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Montoya AL, Gil ER, Vinales I, Estevao IL, Taboada P, Torrico MC, Torrico F, Marco JD, Almeida IC, Michael K. Big is not better: Comparing two alpha-Gal-bearing glycotopes in neoglycoproteins as biomarkers for Leishmania (Viannia) braziliensis infection. Carbohydr Res 2024; 536:109015. [PMID: 38198982 DOI: 10.1016/j.carres.2023.109015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 12/15/2023] [Accepted: 12/15/2023] [Indexed: 01/12/2024]
Abstract
The protozoan parasite Leishmania (Viannia) braziliensis is among Latin America's most widespread Leishmania species and is responsible for tegumentary leishmaniasis (TL). This disease has multiple clinical presentations, with cutaneous leishmaniasis (CL) being the most frequent. It manifests as one or a few localized skin ulcers, which can spread to other body areas. Hence, early diagnosis and treatment, typically with pentavalent antimonials, is critical. Traditional diagnostic methods, like parasite culture, microscopy, or the polymerase chain reaction (PCR) for detection of the parasite DNA, have limitations due to the uneven distribution of parasites in biopsy samples. Nonetheless, studies have revealed high levels of parasite-specific anti-α-Gal antibodies in L. (V.) braziliensis-infected patients. Previously, we demonstrated that the neoglycoprotein NGP28b, consisting of the L. (Leishmania) major type-2 glycoinositolphospholipid (GIPL)-3-derived trisaccharide Galpα1,6Galpα1,3Galfβ conjugated to bovine serum albumin (BSA) via a linker, acts as a reliable serological biomarker (BMK) for L. (V.) braziliensis infection in Brazil. This indicates the presence of GIPL-3 or a similar structure in this parasite, and its terminal trisaccharide either functions as or is part of an immunodominant glycotope. Here, we explored whether extending the trisaccharide with a mannose unit would enhance its efficacy as a biomarker for the serological detection of L. (V.) braziliensis. We synthesized the tetrasaccharide Galpα1,6Galpα1,3Galfβ1,3Manpα(CH2)3SH (G31SH) and conjugated it to maleimide-functionalized BSA to afford NGP31b. When we assessed the efficacy of NGP28b and NGP31b by chemiluminescent enzyme-linked immunosorbent assay on a cohort of CL patients with L. (V.) braziliensis infection from Bolivia and Argentina against a healthy control group, both NGPs exhibited similar or identical sensitivity, specificity, and accuracy. This finding implies that the mannose moiety at the reducing end is not part of the glycotope recognized by the parasite-specific anti-α-Gal antibodies in patients' sera, nor does it exert a relevant influence on the terminal trisaccharide's conformation. Moreover, the mannose does not seem to inhibit glycan-antibody interactions. Therefore, NGP31b is a viable and dependable BMK for the serodiagnosis of CL caused by L. (V.) braziliensis.
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Affiliation(s)
- Alba L Montoya
- Department of Chemistry and Biochemistry, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, TX, 79968, USA
| | - Eileni R Gil
- Department of Chemistry and Biochemistry, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, TX, 79968, USA
| | - Irodiel Vinales
- Department of Chemistry and Biochemistry, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, TX, 79968, USA
| | - Igor L Estevao
- Department of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, TX, 79968, USA
| | - Paola Taboada
- Department of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, TX, 79968, USA
| | - Mary Cruz Torrico
- Universidad Mayor de San Simón, Faculty of Medicine, and Fundación CEADES, Cochabamba, Bolivia
| | - Faustino Torrico
- Universidad Mayor de San Simón, Faculty of Medicine, and Fundación CEADES, Cochabamba, Bolivia
| | - Jorge Diego Marco
- Universidad Nacional de Salta (UNSa)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Patología Experimental, Facultad de Ciencias de la Salud, Universidad Nacional de Salta, Salta, Argentina
| | - Igor C Almeida
- Department of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, TX, 79968, USA.
| | - Katja Michael
- Department of Chemistry and Biochemistry, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, TX, 79968, USA.
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2
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Bulmer GS, Yuen FW, Begum N, Jones BS, Flitsch SL, van Munster JM. Biochemical characterization of a glycoside hydrolase family 43 β-D-galactofuranosidase from the fungus Aspergillus niger. Enzyme Microb Technol 2023; 164:110170. [PMID: 36521309 DOI: 10.1016/j.enzmictec.2022.110170] [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: 07/19/2022] [Revised: 11/27/2022] [Accepted: 11/30/2022] [Indexed: 12/11/2022]
Abstract
β-D-Galactofuranose (Galf) and its polysaccharides are found in bacteria, fungi and protozoa but do not occur in mammalian tissues, and thus represent a specific target for anti-pathogenic drugs. Understanding the enzymatic degradation of these polysaccharides is therefore of great interest, but the identity of fungal enzymes with exclusively galactofuranosidase activity has so far remained elusive. Here we describe the identification and characterization of a galactofuranosidase from the industrially important fungus Aspergillus niger. Analysis of glycoside hydrolase family 43 subfamily 34 (GH43_34) members via conserved unique peptide patterns and phylogeny, revealed the occurrence of distinct clusters and, by comparison with specificities of characterized bacterial members, suggested a basis for prediction of enzyme specificity. Using this rationale, in tandem with molecular docking, we identified a putative β-D-galactofuranosidase from A. niger which was recombinantly produced in Escherichia coli. The Galf-specific hydrolase, encoded by xynD demonstrates maximum activity at pH 5, 25 °C towards 4-nitrophenyl-β-galactofuranoside (pNP-β-Galf), with a Km of 17.9 ± 1.9 mM and Vmax of 70.6 ± 5.3 µM min-1. The characterization of this first fungal GH43 galactofuranosidase offers further molecular insight into the degradation of Galf-containing structures.
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Affiliation(s)
- Gregory S Bulmer
- Manchester Institute of Biotechnology (MIB) & School of Natural Sciences, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Fang Wei Yuen
- Manchester Institute of Biotechnology (MIB) & School of Natural Sciences, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Naimah Begum
- Manchester Institute of Biotechnology (MIB) & School of Natural Sciences, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Bethan S Jones
- Manchester Institute of Biotechnology (MIB) & School of Natural Sciences, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Sabine L Flitsch
- Manchester Institute of Biotechnology (MIB) & School of Natural Sciences, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Jolanda M van Munster
- Manchester Institute of Biotechnology (MIB) & School of Natural Sciences, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom; Scotland's Rural College, West Mains Road, King's Buildings, Edinburgh EH9 3JG, United Kingdom.
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3
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Liang XY, Liu AL, Shawn Fan HJ, Wang L, Xu ZN, Ding XG, Huang BS. TsOH-catalyzed acyl migration reaction of the Bz-group: innovative assembly of various building blocks for the synthesis of saccharides. Org Biomol Chem 2023; 21:1537-1548. [PMID: 36723045 DOI: 10.1039/d2ob02052a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
We developed an efficient method to achieve the regioselective acyl migration of benzoyl ester. In all the cases, the reactions required only the commercially available organic acid catalyst TsOH·H2O. This method enables the benzoyl group to migrate from secondary groups to primary hydroxyl groups, or from equatorial secondary hydroxyl groups to axial hydroxyl groups. The 1,2 or 1,3 acyl migration would potentially occur via five- and six-membered cyclic ortho acid intermediates. A wide range of orthogonally protected monosaccharides, which are useful intermediates for the synthesis of natural oligosaccharides, were synthesized. Finally, to demonstrate the utility of the method, a tetrasaccharide portion from a mycobacterial cell wall polysaccharide was assembled.
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Affiliation(s)
- Xing-Yong Liang
- School of Chemistry Engineering, Sichuan University of Science & Engineering, Zigong 643000, China.
| | - An-Lin Liu
- School of Chemistry Engineering, Sichuan University of Science & Engineering, Zigong 643000, China.
| | - Hua-Jun Shawn Fan
- School of Chemistry Engineering, Sichuan University of Science & Engineering, Zigong 643000, China.
| | - Lei Wang
- School of Chemistry Engineering, Sichuan University of Science & Engineering, Zigong 643000, China.
| | - Zhi-Ning Xu
- School of Chemistry Engineering, Sichuan University of Science & Engineering, Zigong 643000, China.
| | - Xin-Gang Ding
- School of Chemistry Engineering, Sichuan University of Science & Engineering, Zigong 643000, China.
| | - Bo-Shun Huang
- Division of Chemistry and Chemical Engineering, California Institute of Technology and Howard Hughes Medical Institute, 1200 East California Boulevard, Pasadena, California 91125, USA.
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4
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Specific Recognition of β-Galactofuranose-Containing Glycans of Synthetic Neoglycoproteins by Sera of Chronic Chagas Disease Patients. Molecules 2022; 27:molecules27020411. [PMID: 35056727 PMCID: PMC8781757 DOI: 10.3390/molecules27020411] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 12/26/2021] [Accepted: 12/29/2021] [Indexed: 11/20/2022] Open
Abstract
Chagas disease (CD) can be accurately diagnosed by detecting Trypanosoma cruzi in patients’ blood using polymerase chain reaction (PCR). However, parasite-derived biomarkers are of great interest for the serological diagnosis and early evaluation of chemotherapeutic efficacy when PCR may fail, owing to a blood parasite load below the method’s limit of detection. Previously, we focused on the detection of specific anti-α-galactopyranosyl (α-Gal) antibodies in chronic CD (CCD) patients elicited by α-Gal glycotopes copiously expressed on insect-derived and mammal-dwelling infective parasite stages. Nevertheless, these stages also abundantly express cell surface glycosylphosphatidylinositol (GPI)-anchored glycoproteins and glycoinositolphospholipids (GIPLs) bearing nonreducing terminal β-galactofuranosyl (β-Galf) residues, which are equally foreign to humans and, therefore, highly immunogenic. Here we report that CCD patients’ sera react specifically with synthetic β-Galf-containing glycans. We took a reversed immunoglycomics approach that entailed: (a) Synthesis of T. cruzi GIPL-derived Galfβ1,3Manpα-(CH2)3SH (glycan G29SH) and Galfβ1,3Manpα1,2-[Galfβ1,3]Manpα-(CH2)3SH (glycan G32SH); and (b) preparation of neoglycoproteins NGP29b and NGP32b, and their evaluation in a chemiluminescent immunoassay. Receiver-operating characteristic analysis revealed that NGP32b can distinguish CCD sera from sera of healthy individuals with 85.3% sensitivity and 100% specificity. This suggests that Galfβ1,3Manpα1,2-[Galfβ1,3]Manpα is an immunodominant glycotope and that NGP32b could potentially be used as a novel CCD biomarker.
