51
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Baldoni L, Marino C. Synthesis of S- and C-galactofuranosides via a galactofuranosyl iodide. Isolable 1-galactofuranosylthiol derivative as a new glycosyl donor. Carbohydr Res 2012; 362:70-8. [DOI: 10.1016/j.carres.2012.08.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 08/26/2012] [Accepted: 08/27/2012] [Indexed: 12/12/2022]
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52
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Kashiwagi GA, Mendoza VM, de Lederkremer RM, Gallo-Rodriguez C. Synthesis of the O-linked hexasaccharide containing β-D-Galf-(1→2)-β-D-Galf in Trypanosoma cruzi mucins. Org Biomol Chem 2012; 10:6322-32. [PMID: 22735493 DOI: 10.1039/c2ob25741f] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The hexasaccharide β-D-Galp-(1→2)-[β-D-Galp-(1→3)]-β-D-Galp-(1→6)-[β-D-Galf(1→2)-β-D-Galf(1→4)]-D-GlcNAc (1) is the largest carbohydrate structure released as alditol by reductive β-elimination from mucins of some strains of T. cruzi. The terminal β-D-Galp units are sites of sialylation by trans-sialidase which transfers sialic acid from the host to the parasite. Hexasaccharide 1 was synthesized by a [3 + 3]-convergent strategy based on a nitrile assisted glycosylation, using the trichloroacetimidate method. The β-D-Galf-(1→2)-β-D-Galf-D-GlcNAc synthon was sequentially constructed from the reducing end to the non-reducing end employing benzyl α-D-galactofuranoside as starting material for the internal Galf unit. The choice of this novel precursor, obtained in one-reaction step from galactose, allowed the introduction of an orthogonal and participating levulinoyl group at O-2. Thus, the diastereoselective construction of the Galf-β(1→4)-GlcNAc linkage by the trichloroacetimidate method of glycosylation was achieved. The (1)H NMR spectrum of alditol 2 was identical to the product released by β-elimination from the parasite mucin.
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Affiliation(s)
- Gustavo A Kashiwagi
- CIHIDECAR, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina
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53
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Zhu SY, Yang JS. Synthesis of tetra- and hexasaccharide fragments corresponding to the O-antigenic polysaccharide of Klebsiella pneumoniae. Tetrahedron 2012. [DOI: 10.1016/j.tet.2012.03.074] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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54
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Poulin MB, Zhou R, Lowary TL. Synthetic UDP-galactofuranose analogs reveal critical enzyme-substrate interactions in GlfT2-catalyzed mycobacterial galactan assembly. Org Biomol Chem 2012; 10:4074-87. [PMID: 22499274 DOI: 10.1039/c2ob25159k] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mycobacterial cell wall galactan, composed of alternating β-(1→5) and β-(1→6) galactofuranosyl residues, is assembled by the action of two bifunctional galactofuranosyltransferases, GlfT1 and GlfT2, which use UDP-galactofuranose (UDP-Galf) as the donor substrate. Kinetic analysis of synthetic UDP-Galf analogs identified critical interactions involved in donor substrate recognition by GlfT2, a processive polymerizing glycosyltransferase. Testing of methylated UDP-Galf analogs showed the donor substrate-binding pocket is sterically crowded. Evaluation of deoxy UDP-Galf analogs revealed that the C-6 hydroxyl group is not essential for substrate activity, and that interactions with the UDP-Galf C-3 hydroxyl group orient the substrate for turnover but appears to play no role in substrate recognition, making the 3-deoxy-analog a moderate competitive inhibitor of the enzyme. Moreover, the addition of a Galf residue deoxygenated at C-5 or C-6, or an l-arabinofuranose residue, to the growing galactan chain resulted in "dead end" reaction products, which no longer act as an acceptor for the enzyme. This finding shows dual recognition of both the terminal C-5 and C-6 hydroxyl groups of the acceptor substrate are required for GlfT2 activity, which is consistent with a recent model developed based upon a crystal structure of the enzyme. These observations provide insight into specific protein-carbohydrate interactions in the GlfT2 active site and may facilitate the design of future inhibitors.
