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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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2
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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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Mugunthan G, Sriram D, Yogeeswari P, Kartha KPR. Synthesis and Preliminary Screening ofO-β-D-Galactopyranosides as Potential Mimic of UDP-GalpagainstMycobacterium tuberculosis. J Carbohydr Chem 2012. [DOI: 10.1080/07328303.2011.654017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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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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5
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Synthetic analogues of mycobacterial arabinogalactan linkage-disaccharide part II: synthesis and preliminary screening of lipophilic O-alkyl glycosides. Carbohydr Res 2011; 346:2401-5. [PMID: 21962454 DOI: 10.1016/j.carres.2011.08.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 08/17/2011] [Accepted: 08/25/2011] [Indexed: 11/24/2022]
Abstract
Lipophilic analogues of the linkage-disaccharide found in the mycobacterial cell wall were synthesized and the synthetic analogues when biologically evaluated showed promising antimycobacterial property with MIC value in the range 3.13-12.50 μg/mL against Mycobacterium tuberculosis H(37)Rv.
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6
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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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7
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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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8
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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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9
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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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10
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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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Pathak AK, Pathak V, Suling WJ, Riordan JR, Gurcha SS, Besra GS, Reynolds RC. Synthesis of deoxygenated alpha(1-->5)-linked arabinofuranose disaccharides as substrates and inhibitors of arabinosyltransferases of Mycobacterium tuberculosis. Bioorg Med Chem 2009; 17:872-81. [PMID: 19056279 PMCID: PMC2707774 DOI: 10.1016/j.bmc.2008.11.027] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 11/10/2008] [Accepted: 11/12/2008] [Indexed: 10/21/2022]
Abstract
Arabinosyltransferases (AraTs) play a critical role in mycobacterial cell wall biosynthesis and are potential drug targets for the treatment of tuberculosis, especially multi-drug resistant forms of M. tuberculosis (MTB). Herein, we report the synthesis and acceptor/inhibitory activity of Araf alpha(1-->5) Araf disaccharides possessing deoxygenation at the reducing sugar of the disaccharide. Deoxygenation at either the C-2 or C-3 position of Araf was achieved via a free radical procedure using xanthate derivatives of the hydroxyl group. The alpha(1-->5)-linked disaccharides were produced by coupling n-octyl alpha-Araf 2-/3-deoxy, 2-fluoro glycosyl acceptors with an Araf thioglycosyl donor. The target disaccharides were tested in a cell free mycobacterial AraTs assay as well as an in vitro assay against MTB H(37)Ra and M. avium complex strains.
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Affiliation(s)
- Ashish K. Pathak
- Drug Discovery Division, Southern Research Institute, P.O. Box 55305, Birmingham, AL 35255, USA
| | - Vibha Pathak
- Drug Discovery Division, Southern Research Institute, P.O. Box 55305, Birmingham, AL 35255, USA
| | - William J. Suling
- Drug Discovery Division, Southern Research Institute, P.O. Box 55305, Birmingham, AL 35255, USA
| | - James R. Riordan
- Drug Discovery Division, Southern Research Institute, P.O. Box 55305, Birmingham, AL 35255, USA
| | - Sudagar S. Gurcha
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Gurdyal S. Besra
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Robert C. Reynolds
- Drug Discovery Division, Southern Research Institute, P.O. Box 55305, Birmingham, AL 35255, USA
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Completo GC, Lowary TL. Synthesis of Galactofuranose-Containing Acceptor Substrates for Mycobacterial Galactofuranosyltransferases. J Org Chem 2008; 73:4513-25. [DOI: 10.1021/jo800457j] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gladys C. Completo
- Alberta Ingenuity Centre for Carbohydrate Science and Department of Chemistry, The University of Alberta, Gunning-Lemieux Chemistry Centre, Edmonton, Alberta, T6G 2G2 Canada