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Tremblay T, Alcée JB, Giguère D. Protecting-group-free synthesis of clevudine ( l-FMAU), a treatment of the hepatitis B virus. Org Biomol Chem 2022; 20:8859-8863. [DOI: 10.1039/d2ob01814d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A new strategy for the synthesis of unnatural 2′-deoxy-2′-fluoro-l-nucleoside is described.
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Affiliation(s)
- Thomas Tremblay
- Département de Chimie, 1045 av. De la Médecine, Université Laval, Québec City, Qc, Canada G1V 0A6
| | - Jessica B. Alcée
- Département de Chimie, 1045 av. De la Médecine, Université Laval, Québec City, Qc, Canada G1V 0A6
| | - Denis Giguère
- Département de Chimie, 1045 av. De la Médecine, Université Laval, Québec City, Qc, Canada G1V 0A6
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6
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Montoya AL, Austin VM, Portillo S, Vinales I, Ashmus RA, Estevao I, Jankuru SR, Alraey Y, Al-Salem WS, Acosta-Serrano Á, Almeida IC, Michael K. Reversed Immunoglycomics Identifies α-Galactosyl-Bearing Glycotopes Specific for Leishmania major Infection. JACS AU 2021; 1:1275-1287. [PMID: 34467365 PMCID: PMC8397363 DOI: 10.1021/jacsau.1c00201] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Indexed: 06/13/2023]
Abstract
All healthy humans have high levels of natural anti-α-galactosyl (α-Gal) antibodies (elicited by yet uncharacterized glycotopes), which may play important roles in immunoglycomics: (a) potential protection against certain parasitic and viral zoonotic infections; (b) targeting of α-Gal-engineered cancer cells; (c) aiding in tissue repair; and (d) serving as adjuvants in α-Gal-based vaccines. Patients with certain protozoan infections have specific anti-α-Gal antibodies, elicited against parasite-derived α-Gal-bearing glycotopes. These glycotopes, however, remain elusive except for the well-characterized glycotope Galα1,3Galβ1,4GlcNAcα, expressed by Trypanosoma cruzi. The discovery of new parasitic glycotopes is greatly hindered by the enormous structural diversity of cell-surface glycans and the technical challenges of classical immunoglycomics, a top-down approach from cultivated parasites to isolated glycans. Here, we demonstrate that reversed immunoglycomics, a bottom-up approach, can identify parasite species-specific α-Gal-bearing glycotopes by probing synthetic oligosaccharides on neoglycoproteins. This method was tested here seeking to identify as-yet unknown glycotopes specific for Leishmania major, the causative agent of Old-World cutaneous leishmaniasis (OWCL). Neoglycoproteins decorated with synthetic α-Gal-containing oligosaccharides derived from L. major glycoinositolphospholipids served as antigens in a chemiluminescent enzyme-linked immunosorbent assay using sera from OWCL patients and noninfected individuals. Receiver-operating characteristic analysis identified Galpα1,3Galfβ and Galpα1,3Galfβ1,3Manpα glycotopes as diagnostic biomarkers for L. major-caused OWCL, which can distinguish with 100% specificity from heterologous diseases and L. tropica-caused OWCL. These glycotopes could prove useful in the development of rapid α-Gal-based diagnostics and vaccines for OWCL. Furthermore, this method could help unravel cryptic α-Gal-glycotopes of other protozoan parasites and enterobacteria that elicit the natural human anti-α-Gal antibodies.
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Affiliation(s)
- Alba L. Montoya
- Department
of Chemistry and Biochemistry, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
| | - Victoria M. Austin
- Department
of Vector Biology, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United
Kingdom
| | - Susana Portillo
- Department
of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
| | - Irodiel Vinales
- Department
of Chemistry and Biochemistry, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
| | - Roger A. Ashmus
- Department
of Chemistry and Biochemistry, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
| | - Igor Estevao
- Department
of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
| | - Sohan R. Jankuru
- Department
of Chemistry and Biochemistry, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
| | - Yasser Alraey
- Department
of Vector Biology, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United
Kingdom
| | - Waleed S. Al-Salem
- Department
of Vector Biology, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United
Kingdom
| | - Álvaro Acosta-Serrano
- Department
of Vector Biology, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United
Kingdom
| | - Igor C. Almeida
- Department
of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
| | - Katja Michael
- Department
of Chemistry and Biochemistry, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
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7
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Fittolani G, Tyrikos-Ergas T, Vargová D, Chaube MA, Delbianco M. Progress and challenges in the synthesis of sequence controlled polysaccharides. Beilstein J Org Chem 2021; 17:1981-2025. [PMID: 34386106 PMCID: PMC8353590 DOI: 10.3762/bjoc.17.129] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 07/22/2021] [Indexed: 01/15/2023] Open
Abstract
The sequence, length and substitution of a polysaccharide influence its physical and biological properties. Thus, sequence controlled polysaccharides are important targets to establish structure-properties correlations. Polymerization techniques and enzymatic methods have been optimized to obtain samples with well-defined substitution patterns and narrow molecular weight distribution. Chemical synthesis has granted access to polysaccharides with full control over the length. Here, we review the progress towards the synthesis of well-defined polysaccharides. For each class of polysaccharides, we discuss the available synthetic approaches and their current limitations.
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Affiliation(s)
- Giulio Fittolani
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
- Department of Chemistry and Biochemistry, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
| | - Theodore Tyrikos-Ergas
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
- Department of Chemistry and Biochemistry, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
| | - Denisa Vargová
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Manishkumar A Chaube
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Martina Delbianco
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
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Sabbavarapu NM, Seeberger PH. Automated Glycan Assembly of Oligogalactofuranosides Reveals the Influence of Protecting Groups on Oligosaccharide Stability. J Org Chem 2021; 86:7280-7287. [PMID: 33960786 PMCID: PMC8154612 DOI: 10.1021/acs.joc.1c00505] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
![]()
Galactofurans are
an important structural constituent of arabinogalactan
and lipopolysaccharides (LPS) ubiquitously present on the envelopes
of all Mycobacteria. Key to the automated glycan
assembly (AGA) of linear galactofuranosides as long as 20-mers was
the identification of thioglycoside building blocks with a fine balance
of stereoelectronic and steric effects to ensure the stability of
oligogalactofuranoside during the synthesis. A benzoylated galactofuranose
thioglycoside building block proved most efficient for oligosaccharide
construction.
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Affiliation(s)
| | - Peter H Seeberger
- Department of Biomolecular Systems, Max-Planck-Institute of Colloids and Interfaces, 14476 Potsdam, Germany.,Freie Universität Berlin, Institute of Chemistry and Biochemistry, 14195 Berlin, Germany
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Huang BS, Lowary TL. A Siloxane-Bridged Glycosyl Donor Enables Highly Stereoselective β-Xylulofuranosylation. J Org Chem 2020; 85:15895-15907. [PMID: 32489097 DOI: 10.1021/acs.joc.0c01008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We report a siloxane-protected donor (7) for the highly stereoselective formation of β-(2,3-cis)-xylulofuranosyl bonds. Glycosylation reactions with 7 gave >80% yields, and only β-xylulofuranosides were isolated in all cases. The utility of 7 for the synthesis of complex glycans was shown by its successful application to the preparation of the repeating unit from the lipopolysaccharide O-antigen of Yersinia enterocolitica serovars O:5/O:5,27. This structure is a pentasaccharide with two β-xylulofuranose residues; using 7, both were introduced simultaneously with excellent stereocontrol.
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Affiliation(s)
- Bo-Shun Huang
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Todd L Lowary
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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10
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Ashokcoomar S, Reedoy KS, Senzani S, Loots DT, Beukes D, van Reenen M, Pillay B, Pillay M. Mycobacterium tuberculosis curli pili (MTP) deficiency is associated with alterations in cell wall biogenesis, fatty acid metabolism and amino acid synthesis. Metabolomics 2020; 16:97. [PMID: 32914199 DOI: 10.1007/s11306-020-01720-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 08/28/2020] [Indexed: 12/11/2022]
Abstract
INTRODUCTION In an effort to find alternative therapeutic interventions to combat tuberculosis, a better understanding of the pathophysiology of Mycobacterium tuberculosis is required. The Mycobacterium tuberculosis curli pili (MTP) adhesin, present on the surface of this pathogen, has previously been shown using functional genomics and global transcriptomics, to play an important role in establishing infection, bacterial aggregation, and modulating host response in vitro and in vivo. OBJECTIVE This investigation aimed to determine the role of MTP in modulating the metabolism of M. tuberculosis, using mtp gene-knockout mutant and complemented strains. METHODS Untargeted two-dimensional gas chromatography time-of-flight mass spectrometry, and bioinformatic analyses, were used to identify significant differences in the metabolite profiles among the wild-type, ∆mtp mutant and mtp-complemented strains, and validated with results generated by real-time quantitative PCR. RESULTS A total of 28 metabolites were found to be significantly altered when comparing the ∆mtp mutant and the wild-type strains indicating a decreased utilisation of metabolites in cell wall biogenesis, a reduced efficiency in the breakdown of fatty acids, and decreased amino acid biosynthesis in the former strain. Comparison of the wild-type to mtp-complement, and ∆mtp to mtp-complemented strains revealed 10 and 16 metabolite differences, respectively. Real-time quantitative PCR results supported the metabolomics findings. Complementation of the ∆mtp mutant resulted in a partial restoration of MTP function. CONCLUSION The lack of the MTP adhesin resulted in various bacterial cell wall alterations and related metabolic changes. This study highlights the importance of MTP as a virulence factor and further substantiates its potential use as a suitable biomarker for the development of diagnostic tools and intervention therapeutics against TB.
