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Singh R, Kashif M, Srivastava P, Manna PP. Recent Advances in Chemotherapeutics for Leishmaniasis: Importance of the Cellular Biochemistry of the Parasite and Its Molecular Interaction with the Host. Pathogens 2023; 12:pathogens12050706. [PMID: 37242374 DOI: 10.3390/pathogens12050706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 05/08/2023] [Accepted: 05/09/2023] [Indexed: 05/28/2023] Open
Abstract
Leishmaniasis, a category 1 neglected protozoan disease caused by a kinetoplastid pathogen called Leishmania, is transmitted through dipteran insect vectors (phlebotomine, sand flies) in three main clinical forms: fatal visceral leishmaniasis, self-healing cutaneous leishmaniasis, and mucocutaneous leishmaniasis. Generic pentavalent antimonials have long been the drug of choice against leishmaniasis; however, their success is plagued with limitations such as drug resistance and severe side effects, which makes them redundant as frontline therapy for endemic visceral leishmaniasis. Alternative therapeutic regimens based on amphotericin B, miltefosine, and paromomycin have also been approved. Due to the unavailability of human vaccines, first-line chemotherapies such as pentavalent antimonials, pentamidine, and amphotericin B are the only options to treat infected individuals. The higher toxicity, adverse effects, and perceived cost of these pharmaceutics, coupled with the emergence of parasite resistance and disease relapse, makes it urgent to identify new, rationalized drug targets for the improvement in disease management and palliative care for patients. This has become an emergent need and more relevant due to the lack of information on validated molecular resistance markers for the monitoring and surveillance of changes in drug sensitivity and resistance. The present study reviewed the recent advances in chemotherapeutic regimens by targeting novel drugs using several strategies including bioinformatics to gain new insight into leishmaniasis. Leishmania has unique enzymes and biochemical pathways that are distinct from those of its mammalian hosts. In light of the limited number of available antileishmanial drugs, the identification of novel drug targets and studying the molecular and cellular aspects of these drugs in the parasite and its host is critical to design specific inhibitors targeting and controlling the parasite. The biochemical characterization of unique Leishmania-specific enzymes can be used as tools to read through possible drug targets. In this review, we discuss relevant metabolic pathways and novel drugs that are unique, essential, and linked to the survival of the parasite based on bioinformatics and cellular and biochemical analyses.
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Affiliation(s)
- Ranjeet Singh
- Immunobiology Laboratory, Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - Mohammad Kashif
- Immunobiology Laboratory, Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Prateek Srivastava
- Immunobiology Laboratory, Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India
- Department of Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Partha Pratim Manna
- Immunobiology Laboratory, Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India
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Beaupre BA, Moran GR. N5 Is the New C4a: Biochemical Functionalization of Reduced Flavins at the N5 Position. Front Mol Biosci 2020; 7:598912. [PMID: 33195440 PMCID: PMC7662398 DOI: 10.3389/fmolb.2020.598912] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 10/05/2020] [Indexed: 12/31/2022] Open
Abstract
For three decades the C4a-position of reduced flavins was the known site for covalency within flavoenzymes. The reactivity of this position of the reduced isoalloxazine ring with the dioxygen ground-state triplet established the C4a as a site capable of one-electron chemistry. Within the last two decades new types of reduced flavin reactivity have been documented. These studies reveal that the N5 position is also a protean site of reactivity, that is capable of nucleophilic attack to form covalent bonds with substrates. In addition, though the precise mechanism of dioxygen reactivity is yet to be definitively demonstrated, it is clear that the N5 position is directly involved in substrate oxygenation in some enzymes. In this review we document the lineage of discoveries that identified five unique modes of N5 reactivity that collectively illustrate the versatility of this position of the reduced isoalloxazine ring.