| | - Todd L. Lowary
- Alberta Ingenuity Centre for Carbohydrate Science and Department of Chemistry, The University of Alberta, Gunning-Lemieux Chemistry Centre, Edmonton, Alberta, T6G 2G2 Canada
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Appelmelk BJ, den Dunnen J, Driessen NN, Ummels R, Pak M, Nigou J, Larrouy-Maumus G, Gurcha SS, Movahedzadeh F, Geurtsen J, Brown EJ, Eysink Smeets MM, Besra GS, Willemsen PTJ, Lowary TL, van Kooyk Y, Maaskant JJ, Stoker NG, van der Ley P, Puzo G, Vandenbroucke-Grauls CMJE, Wieland CW, van der Poll T, Geijtenbeek TBH, van der Sar AM, Bitter W. The mannose cap of mycobacterial lipoarabinomannan does not dominate the Mycobacterium–host interaction. Cell Microbiol 2008; 10:930-44. [DOI: 10.1111/j.1462-5822.2007.01097.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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14
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Expression, purification and characterisation of soluble GlfT and the identification of a novel galactofuranosyltransferase Rv3782 involved in priming GlfT-mediated galactan polymerisation in Mycobacterium tuberculosis. Protein Expr Purif 2007; 58:332-41. [PMID: 18248822 DOI: 10.1016/j.pep.2007.11.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Revised: 11/28/2007] [Accepted: 11/28/2007] [Indexed: 11/22/2022]
Abstract
The arabinogalactan (AG) component of the mycobacterial cell wall is an essential branched polysaccharide which tethers mycolic acids (m) to peptidoglycan (P), forming the mAGP complex. Much interest has been focused on the biosynthetic machinery involved in the production of this highly impermeable shield, which is the target for numerous anti-tuberculosis agents. The galactan domain of AG is synthesised via a bifunctional galactofuranosyltransferase (GlfT), which utilises UDP-Galf as its high-energy substrate. However, it has proven difficult to study the protein in its recombinant form due to difficulties in recovering pure soluble protein using standard expression systems. Herein, we describe the effects of glfT co-induction with a range of chaperone proteins, which resulted in an appreciable yield of soluble protein at 5 mg/L after a one-step purification procedure. We have shown that this purified enzyme transfers [14C]Galf to a range of both beta(1-->5) and beta(1-->6) linked digalactofuranosyl neoglycolipid acceptors with a distinct preference for the latter. Ligand binding studies using intrinsic tryptophan fluorescence have provided supporting evidence for the apparent preference of this enzyme to bind the beta(1-->6) disaccharide acceptor. However, we could not detect binding or galactofuranosyltransferase activity with an n-octyl beta-d-Gal-(1-->4)-alpha-l-Rha acceptor, which mimics the reducing terminus of galactan in the mycobacterial cell wall. Conversely, after an extensive bioinformatics analysis of the H37Rv genome, further cloning, expression and functional analysis of the Rv3792 open reading frame indicates that this protein affords galactofuranosyltransferase activity against such an acceptor and paves the way for a better understanding of galactan biosynthesis in Mycobacterium tuberculosis.
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Pathak AK, Pathak V, Seitz L, Gurcha SS, Besra GS, Riordan JM, Reynolds RC. Disaccharide analogs as probes for glycosyltransferases in Mycobacterium tuberculosis. Bioorg Med Chem 2007; 15:5629-50. [PMID: 17544276 PMCID: PMC2699567 DOI: 10.1016/j.bmc.2007.04.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Revised: 04/02/2007] [Accepted: 04/04/2007] [Indexed: 11/25/2022]
Abstract
Glycosyltransferases (GTs) play a crucial role in mycobacterial cell wall biosynthesis and are necessary for the survival of mycobacteria. Hence, these enzymes are potential new drug targets for the treatment of tuberculosis (TB), especially multiple drug-resistant TB (MDR-TB). Herein, we report the efficient syntheses of Araf(alpha 1-->5)Araf, Galf(beta 1-->5)Galf, and Galf(beta 1-->6)Galf disaccharides possessing a 5-N,N-dimethylaminonaphthalene-1-sulfonamidoethyl (dansyl) unit that were prepared as fluorescent disaccharide acceptors for arabinosyl- and galactosyl-transferases, respectively. Such analogs may offer advantages relative to radiolabeled acceptors or donors for studying the enzymes and for assay development and compound screening. Additionally, analogs possessing a 5-azidonaphthalene-1-sulfonamidoethyl unit were prepared as photoaffinity probes for their potential utility in studying active site labeling of the GTs (arabinosyl and galactosyl) in Mycobacterium tuberculosis (MTB). Beyond their preparation, initial biological testing and kinetic analysis of these disaccharides as acceptors toward glycosyltransferases are also presented.