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Affiliation(s)
- S Ashokcoomar
- Discipline of Medical Microbiology, School of Laboratory Medicine and Medical Sciences, College of Health Sciences, University of KwaZulu-Natal, 1st Floor Doris Duke Medical Research Institute, Congella, Private Bag 7, Durban, 4013, South Africa
| | - K S Reedoy
- Discipline of Medical Microbiology, School of Laboratory Medicine and Medical Sciences, College of Health Sciences, University of KwaZulu-Natal, 1st Floor Doris Duke Medical Research Institute, Congella, Private Bag 7, Durban, 4013, South Africa
| | - S Senzani
- Discipline of Medical Microbiology, School of Laboratory Medicine and Medical Sciences, College of Health Sciences, University of KwaZulu-Natal, 1st Floor Doris Duke Medical Research Institute, Congella, Private Bag 7, Durban, 4013, South Africa
| | - D T Loots
- Human Metabolomics, North-West University, Private Bag x6001, Box 269, Potchefstroom, 2531, South Africa
| | - D Beukes
- Human Metabolomics, North-West University, Private Bag x6001, Box 269, Potchefstroom, 2531, South Africa
| | - M van Reenen
- Human Metabolomics, North-West University, Private Bag x6001, Box 269, Potchefstroom, 2531, South Africa
| | - B Pillay
- Discipline of Microbiology, School of Life Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban, 4000, South Africa
| | - M Pillay
- Discipline of Medical Microbiology, School of Laboratory Medicine and Medical Sciences, College of Health Sciences, University of KwaZulu-Natal, 1st Floor Doris Duke Medical Research Institute, Congella, Private Bag 7, Durban, 4013, South Africa.
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11
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Janoš P, Tvaroška I, Dellago C, Koča J. Catalytic Mechanism of Processive GlfT2: Transition Path Sampling Investigation of Substrate Translocation. ACS OMEGA 2020; 5:21374-21384. [PMID: 32905330 PMCID: PMC7469130 DOI: 10.1021/acsomega.0c01434] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 07/29/2020] [Indexed: 06/11/2023]
Abstract
We applied the transition path sampling (TPS) method to study the translocation step of the catalytic mechanism of galactofuranosyl transferase 2 (GlfT2). Using TPS in the field of enzymatic reactions is still relatively rare, and we show its effectiveness on this enzymatic system. We decipher an unknown mechanism of the translocation step and, thus, provide a complete understanding of the catalytic mechanism of GlfT2 at the atomistic level. The GlfT2 enzyme is involved in the formation of the mycobacterial cell wall and transfers galactofuranose (Galf) from UDP-Galf onto a growing acceptor Galf chain. The biosynthesis of the galactan chain is accomplished in a processive manner, with the growing acceptor substrate remaining bound to GlfT2. The glycosidic bond formed by GlfT2 between the two Galf residues alternates between β-(1-6) and β-(1-5) linkages. The translocation of the growing galactan between individual additions of Galf residues is crucial for the function of GlfT2. Analysis of unbiased trajectory ensembles revealed that the translocation proceeds differently depending on the glycosidic linkage between the last two Galf residues. We also showed that the protonation state of the catalytic residue Asp372 significantly influences the translocation. Approximate transition state structures and potential energy reaction barriers of the translocation process were determined. The calculated potential reaction barriers in the range of 6-14 kcal/mol show that the translocation process is not the rate-limiting step in galactan biosynthesis.
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Affiliation(s)
- Pavel Janoš
- Central
European Institute of Technology (CEITEC), Masaryk University, Brno 601 77, Czech Republic
- Faculty
of Science, National Centre for Biomolecular Research, Masaryk University, Brno 601 77, Czech Republic
| | - Igor Tvaroška
- Central
European Institute of Technology (CEITEC), Masaryk University, Brno 601 77, Czech Republic
- Institute
of Chemistry, Slovak Academy of Sciences, Bratislava 84536, Slovak Republic
| | | | - Jaroslav Koča
- Central
European Institute of Technology (CEITEC), Masaryk University, Brno 601 77, Czech Republic
- Faculty
of Science, National Centre for Biomolecular Research, Masaryk University, Brno 601 77, Czech Republic
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12
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Ortiz CLD, Completo GC, Nacario RC, Nellas RB. Potential Inhibitors of Galactofuranosyltransferase 2 (GlfT2): Molecular Docking, 3D-QSAR, and In Silico ADMETox Studies. Sci Rep 2019; 9:17096. [PMID: 31745103 PMCID: PMC6863818 DOI: 10.1038/s41598-019-52764-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 10/01/2019] [Indexed: 11/08/2022] Open
Abstract
A strategy in the discovery of anti-tuberculosis (anti-TB) drug involves targeting the enzymes involved in the biosynthesis of Mycobacterium tuberculosis' (Mtb) cell wall. One of these enzymes is Galactofuranosyltransferase 2 (GlfT2) that catalyzes the elongation of the galactan chain of Mtb cell wall. Studies targeting GlfT2 have so far produced compounds showing minimal inhibitory activity. With the current challenge of designing potential GlfT2 inhibitors with high inhibition activity, computational methods such as molecular docking, receptor-ligand mapping, molecular dynamics, and Three-Dimensional-Quantitative Structure-Activity Relationship (3D-QSAR) were utilized to deduce the interactions of the reported compounds with the target enzyme and enabling the design of more potent GlfT2 inhibitors. Molecular docking studies showed that the synthesized compounds have binding energy values between -3.00 to -6.00 kcal mol-1. Two compounds, #27 and #31, have registered binding energy values of -8.32 ± 0.01, and -8.08 ± 0.01 kcal mol-1, respectively. These compounds were synthesized as UDP-Galactopyranose mutase (UGM) inhibitors and could possibly inhibit GlfT2. Interestingly, the analogs of the known disaccharide substrate, compounds #1-4, have binding energy range of -10.00 to -19.00 kcal mol-1. The synthesized and newly designed compounds were subjected to 3D-QSAR to further design compounds with effective interaction within the active site. Results showed improved binding energy from -6.00 to -8.00 kcal mol-1. A significant increase on the binding affinity was observed when modifying the aglycon part instead of the sugar moiety. Furthermore, these top hit compounds were subjected to in silico ADMETox evaluation. Compounds #31, #70, #71, #72, and #73 were found to pass the ADME evaluation and throughout the screening, only compound #31 passed the predicted toxicity evaluation. This work could pave the way in the design and synthesis of GlfT2 inhibitors through computer-aided drug design and can be used as an initial approach in identifying potential novel GlfT2 inhibitors with promising activity and low toxicity.
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Affiliation(s)
- Christopher Llynard D Ortiz
- Institute of Chemistry, College of Arts and Sciences, University of the Philippines Los Banos, College, Laguna, 4031, Philippines
- Institute of Chemistry, College of Science, University of the Philippines Diliman, Diliman, Quezon City, 1101, Philippines
| | - Gladys C Completo
- Institute of Chemistry, College of Arts and Sciences, University of the Philippines Los Banos, College, Laguna, 4031, Philippines
| | - Ruel C Nacario
- Institute of Chemistry, College of Arts and Sciences, University of the Philippines Los Banos, College, Laguna, 4031, Philippines
| | - Ricky B Nellas
- Institute of Chemistry, College of Science, University of the Philippines Diliman, Diliman, Quezon City, 1101, Philippines.
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13
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Pal D, Mukhopadhyay B. Chemical synthesis of the pentasaccharide repeating unit of the O-specific polysaccharide from Escherichia coli O132 in the form of its 2-aminoethyl glycoside. Beilstein J Org Chem 2019; 15:2563-2568. [PMID: 31728170 PMCID: PMC6839562 DOI: 10.3762/bjoc.15.249] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 10/07/2019] [Indexed: 11/23/2022] Open
Abstract
The total chemical synthesis of the pentasaccharide repeating unit of the O-polysaccharide from E. coli O132 is accomplished in the form of its 2-aminoethyl glycoside. The 2-aminoethyl glycoside is particularly important as it allows further glycoconjugate formation utilizing the terminal amine without affecting the stereochemistry of the reducing end. The target was achieved through a [3 + 2] strategy where the required monosaccharide building blocks are prepared from commercially available sugars through rational protecting group manipulation. The NIS-mediated activation of thioglycosides was used extensively for the glycosylation reactions throughout.
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Affiliation(s)
- Debasish Pal
- Sweet Lab, Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, Nadia 741246, India
| | - Balaram Mukhopadhyay
- Sweet Lab, Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, Nadia 741246, India
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14
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Krylov VB, Argunov DA, Solovev AS, Petruk MI, Gerbst AG, Dmitrenok AS, Shashkov AS, Latgé JP, Nifantiev NE. Synthesis of oligosaccharides related to galactomannans from Aspergillus fumigatus and their NMR spectral data. Org Biomol Chem 2019; 16:1188-1199. [PMID: 29376539 DOI: 10.1039/c7ob02734f] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The synthesis of model oligosaccharides related to antigenic galactomannans of the dangerous fungal pathogen Aspergillus fumigatus has been performed employing pyranoside-into-furanoside (PIF) rearrangement and controlled O(5) → O(6) benzoyl migration as key synthetic methods. The prepared compounds along with some previously synthesized oligosaccharides were studied by NMR spectroscopy with the full assignment of 1H and 13C signals and the determination of 13C NMR glycosylation effects. The obtained NMR database on 13C NMR chemical shifts for oligosaccharides representing galactomannan fragments forms the basis for further structural analysis of galactomannan related polysaccharides by a non-destructive approach based on the calculation of the 13C NMR spectra of polysaccharides by additive schemes.
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Affiliation(s)
- V B Krylov
- Laboratory of Glycoconjugate Chemistry, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, 119991 Moscow, Russia.
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15
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Shit P, Misra AK. Synthesis of a hexasaccharide repeating unit of the cell wall polysaccharide of Bifidobacterium animalis subsp. lactis LKM512. Carbohydr Res 2019; 473:12-17. [PMID: 30599388 DOI: 10.1016/j.carres.2018.12.014] [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: 12/05/2018] [Revised: 12/18/2018] [Accepted: 12/23/2018] [Indexed: 10/27/2022]
Abstract
A convergent synthesis of the hexasaccharide as its 2-aminoethyl glycoside corresponding to the repeating unit of the cell wall polysaccharide of Bifidobacterium animalis subsp. lactis LKM512 has been achieved applying a [4 + 2] glycosylation strategy. The disaccharide thioglycoside donor was prepared by combining a d-galactofuranosyl thioglycoside with another l-rhamnosyl thioglycoside acceptor. The yields of the individual glycosylation steps were highly satisfactory with excellent stereo outcome. An α-glycosidic linkage of the d-galactofuranosyl moiety in the hexasaccharide was achieved in very good yield.
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Affiliation(s)
- Pradip Shit
- Bose Institute, Division of Molecular Medicine, P-1/12, C.I.T. Scheme VII-M, Kolkata, 700054, India
| | - Anup Kumar Misra
- Bose Institute, Division of Molecular Medicine, P-1/12, C.I.T. Scheme VII-M, Kolkata, 700054, India.