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Affiliation(s)
- Myles B Poulin
- Alberta Glycomics Centre and Department of Chemistry, Gunning-Lemieux Chemistry Centre, University of Alberta, Edmonton, AB T6G 2G2, Canada
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55
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Deng LM, Liu X, Liang XY, Yang JS. Regioselective glycosylation method using partially protected arabino- and galactofuranosyl thioglycosides as key glycosylating substrates and its application to one-pot synthesis of oligofuranoses. J Org Chem 2012; 77:3025-37. [PMID: 22369586 DOI: 10.1021/jo300084g] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
We describe in this paper the development of a novel regioselective furanosylation methodology using partially protected furanosyl thioglycosides as central glycosylating building blocks and its application in the efficient one-pot synthesis of a series of linear and branched-type arabino- and galactofuranoside fragments structurally related to the cell wall polysaccharides of Mycobacterium tuberculosis , Streptococcus pneumoniae serostype 35A, and sugar beet.
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Affiliation(s)
- Li-Min Deng
- 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, People's Republic of China
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56
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de Talancé VL, Thiery E, Eppe G, Bkassiny SE, Mortier J, Vincent SP. A Simple Synthesis of D-Galactono-1,4-Lactone and Key Building Blocks for the Preparation of Galactofuranosides. J Carbohydr Chem 2011. [DOI: 10.1080/07328303.2011.616273] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Affiliation(s)
- Vincent Lemau de Talancé
- a University of Namur (FUNDP), Académie Louvain, Département de Chimie, Laboratoire de Chimie Bio-Organique , rue de Bruxelles 61, B-5000, Namur , Belgium
| | - Emilie Thiery
- a University of Namur (FUNDP), Académie Louvain, Département de Chimie, Laboratoire de Chimie Bio-Organique , rue de Bruxelles 61, B-5000, Namur , Belgium
| | - Guillaume Eppe
- a University of Namur (FUNDP), Académie Louvain, Département de Chimie, Laboratoire de Chimie Bio-Organique , rue de Bruxelles 61, B-5000, Namur , Belgium
| | - Sandy El Bkassiny
- a University of Namur (FUNDP), Académie Louvain, Département de Chimie, Laboratoire de Chimie Bio-Organique , rue de Bruxelles 61, B-5000, Namur , Belgium
| | - Jérémie Mortier
- a University of Namur (FUNDP), Académie Louvain, Département de Chimie, Laboratoire de Chimie Bio-Organique , rue de Bruxelles 61, B-5000, Namur , Belgium
| | - Stéphane P. Vincent
- a University of Namur (FUNDP), Académie Louvain, Département de Chimie, Laboratoire de Chimie Bio-Organique , rue de Bruxelles 61, B-5000, Namur , Belgium
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57
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Repetto E, Manzano VE, Uhrig ML, Varela O. Synthesis of Branched Dithiotrisaccharides via Ring-Opening Reaction of Sugar Thiiranes. J Org Chem 2011; 77:253-65. [DOI: 10.1021/jo2018685] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Evangelina Repetto
- CIHIDECAR-CONICET, Departamento de Química Orgánica,
Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
| | - Verónica E. Manzano
- CIHIDECAR-CONICET, Departamento de Química Orgánica,
Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
| | - María Laura Uhrig
- CIHIDECAR-CONICET, Departamento de Química Orgánica,
Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
| | - Oscar Varela
- CIHIDECAR-CONICET, Departamento de Química Orgánica,
Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
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58
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Santra S, Jonas E, Bourgault JP, El-Baba T, Andreana PR. Kinetic Products Under Thermal Conditions: Rapid Entry into α/β-D-Galactofuranosides Using Microwave Irradiation and Selective Lewis Acids. J Carbohydr Chem 2011. [DOI: 10.1080/07328303.2011.585259] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Soumava Santra
- a Department of Chemistry , Wayne State University , Detroit, Michigan, 48202, USA
| | - Emily Jonas
- a Department of Chemistry , Wayne State University , Detroit, Michigan, 48202, USA
| | - Jean-Paul Bourgault
- a Department of Chemistry , Wayne State University , Detroit, Michigan, 48202, USA
| | - Tarick El-Baba
- a Department of Chemistry , Wayne State University , Detroit, Michigan, 48202, USA
| | - Peter R. Andreana