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Affiliation(s)
- Ashish K. Pathak
- Drug Discovery Division, Southern Research Institute, P.O. Box 55305, Birmingham, AL 35255, USA
| | - Vibha Pathak
- Drug Discovery Division, Southern Research Institute, P.O. Box 55305, Birmingham, AL 35255, USA
| | - Lainne Seitz
- Drug Discovery Division, Southern Research Institute, P.O. Box 55305, Birmingham, AL 35255, USA
| | - Sudagar S. Gurcha
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Gurdyal S. Besra
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - James M. Riordan
- Drug Discovery Division, Southern Research Institute, P.O. Box 55305, Birmingham, AL 35255, USA
| | - Robert C. Reynolds
- Drug Discovery Division, Southern Research Institute, P.O. Box 55305, Birmingham, AL 35255, USA
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16
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Bhowruth V, Dover LG, Besra GS. 4Tuberculosis Chemotherapy: Recent Developments and Future Perspectives. PROGRESS IN MEDICINAL CHEMISTRY 2007; 45:169-203. [PMID: 17280904 DOI: 10.1016/s0079-6468(06)45504-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Veemal Bhowruth
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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17
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Rémond C, Plantier-Royon R, Aubry N, O'Donohue MJ. An original chemoenzymatic route for the synthesis of β-d-galactofuranosides using an α-l-arabinofuranosidase. Carbohydr Res 2005; 340:637-44. [PMID: 15721334 DOI: 10.1016/j.carres.2005.01.016] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2004] [Accepted: 01/20/2005] [Indexed: 11/28/2022]
Abstract
DGalactofuranose is a widespread component of cell wall polysaccharides in bacteria, protozoa and fungi, but is totally absent in mammals. Importantly, galactofuranose is a key constituent of major cell envelope polysaccharides in pathogenic mycobacteria. In this respect, galactofuranose-based glycoconjugates are interesting target molecules for drug design. O-Glycosidases and notably beta-D-galactofuranosidases could be useful tools for the chemoenzymatic synthesis of galactofuranosides, but to date no studies of this type have been reported. Here we report the use of a GH 51 alpha-l-arabinofuranosidase for the synthesis of beta-D-galactofuranosides. We have demonstrated that this enzyme can catalyse both the autocondensation of p-nitrophenyl-beta-D-galactofuranoside and the transgalactofuranosylation of benzyl alpha-D-xylopyranoside, forming p-nitrophenyl beta-D-galactofuranosyl-(1-->2)-beta-D-galactofuranoside and benzyl beta-D-galactofuranosyl-(1-->2)-alpha-D-xylopyranoside, respectively. Both reactions were very regiospecific and the reaction involving benzyl alpha-D-xylopyranoside afforded very high yields (74.8%) of the major product. To our knowledge, this demonstration of chemoenzymatic synthesis of galactofuranosides constitutes the very first use of an O-glycosidase for the synthesis of galactofuranosides.
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Affiliation(s)
- Caroline Rémond
- Laboratoire de Technologie Enzymatique et Physico-chimie des Agroressources, UMR URCA/INRA FARE, 8 rue Gabriel Voisin, BP 316, F-51688 Reims, France
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Pathak AK, Pathak V, Riordan JM, Gurcha SS, Besra GS, Reynolds RC. Synthesis of mannopyranose disaccharides as photoaffinity probes for mannosyltransferases in Mycobacterium tuberculosis. Carbohydr Res 2004; 339:683-91. [PMID: 15013406 DOI: 10.1016/j.carres.2003.10.031] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2003] [Accepted: 10/30/2003] [Indexed: 11/21/2022]
Abstract
Mannosyltransferases play a crucial role in mycobacterial cell-wall biosynthesis and are potential new drug targets for the treatment of tuberculosis. Herein, we describe the synthesis of alpha-(1-->2)- and alpha-(1-->6)-linked mannopyranosyl disaccharides possessing a 5-azidonaphthlene-1-sulfonamidoethyl group as photoaffinity probes for active-site labeling studies of mannosyltransferases in Mycobacterium tuberculosis.
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Affiliation(s)
- Ashish K Pathak
- Drug Discovery Division, Southern Research Institute, PO Box 55305, Birmingham, AL 35225-5305, USA
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20
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Wen X, Crick DC, Brennan PJ, Hultin PG. Analogues of the mycobacterial arabinogalactan linkage disaccharide as cell wall biosynthesis inhibitors. Bioorg Med Chem 2003; 11:3579-87. [PMID: 12901902 DOI: 10.1016/s0968-0896(03)00366-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The mycobacterial arabinogalactan linkage disaccharide [alpha-L-Rha-(1-->3)-alpha-D-GlcNAc] provides a basis for the design of new antitubercular drugs, since it supports a key skeletal structure in the bacterial cell wall. A series of analogues of the linker was synthesized by coupling appropriate thiorhamnosyl donors modified at their 4-positions, with an N-acetyl glucosamine acceptor. In a cell-free enzyme inhibition assay, three analogues inhibited the activity of the galactosyltransferase that adds a Galf residue to the linkage disaccharide. Although the compounds were modest inhibitors, these data confirm the viability of this approach to anti-mycobacterial agents. It is especially significant that the three effective compounds are modified at the site of the acceptor atom in the natural substrate.