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16
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Ota R, Okamoto Y, Vavricka CJ, Oka T, Matsunaga E, Takegawa K, Kiyota H, Izumi M. Chemo-enzymatic synthesis of p-nitrophenyl β-D-galactofuranosyl disaccharides from Aspergillus sp. fungal-type galactomannan. Carbohydr Res 2019; 473:99-103. [PMID: 30658252 DOI: 10.1016/j.carres.2019.01.005] [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] [Received: 12/18/2018] [Revised: 01/10/2019] [Accepted: 01/10/2019] [Indexed: 11/28/2022]
Abstract
β-d-Galactofuranose (Galf) is a component of polysaccharides and glycoconjugates. There are few reports about the involvement of galactofuranosyltransferases and galactofuranosidases (Galf-ases) in the synthesis and degradation of galactofuranose-containing glycans. The cell walls of filamentous fungi in the genus Aspergillus include galactofuranose-containing polysaccharides and glycoconjugates, such as O-glycans, N-glycans, and fungal-type galactomannan, which are important for cell wall integrity. In this study, we investigated the synthesis of p-nitrophenyl β-d-galactofuranoside and its disaccharides by chemo-enzymatic methods including use of galactosidase. The key step was selective removal of the concomitant pyranoside by enzymatic hydrolysis to purify p-nitrophenyl β-d-galactofuranoside, a promising substrate for β-d-galactofuranosidase from Streptomyces species.
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Affiliation(s)
- Ryo Ota
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Okayama, 700-8530, Japan
| | - Yumi Okamoto
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Okayama, 700-8530, Japan
| | - Christopher J Vavricka
- Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan
| | - Takuji Oka
- Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, Ikeda, 4-22-1, Kumamoto 860-0082, Japan
| | - Emiko Matsunaga
- Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Fukuoka, 812-8581, Japan
| | - Kaoru Takegawa
- Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Fukuoka, 812-8581, Japan
| | - Hiromasa Kiyota
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Okayama, 700-8530, Japan
| | - Minoru Izumi
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Okayama, 700-8530, Japan.
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17
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The singular Corynebacterium glutamicum Emb arabinofuranosyltransferase polymerises the α(1 → 5) arabinan backbone in the early stages of cell wall arabinan biosynthesis. ACTA ACUST UNITED AC 2018; 2:38-53. [PMID: 30046665 PMCID: PMC6053596 DOI: 10.1016/j.tcsw.2018.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 06/14/2018] [Accepted: 06/15/2018] [Indexed: 11/20/2022]
Abstract
The arabinan-containing polysaccharides, arabinogalactan (AG) and lipoarabinomannan (LAM), are key cell wall components of the Corynebacterineae, which include Corynebacteria, Norcadia and Mycobacteria. Both AG and LAM contain elaborate arabinan domains composed of distinct structural motifs. Mycobacterial EmbA, EmbB and EmbC, collectively known as the Emb proteins, have been identified as arabinosyltransferases (ArafTs), which are targeted by the front-line anti-tubercular drug ethambutol. Previous studies have established that EmbA and EmbB play a role in the synthesis of the characteristic terminal hexa-arabinosuranosyl motif, whilst EmbC is involved exclusively in the biosynthesis of LAM. Herein, we have investigated the role of the singular Emb protein from Corynebacterium glutamicum through the detailed biochemical and chemical analysis of a double ΔaftAΔemb mutant, where the priming Cg-AftA protein, which generates the substrate for Cg-Emb has been deleted. Analysis of its cell wall revealed a complete absence of arabinose resulting in a truncated cell wall containing only a galactan backbone accompanied with complete loss of cell wall bound mycolates. In vitro cell-free assays using C. glutamicumΔaftA, C. glutamicumΔemb, C. glutamicumΔaftAΔemb and C. glutamicumΔaftBΔaftD and two synthetic acceptors, which mimick the arabinofuranose (Araf) “primed” galactan chain, demonstrated that Cg-Emb is able to transfer an Araf residue to the C5 of the Araf positioned on the synthetic acceptor(s). These results indicate that Cg-Emb acts as an α(1 → 5) ArafT and elongates the arabinan core during the early stages of arabinan biosynthesis in C. glutamicum.
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18
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Kulkarni SS, Wang CC, Sabbavarapu NM, Podilapu AR, Liao PH, Hung SC. "One-Pot" Protection, Glycosylation, and Protection-Glycosylation Strategies of Carbohydrates. Chem Rev 2018; 118:8025-8104. [PMID: 29870239 DOI: 10.1021/acs.chemrev.8b00036] [Citation(s) in RCA: 181] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Carbohydrates, which are ubiquitously distributed throughout the three domains of life, play significant roles in a variety of vital biological processes. Access to unique and homogeneous carbohydrate materials is important to understand their physical properties, biological functions, and disease-related features. It is difficult to isolate carbohydrates in acceptable purity and amounts from natural sources. Therefore, complex saccharides with well-defined structures are often most conviently accessed through chemical syntheses. Two major hurdles, regioselective protection and stereoselective glycosylation, are faced by carbohydrate chemists in synthesizing these highly complicated molecules. Over the past few years, there has been a radical change in tackling these problems and speeding up the synthesis of oligosaccharides. This is largely due to the development of one-pot protection, one-pot glycosylation, and one-pot protection-glycosylation protocols and streamlined approaches to orthogonally protected building blocks, including those from rare sugars, that can be used in glycan coupling. In addition, new automated strategies for oligosaccharide syntheses have been reported not only for program-controlled assembly on solid support but also by the stepwise glycosylation in solution phase. As a result, various sugar molecules with highly complex, large structures could be successfully synthesized. To summarize these recent advances, this review describes the methodologies for one-pot protection and their one-pot glycosylation into the complex glycans and the chronological developments associated with automated syntheses of oligosaccharides.
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Affiliation(s)
- Suvarn S Kulkarni
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India
| | | | | | - Ananda Rao Podilapu
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India
| | - Pin-Hsuan Liao
- Institute of Chemistry , Academia Sinica , Taipei 115 , Taiwan
| | - Shang-Cheng Hung
- Genomics Research Center , Academia Sinica , Taipei 115 , Taiwan
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19
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1-C-phosphonomethyl- and 1-C-difluorophosphonomethyl-1,4-imino-l-arabinitols as Galf transferase inhibitors: A comparison. Carbohydr Res 2018; 461:45-50. [DOI: 10.1016/j.carres.2018.03.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 03/09/2018] [Accepted: 03/16/2018] [Indexed: 12/11/2022]
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20
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Janoš P, Kozmon S, Tvaroška I, Koča J. How Mycobacterium tuberculosis
Galactofuranosyl Transferase 2 (GlfT2) Generates Alternating β-(1-6) and β-(1-5) Linkages: A QM/MM Molecular Dynamics Study of the Chemical Steps. Chemistry 2018; 24:7051-7059. [DOI: 10.1002/chem.201800558] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Indexed: 11/12/2022]
Affiliation(s)
- Pavel Janoš
- Central European Institute of Technology (CEITEC); Masaryk University; Kamenice 5 625 00 Brno Czech Republic
- Faculty of Science-National Centre for Biomolecular Research; Masaryk University; Kamenice 5 625 00 Brno Czech Republic
| | - Stanislav Kozmon
- Central European Institute of Technology (CEITEC); Masaryk University; Kamenice 5 625 00 Brno Czech Republic
- Institute of Chemistry; Slovak Academy of Sciences; Dúbravská cesta 9 SK-845 38 Bratislava Slovakia
| | - Igor Tvaroška
- Central European Institute of Technology (CEITEC); Masaryk University; Kamenice 5 625 00 Brno Czech Republic
- Institute of Chemistry; Slovak Academy of Sciences; Dúbravská cesta 9 SK-845 38 Bratislava Slovakia
| | - Jaroslav Koča
- Central European Institute of Technology (CEITEC); Masaryk University; Kamenice 5 625 00 Brno Czech Republic
- Faculty of Science-National Centre for Biomolecular Research; Masaryk University; Kamenice 5 625 00 Brno Czech Republic
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21
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Yang DM, Chen Y, Sweeney RP, Lowary TL, Liang XY. Stereocontrolled Synthesis of 2-Deoxy-galactopyranosides via Isopropylidene-Protected 6-O-Silylated Donors. Org Lett 2018; 20:2287-2290. [DOI: 10.1021/acs.orglett.8b00632] [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)
- Dan-Mei Yang
- School of Chemistry Engineering, Sichuan University of Science & Engineering, Zigong 643000, China
| | - Yue Chen
- School of Chemistry Engineering, Sichuan University of Science & Engineering, Zigong 643000, China
| | - Ryan P. Sweeney
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada
| | - Todd L. Lowary
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada
| | - Xing-Yong Liang
- School of Chemistry Engineering, Sichuan University of Science & Engineering, Zigong 643000, China
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22
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Xue X, Zheng RB, Koizumi A, Han L, Klassen JS, Lowary TL. Synthetic polyprenol-pyrophosphate linked oligosaccharides are efficient substrates for mycobacterial galactan biosynthetic enzymes. Org Biomol Chem 2018; 16:1939-1957. [DOI: 10.1039/c8ob00316e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Synthetic glycosyl polyprenol phosphates are substrates for enzymes required for cell wall assembly in mycobacteria, including the organism that causes tuberculosis.