- a Department of Chemistry , Wayne State University , Detroit, Michigan, 48202, USA
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59
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Peltier P, Beláňová M, Dianišková P, Zhou R, Zheng RB, Pearcey JA, Joe M, Brennan PJ, Nugier-Chauvin C, Ferrières V, Lowary TL, Daniellou R, Mikušová K. Synthetic UDP-furanoses as potent inhibitors of mycobacterial galactan biogenesis. ACTA ACUST UNITED AC 2011; 17:1356-66. [PMID: 21168771 DOI: 10.1016/j.chembiol.2010.10.014] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 10/25/2010] [Accepted: 10/27/2010] [Indexed: 11/29/2022]
Abstract
UDP-galactofuranose (UDP-Galf) is a substrate for two types of enzymes, UDP-galactopyranose mutase and galactofuranosyltransferases, which are present in many pathogenic organisms but absent from mammals. In particular, these enzymes are involved in the biosynthesis of cell wall galactan, a polymer essential for the survival of the causative agent of tuberculosis, Mycobacterium tuberculosis. We describe here the synthesis of derivatives of UDP-Galf modified at C-5 and C-6 using a chemoenzymatic route. In cell-free assays, these compounds prevented the formation of mycobacterial galactan, via the production of short "dead-end" intermediates resulting from their incorporation into the growing oligosaccharide chain. Modified UDP-furanoses thus constitute novel probes for the study of the two classes of enzymes involved in mycobacterial galactan assembly, and studies with these compounds may ultimately facilitate the future development of new therapeutic agents against tuberculosis.
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Affiliation(s)
- Pauline Peltier
- Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 35708 Rennes, Cedex 7, France
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60
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Danalev D, Legentil L, Daniellou R, Nugier-Chauvin C, Ferrières V. Direct access to new β-d-galactofuranoconjugates: application to the synthesis of galactofuranosyl-l-cysteine and l-serine. Tetrahedron Lett 2011. [DOI: 10.1016/j.tetlet.2011.01.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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61
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Nisic F, Bernardi A. Stereoselective synthesis of N-galactofuranosyl amides. Carbohydr Res 2011; 346:465-71. [DOI: 10.1016/j.carres.2010.12.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 12/23/2010] [Accepted: 12/23/2010] [Indexed: 11/15/2022]
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62
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63
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Gandolfi-Donadío L, Santos M, de Lederkremer RM, Gallo-Rodriguez C. Synthesis of arabinofuranose branched galactofuran tetrasaccharides, constituents of mycobacterial arabinogalactan. Org Biomol Chem 2011; 9:2085-97. [DOI: 10.1039/c0ob00989j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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64
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Pragani R, Seeberger PH. Total synthesis of the Bacteroides fragilis zwitterionic polysaccharide A1 repeating unit. J Am Chem Soc 2010; 133:102-7. [PMID: 21142035 DOI: 10.1021/ja1087375] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Nearly all bacteria capsular polysaccharides are T-cell-independent antigens that do not promote immunoglobulin class switching from IgM to IgG nor memory responses. In contrast, zwitterionic polysaccharides activate T-cell-dependent immune responses by major histocompatability complex class II presentation, a mechanism previously believed to be reserved for peptidic antigens. The best studied zwitterionic polysaccharide, polysaccharide A1 (PS A1) is found on the capsule of the commensal bacteria Bacteroides fragilis . Its potent immunomodulatory properties have been linked to postoperative intra-abdominal abscess formation. Here, we report the synthesis of the PS A1 tetrasaccharide repeating unit (2) as a tool to investigate the biological role of this polysaccharide. A modular synthetic strategy originating from the reducing end of the PS A1 repeating unit was unsuccessful and illustrated the limitations of glycosylation reactions between highly armed glycosylating agents and poor nucleophiles. Thus, a [3 + 1] glycosylation relying on trisaccharide 5 and pyruvalated galactose 6 was used to complete the first total synthesis of the PS A1 repeating unit (2).
