic α-imino-esters serve as competent pronucleophiles in the alkylation, which affords α-amino acid derivatives bearing either a trisubstituted or a tetrasubstituted stereogenic carbon center in high to excellent enantioselectivity. Control experiments indicate that the α-imino-ester is activated by a chiral copper(I)-phosphine complex through coordination, thus enabling facile deprotonation to provide a stabilized copper(I)-enolate in the presence of a mild base. Finally, the mildly basic nature allows the asymmetric alkylation of chiral dipeptides with excellent both chemo- and enantioselectivities.
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Affiliation(s)
- Zong-Ci Liu
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, 200032, Shanghai, China
| | - Zi-Qing Wang
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, 200032, Shanghai, China
| | - Xuan Zhang
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, 200032, Shanghai, China
| | - Liang Yin
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, 200032, Shanghai, China.
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2
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Jaeger-Honz S, Nitschke J, Altaner S, Klein K, Dietrich DR, Schreiber F. Investigation of microcystin conformation and binding towards PPP1 by molecular dynamics simulation. Chem Biol Interact 2022; 351:109766. [PMID: 34861245 DOI: 10.1016/j.cbi.2021.109766] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/18/2021] [Accepted: 11/19/2021] [Indexed: 11/30/2022]
Abstract
Microcystins (MC) are a group of structurally similar cyanotoxins with currently 279 described structural variants. Human exposure is frequent by consumption of contaminated water, food or food supplements. MC can result in serious intoxications, commensurate with ensuing pathology in various organs or in rare cases even mortality. The current WHO risk assessment primarily considers MC-LR, while all other structural variants are treated as equivalent to MC-LR, despite that current data strongly suggest that MC-LR is not the most toxic MC, and toxicity can be very different for MC congeners. To investigate and analyse binding and conformation of different MC congeners, we applied for the first time Molecular Dynamics (MD) simulation to four MC congeners (MC-LR, MC-LF, [Enantio-Adda5]MC-LF, [β-D-Asp3,Dhb7]MC-RR). We could show that ser/thr protein phosphatase 1 is stable in all MD simulations and that MC-LR backbone adopts to a second conformation in solvent MD simulation, which was previously unknown. We could also show that MC congeners can adopt to different backbone conformation when simulated in solvent or in complex with ser/thr protein phosphatase 1 and differ in their binding behaviour. Our findings suggest that MD Simulation of different MC congeners aid in understanding structural differences and binding of this group of structurally similar cyanotoxins.
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Affiliation(s)
- Sabrina Jaeger-Honz
- Department of Computer and Information Science, University of Konstanz, Germany
| | - Jahn Nitschke
- Department of Biology, University of Konstanz, Germany
| | | | - Karsten Klein
- Department of Computer and Information Science, University of Konstanz, Germany
| | | | - Falk Schreiber
- Department of Computer and Information Science, University of Konstanz, Germany; Faculty of Information Technology, Monash University, Australia.
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3
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Fournier C, Riehle E, Dietrich DR, Schleheck D. Is Toxin-Producing Planktothrix sp. an Emerging Species in Lake Constance? Toxins (Basel) 2021; 13:toxins13090666. [PMID: 34564670 PMCID: PMC8472890 DOI: 10.3390/toxins13090666] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 09/13/2021] [Accepted: 09/15/2021] [Indexed: 01/04/2023] Open
Abstract
Recurring blooms of filamentous, red-pigmented and toxin-producing cyanobacteria Planktothrix rubescens have been reported in numerous deep and stratified prealpine lakes, with the exception of Lake Constance. In a 2019 and 2020 Lake Constance field campaign, we collected samples from a distinct red-pigmented biomass maximum below the chlorophyll-a maximum, which was determined using fluorescence probe measurements at depths between 18 and 20 m. Here, we report the characterization of these deep water red pigment maxima (DRM) as cyanobacterial blooms. Using 16S rRNA gene-amplicon sequencing, we found evidence that the blooms were, indeed, contributed by Planktothrix spp., although phycoerythrin-rich Synechococcus taxa constituted most of the biomass (>96% relative read abundance) of the cyanobacterial DRM community. Through UPLC-MS/MS, we also detected toxic microcystins (MCs) in the DRM in the individual sampling days at concentrations of ≤1.5 ng/L. Subsequently, we reevaluated the fluorescence probe measurements collected over the past decade and found that, in the summer, DRM have been present in Lake Constance, at least since 2009. Our study highlights the need for a continuous monitoring program also targeting the cyanobacterial DRM in Lake Constance, and for future studies on the competition of the different cyanobacterial taxa. Future studies will address the potential community composition changes in response to the climate change driven physiochemical and biological parameters of the lake.