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Affiliation(s)
- Xiaochao Xue
- Alberta Glycomics Centre and Department of Chemistry
- University of Alberta
- Edmonton
- Canada
| | - Ruixiang Blake Zheng
- Alberta Glycomics Centre and Department of Chemistry
- University of Alberta
- Edmonton
- Canada
| | - Akihiko Koizumi
- Alberta Glycomics Centre and Department of Chemistry
- University of Alberta
- Edmonton
- Canada
| | - Ling Han
- Alberta Glycomics Centre and Department of Chemistry
- University of Alberta
- Edmonton
- Canada
| | - John S. Klassen
- Alberta Glycomics Centre and Department of Chemistry
- University of Alberta
- Edmonton
- Canada
| | - Todd L. Lowary
- Alberta Glycomics Centre and Department of Chemistry
- University of Alberta
- Edmonton
- Canada
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23
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Cocaud C, Maujoin A, Zheng RB, Lowary TL, Rodrigues N, Percina N, Chartier A, Buron F, Routier S, Nicolas C, Martin OR. Triazole-Linked Iminosugars and Aromatic Systems as Simplified UDP-Galf
Mimics: Synthesis and Preliminary Evaluation as Galf
-Transferase Inhibitors. European J Org Chem 2017. [DOI: 10.1002/ejoc.201701283] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Chloé Cocaud
- Institut de Chimie Organique et Analytique; UMR CNRS 7311; Université d'Orléans; Rue de Chartres, BP 6759 45067 Orléans CEDEX 2 France
| | - Audrey Maujoin
- Institut de Chimie Organique et Analytique; UMR CNRS 7311; Université d'Orléans; Rue de Chartres, BP 6759 45067 Orléans CEDEX 2 France
| | - Ruixiang B. Zheng
- Alberta Glycomics Centre and Department of Chemistry; University of Alberta; GunningLemieux Chemistry Centre; 11227 Saskatchewan Drive T6G 2G2 Edmonton, Alberta Canada
| | - Todd L. Lowary
- Alberta Glycomics Centre and Department of Chemistry; University of Alberta; GunningLemieux Chemistry Centre; 11227 Saskatchewan Drive T6G 2G2 Edmonton, Alberta Canada
| | - Nuno Rodrigues
- Institut de Chimie Organique et Analytique; UMR CNRS 7311; Université d'Orléans; Rue de Chartres, BP 6759 45067 Orléans CEDEX 2 France
| | - Nathalie Percina
- Institut de Chimie Organique et Analytique; UMR CNRS 7311; Université d'Orléans; Rue de Chartres, BP 6759 45067 Orléans CEDEX 2 France
| | - Agnes Chartier
- Institut de Chimie Organique et Analytique; UMR CNRS 7311; Université d'Orléans; Rue de Chartres, BP 6759 45067 Orléans CEDEX 2 France
| | - Frédéric Buron
- Institut de Chimie Organique et Analytique; UMR CNRS 7311; Université d'Orléans; Rue de Chartres, BP 6759 45067 Orléans CEDEX 2 France
| | - Sylvain Routier
- Institut de Chimie Organique et Analytique; UMR CNRS 7311; Université d'Orléans; Rue de Chartres, BP 6759 45067 Orléans CEDEX 2 France
| | - Cyril Nicolas
- Institut de Chimie Organique et Analytique; UMR CNRS 7311; Université d'Orléans; Rue de Chartres, BP 6759 45067 Orléans CEDEX 2 France
| | - Olivier R. Martin
- Institut de Chimie Organique et Analytique; UMR CNRS 7311; Université d'Orléans; Rue de Chartres, BP 6759 45067 Orléans CEDEX 2 France
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24
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Legentil L, Cabezas Y, Tasseau O, Tellier C, Daligault F, Ferrières V. Regioselective Galactofuranosylation for the Synthesis of Disaccharide Patterns Found in Pathogenic Microorganisms. J Org Chem 2017. [DOI: 10.1021/acs.joc.7b00565] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Laurent Legentil
- Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée
de Beaulieu, CS 50837, 35708 Rennes Cedex 7, France
| | - Yari Cabezas
- Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée
de Beaulieu, CS 50837, 35708 Rennes Cedex 7, France
| | - Olivier Tasseau
- Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée
de Beaulieu, CS 50837, 35708 Rennes Cedex 7, France
| | - Charles Tellier
- Université de Nantes, UMR CNRS 6286, 2 Rue de la Houssinière, 44322 Nantes Cedex 3, France
| | - Franck Daligault
- Université de Nantes, UMR CNRS 6286, 2 Rue de la Houssinière, 44322 Nantes Cedex 3, France
| | - Vincent Ferrières
- Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée
de Beaulieu, CS 50837, 35708 Rennes Cedex 7, France
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25
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Galactofuranose antigens, a target for diagnosis of fungal infections in humans. Future Sci OA 2017; 3:FSO199. [PMID: 28883999 PMCID: PMC5583699 DOI: 10.4155/fsoa-2017-0030] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 03/20/2017] [Indexed: 12/02/2022] Open
Abstract
The use of biomarkers for the detection of fungal infections is of interest to complement histopathological and culture methods. Since the production of antibodies in immunocompromised patients is scarce, detection of a specific antigen could be effective for early diagnosis. D-Galactofuranose (Galf) is the antigenic epitope in glycoconjugates of several pathogenic fungi. Since Galf is not biosynthesized by mammals, it is an attractive candidate for diagnosis of infection. A monoclonal antibody that recognizes Galf is commercialized for detection of aspergillosis. The linkage of Galf in the natural glycans and the chemical structures of the synthesized Galf-containing oligosaccharides are described in this paper. The oligosaccharides could be used for the synthesis of artificial carbohydrate-based antigens, not enough exploited for diagnosis. D-Galactofuranose (Galf) is the unit in polysaccharides and glycoconjugates of several pathogenic fungi that is recognized by the immune system. Since Galf is not synthesized by mammals, it is an attractive candidate for diagnosis of infection. Since the production of antibodies in immunocompromised patients is scarce, detection of a specific antigen could be effective for early diagnosis. An antibody that recognizes Galf is commercialized for the detection of aspergillosis. Chemically synthesized Galf-containing oligosaccharides, reviewed in this paper, could therefore be used for the synthesis of artificial carbohydrate-based antigens and in diagnosis.
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26
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Total synthesis of mycobacterial arabinogalactan containing 92 monosaccharide units. Nat Commun 2017; 8:14851. [PMID: 28300074 PMCID: PMC5357306 DOI: 10.1038/ncomms14851] [Citation(s) in RCA: 124] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 02/07/2017] [Indexed: 01/21/2023] Open
Abstract
Carbohydrates are diverse bio-macromolecules with highly complex structures that are involved in numerous biological processes. Well-defined carbohydrates obtained by chemical synthesis are essential to the understanding of their functions. However, synthesis of carbohydrates is greatly hampered by its insufficient efficiency. So far, assembly of long carbohydrate chains remains one of the most challenging tasks for synthetic chemists. Here we describe a highly efficient assembly of a 92-mer polysaccharide by the preactivation-based one-pot glycosylation protocol. Several linear and branched oligosaccharide/polysaccharide fragments ranging from 5-mer to 31-mer in length have been rapidly constructed in one-pot manner, which enables the first total synthesis of a biologically important mycobacterial arabinogalactan through a highly convergent [31+31+30] coupling reaction. Our results show that the preactivation-based one-pot glycosylation protocol may provide access to the construction of long and complicated carbohydrate chains. Due to the vast number of potential isomers, the chemical synthesis of large carbohydrates is challenging. Here the authors report the synthesis of mycobacterial arabinogalactan, a biologically important natural product composed of 92 monosaccharide units, the largest synthetic polysaccharide to date.
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27
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Joe M, Lowary TL. Synthesis of a homologous series of galactofuranose-containing mycobacterial arabinogalactan fragments. CAN J CHEM 2016. [DOI: 10.1139/cjc-2016-0416] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mycobacteria, including the human pathogen Mycobacterium tuberculosis, the causative agent of tuberculosis, produce a complex cell wall structure made of carbohydrates and lipids. The major structural element of the mycobacterial cell wall is a glycoconjugate called the mycolic acid – arabinogalactan – peptidoglycan (mAGP) complex. Inhibition of mAGP biosynthesis is a proven strategy for developing anti-mycobacterial drugs, and thus, understanding the pathways and enzymes involved in the assembly of this molecule is of interest. In this paper, we describe the chemical synthesis of a panel of nine oligosaccharide fragments (4–12) of the galactan domain of the mAGP complex designed as biosynthetic probes. These structures, ranging in size from a hexasaccharide to a tetradecasaccharide, are potential substrates for two biosynthetic enzymes, GlfT2 and AftA, and represent the largest mycobacterial galactan fragments synthesized to date. The route developed was iterative and provided multimilligram quantities of the target molecules 4–12 in good overall yield.
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Affiliation(s)
- Maju Joe
- Alberta Glycomics Centre and Department of Chemistry, The University of Alberta, Edmonton, AB T6G 2G2, Canada
- Alberta Glycomics Centre and Department of Chemistry, The University of Alberta, Edmonton, AB T6G 2G2, Canada
| | - Todd L. Lowary
- Alberta Glycomics Centre and Department of Chemistry, The University of Alberta, Edmonton, AB T6G 2G2, Canada
- Alberta Glycomics Centre and Department of Chemistry, The University of Alberta, Edmonton, AB T6G 2G2, Canada
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Argunov DA, Krylov VB, Nifantiev NE. The Use of Pyranoside-into-Furanoside Rearrangement and Controlled O(5) → O(6) Benzoyl Migration as the Basis of a Synthetic Strategy To Assemble (1→5)- and (1→6)-Linked Galactofuranosyl Chains. Org Lett 2016; 18:5504-5507. [PMID: 27759393 DOI: 10.1021/acs.orglett.6b02735] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A new pyranoside-into-furanoside (PIF) rearrangement of selectively protected galactopyranosides, followed by controlled O(5) → O(6) benzoate migration, gives either 5-OH or 6-OH products. It has been applied for the synthesis of four oligosaccharides related to the galactomannan from Aspergillus fumigatus. The assembly of target oligosaccharides containing both (1→5) and (1→6) linkages between galactofuranosyl residues was performed by applying terminal mannoside and digalactofuranoside blocks, forming a versatile approach toward fungal and bacterial carbohydrate antigens containing both 5-O- and 6-O-substituted galactofuranoside residues.
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Affiliation(s)
- Dmitry A Argunov
- Laboratory of Glycoconjugate Chemistry, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences , Leninsky Prospect 47, 119991 Moscow, Russian Federation
| | - Vadim B Krylov
- Laboratory of Glycoconjugate Chemistry, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences , Leninsky Prospect 47, 119991 Moscow, Russian Federation
| | - Nikolay E Nifantiev
- Laboratory of Glycoconjugate Chemistry, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences , Leninsky Prospect 47, 119991 Moscow, Russian Federation
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29
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Tilve MJ, Cori CR, Gallo-Rodriguez C. Regioselective 5-O-Opening of Conformationally Locked 3,5-O-Di-tert-butylsilylene-d-galactofuranosides. Synthesis of (1→5)-β-d-Galactofuranosyl Derivatives. J Org Chem 2016; 81:9585-9594. [PMID: 27673745 DOI: 10.1021/acs.joc.6b01562] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The use of thiogalactofuranoside as donors for the construction of internal Galf containing oligosaccharide is limited, probably due to the difficulty to functionalize thiogalactofuranoside derivatives showing O-2, O-3, and O-5 with similar reactivity. An efficient method for complete regioselective 5-O-opening of conformationally restricted 3,5-O-di-tert-butylsilylene-d-galactofuranoside derivatives was developed. The use of a solution nBu4NF (1.1 equiv) in CH2Cl2 on 6 gave the 5-OH free derivative 10 as the only product (90%). 3-O-Di-tert-butylhydroxysilyl derivative 10 was stable upon purification and glycosylation reaction. Preactivation of conformationally restricted thioglycoside 6 employing p-NO2-benzensulfenyl chloride/AgOTf followed by condensation over the 5-OH thioglycoside acceptor 10 gave the corresponding disaccharide 12 without autocondensation byproduct. Regioselective 5-O-deprotection was also successfully performed over the (1→5)-β-d-galactofuranosyl di- and trisaccharide derivatives 12 and 13. This methodology allowed the differentiation between the secondary hydroxyl groups OH-3 and OH-5 of 1,2-cis or 1,2-trans d-galactofuranoside derivatives, and it still constitutes an innovative approach to access oligosaccharides of pharmacological importance.