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Affiliation(s)
- Brett A Beaupre
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, IL, United States
| | - Graham R Moran
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, IL, United States
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Martín Del Campo JS, Eckshtain-Levi M, Sobrado P. Identification of eukaryotic UDP-galactopyranose mutase inhibitors using the ThermoFAD assay. Biochem Biophys Res Commun 2017; 493:58-63. [PMID: 28919416 DOI: 10.1016/j.bbrc.2017.09.074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 09/14/2017] [Indexed: 11/26/2022]
Abstract
Aspergillus fumigatus is a human pathogen responsible for deadly infections in immune-compromised patients. A potential strategy for treating A. fumigatus infections is by targeting the biosynthesis of cell wall components, such as galactofuranase, which is absent in humans. Galactofuranose biosynthesis is initiated by the flavoenzyme UDP-galactopyranose mutase (UGM), which converts UDP-galactopyranose (UDP-Galp) to UDP-galactofuranose (UDP-Galf). UGM requires the reduced form of the flavin for activity, which is obtained by reacting with NADPH. We aimed to identify inhibitors of UGM by screening a kinase inhibitor library using ThermoFAD, a flavin fluorescence thermal shift assay. The screening assay identified flavopiridol as a compound that increased the melting temperature of A. fumigatus UGM. Further characterization showed that flavopiridol is a non-competitive inhibitor of UGM and docking studies suggest that it binds in the active site. This compound does not inhibit the prokaryotic UGM from Mycobacteria tuberculosis.
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Affiliation(s)
| | | | - Pablo Sobrado
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA; Virginia Tech Center for Drug Discovery, Virginia Tech, Blacksburg, VA 24061, USA.
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Villaume SA, Fu J, N'Go I, Liang H, Lou H, Kremer L, Pan W, Vincent SP. Natural and Synthetic Flavonoids as Potent
Mycobacterium tuberculosis
UGM Inhibitors. Chemistry 2017; 23:10423-10429. [DOI: 10.1002/chem.201701812] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Indexed: 01/16/2023]
Affiliation(s)
- Sydney A. Villaume
- Department of ChemistryUniversity of Namur Rue de Bruxelles 61 5000 Namur Belgium
| | - Jian Fu
- Department of ChemistryUniversity of Namur Rue de Bruxelles 61 5000 Namur Belgium
| | - Inès N'Go
- Department of ChemistryUniversity of Namur Rue de Bruxelles 61 5000 Namur Belgium
| | - Hui Liang
- State Key Laboratory of Functions and Applications of Medicinal PlantsGuizhou Medical University 3491 Baijin Road Guiyang 550014 P. R. China
| | - Huayong Lou
- State Key Laboratory of Functions and Applications of Medicinal PlantsGuizhou Medical University 3491 Baijin Road Guiyang 550014 P. R. China
| | - Laurent Kremer
- IRIM (ex-CPBS)-UMR 9004Infectious Disease Research Institute of Montpellier (IDRIM)Université de Montpellier, CNRS 34293 Montpellier France
- INSERMIRIM 34293 Montpellier France
| | - Weidong Pan
- State Key Laboratory of Functions and Applications of Medicinal PlantsGuizhou Medical University 3491 Baijin Road Guiyang 550014 P. R. China
| | - Stéphane P. Vincent
- Department of ChemistryUniversity of Namur Rue de Bruxelles 61 5000 Namur Belgium
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Misra S, Valicherla GR, Mohd Shahab, Gupta J, Gayen JR, Misra-Bhattacharya S. UDP-galactopyranose mutase, a potential drug target against human pathogenic nematodeBrugia malayi. Pathog Dis 2016; 74:ftw072. [DOI: 10.1093/femspd/ftw072] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/13/2016] [Indexed: 01/02/2023] Open
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Cabezas Y, Legentil L, Robert-Gangneux F, Daligault F, Belaz S, Nugier-Chauvin C, Tranchimand S, Tellier C, Gangneux JP, Ferrières V. Leishmania cell wall as a potent target for antiparasitic drugs. A focus on the glycoconjugates. Org Biomol Chem 2016; 13:8393-404. [PMID: 26130402 DOI: 10.1039/c5ob00563a] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Although leishmaniasis has been studied for over a century, the fight against cutaneous, mucocutaneous and visceral forms of the disease remains a hot topic. This review refers to the parasitic cell wall and more particularly to the constitutive glycoconjugates. The structures of the main glycolipids and glycoproteins, which are species-dependent, are described. The focus is on the disturbance of the lipid membrane by existing drugs and possible new ones, in order to develop future therapeutic agents.
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Affiliation(s)
- Yari Cabezas
- Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée de Beaulieu, CS 50837, 35708 Rennes Cedex 7, France.