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Affiliation(s)
- Xianghui Wen
- Department of Chemistry, University of Manitoba, R3T 2N2, Winnipeg, MB, Canada
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Pathak AK, Pathak V, Gurcha SS, Besra GS, Reynolds RC. Synthesis of an arabinofuranosyl disaccharide photoaffinity probe for arabinosyltransferase activity in Mycobacterium tuberculosis. Bioorg Med Chem Lett 2002; 12:2749-52. [PMID: 12217368 DOI: 10.1016/s0960-894x(02)00536-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
(5-Azidonaphthalene-1-sulfonamidoethyl)-5-O-(alpha-arabinofuranosyl)-alpha-D-arabinofuranoside 1 was synthesized as a photoaffinity probe for the determination of arabinosyl transferase activity and for the identification of binding and functional sites in Mycobacterium tuberculosis.
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Affiliation(s)
- Ashish K Pathak
- Department of Organic Chemistry, Southern Research Institute, Birmingham, AL 35255, USA
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Pathak AK, Pathak V, Suling WJ, Gurcha SS, Morehouse CB, Besra GS, Maddry JA, Reynolds RC. Studies on n-octyl-5-(alpha-D-arabinofuranosyl)-beta-D-galactofuranosides for mycobacterial glycosyltransferase activity. Bioorg Med Chem 2002; 10:923-8. [PMID: 11836099 DOI: 10.1016/s0968-0896(01)00343-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The mycobacterial cell wall is a potential target for new drug development. Herein we report the preparation and activity of several n-octyl-5-(alpha-D-arabinofuranosyl)-beta-D-galactofuranoside derivatives. A cell-free assay system has been utilized for determination of the ability of disaccharide analogues to act as arabinosyltransferase acceptors using [14C]-DPA as the glycosyl donor. In addition, in vitro inhibitory activity has been determined in a colorimetric broth microdilution assay system against MTB H37Ra and three clinical isolates of Mycobacterium avium complex (MAC). One of these disaccharides showed moderate activity against MTB. The biological evaluation of these disaccharides suggests that more hydrophobic analogues with a blocked reducing end showed better activity as compared to a totally deprotected disaccharide that more closely resembles the natural substrates in cell wall biosynthesis.
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Affiliation(s)
- Ashish K Pathak
- Department of Organic Chemistry, Southern Research Institute, PO Box 55305, Birmingham, AL 35255, USA
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Pathak AK, Pathak V, Seitz L, Maddry JA, Gurcha SS, Besra GS, Suling WJ, Reynolds RC. Studies on (beta,1-->5) and (beta,1-->6) linked octyl Gal(f) disaccharides as substrates for mycobacterial galactosyltransferase activity. Bioorg Med Chem 2001; 9:3129-43. [PMID: 11711288 DOI: 10.1016/s0968-0896(01)00179-1] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The emergence of multi-drug resistant (MDR) strains of Mycobacterium tuberculosis (MTB) and the continuing pandemic of tuberculosis emphasizes the urgent need for the development of new anti-tubercular agents with novel drug targets. The recent structural elucidation of the mycobacterial cell wall highlights a large variety of structurally unique components that may be a basis for new drug development. This publication describes the synthesis, characterization, and screening of several octyl Galf(beta,1-->5)Galf and octyl Galf(beta,1-->6)Galf derivatives. A cell-free assay system has been utilized for galactosyltransferase activity using UDP[14C]Galf as the glycosyl donor, and in vitro inhibitory activity has been determined in a colorimetric broth microdilution assay system against MTB H37Ra and three clinical isolates of Mycobacterium avium complex (MAC). Certain derivatives showed moderate activities against MTB and MAC. The biological evaluation of these disaccharides suggests that more hydrophobic analogues with a blocked reducing end showed better activity as compared to totally deprotected disaccharides that more closely resemble the natural substrates in cell wall biosynthesis.