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Affiliation(s)
- Mariano J Tilve
- CIHIDECAR, Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Orgánica, Ciudad Universitaria , Pabellón II, 1428 Buenos Aires, Argentina
| | - Carmen R Cori
- CIHIDECAR, Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Orgánica, Ciudad Universitaria , Pabellón II, 1428 Buenos Aires, Argentina
| | - Carola Gallo-Rodriguez
- CIHIDECAR, Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Orgánica, Ciudad Universitaria , Pabellón II, 1428 Buenos Aires, Argentina
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30
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Frédéric CJM, Tikad A, Fu J, Pan W, Zheng RB, Koizumi A, Xue X, Lowary TL, Vincent SP. Synthesis of Unprecedented Sulfonylated Phosphono-exo-Glycals Designed as Inhibitors of the Three Mycobacterial Galactofuranose Processing Enzymes. Chemistry 2016; 22:15913-15920. [PMID: 27628709 DOI: 10.1002/chem.201603161] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Indexed: 11/06/2022]
Abstract
This study reports a new methodology to synthesize exo-glycals bearing both a sulfone and a phosphonate. This synthetic strategy provides a way to generate exo-glycals displaying two electron-withdrawing groups and was applied to eight different carbohydrates from the furanose and pyranose series. The Z/E configurations of these tetrasubstituted enol ethers could be ascertained using NMR spectroscopic techniques. Deprotection of an exo-glycal followed by an UMP (uridine monophosphate) coupling generated two new UDP (uridine diphosphate)-galactofuranose analogues. These two Z/E isomers were evaluated as inhibitors of UGM, GlfT1, and GlfT2, the three mycobacterial galactofuranose processing enzymes. Molecule 46-(E) is the first characterized inhibitor of GlfT1 reported to date and was also found to efficiently inhibit UGM in a reversible manner. Interestingly, GlfT2 showed a better affinity for the (Z) isomer. The three enzymes studied in the present work are not only interesting because, mechanistically, they are still the topic of intense investigations, but also because they constitute very important targets for the development of novel antimycobacterial agents.
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Affiliation(s)
- Christophe J-M Frédéric
- University of Namur (UNamur), Département de Chimie, Laboratoire de Chimie Bio-Organique, rue de Bruxelles 61, 5000, Namur, Belgium
| | - Abdellatif Tikad
- University of Namur (UNamur), Département de Chimie, Laboratoire de Chimie Bio-Organique, rue de Bruxelles 61, 5000, Namur, Belgium
| | - Jian Fu
- University of Namur (UNamur), Département de Chimie, Laboratoire de Chimie Bio-Organique, rue de Bruxelles 61, 5000, Namur, Belgium
| | - Weidong Pan
- The Key Laboratory of Chemistry for Natural Products of Guizhou Province, Chinese Academy of Sciences, 202, Sha-chong South Road, Guiyang, 550002, P. R. China
| | - Ruixiang B Zheng
- Department of Chemistry and Alberta Glycomics Centre, University of Alberta, Gunning-Lemieux Chemistry Centre, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2, Canada
| | - Akihiko Koizumi
- Department of Chemistry and Alberta Glycomics Centre, University of Alberta, Gunning-Lemieux Chemistry Centre, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2, Canada
| | - Xiaochao Xue
- Department of Chemistry and Alberta Glycomics Centre, University of Alberta, Gunning-Lemieux Chemistry Centre, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2, Canada
| | - Todd L Lowary
- Department of Chemistry and Alberta Glycomics Centre, University of Alberta, Gunning-Lemieux Chemistry Centre, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2, Canada
| | - Stéphane P Vincent
- University of Namur (UNamur), Département de Chimie, Laboratoire de Chimie Bio-Organique, rue de Bruxelles 61, 5000, Namur, Belgium.
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Poulin MB, Lowary TL. Chemical Insight into the Mechanism and Specificity of GlfT2, a Bifunctional Galactofuranosyltransferase from Mycobacteria. J Org Chem 2016; 81:8123-30. [PMID: 27557056 DOI: 10.1021/acs.joc.6b01501] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mycobacteria, including the human pathogen Mycobacterium tuberculosis, produce a complex cell wall structure that is essential to survival. A key component of this structure is a glycoconjugate, the mycolyl-arabinogalactan-peptidoglycan complex, which has at its core a galactan domain composed of galactofuranose (Galf) residues linked to peptidoglycan. Because galactan biosynthesis is essential for mycobacterial viability, compounds that interfere with this process are potential therapeutic agents for treating mycobacterial diseases, including tuberculosis. Galactan biosynthesis in mycobacteria involves two glycosyltransferases, GlfT1 and GlfT2, which have been the subject of increasing interest in recent years. This Synopsis summarizes efforts to characterize the mechanism and specificity of GlfT2, which is responsible for introducing the majority of the Galf residues into mycobacterial galactan.
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Affiliation(s)
- Myles B Poulin
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
| | - Todd L Lowary
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
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32
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Synthesis and Evaluation of Bicyclo[3.1.0]hexane-Based UDP-Galf Analogues as Inhibitors of the Mycobacterial Galactofuranosyltransferase GlfT2. Molecules 2016; 21:molecules21081053. [PMID: 27529206 PMCID: PMC6272867 DOI: 10.3390/molecules21081053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 08/05/2016] [Accepted: 08/06/2016] [Indexed: 11/17/2022] Open
Abstract
UDP-galactofuranose (UDP-Galf) is the donor substrate for both bifunctional galactofuranosyltransferases, GlfT1 and GlfT2, which are involved in the biosynthesis of mycobacterial galactan. In this paper, a group of UDP-Galf mimics were synthesized via reductive amination of a bicyclo[3.1.0]hexane-based amine by reacting with aromatic, linear, or uridine-containing aldehydes. These compounds were evaluated against GlfT2 using a coupled spectrophotometric assay, and were shown to be weak inhibitors of the enzyme.
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33
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Lcp1 Is a Phosphotransferase Responsible for Ligating Arabinogalactan to Peptidoglycan in Mycobacterium tuberculosis. mBio 2016; 7:mBio.00972-16. [PMID: 27486192 PMCID: PMC4981717 DOI: 10.1128/mbio.00972-16] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
UNLABELLED Mycobacterium tuberculosis, the etiological agent of tuberculosis (TB), has a unique cell envelope which accounts for its unusual low permeability and contributes to resistance against common antibiotics. The main structural elements of the cell wall consist of a cross-linked network of peptidoglycan (PG) in which some of the muramic acid residues are covalently attached to a complex polysaccharide, arabinogalactan (AG), via a unique α-l-rhamnopyranose-(1→3)-α-d-GlcNAc-(1→P) linker unit. While the molecular genetics associated with PG and AG biosynthetic pathways have been largely delineated, the mechanism by which these two major pathways converge has remained elusive. In Gram-positive organisms, the LytR-CpsA-Psr (LCP) family of proteins are responsible for ligating cell wall teichoic acids to peptidoglycan, through a linker unit that bears a striking resemblance to that found in mycobacterial arabinogalactan. In this study, we have identified Rv3267 as a mycobacterial LCP homolog gene that encodes a phosphotransferase which we have named Lcp1. We demonstrate that lcp1 is an essential gene required for cell viability and show that recombinant Lcp1 is capable of ligating AG to PG in a cell-free radiolabeling assay. IMPORTANCE Tuberculosis is an infectious disease caused by the bacterial organism Mycobacterium tuberculosis Survival of M. tuberculosis rests critically on the integrity of its unique cell wall; therefore, a better understanding of how the genes and enzymes involved in cell wall assembly work is fundamental for us to develop new drugs to treat this disease. In this study, we have identified Lcp1 as an essential phosphotransferase that ligates together arabinogalactan and peptidoglycan, two crucial cell wall macromolecules found within the mycobacterial cell wall. The discovery of Lcp1 sheds new light on the final stages of mycobacterial cell wall assembly and represents a key biosynthetic step that could be exploited for new anti-TB drug discovery.
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Abstract
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The cell surface (or cell wall) of bacteria is coated with carbohydrate
(or glycan) structures that play a number of important roles. These
include providing structural integrity, serving as a permeability
barrier to extracellular compounds (e.g., drugs) and modulating the
immune system of the host. Of interest to this Account is the cell
wall structure of mycobacteria. There are a host of different mycobacterial
species, some of which cause human disease. The most well-known is Mycobacterium tuberculosis, the causative agent of tuberculosis.
The mycobacterial cell wall is characterized by the presence of unusual
carbohydrate structures that fulfill the roles described above. However,
in many cases, a molecular-level understanding of how mycobacterial
cell wall glycans mediate these processes is lacking. Inspired
by a seminar he heard as a postdoctoral fellow, the author
began his independent research program with a focus on the chemical
synthesis of mycobacterial glycans. The goals were not only to develop
synthetic approaches to these unique structures but also to provide
molecules that could be used to probe their biological function. Initial
work addressed the preparation of fragments of two key polysaccharides,
arabinogalactan and lipoarabinomannan, which contain large numbers
of sugar residues in the furanose (five-membered) ring form. At the
time these investigations began, there were few methods reported for
the synthesis of oligosaccharides containing furanose rings. Thus,
early in the program, a major area of interest was methodology development,
particularly for the preparation of 1,2-cis-furanosides.
To solve this challenge, a range of conformationally restricted donors
have been developed, both in the author’s group and others,
which provide 1,2-cis-furanosidic linkages with high
stereoselectivity. These investigations were followed by application
of the developed
methods to the synthesis of a range of target molecules containing
arabinofuranose and galactofuranose residues. These molecules have
now found application in biochemical, immunological, and structural
biology investigations, which have shed light on their biosynthesis
and how these motifs are recognized by both the innate and adaptive
immune systems. More recently, attention has been directed toward
the synthesis
of another class of immunologically active mycobacterial cell wall
glycans, the extractable glycolipids. In this case, efforts have been
primarily on phenolic glycolipids, and the compounds synthesized have
been used to evaluate their ability to modulate cytokine release.
