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Dissection of the anti-Candida albicans mannan immune response using synthetic oligomannosides reveals unique properties of β-1,2 mannotriose protective epitopes. Sci Rep 2021; 11:10825. [PMID: 34031516 PMCID: PMC8144402 DOI: 10.1038/s41598-021-90402-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 05/10/2021] [Indexed: 12/21/2022] Open
Abstract
Candida albicans mannan consists of a large repertoire of oligomannosides with different types of mannose linkages and chain lengths, which act as individual epitopes with more or less overlapping antibody specificities. Although anti-C. albicans mannan antibody levels are monitored for diagnostic purposes nothing is known about the qualitative distribution of these antibodies in terms of epitope specificity. We addressed this question using a bank of previously synthesized biotin sulfone tagged oligomannosides (BSTOs) of α and β anomery complemented with a synthetic β-mannotriose described as a protective epitope. The reactivity of these BSTOs was analyzed with IgM isotype monoclonal antibodies (MAbs) of known specificity, polyclonal sera from patients colonized or infected with C. albicans, and mannose binding lectin (MBL). Surface plasmon resonance (SPR) and multiple analyte profiling (MAP) were used. Both methods confirmed the usual reactivity of MAbs against either α or β linkages, excepted for MAb B6.1 (protective epitope) reacting with β-Man whereas the corresponding BSTO reacted with anti-α-Man. These results were confirmed in western blots with native C. albicans antigens. Using patients' sera in MAP, a significant correlation was observed between the detection of anti-mannan antibodies recognizing β- and α-Man epitopes and detection of antibodies against β-linked mannotriose suggesting that this epitope also reacts with human polyclonal antibodies of both specificities. By contrast, the reactivity of human sera with other α- and β-linked BSTOs clearly differed according to their colonized or infected status. In these cases, the establishment of an α/β ratio was extremely discriminant. Finally SPR with MBL, an important lectin of innate immunity to C. albicans, classically known to interact with α-mannose, also interacted in an unexpected way with the protective epitope. These cumulative data suggest that structure/activity investigations of the finely tuned C. albicans anti-mannose immune response are worthwhile to increase our basic knowledge and for translation in medicine.
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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
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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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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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Krylov VB, Nifantiev NE. Synthetic Oligosaccharides Mimicking Fungal Cell Wall Polysaccharides. Curr Top Microbiol Immunol 2019; 425:1-16. [PMID: 31875266 DOI: 10.1007/82_2019_187] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The cell wall of pathogenic fungi is highly important for the development of fungal infections and is the first cellular component to interact with the host immune system. The fungal cell wall is mainly built up of different polysaccharides representing ligands for pattern recognition receptors (PRRs) on immune cells and antibodies. Purified fungal polysaccharides are not easily available; in addition, they are structurally heterogenic and have wide molecular weight distribution that limits the possibility to use natural polysaccharides to assess the structure of their active determinants. The synthetic oligosaccharides of definite structure representing distinct polysaccharide fragments are indispensable tools for a variety of biological investigations and represent an advantageous alternative to natural polysaccharides. The attachment of a spacer group to these oligosaccharides permits their efficient transformation into immunogenic glycoconjugates as well as their immobilization on plates or microbeads. Herein, we summarize current information on synthetic availability of the variety of oligosaccharides related to main types of fungal cell wall components: galactomannan, α- and β-mannan, α- and β-(1 → 3)-glucan, chitin, chitosan, and others. These data are supplemented with published results of biochemical and immunological applications of synthetic oligosaccharides as molecular probes especially as the components of thematic glycoarrays suitable for characterization of anti-polysaccharide antibodies and cellular lectins or PRRs.
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Affiliation(s)
- Vadim B Krylov
- Laboratory of Glycoconjugate Chemistry, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, 119991, Moscow, Russia
| | - Nikolay E Nifantiev
- 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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5
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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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6
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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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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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Argunov DA, Krylov VB, Nifantiev NE. Convergent synthesis of isomeric heterosaccharides related to the fragments of galactomannan from Aspergillus fumigatus. Org Biomol Chem 2015; 13:3255-67. [PMID: 25643073 DOI: 10.1039/c4ob02634a] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Aspergillus fumigatus is a very common fungus with high pathogenic potential for immunosuppressed hospital patients. A. fumigatus galactomannan, being the part of its cell wall, is considered as a promising candidate for vaccine and diagnostic test-systems. In this article we report the convergent synthesis of pentasaccharide fragments of the galactomannan containing the β-(1→5)-linked galactofuranoside chain attached to O-3 or O-6 of a spacer-armed mannopyranoside residue. The synthesis of selectively protected galactofuranoside precursors has been performed using recently developed pyranoside-into-furanoside (PIF) rearrangement. For assembling the target galactomannan structures the [1 + 2 + 2]-scheme was applied. This strategy was shown to be highly efficient and can easily be extended to the synthesis of longer fragments of thegalactomannan.
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Affiliation(s)
- D A Argunov
- 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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9
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(13)C-NMR glycosylation effects in (1→3)-linked furanosyl-pyranosides. Carbohydr Res 2015; 417:1-10. [PMID: 26382080 DOI: 10.1016/j.carres.2015.08.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 08/22/2015] [Accepted: 08/24/2015] [Indexed: 11/21/2022]
Abstract
Synthesis, theoretical conformational analysis (molecular mechanics and DFT calculations) and NMR spectral data including the (13)C-NMR glycosylation effects for six pairs of isomeric furanosyl-(1→3)-pyranosides with different anomeric and absolute configurations of furanosyl units as well as configurations of C2 and C4 in the pyranoside units are described. The determined (13)C-NMR glycosylation effects were shown to correlate with the pattern of intramolecular interactions around the inter-unit bonds.