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Affiliation(s)
- Corentin Fournier
- Microbial Ecology and Limnic Microbiology, University of Konstanz, 78457 Konstanz, Germany;
| | - Eva Riehle
- Human and Environmental Toxicology, University of Konstanz, 78457 Konstanz, Germany;
| | - Daniel R. Dietrich
- Human and Environmental Toxicology, University of Konstanz, 78457 Konstanz, Germany;
- Correspondence: (D.R.D.); (D.S.)
| | - David Schleheck
- Microbial Ecology and Limnic Microbiology, University of Konstanz, 78457 Konstanz, Germany;
- Limnological Institute, University of Konstanz, 78457 Konstanz, Germany
- Correspondence: (D.R.D.); (D.S.)
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5
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Weisbrod B, Riehle E, Helmer M, Martin-Creuzburg D, Dietrich DR. Can toxin warfare against fungal parasitism influence short-term Dolichospermum bloom dynamics? - A field observation. HARMFUL ALGAE 2020; 99:101915. [PMID: 33218440 DOI: 10.1016/j.hal.2020.101915] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 08/20/2020] [Accepted: 10/04/2020] [Indexed: 06/11/2023]
Abstract
Cyanobacterial blooms often consist of numerous co-existing cyanobacterial species, with predominant taxa dynamically varying intra-annually. Parasitism by fungi (chytrids) has come into focus as an important factor driving short-term bloom dynamics. Using microscopic analysis, Illumina sequencing and cyanobacterial toxin analyses, we monitored the seasonal succession of Dolichospermum blooms in a reservoir along with environmental parameters. We identified two consecutive Dolichospermum blooms that were characterized by a straight and a coiled morphotype, separated by a complete bloom collapse. Phylotyping provided evidence for three putative Dolichospermum amplicon sequence variants (ASVs); i.e. Dolichospermum1 & 2 in the first bloom (straight filaments) and Dolichospermum3 in the second bloom (coiled filaments). Morphotype succession as well as total filament concentration did not correlate with any of the measured environmental parameters. Fungal parasitism by the chytrid Rhizosiphon crassum occurred in straight Dolichospermum filaments only. Coiled filaments showed no infection despite ambient presence of chytrids, deduced from fungal ASVs, throughout the entire observation period. Toxin concentrations (microcystins (MCs) and anabaenopeptins) correlated significantly with the abundance of the straight Dolichospermum morphotype. Enhanced cyanotoxin biosynthesis in the straight Dolichospermum morphotype, interpreted as a defensive reaction to fungal parasitism, appeared to come at the expense of lowered competitiveness with the co-occurring coiled morphotype. Our findings support the hypothesis that selective parasitism by chytrids is an important factor driving short-term morphotype and toxin dynamics within cyanobacterial blooms.
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Affiliation(s)
- B Weisbrod
- Human and Environmental Toxicology, University of Konstanz, Universitätsstrasse 10, 78464 Konstanz, Germany.
| | - E Riehle
- Human and Environmental Toxicology, University of Konstanz, Universitätsstrasse 10, 78464 Konstanz, Germany
| | - M Helmer
- Limnological Institute, University of Konstanz, Mainaustrasse 252, 78464 Konstanz, Germany
| | - D Martin-Creuzburg
- Limnological Institute, University of Konstanz, Mainaustrasse 252, 78464 Konstanz, Germany
| | - D R Dietrich
- Human and Environmental Toxicology, University of Konstanz, Universitätsstrasse 10, 78464 Konstanz, Germany
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Moschny J, Lorenzen W, Hilfer A, Eckenstaler R, Jahns S, Enke H, Enke D, Schneider P, Benndorf RA, Niedermeyer THJ. Precursor-Directed Biosynthesis and Fluorescence Labeling of Clickable Microcystins. JOURNAL OF NATURAL PRODUCTS 2020; 83:1960-1970. [PMID: 32464061 DOI: 10.1021/acs.jnatprod.0c00251] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Microcystins, cyclic nonribosomal heptapeptides, are the most well-known cyanobacterial toxins. They are exceptionally well studied, but open questions remain concerning their physiological role for the producing microorganism or their suitability as lead compounds for anticancer drug development. One means to study specialized metabolites in more detail is the introduction of functional groups that make a compound amenable for bioorthogonal, so-called click reactions. Although it was reported that microcystins cannot be derivatized by precursor-directed biosynthesis, we successfully used this approach to prepare clickable microcystins. Supplementing different azide- or terminal alkyne containing amino acid analogues into the cultivation medium of microcystin-producing cyanobacteria strains, we found that these strains differ strongly in their substrate acceptance. Exploiting this flexibility, we generated more than 40 different clickable microcystins. We conjugated one of these derivatives with a fluorogenic dye and showed that neither incorporation of the unnatural amino acid analogue nor attachment of the fluorescent label significantly affects the cytotoxicity against cell lines expressing the human organic anion transporting polypeptides 1B1 or 1B3. Using time-lapse microscopy, we observed that the fluorescent microcystin is rapidly taken up into eukaryotic cells expressing these transporters.