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Affiliation(s)
- Rajan Pragani
- Max Planck Institute of Colloids and Interfaces, Department of Biomolecular Systems, Am Mühlenberg 1, 14476 Potsdam, Germany
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65
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Synthesis of the hexasaccharide repeating unit corresponding to the cell wall lipopolysaccharide of Azospirillum irakense KBC1. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/j.tetasy.2010.11.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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66
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Bordoni A, de Lederkremer RM, Marino C. Synthesis of 5-deoxy-β-d-galactofuranosides as tools for the characterization of β-d-galactofuranosidases. Bioorg Med Chem 2010; 18:5339-45. [DOI: 10.1016/j.bmc.2010.05.038] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 05/13/2010] [Accepted: 05/14/2010] [Indexed: 10/19/2022]
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67
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Szczepina MG, Zheng RB, Completo GC, Lowary TL, Pinto BM. STD-NMR studies of two acceptor substrates of GlfT2, a galactofuranosyltransferase from Mycobacterium tuberculosis: epitope mapping studies. Bioorg Med Chem 2010; 18:5123-8. [PMID: 20591680 DOI: 10.1016/j.bmc.2010.05.069] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2010] [Revised: 05/23/2010] [Accepted: 05/25/2010] [Indexed: 10/19/2022]
Abstract
The major structural component of the mycobacterial cell wall, the mycolyl-arabinogalactan-peptidoglycan complex, possesses a galactan core composed of approximately 30 galactofuranosyl (Galf) resides attached via alternating beta-(1-->6) and beta-(1-->5) linkages. Recent studies have shown that the entire galactan is synthesized by two bifunctional galactofuranosyltransferases, GlfT1 and GlfT2. We report here saturation transfer difference (STD) NMR studies GlfT2 using two trisaccharide acceptor substrates, beta-D-Galf-(1-->6)-beta-D-Galf-(1-->5)-beta-D-Galf-O(CH2)7CH3 (2) and beta-D-Galf-(1-->5)-beta-D-Galf-(1-->6)-beta-D-Galf-O(CH2)7CH3 (3), as well as the donor substrate for the enzyme, UDP-Galf. Epitope mapping demonstrated a greater enhancement toward the 'reducing' ends of both trisaccharides, and that UDP-galactofuranose (UDP-Galf) made more intimate contacts through its nucleotide moiety. This observation is consistent with the greater flexibility required within the active site of the reaction between the growing polymer acceptor and the UDP-Galf donor. The addition of UDP-Galf to either 2 or 3 in the presence of GlfT2 generated a tetrasaccharide product, indicating that the enzyme was catalytically active.
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Affiliation(s)
- Monica G Szczepina
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
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68
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Abstract
Carbohydrates in the thermodynamically disfavored furanose ring conformation are not present in mammalian glycoconjugates, but are widespread in the glycans produced by many bacterial pathogens. In bacteria, these furanose sugars are often found in cell surface glycoconjugates, and are essential for the viability or virulence of the organisms. As a result, the enzymes involved in the biosynthesis of bacterial furanosides are attractive targets as potential selective antimicrobial chemotherapeutics. However, before such chemotherapeutics can be designed, synthesized, and evaluated, more information about the activity and specificity of these enzymes is required. This chapter describes assays that have been used to study enzymes involved in the biosynthesis of one of the most abundant naturally occurring furanose residues, galactofuranose (Galf). In particular, the focus is on UDP-galactopyranose mutase and galactofuranosyltransferases. The assays described in this chapter require UDP-galactofuranose (UDP-Galf); therefore, a procedure for the preparation of UDP-Galf, as well as various UDP-Galf derivatives, using a three-enzyme chemoenzymatic procedure, is also described.