Over the past 20 years, the use of chemical synthesis to provide increasingly
complex glycan structures has provided significant benefit to the
burgeoning field of mycobacterial glycobiology. Through the efforts
of groups from around the globe, access to these compounds is now
possible via relatively straightforward methods. As the pool of mycobacterial
glycans continues to grow, so too will our understanding of their
role in disease, which will undoubtedly lead to new strategies to
prevent or treat mycobacterial infections.
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Affiliation(s)
- Todd L. Lowary
- Alberta Glycomics Centre
and Department of Chemistry, University of Alberta, Gunning−Lemieux
Chemistry Centre, Edmonton, Alberta T6G 2G2, Canada
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35
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Abstract
The cell surface (or cell wall) of bacteria is coated with carbohydrate (or glycan) structures that play a number of important roles. These include providing structural integrity, serving as a permeability barrier to extracellular compounds (e.g., drugs) and modulating the immune system of the host. Of interest to this Account is the cell wall structure of mycobacteria. There are a host of different mycobacterial species, some of which cause human disease. The most well-known is Mycobacterium tuberculosis, the causative agent of tuberculosis. The mycobacterial cell wall is characterized by the presence of unusual carbohydrate structures that fulfill the roles described above. However, in many cases, a molecular-level understanding of how mycobacterial cell wall glycans mediate these processes is lacking. Inspired by a seminar he heard as a postdoctoral fellow, the author began his independent research program with a focus on the chemical synthesis of mycobacterial glycans. The goals were not only to develop synthetic approaches to these unique structures but also to provide molecules that could be used to probe their biological function. Initial work addressed the preparation of fragments of two key polysaccharides, arabinogalactan and lipoarabinomannan, which contain large numbers of sugar residues in the furanose (five-membered) ring form. At the time these investigations began, there were few methods reported for the synthesis of oligosaccharides containing furanose rings. Thus, early in the program, a major area of interest was methodology development, particularly for the preparation of 1,2-cis-furanosides. To solve this challenge, a range of conformationally restricted donors have been developed, both in the author's group and others, which provide 1,2-cis-furanosidic linkages with high stereoselectivity. These investigations were followed by application of the developed methods to the synthesis of a range of target molecules containing arabinofuranose and galactofuranose residues. These molecules have now found application in biochemical, immunological, and structural biology investigations, which have shed light on their biosynthesis and how these motifs are recognized by both the innate and adaptive immune systems. More recently, attention has been directed toward the synthesis of another class of immunologically active mycobacterial cell wall glycans, the extractable glycolipids. In this case, efforts have been primarily on phenolic glycolipids, and the compounds synthesized have been used to evaluate their ability to modulate cytokine release. Over the past 20 years, the use of chemical synthesis to provide increasingly complex glycan structures has provided significant benefit to the burgeoning field of mycobacterial glycobiology. Through the efforts of groups from around the globe, access to these compounds is now possible via relatively straightforward methods. As the pool of mycobacterial glycans continues to grow, so too will our understanding of their role in disease, which will undoubtedly lead to new strategies to prevent or treat mycobacterial infections.
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Affiliation(s)
- Todd L Lowary
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta , Gunning-Lemieux Chemistry Centre, Edmonton, Alberta T6G 2G2, Canada
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36
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Yamatsugu K, Splain RA, Kiessling LL. Fidelity and Promiscuity of a Mycobacterial Glycosyltransferase. J Am Chem Soc 2016; 138:9205-11. [PMID: 27302377 DOI: 10.1021/jacs.6b04481] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Members of the genus Mycobacterium cause devastating human diseases, including tuberculosis. Mycobacterium tuberculosis can resist some antibiotics because of its durable and impermeable cell envelope. This barrier is assembled from saccharide building blocks not found in mammals, including galactofuranose (Galf). Within the cell envelope, Galf residues are linked together to afford an essential polysaccharide, termed the galactan. The formation of this polymer is catalyzed by the glycosyltransferase GlfT2, a processive carbohydrate polymerase, which generates a sequence-specific polysaccharide with alternating regioisomeric β(1-5) and β(1-6) Galf linkages. GlfT2 exhibits high fidelity in linkage formation, as it will terminate polymerization rather than deviate from its linkage pattern. These findings suggest that GlfT2 would prefer an acceptor with a canonical alternating β(1-5) and β(1-6) Galf sequence. To test this hypothesis, we devised a synthetic route to assemble oligosaccharides with natural and non-natural sequences. GlfT2 could elongate each of these acceptors, even those with non-natural linkage patterns. These data indicate that the glycosyltransferase is surprisingly promiscuous in its substrate preferences. However, GlfT2 did favor some substrates: it preferentially acted on those in which the lipid-bearing Galf residue was connected to the sequence by a β(1-6) glycosidic linkage. The finding that the relative positioning of the lipid and the non-reducing end of the acceptor influences substrate selectivity is consistent with a role for the lipid in acceptor binding. The data also suggest that the fidelity of GlfT2 for generating an alternating β(1-5) and β(1-6) pattern of Galf residues arises not from preferential substrate binding but during processive elongation. These observations suggest that inhibiting the action of GlfT2 will afford changes in cell wall structure.
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Affiliation(s)
- Kenzo Yamatsugu
- Department of Chemistry, University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Rebecca A Splain
- Department of Chemistry, University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Laura L Kiessling
- Department of Chemistry, University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States.,Department of Biochemistry, University of Wisconsin-Madison , 433 Babcock Drive, Madison, Wisconsin 53706, United States
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37
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38
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Eppe G, El Bkassiny S, Vincent SP. Galactofuranose Biosynthesis: Discovery, Mechanisms and Therapeutic Relevance. CARBOHYDRATES IN DRUG DESIGN AND DISCOVERY 2015. [DOI: 10.1039/9781849739993-00209] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Galactofuranose, the atypical and thermodynamically disfavored form of d-galactose, has in reality a very old history in chemistry and biochemistry. The purpose of this book chapter is to give an overview on the fundamental aspects of the galactofuranose biosynthesis, from the biological occurrence to the search of inhibitors.
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Affiliation(s)
- Guillaume Eppe
- University of Namur, Département de Chimie, Laboratoire de Chimie Bio-Organique rue de Bruxelles 61 B-5000 Namur Belgium
| | - Sandy El Bkassiny
- University of Namur, Département de Chimie, Laboratoire de Chimie Bio-Organique rue de Bruxelles 61 B-5000 Namur Belgium
| | - Stéphane P. Vincent
- University of Namur, Département de Chimie, Laboratoire de Chimie Bio-Organique rue de Bruxelles 61 B-5000 Namur Belgium
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39
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Wang S, Meng X, Huang W, Yang JS. Influence of silyl protections on the anomeric reactivity of galactofuranosyl thioglycosides and application of the silylated thiogalactofuranosides to one-pot synthesis of diverse β-D-oligogalactofuranosides. J Org Chem 2014; 79:10203-17. [PMID: 25310684 DOI: 10.1021/jo5018684] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We describe in this paper the tuning effect of silyl protecting groups on the donor reactivity of galactofuranosyl phenyl thioglycosides. Silyl ethers on the galactofuranose ring are found to have an arming effect on the glycosylation reactivity, but the cyclic 3,5-acetal protecting group decreases the reactivity. The reactive phenyl 2,6-di-O-Bz-3,5-di-O-TBS-1-thio-β-d-galactofuranoside 3 is proved to be a useful glycosyl building block. By taking advantage of this donor, we achieved the highly efficient one-pot solution-phase assembly of a panel of β-d-galactofuranosyl tri- and tetrasaccharides possessing diverse glycosidic linkages.
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Affiliation(s)
- Shuai Wang
- Key Laboratory of Drug Targeting, Ministry of Education, and Department of Chemistry of Medicinal Natural Products, West China School of Pharmacy, Sichuan University , Chengdu 610041, P. R. China
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Dumitrescu L, Eppe G, Tikad A, Pan W, El Bkassiny S, Gurcha SS, Ardá A, Jiménez-Barbero J, Besra GS, Vincent SP. Selectfluor and NFSI exo-glycal fluorination strategies applied to the enhancement of the binding affinity of galactofuranosyltransferase GlfT2 inhibitors. Chemistry 2014; 20:15208-15. [PMID: 25251918 DOI: 10.1002/chem.201404180] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Indexed: 12/31/2022]
Abstract
Two complementary methods for the synthesis of fluorinated exo-glycals have been developed, for which previously no general reaction had been available. First, a Selectfluor-mediated fluorination was optimized after detailed analysis of all the reaction parameters. A dramatic effect of molecular sieves on the course of the reaction was observed. The reaction was generalized with a set of biologically relevant furanosides and pyranosides. A second direct approach involving carbanionic chemistry and the use of N-fluorobenzenesulfonimide (NFSI) was performed and this method gave better diastereoselectivities. Assignment of the Z/E configuration of all the fluorinated exo-glycals was achieved based on the results of HOESY experiments. Furthermore, fluorinated exo-glycal analogues of UDP-galactofuranose were prepared and assayed against GlfT2, which is a key enzyme involved in the cell-wall biosynthesis of major pathogens. The fluorinated exo-glycals proved to be potent inhibitors as compared with a series of C-glycosidic analogues of UDP-Galf, thus demonstrating the double beneficial effect of the exocyclic enol ether functionality and the fluorine atom.
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Affiliation(s)
- Lidia Dumitrescu
- University of Namur (UNamur), Département de Chimie, Laboratoire de Chimie Bio-Organique rue de Bruxelles 61, B-5000 Namur (Belgium), Fax: (+32) 81-72-45-17
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41
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42
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Martinez Farias MA, Kincaid VA, Annamalai VR, Kiessling LL. Isoprenoid phosphonophosphates as glycosyltransferase acceptor substrates. J Am Chem Soc 2014; 136:8492-5. [PMID: 24866828 PMCID: PMC4073833 DOI: 10.1021/ja500622v] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
![]()
Glycosyltransferases that act on
polyprenol pyrophosphate substrates
are challenging to study because their lipid-linked substrates are
difficult to isolate from natural sources and arduous to synthesize.