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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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8
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Agrobacterium tumefaciens exoR controls acid response genes and impacts exopolysaccharide synthesis, horizontal gene transfer, and virulence gene expression. J Bacteriol 2014; 196:3221-33. [PMID: 24982308 DOI: 10.1128/jb.01751-14] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Agrobacterium tumefaciens is a facultative plant pathogen and the causative agent of crown gall disease. The initial stage of infection involves attachment to plant tissues, and subsequently, biofilms may form at these sites. This study focuses on the periplasmic ExoR regulator, which was identified based on the severe biofilm deficiency of A. tumefaciens exoR mutants. Genome-wide expression analysis was performed to elucidate the complete ExoR regulon. Overproduction of the exopolysaccharide succinoglycan is a dramatic phenotype of exoR mutants. Comparative expression analyses revealed that the core ExoR regulon is unaffected by succinoglycan synthesis. Several findings are consistent with previous observations: genes involved in succinoglycan biosynthesis, motility, and type VI secretion are differentially expressed in the ΔexoR mutant. In addition, these studies revealed new functional categories regulated by ExoR, including genes related to virulence, conjugation of the pAtC58 megaplasmid, ABC transporters, and cell envelope architecture. To address how ExoR exerts a broad impact on gene expression from its periplasmic location, a genetic screen was performed to isolate suppressor mutants that mitigate the exoR motility phenotype and identify downstream components of the ExoR regulatory pathway. This suppression analysis identified the acid-sensing two-component system ChvG-ChvI, and the suppressor mutant phenotypes suggest that all or most of the characteristic exoR properties are mediated through ChvG-ChvI. Subsequent analysis indicates that exoR mutants are simulating a response to acidic conditions, even in neutral media. This work expands the model for ExoR regulation in A. tumefaciens and underscores the global role that this regulator plays on gene expression.
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Kizjakina K, Tanner JJ, Sobrado P. Targeting UDP-galactopyranose mutases from eukaryotic human pathogens. Curr Pharm Des 2013; 19:2561-73. [PMID: 23116395 PMCID: PMC3624792 DOI: 10.2174/1381612811319140007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 10/30/2012] [Indexed: 12/19/2022]
Abstract
UDP-Galactopyranose mutase (UGM) is a unique flavin-dependent enzyme that catalyzes the conversion of UDP-galactopyranose(UDP-Galp) to UDP-galactofuranose (UDP-Galf). The product of this reaction is the precursor to Galf, a major component of the cell wall and of cell surface glycoproteins and glycolipids in many eukaryotic and prokaryotic human pathogens. The function of UGM is important in the virulence of fungi, parasites, and bacteria. Its role in virulence and its absence in humans suggest that UGM is an ideal drug target. Significant structural and mechanistic information has been accumulated on the prokaryotic UGMs; however, in the past few years the research interest has shifted to UGMs from eukaryotic human pathogens such as fungi and protozoan parasites. It has become clear that UGMs from prokaryotic and eukaryotic organisms have different structural and mechanistic features. The amino acid sequence identity between these two classes of enzymes is low, resulting in differences in oligomeric states, substrate binding, active site flexibility, and interaction with redox partners. However, the unique role of the flavin cofactor in catalysis is conserved among this enzyme family. In this review, recent findings on eukaryotic UGMs are discussed and presented in comparison with prokaryotic UGMs.
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Affiliation(s)
- Karina Kizjakina
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA
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Fonseca IO, Kizjakina K, Sobrado P. UDP-galactopyranose mutases from Leishmania species that cause visceral and cutaneous leishmaniasis. Arch Biochem Biophys 2013; 538:103-10. [PMID: 24012809 DOI: 10.1016/j.abb.2013.08.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 08/21/2013] [Accepted: 08/24/2013] [Indexed: 01/18/2023]
Abstract
Leishmaniasis is a vector-borne, neglected tropical disease caused by parasites from the genus Leishmania. Galactofuranose (Galf) is found on the cell surface of Leishmania parasites and is important for virulence. The flavoenzyme that catalyzes the isomerization of UDP-galactopyranose to UDP-Galf, UDP-galactopyranose mutase (UGM), is a validated drug target in protozoan parasites. UGMs from L. mexicana and L. infantum were recombinantly expressed, purified, and characterized. The isolated enzymes contained tightly bound flavin cofactor and were active only in the reduced form. NADPH is the preferred redox partner for both enzymes. A kcat value of 6 ± 0.4s(-1) and a Km value of 252 ± 42 μM were determined for L. infantum UGM. For L. mexicana UGM, these values were ∼4-times lower. Binding of UDP-Galp is enhanced 10-20 fold in the reduced form of the enzymes. Changes in the spectra of the reduced flavin upon interaction with the substrate are consistent with formation of a flavin-iminium ion intermediate.