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Affiliation(s)
- Julia Moschny
- Department of Pharmaceutical Biology/Pharmacognosy, Institute of Pharmacy, University of Halle-Wittenberg, 06120 Halle (Saale), Germany
- Interfaculty Institute of Microbiology and Infection Medicine, Eberhard Karls University Tübingen, 72076 Tübingen, Germany
| | | | | | - Robert Eckenstaler
- Department of Clinical Pharmacy and Pharmacotherapy, Institute of Pharmacy, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | | | - Heike Enke
- Cyano Biotech GmbH, 12489 Berlin, Germany
| | - Dan Enke
- Cyano Biotech GmbH, 12489 Berlin, Germany
| | - Philipp Schneider
- Interfaculty Institute of Microbiology and Infection Medicine, Eberhard Karls University Tübingen, 72076 Tübingen, Germany
| | - Ralf A Benndorf
- Department of Clinical Pharmacy and Pharmacotherapy, Institute of Pharmacy, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Timo H J Niedermeyer
- Department of Pharmaceutical Biology/Pharmacognosy, Institute of Pharmacy, University of Halle-Wittenberg, 06120 Halle (Saale), Germany
- Interfaculty Institute of Microbiology and Infection Medicine, Eberhard Karls University Tübingen, 72076 Tübingen, Germany
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Kurmayer R, Entfellner E, Weisse T, Offterdinger M, Rentmeister A, Deng L. Chemically labeled toxins or bioactive peptides show a heterogeneous intracellular distribution and low spatial overlap with autofluorescence in bloom-forming cyanobacteria. Sci Rep 2020; 10:2781. [PMID: 32066776 PMCID: PMC7026079 DOI: 10.1038/s41598-020-59381-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 01/21/2020] [Indexed: 11/08/2022] Open
Abstract
Harmful algal blooms formed by colony-forming cyanobacteria deteriorate water resources by producing cyanotoxins, which frequently occur at high intracellular concentrations. We aimed to localize toxic microcystins (MCs) and bioactive anabaenopeptins (APs) at the subcellular level under noninvasive conditions. Since both metabolites are synthesized nonribosomally, the relaxed specificity of key enzymes catalyzing substrate activation allowed chemical labeling through a standard copper-catalyzed click chemistry reaction. The genera Planktothrix and Microcystis specifically incorporated unnatural amino acids such as N-propargyloxy-carbonyl-L-lysine or O-propargyl-L-tyrosine, resulting in modified AP or MC peptides carrying the incorporated alkyne moiety. The labeled cells were quantitatively differentiated from the unlabeled control cells. MCs and APs occurred intracellularly as distinct entities showing a cell-wide distribution but a lowered spatial overlap with natural autofluorescence. Using the immunofluorescence technique, colocalization with markers of individual organelles was utilized to relate the distribution of labeled MCs to cellular compartments, e.g., using RbcL and FtsZ (cytosol) and PsbA (thylakoids). The colocalization correlation coefficients calculated pairwise between organelles and autofluorescence were highly positive as opposed to the relatively low positive indices derived from labeled MCs. The lower correlation coefficients imply that only a portion of the labeled MC molecules were related spatially to the organelles in the cell.
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Affiliation(s)
- Rainer Kurmayer
- University of Innsbruck, Research Department for Limnology, Mondseestrasse 9, 5310, Mondsee, Austria.