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10
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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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11
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Krylov VB, Argunov DA, Vinnitskiy DZ, Verkhnyatskaya SA, Gerbst AG, Ustyuzhanina NE, Dmitrenok AS, Huebner J, Holst O, Siebert HC, Nifantiev NE. Pyranoside-into-furanoside rearrangement: new reaction in carbohydrate chemistry and its application in oligosaccharide synthesis. Chemistry 2014; 20:16516-22. [PMID: 25319316 DOI: 10.1002/chem.201405083] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Indexed: 01/24/2023]
Abstract
Great interest in natural furanoside-containing compounds has challenged the development of preparative methods for their synthesis. Herein a novel reaction in carbohydrate chemistry, namely a pyranoside-into-furanoside (PIF) rearrangement permitting the transformation of selectively O-substituted pyranosides into the corresponding furanosides is reported. The discovered process includes acid-promoted sulfation accompanied by rearrangement of the pyranoside ring into a furanoside ring followed by solvolytic O-desulfation. This process, which has no analogy in organic chemistry, was shown to be a very useful tool for the synthesis of furanoside-containing complex oligosaccharides, which was demonstrated by synthesizing disaccharide derivatives α-D-Galp-(1→3)-β-D-Galf-OPr, 3-O-s-lactyl-β-D-Galf-(1→3)-β-D-Glcp-OPr, and α-L-Fucf-(1→4)-β-D-GlcpA-OPr related to polysaccharides from the bacteria Klebsiella pneumoniae and Enterococcus faecalis and the brown seaweed Chordaria flagelliformis.
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Affiliation(s)
- 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)
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12
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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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Improved methods for the stereoselective synthesis of mannoheptosyl donors and their glycosides: toward the synthesis of the trisaccharide repeating unit of the Campylobacter jejuni RM1221 capsular polysaccharide. Tetrahedron 2013. [DOI: 10.1016/j.tet.2013.04.094] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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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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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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Oppenheimer M, Valenciano AL, Kizjakina K, Qi J, Sobrado P. Chemical mechanism of UDP-galactopyranose mutase from Trypanosoma cruzi: a potential drug target against Chagas' disease. PLoS One 2012; 7:e32918. [PMID: 22448231 PMCID: PMC3308961 DOI: 10.1371/journal.pone.0032918] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 02/06/2012] [Indexed: 01/06/2023] Open
Abstract
UDP-galactopyranose mutase (UGM) is a flavoenzyme that catalyzes the conversion of UDP-galactopyranose to UDP-galactofuranose, the precursor of galactofuranose (Galf). Galf is found in several pathogenic organisms, including the parasite Trypanosoma cruzi, the causative agent of Chagas' disease. Galf) is important for virulence and is not present in humans, making its biosynthetic pathway an attractive target for the development of new drugs against T. cruzi. Although UGMs catalyze a non-redox reaction, the flavin must be in the reduced state for activity and the exact role of the flavin in this reaction is controversial. The kinetic and chemical mechanism of TcUGM was probed using steady state kinetics, trapping of reaction intermediates, rapid reaction kinetics, and fluorescence anisotropy. It was shown for the first time that NADPH is an effective redox partner of TcUGM. The substrate, UDP-galactopyranose, protects the enzyme from reacting with molecular oxygen allowing TcUGM to turnover ∼1000 times for every NADPH oxidized. Spectral changes consistent with a flavin iminium ion, without the formation of a flavin semiquinone, were observed under rapid reaction conditions. These data support the proposal of the flavin acting as a nucleophile. In support of this role, a flavin-galactose adduct was isolated and characterized. A detailed kinetic and chemical mechanism for the unique non-redox reaction of UGM is presented.
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Affiliation(s)
- Michelle Oppenheimer
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia, United States of America
- Enzyme Research and Drug Discovery Laboratory, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Ana Lisa Valenciano
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia, United States of America
- Enzyme Research and Drug Discovery Laboratory, Virginia Tech, Blacksburg, Virginia, United States of America
- Instituto Tecnológico de Costa Rica, Cartago, Costa Rica
| | - Karina Kizjakina
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia, United States of America
- Enzyme Research and Drug Discovery Laboratory, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Jun Qi
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia, United States of America
- Enzyme Research and Drug Discovery Laboratory, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Pablo Sobrado
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia, United States of America
- Enzyme Research and Drug Discovery Laboratory, Virginia Tech, Blacksburg, Virginia, United States of America
- Instituto Tecnológico de Costa Rica, Cartago, Costa Rica
- Fralin Life Science Institute, Virginia Tech, Blacksburg, Virginia, United States of America
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Despras G, Robert R, Sendid B, Machez E, Poulain D, Mallet JM. Biotin sulfone tagged oligomannosides as immunogens for eliciting antibodies against specific mannan epitopes. Bioorg Med Chem 2012; 20:1817-31. [DOI: 10.1016/j.bmc.2011.12.048] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 12/19/2011] [Accepted: 12/21/2011] [Indexed: 11/28/2022]
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18
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