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Affiliation(s)
- Myles B Poulin
- The Alberta Ingenuity Centre for Carbohydrate Science, Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
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69
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Efficient one-pot syntheses of α-d-arabinofuranosyl tri- and tetrasaccharides present in cell wall polysaccharide of Mycobacterium tuberculosis. Tetrahedron 2010. [DOI: 10.1016/j.tet.2009.11.038] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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70
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Mendoza VM, Kashiwagi GA, de Lederkremer RM, Gallo-Rodriguez C. Synthesis of trisaccharides containing internal galactofuranose O-linked in Trypanosoma cruzi mucins. Carbohydr Res 2009; 345:385-96. [PMID: 20044082 DOI: 10.1016/j.carres.2009.12.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Revised: 11/24/2009] [Accepted: 12/05/2009] [Indexed: 11/19/2022]
Abstract
The trisaccharides beta-D-Galf-(1-->2)-beta-D-Galf-(1-->4)-D-GlcNAc (5) and beta-D-Galp-(1-->2)-beta-D-Galf-(1-->4)-D-GlcNAc (6) constitute novel structures isolated as alditols when released by reductive beta-elimination from mucins of Trypanosoma cruzi (Tulahuen strain). Trisaccharides 5 and 6 were synthesized employing the aldonolactone approach. Thus, a convenient D-galactono-1,4-lactone derivative was used for the introduction of the internal galactofuranose and the trichloroacetimidate method was employed for glycosylation reactions. Due to the lack of anchimeric assistance on O-2 of the galactofuranosyl precursor, glycosylation studies were performed under different conditions. The nature of the solvent strongly determined the stereochemical course of the glycosylation reactions when the galactofuranosyl donor was substituted either by 2-O-Galp or 2-O-Galf.
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Affiliation(s)
- Verónica M Mendoza
- CIHIDECAR, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina
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71
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Richards MR, Lowary TL. Chemistry and biology of galactofuranose-containing polysaccharides. Chembiochem 2009; 10:1920-38. [PMID: 19591187 DOI: 10.1002/cbic.200900208] [Citation(s) in RCA: 170] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The thermodynamically less stable form of galactose-galactofuranose (Galf)-is essential for the viability of several pathogenic species of bacteria and protozoa but absent in this form in mammals, so the biochemical pathways by which Galf-containing glycans are assembled and catabolysed are attractive sites for drug action. This potential has led to increasing interest in the synthesis of molecules containing Galf residues, their subsequent use in studies directed towards understanding the enzymes that process these residues and the identification of potential inhibitors of these pathways. Major achievements of the past several years have included an in-depth understanding of the mechanism of UDP-galactopyranose mutase (UGM), the enzyme that produces UDP-Galf, which is the donor species for galactofuranosyltransferases. A number of methods for the synthesis of galactofuranosides have also been developed, and practitioners in the field now have many options for the initiation of a synthesis of glycoconjugates containing either alpha- or beta-Galf residues. UDP-Galf has also been prepared by a number of approaches, and it appears that a chemoenzymatic approach is currently the most viable method for producing multi-milligram amounts of this important intermediate. Recent advances both in the understanding of the mechanism of UGM and in the synthesis of galactofuranose and its derivatives are highlighted in this review.