| | - Elisabeth Entfellner
- University of Innsbruck, Research Department for Limnology, Mondseestrasse 9, 5310, Mondsee, Austria
| | - Thomas Weisse
- University of Innsbruck, Research Department for Limnology, Mondseestrasse 9, 5310, Mondsee, Austria
| | - Martin Offterdinger
- Innsbruck Medical University, Division of Neurobiochemistry, Biooptics Core Facility, Innrain 80, 6020, Innsbruck, Austria
| | - Andrea Rentmeister
- University of Muenster, Department of Chemistry, Institute of Biochemistry, Wilhelm-Klemm-Strasse 2, 48149, Muenster, Germany
| | - Li Deng
- Helmholtz Centre Munich, Institute of Virology, Ingolstaedter Landstrasse 1, 85764, Neuherberg, Germany
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8
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Simultaneous Detection of 14 Microcystin Congeners from Tissue Samples Using UPLC- ESI-MS/MS and Two Different Deuterated Synthetic Microcystins as Internal Standards. Toxins (Basel) 2019; 11:toxins11070388. [PMID: 31269739 PMCID: PMC6669509 DOI: 10.3390/toxins11070388] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 06/21/2019] [Accepted: 06/28/2019] [Indexed: 02/02/2023] Open
Abstract
Cyanobacterial microcystins (MCs), potent serine/threonine-phosphatase inhibitors, pose an increasing threat to humans. Current detection methods are optimised for water matrices with only a few MC congeners simultaneously detected. However, as MC congeners are known to differ in their toxicity, methods are needed that simultaneously quantify the congeners present, thus allowing for summary hazard and risk assessment. Moreover, detection of MCs should be expanded to complex matrices, e.g., blood and tissue samples, to verify in situ MC concentrations, thus providing for improved exposure assessment and hazard interpretation. To achieve this, we applied two synthetic deuterated MC standards and optimised the tissue extraction protocol for the simultaneous detection of 14 MC congeners in a single ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) run. This procedure was validated using plasma and liver homogenates of mice (male and female) spiked with deuterated MC standards. For proof of concept, tissue and plasma samples from mice i.p. injected with MC-LR and MC-LF were analysed. While MC-LF was detected in all tissue samples of both sexes, detection of MC-LR was restricted to liver samples of male mice, suggesting different toxicokinetics in males, e.g., transport, conjugation or protein binding. Thus, deconjugation/-proteinisation steps should be employed to improve detection of bound MC.
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9
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Microcystins: Synthesis and structure–activity relationship studies toward PP1 and PP2A. Bioorg Med Chem 2018; 26:1118-1126. [DOI: 10.1016/j.bmc.2017.08.040] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 08/19/2017] [Accepted: 08/23/2017] [Indexed: 11/19/2022]
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Liu T, Mazmouz R, Ongley SE, Chau R, Pickford R, Woodhouse JN, Neilan BA. Directing the Heterologous Production of Specific Cyanobacterial Toxin Variants. ACS Chem Biol 2017; 12:2021-2029. [PMID: 28570054 DOI: 10.1021/acschembio.7b00181] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Microcystins are globally the most commonly occurring freshwater cyanotoxins, causing acute poisoning and chronically inducing hepatocellular carcinoma. However, the detection and toxicological study of microcystins is hampered by the limited availability and high cost of pure toxin standards. Biosynthesis of microcystin variants in a fast-growing heterologous host offers a promising method of achieving reliable and economically viable alternative to isolating toxin from slow-growing cyanobacterial cultures. Here, we report the heterologous expression of recombinant microcystin synthetases in Escherichia coli to produce [d-Asp3]microcystin-LR and microcystin-LR. We assembled a 55 kb hybrid polyketide synthase/nonribosomal peptide synthetase gene cluster from Microcystis aeruginosa PCC 7806 using Red/ET recombineering and replaced the native promoters with an inducible PtetO promoter to yield microcystin titers superior to M. aeruginosa. The expression platform described herein can be tailored to heterologously produce a wide variety of microcystin variants, and potentially other cyanobacterial natural products of commercial relevance.
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Affiliation(s)
- Tianzhe Liu
- School
of Biotechnology and Biomolecular Sciences, The University of New South Wales, New South Wales 2052, Sydney, Australia
| | - Rabia Mazmouz
- School
of Biotechnology and Biomolecular Sciences, The University of New South Wales, New South Wales 2052, Sydney, Australia
- School
of Environmental and Life Sciences, The University of Newcastle, New
South Wales 2308, Callaghan, Australia
| | - Sarah E. Ongley
- School
of Biotechnology and Biomolecular Sciences, The University of New South Wales, New South Wales 2052, Sydney, Australia
- School
of Environmental and Life Sciences, The University of Newcastle, New
South Wales 2308, Callaghan, Australia
| | - Rocky Chau
- School
of Biotechnology and Biomolecular Sciences, The University of New South Wales, New South Wales 2052, Sydney, Australia
| | - Russell Pickford
- Bioanalytical
Mass Spectrometry Facility, The University of New South Wales, New
South Wales 2052, Sydney, Australia
| | - Jason N. Woodhouse
- School
of Biotechnology and Biomolecular Sciences, The University of New South Wales, New South Wales 2052, Sydney, Australia
- Leibniz
Institute of Freshwater Ecology and Inland Fisheries (IGB), Experimental Limnology, 12587, Berlin, Germany
| | - Brett A. Neilan
- School
of Biotechnology and Biomolecular Sciences, The University of New South Wales, New South Wales 2052, Sydney, Australia
- School
of Environmental and Life Sciences, The University of Newcastle, New
South Wales 2308, Callaghan, Australia
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