To facilitate access to glycosyl acceptors, we assembled phosphonophosphate
analogues and showed these are effective substrate surrogates for
GlfT1, the essential product of mycobacterial gene Rv3782. Under chemically defined conditions, the galactofuranosyltransferase
GlfT1 catalyzes the formation of a tetrasaccharide sequence en route
to assembly of the mycobacterial galactan.
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Affiliation(s)
- Mario A Martinez Farias
- Department of Chemistry and ‡Department of Biochemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
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43
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Marino C, Baldoni L. Synthesis of D-galactofuranose-containing molecules: design of galactofuranosyl acceptors. Chembiochem 2014; 15:188-204. [PMID: 24420700 DOI: 10.1002/cbic.201300638] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Indexed: 11/11/2022]
Abstract
D-Galactofuranose (D-Galf) is present in glycoconjugates of several pathogenic microorganisms but is absent in mammals, so it is a good target for the development of chemotherapeutic agents for the treatment of microbial infections. This fact has increased interest in the synthesis of D-Galf-containing molecules for corresponding glycobiological studies. The synthesis of oligosaccharides, glycoconjugates, and mimetics of D-Galf requires specific methods for the preparation of galactose derivatives in the furanosic configuration, the synthesis of appropriate acceptors, and efficient glycosylation methods for the construction of α- and β-D-Galf linkages. This review summarizes the different strategies developed for the preparation of partially protected derivatives of D-Galf, suitable as acceptors for the construction of (1→2), (1→3), (1→5), and (1→6) link- ages, and describes recent applications.
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Affiliation(s)
- Carla Marino
- CIHIDECAR-CONICET-UBA, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, Ciudad Universitaria, 1428 Buenos Aires (Argentina).
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Li J, Lowary TL. Sulfonium ions as inhibitors of the mycobacterial galactofuranosyltransferase GlfT2. MEDCHEMCOMM 2014. [DOI: 10.1039/c4md00067f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The mycobacterial cell wall possesses a core galactan moiety composed of approximately 30 galactofuranosyl residues attached via alternating β-(1→5) and β-(1→6) linkages.
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Affiliation(s)
- Jing Li
- Alberta Glycomics Centre and Department of Chemistry
- The University of Alberta
- Gunning–Lemieux Chemistry Centre
- Edmonton
- Canada
| | - Todd L. Lowary
- Alberta Glycomics Centre and Department of Chemistry
- The University of Alberta
- Gunning–Lemieux Chemistry Centre
- Edmonton
- Canada
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Boechi L, de Oliveira CAF, Da Fonseca I, Kizjakina K, Sobrado P, Tanner JJ, McCammon JA. Substrate-dependent dynamics of UDP-galactopyranose mutase: Implications for drug design. Protein Sci 2013; 22:1490-501. [PMID: 23934860 DOI: 10.1002/pro.2332] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 07/26/2013] [Accepted: 07/31/2013] [Indexed: 02/04/2023]
Abstract
Trypanosoma cruzi is the causative agent of Chagas disease, a neglected tropical disease that represents one of the major health challenges of the Latin American countries. Successful efforts were made during the last few decades to control the transmission of this disease, but there is still no treatment for the 10 million adults in the chronic phase of the disease. In T. cruzi, as well as in other pathogens, the flavoenzyme UDP-galactopyranose mutase (UGM) catalyzes the conversion of UDP-galactopyranose to UDP-galactofuranose, a precursor of the cell surface β-galactofuranose that is involved in the virulence of the pathogen. The fact that UGM is not present in humans makes inhibition of this enzyme a good approach in the design of new Chagas therapeutics. By performing a series of computer simulations of T. cruzi UGM in the presence or absence of an active site ligand, we address the molecular details of the mechanism that controls the uptake and retention of the substrate. The simulations suggest a modular mechanism in which each moiety of the substrate controls the flexibility of a different protein loop. Furthermore, the calculations indicate that interactions with the substrate diphosphate moiety are especially important for stabilizing the closed active site. This hypothesis is supported with kinetics measurements of site-directed mutants of T. cruzi UGM. Our results extend our knowledge of UGM dynamics and offer new alternatives for the prospective design of drugs.
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Affiliation(s)
- Leonardo Boechi
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California
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Sassaki GL, Rattmann YD, Santana-Filho AP, Riter DS, Iagher F, Trindade ES, da Silva MD, Santos ARS, de Souza LM, Iacomini M, Gorin PAJ. Galactofuranosyl glycosides: immunomodulatory effects on macrophages and in vivo enhancement of lethality on sepsis. Chem Biol Interact 2013; 205:29-37. [PMID: 23756126 DOI: 10.1016/j.cbi.2013.05.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 05/09/2013] [Accepted: 05/30/2013] [Indexed: 02/08/2023]
Abstract
Galactofuranoside derivatives were synthesised by the classic Fischer glycosydation method, and their immune modulation properties were studied in vitro and in vivo. NMR spectroscopic and ESI-MS analyses confirmed the purity and authenticity of all derivatives. Their phagocyte capacities were tested in resident macrophages. Methyl β-galactofuranoside (GFB-Me) and n-octyl β-galactofuranoside (GFB-O) had an immune stimulant effect at 25μmolml(-1) with an enhancement of 35.12%±0.06 SD and 17.49%±0.11 SD, respectively, but Methyl α-galactofuranoside (GFA-Me) and n-octyl α-galactofuranoside (GFA-O) gave a low immune response. Methyl α-galactofuranoside 5,6-O-isopropylidene (GFA-IP) and Methyl β-galactofuranoside 5,6-O-isopropylidene (GFB-IP) had negative values relative to the control group of minus 4.96%±0.10 SD and -40.72%±0.07 SD, respectively. Furthermore, GFB-Me and GFB-Me-IP were evaluated in vivo on the lethality induced by cecal ligation and puncture. Cytokine levels and iNOS expression were determined and correlated to mortality data. The results showed that the free HO-5 and HO-6 and the β-configuration are essential for the induction of phagocytic activity by the galactofuranosyl units. The methyl β-galactofuranosides also enhanced lethality during sepsis, increasing the levels of pro-inflammatory cytokines and iNOS expression.
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Affiliation(s)
- Guilherme L Sassaki
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, Curitiba, PR, Brazil.
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Richards MR, Bai Y, Lowary TL. Comparison between DFT- and NMR-based conformational analysis of methyl galactofuranosides. Carbohydr Res 2013; 374:103-14. [PMID: 23660004 DOI: 10.1016/j.carres.2013.03.030] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 03/26/2013] [Accepted: 03/28/2013] [Indexed: 11/26/2022]
Abstract
Galactofuranose (Galf) residues are found in a number of microbial polysaccharides, and knowledge of their conformation is key for developing a molecular-level understanding of their biological roles. To this end, we studied 180 conformations of methyl α- and β-Galf in aqueous solution (COSMO solvation model) using density functional theory (DFT). We compare the calculated low energy conformations to those determined from the program PSEUROT using (1)H NMR data. The lowest energy ring conformation for methyl α-Galf is (2)E, and this conformer is also the major solution conformation obtained by NMR spectroscopy. For methyl β-Galf, (4)E is the lowest energy ring conformation; however, DFT results do not agree with the solution NMR spectroscopic results. Additionally, we developed Galf-specific Karplus-like equations from these conformations.
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Affiliation(s)
- Michele R Richards
- Alberta Glycomics Centre and Department of Chemistry, Gunning-Lemieux Chemistry Centre, University of Alberta, Edmonton, AB, Canada
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Baldoni L, Marino C. Synthetic tools for the characterization of galactofuranosyl transferases: glycosylations via acylated glycosyl iodides. Carbohydr Res 2013; 374:75-81. [PMID: 23643834 DOI: 10.1016/j.carres.2013.03.032] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 03/26/2013] [Accepted: 03/28/2013] [Indexed: 02/04/2023]
Abstract
With the aim of developing synthetic tools for the characterization of galactofuranosyltransferases, the synthesis of 9-decenyl glycosides of D-Manp, D-Galf, and β-D-Galf-(1→3)-D-Manp was targeted. The interest in the alkenyl aglycone arises via potential conjugation reactions, once the terminal double bond has been conveniently functionalized. The glycosylation of β-D-Galf-(1→3)-D-Manp was attempted by two different approaches: the trichloroacetimidate method and the glycosylation via the glycosyl iodide. The conditions for the latter were established on the basis of glycosylation assays of per-O-acetylmannose. On the other hand, the study of glycosylation reactions via per-O-benzoylated galactofuranosyl iodide confirms the versatility of glycosyl iodides as donors.
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Affiliation(s)
- Luciana Baldoni
- CIHIDECAR-CONICET, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires 1428, Argentina
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Liang XY, Liu QW, Bin HC, Yang JS. One-pot synthesis of branched oligosaccharides by use of galacto- and mannopyranosyl thioglycoside diols as key glycosylating agents. Org Biomol Chem 2013; 11:3903-17. [DOI: 10.1039/c3ob40421h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Marino C, Lima C, Mariño K, de Lederkremer RM. Synthesis of a derivative of α-D-Glcp(1->2)-D-Galf suitable for further glycosylation and of α-D-Glcp(1->2)-D-Gal, a disaccharide fragment obtained from varianose. Beilstein J Org Chem 2012; 8:2142-8. [PMID: 23243476 PMCID: PMC3520571 DOI: 10.3762/bjoc.8.241] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 11/22/2012] [Indexed: 11/23/2022] Open
Abstract
The presence of galactofuranoyl units in infectious microorganisms has prompted the study of the metabolic pathways involved in their incorporation in glycans. Although much progress has been made with respect to the biosynthesis of β-D-Galf-containing glycoconjugates, the mechanisms by which α-D-Galf units are incorporated remain unclear. Penicillium varians is a non-pathogenic fungus that produces varianose, a polysaccharide containing both α- and β-D-Galf units, which can be used as a model for biosynthetic studies on α-D-Galf incorporation. Synthetic oligosaccharide fragments related to varianose are useful as potential substrates or standards for characterization of the α-galactofuranosyl transferases. In this paper we report a straightforward procedure for the synthesis of α-D-Glcp(1→2)-D-Gal (1) and the use of this compound to monitor the natural disaccharide released from varianose by mild acid degradation. The synthesis, performed by the glycosylaldonolactone approach, involved a glucosylgalactofuranose derivative, suitable for the synthesis of higher oligosaccharides with an internal D-Galf.
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Affiliation(s)
- Carla Marino
- CIHIDECAR-CONICET-UBA, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, UBA, Buenos Aires (1428), Argentina
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