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Affiliation(s)
- Michele R Richards
- Alberta Ingenuity Centre for Carbohydrate Science and Department of Chemistry, University of Alberta, Gunning-Lemieux Chemistry Centre, Edmonton, AB T6G 2G2 (Canada)
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72
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Szczepina MG, Zheng RB, Completo GC, Lowary TL, Pinto BM. STD-NMR studies suggest that two acceptor substrates for GlfT2, a bifunctional galactofuranosyltransferase required for the biosynthesis of Mycobacterium tuberculosis arabinogalactan, compete for the same binding site. Chembiochem 2009; 10:2052-9. [PMID: 19575371 DOI: 10.1002/cbic.200900202] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The mycobacterial cell wall is a complex architecture, which has, as its major structural component, a lipidated polysaccharide covalently bound to peptidoglycan. This structure, termed the mycolyl-arabinogalactan-peptidoglycan complex, possesses a core galactan moiety composed of approximately 30 galactofuranosyl (Galf) resides attached via alternating beta-(1-->6) and beta-(1-->5) linkages. Recent studies have shown that the entire galactan is synthesized by the action of only two bifunctional galactofuranosyltransferases, GlfT1 and GlfT2. We report here saturation-transfer difference (STD) NMR spectroscopy studies with GlfT2 using two trisaccharide acceptor substrates, beta-D-Galf-(1-->6)-beta-D-Galf-(1-->5)-beta-D-Galf-O(CH(2))(7)CH(3) (2) and beta-D-Galf-(1-->5)-beta-D-Galf-(1-->6)-beta-D-Galf-O(CH(2))(7)CH(3) (3), as well as the donor substrate for the enzyme, UDP-Galf. Competition STD-NMR titration experiments and saturation transfer double difference (STDD) experiments with 2 and 3 were undertaken to explore the bifunctionality of this enzyme, in particular to answer whether one or two active sites are responsible for the formation of both beta-(1-->5)- and beta-(1-->6)-Galf linkages. It was demonstrated that 2 and 3 bind competitively at the same site; this suggests that GlfT2 has one active site pocket capable of catalyzing both beta-(1-->5) and beta-(1-->6) galactofuranosyl transfer reactions. The addition of UDP-Galf to GlfT2 in the presence of either 2 or 3 generated a tetrasaccharide product; this indicates that the enzyme was catalytically active under the conditions at which the STD-NMR experiments were carried out.
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Affiliation(s)
- Monica G Szczepina
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia (Canada)
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73
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74
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Baldoni L, Marino C. Facile Synthesis of per-O-tert-Butyldimethylsilyl-β-d-galactofuranose and Efficient Glycosylation via the Galactofuranosyl Iodide. J Org Chem 2009; 74:1994-2003. [DOI: 10.1021/jo8025274] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Luciana Baldoni
- CIHIDECAR-CONICET, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, Ciudad Universitaria, 1428 Buenos Aires, Argentina
| | - Carla Marino
- CIHIDECAR-CONICET, 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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Transfer of the first arabinofuranose residue to galactan is essential for Mycobacterium smegmatis viability. J Bacteriol 2008; 190:5248-55. [PMID: 18556798 DOI: 10.1128/jb.00028-08] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mycobacterial arabinan is an elaborate component of the cell wall with multiple glycosyl linkages and no repeating units. In Mycobacterium spp., the Emb proteins (EmbA, EmbB, and EmbC) have been identified as putative mycobacterial arabinosyltransferases implicated in the biogenesis of the cell wall arabinan. Furthermore, it is now evident that the EmbA and EmbB proteins are involved in the assembly of the nonreducing terminal motif of arabinogalactan and EmbC is involved in transferring arabinose, perhaps in the early stage of arabinan synthesis in lipoarabinomannan. It has also been shown that the Emb proteins are a target of the antimycobacterial drug ethambutol (EMB). In the search for additional mycobacterial arabinosyltransferases in addition to the Emb proteins, we disrupted MSMEG_6386 (an orthologue of Rv3792 and a gene upstream of embC) in Mycobacterium smegmatis. Allelic exchange at the chromosomal MSMEG_6386 locus of M. smegmatis could only be achieved in the presence of a rescue plasmid carrying a functional copy of MSMEG_6386 or Rv3792, strongly suggesting that MSMEG_6386 is essential. An in vitro arabinosyltransferase assay using a membrane preparation from M. smegmatis expressing Rv3792 and synthetic beta-d-Galf-(1-->5)-beta-D-Galf-(1-->6)-beta-D-Galf-octyl and beta-D-Galf-(1-->6)-beta-D-Galf-(1-->5)-beta-D-Galf-octyl showed that Rv3792 gene product can transfer an arabinose residue to the C-5 position of the internal 6-linked galactose. The reactions were insensitive to EMB, and when alpha-d-Manp-(1-->6)-alpha-D-Manp-(1-->6)-alpha-D-Manp-octylthiomethyl was used as an acceptor, no product was formed. These observations indicate that transfer of the first arabinofuranose residue to galactan is essential for M. smegmatis viability.
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