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Affiliation(s)
- Isabel O Fonseca
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, United States; Fralin Life Science Institute, Virginia Tech, Blacksburg, VA 24061, United States
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Abstract
Nematodes represent a diverse phylum of both free living and parasitic species. While the species Caenorhabditis elegans is a valuable model organism, parasitic nematodes or helminths pose a serious threat to human health. Indeed, helminths cause many neglected tropical diseases that afflict humans. Nematode glycoconjugates have been implicated in evasive immunomodulation, a hallmark of nematode infections. One monosaccharide residue present in the glycoconjugates of several human pathogens is galactofuranose (Galf). This five-membered ring isomer of galactose has not been detected in mammals, making Galf metabolic enzymes attractive therapeutic targets. The only known pathway for biosynthetic incorporation of Galf into glycoconjugates depends upon generation of the glycosyl donor UDP-Galf by the flavoenzyme uridine 5'-diphosphate (UDP) galactopyranose mutase (UGM or Glf). A putative UGM encoding gene (glf-1) was recently identified in C. elegans. We sought to assess the catalytic activity of the corresponding gene product (CeUGM). CeUGM catalyzes the isomerization of UDP-Galf and UDP-galactopyranose (UDP-Galp). In the presence of enzyme, substrate, and a hydride source, a galactose-N5-FAD adduct was isolated, suggesting the CeUGM flavin adenine dinucleotide (FAD) cofactor serves as a nucleophile in covalent catalysis. Homology modeling and protein variants indicate that CeUGM possesses an active site similar to that of prokaryotic enzymes, despite the low sequence identity (∼15%) between eukaryotic and prokaryotic UGM proteins. Even with the primary sequence differences, heterocyclic UGM inhibitors developed against prokaryotic proteins also inhibit CeUGM activity. We postulate that inhibitors of CeUGM can serve as chemical probes of Galf in nematodes and as anthelmintic leads. The available data suggest that CeUGM facilitates the biosynthetic incorporation of Galf into nematode glycoconjugates through generation of the glycosyl donor UDP-Galf.
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Affiliation(s)
- Darryl A. Wesener
- Department of Biochemistry, University of Wisconsin–Madison, 433 Babcock Drive, Madison, WI 53706-1544 USA
| | - John F. May
- Department of Biochemistry, University of Wisconsin–Madison, 433 Babcock Drive, Madison, WI 53706-1544 USA
| | - Elizabeth M. Huffman
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue, Madison, WI 53706-1322 USA
| | - Laura L. Kiessling
- Department of Biochemistry, University of Wisconsin–Madison, 433 Babcock Drive, Madison, WI 53706-1544 USA
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue, Madison, WI 53706-1322 USA
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Abstract
Enzymes containing flavin cofactors are predominantly involved in redox reactions in numerous cellular processes where the protein environment modulates the chemical reactivity of the flavin to either transfer one or two electrons. Some flavoenzymes catalyze reactions with no net redox change. In these reactions, the protein environment modulates the reactivity of the flavin to perform novel chemistries. Recent mechanistic and structural data supporting novel flavin functionalities in reactions catalyzed by chorismate synthase, type II isopentenyl diphosphate isomerase, UDP-galactopyranose mutase, and alkyl-dihydroxyacetonephosphate synthase are presented in this review. In these enzymes, the flavin plays either a direct role in acid/base reactions or as a nucleophile or electrophile. In addition, the flavin cofactor is proposed to function as a "molecular scaffold" in the formation of UDP-galactofuranose and alkyl-dihydroxyacetonephosphate by forming a covalent adduct with reaction intermediates.
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Affiliation(s)
- Pablo Sobrado
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA.