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Affiliation(s)
- A K Pathak
- Department of Organic Chemistry, Southern Research Institute, PO Box 55305, Birmingham, AL 35255-5305, USA
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Pathak AK, Pathak V, Maddry JA, Suling WJ, Gurcha SS, Besra GS, Reynolds RC. Studies on alpha(1-->5) linked octyl arabinofuranosyl disaccharides for mycobacterial arabinosyl transferase activity. Bioorg Med Chem 2001; 9:3145-51. [PMID: 11711289 DOI: 10.1016/s0968-0896(01)00180-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The appearance multi-drug resistant Mycobacterium tuberculosis (MTB) throughout the world has prompted a search for new, safer and more active agents against tuberculosis. Based on studies of the biosynthesis of mycobacterial cell wall polysaccharides, octyl 5-O-(alpha-D-arabinofuranosyl)-alpha-D-arabinofuranoside analogues were synthesized and evaluated as inhibitors for M. tuberculosis and Mycobacterium avium. A cell free assay system has been used for the evaluation of these disaccharides as substrates for mycobacterial arabinosyltransferase activity.
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Affiliation(s)
- A K Pathak
- Department of Organic Chemistry, Southern Research Institute, PO Box 55305, Birmingham, AL 35255, USA
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Brown JR, Field RA, Barker A, Guy M, Grewal R, Khoo KH, Brennan PJ, Besra GS, Chatterjec D. Synthetic mannosides act as acceptors for mycobacterial α1-6 mannosyltransferase. Bioorg Med Chem 2001; 9:815-24. [PMID: 11354664 DOI: 10.1016/s0968-0896(00)00300-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A series of synthetic mannosides was screened in a cell-free system for their ability to act as acceptor substrates for mycobacterial mannosyltransferases. Evaluation of these compounds demonstrated the incorporation of [14C]Man from GDP-[14C]Man into a radiolabeled organic-soluble fraction and analysis by thin layer chromatography and autoradiography revealed the formation of two radiolabeled products. Each synthetic acceptor was capable of accepting one or two mannose residues, resulting in a major and a minor mannosylated product. Both products from each acceptor were isolated and their mass was confirmed by fast-atom bombardment-mass spectrometry (FABMS). Characterization of each mannosylated product by exo-glycosidase digestion. acetolysis and linkage analysis by gas chromatography mass spectrometry of partially per-O-methylated alditols, revealed only alpha1-6-linked products. In addition. the antibiotic amphomycin selectively inhibited the formation of mannosylated products suggesting polyprenolmonophosphate-mannose (C15 50-P-Man) was the immediate mannose donor in all mannosylation reactions observed. The ability of synthetic disaccharides to act as acceptor substrates in this system, is most likely due to the action of a mycobacterial polyprenol-P-Man:mannan alpha1-6 mannosyltransferase involved in the biosynthesis of linear alpha1-6-linked lipomannan.
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Affiliation(s)
- J R Brown
- Department of Microbiology, Colorado State University, Fort Collins 80523, USA.
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Wallis GL, Hemming FW, Peberdy JF. An extracellular beta-galactofuranosidase from Aspergillus niger and its use as a tool for glycoconjugate analysis. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1525:19-28. [PMID: 11342249 DOI: 10.1016/s0304-4165(00)00150-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Aspergillus niger produces an extracellular beta-galactofuranosidase, which can specifically hydrolyse beta-D-galactofuranose (Galf) from glycoconjugates. The production of this enzyme can be induced by the addition of a Galf-containing A. niger mycelial wall extract. However, on other carbon sources accumulation occurred only during the starvation conditions of the late stationary phase. Extracellular glucoamylases from this stage of cultivation possessed significantly lower levels of Galf than those from the earlier exponential growth phase when beta-galactofuranosidase is absent, suggesting in situ beta-galactofuranosidic hydrolysis. The beta-galactofuranosidase responsible was subsequently purified to homogeneity and characterised. It is a glycoprotein of 90 kDa (determined by SDS-PAGE) with activity against beta-linked Galf residues, with a Km of 4 mM against p-nitrophenyl-beta-D-galactofuranoside and a pH optimum of 3-4. The preparation did not contain other contaminating glycosidase activities; p-nitrophenyl-beta-D- and -alpha-D-galactopyranose, and alpha-D-methyl-Galf were not hydrolysed. Results are presented to show that this enzyme could be employed as a useful tool for the analysis of glycoconjugates containing biologically important Galf components.
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Affiliation(s)
- G L Wallis
- School of Biological Sciences, University of Nottingham, UK.
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Pathak AK, Pathak V, Bansal N, Maddry JA, Reynolds RC. Synthesis of a fluorescent arabinofuranosyl disaccharide: a probe for arabinosyltransferase activity in Mycobacterium tuberculosis. Tetrahedron Lett 2001. [DOI: 10.1016/s0040-4039(00)02161-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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