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Chlubnova I, Legentil L, Dureau R, Pennec A, Almendros M, Daniellou R, Nugier-Chauvin C, Ferrières V. Specific and non-specific enzymes for furanosyl-containing conjugates: biosynthesis, metabolism, and chemo-enzymatic synthesis. Carbohydr Res 2012; 356:44-61. [PMID: 22554502 DOI: 10.1016/j.carres.2012.04.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2012] [Revised: 04/02/2012] [Accepted: 04/03/2012] [Indexed: 11/27/2022]
Abstract
There is no doubt now that the synthesis of compounds of varying complexity such as saccharides and derivatives thereof continuously grows with enzymatic methods. This review focuses on recent basic knowledge on enzymes specifically involved in the biosynthesis and degradation of furanosyl-containing polysaccharides and conjugates. Moreover, and when possible, biocatalyzed approaches, alternative to standard synthesis, will be detailed in order to strengthen the high potential of these biocatalysts to go further with the preparation of rare furanosides. Interesting results will be also proposed with chemo-enzymatic processes based on nonfuranosyl-specific enzymes.
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Affiliation(s)
- Ilona Chlubnova
- Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, Avenue du Général Leclerc, CS 50837, 35708 Rennes Cedex 7, France
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van Straaten KE, Routier FH, Sanders DAR. Towards the crystal structure elucidation of eukaryotic UDP-galactopyranose mutase. Acta Crystallogr Sect F Struct Biol Cryst Commun 2012; 68:455-9. [PMID: 22505419 PMCID: PMC3325819 DOI: 10.1107/s1744309112006914] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 02/15/2012] [Indexed: 11/10/2022]
Abstract
UDP-galactopyranose mutase (UGM) catalyzes the interconversion of UDP-galactopyranose and UDP-galactofuranose. Eukaryotic UGMs from Aspergillus fumigatus and Leishmania major have been purified to homogeneity by means of Ni(2+)-affinity chromatography and crystallized. Eukaryotic UGM structure elucidation was not straightforward owing to high pseudo-symmetry, twinning and very low anomalous signal. Phasing to 2.8 Å resolution using SAD was successful for L. major UGM. However, the maps could only be improved by iterative density modification and manual model building. High pseudo-symmetry and twinning prevented correct space-group assignment and the completion of structure refinement. The structure of A. fumigatus UGM to 2.52 Å resolution was determined by molecular replacement using the incomplete 2.8 Å resolution L. major UGM model.
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Affiliation(s)
- Karin E. van Straaten
- Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan S7N 5C9, Canada
| | - Francoise H. Routier
- Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - David A. R. Sanders
- Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan S7N 5C9, Canada
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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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van Straaten KE, Routier FH, Sanders DAR. Structural insight into the unique substrate binding mechanism and flavin redox state of UDP-galactopyranose mutase from Aspergillus fumigatus. J Biol Chem 2012; 287:10780-90. [PMID: 22334662 PMCID: PMC3322874 DOI: 10.1074/jbc.m111.322974] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
UDP-galactopyranose mutase (UGM) is a flavin-containing enzyme that catalyzes the reversible conversion of UDP-galactopyranose (UDP-Galp) to UDP-galactofuranose (UDP-Galf). As in prokaryotic UGMs, the flavin needs to be reduced for the enzyme to be active. Here we present the first eukaryotic UGM structures from Aspergillus fumigatus (AfUGM). The structures are of UGM alone, with the substrate UDP-Galp and with the inhibitor UDP. Additionally, we report the structures of AfUGM bound to substrate with oxidized and reduced flavin. These structures provide insight into substrate recognition and structural changes observed upon substrate binding involving the mobile loops and the critical arginine residues Arg-182 and Arg-327. Comparison with prokaryotic UGM reveals that despite low sequence identity with known prokaryotic UGMs the overall fold is largely conserved. Structural differences between prokaryotic UGM and AfUGM result from inserts in AfUGM. A notable difference from prokaryotic UGMs is that AfUGM contains a third flexible loop (loop III) above the si-face of the isoalloxazine ring that changes position depending on the redox state of the flavin cofactor. This loop flipping has not been observed in prokaryotic UGMs. In addition we have determined the crystals structures and steady-state kinetic constants of the reaction catalyzed by mutants R182K, R327K, R182A, and R327A. These results support our hypothesis that Arg-182 and Arg-327 play important roles in stabilizing the position of the diphosphates of the nucleotide sugar and help to facilitate the positioning of the galactose moiety for catalysis.
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Affiliation(s)
- Karin E van Straaten
- Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9, Canada
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Tefsen B, Ram AF, van Die I, Routier FH. Galactofuranose in eukaryotes: aspects of biosynthesis and functional impact. Glycobiology 2011; 22:456-69. [DOI: 10.1093/glycob/cwr144] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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