In the absence of naturally available galactofuranose-specific lectin, we report herein the bioengineering of GalNeoLect, from the first cloned wild-type galactofuranosidase ( sp. strain JHA19), which recognises and binds a single monosaccharide that is only related to nonmammalian species, usually pathogenic microorganisms. We kinetically characterised the GalNeoLect to confirm attenuation of hydrolytic activity and used competitive inhibition assay, with close structural analogues of Gal, to show that it conserved interaction with its original substrate.
View Article and Find Full Text PDFSepsis induces immune alterations, which last for months after the resolution of illness. The effect of this immunological reprogramming on the risk of developing cancer is unclear. Here we use a national claims database to show that sepsis survivors had a lower cumulative incidence of cancers than matched nonsevere infection survivors.
View Article and Find Full Text PDFThe synthesis of six model trisaccharides representative of galactomannans produced by lichens was performed through stereoselective glycosylation. These standards include linear and branched galactomannans bearing either galactofuranosyl or galactopyranosyl entities. The complete assignment of H and C signals for both forms of synthetically reduced oligosaccharides was performed.
View Article and Find Full Text PDFIn contrast with the predominant pyranose form of galactose, galactofuranose is known to be highly flexible. Such flexibility poses a remarkable challenge in terms of structural studies, thus hindering the in depth understanding of the structure/function relationship in this rare sugar. A thorough computational study based on molecular dynamics and density functional theory supported by vibrational spectroscopy in the gas phase was carried out to provide a better understanding of the instrinsic conformational preferences of galactofuranose.
View Article and Find Full Text PDFAnalysis of glycans remains a difficult task due to their isomeric complexity. Despite recent progress, determining monosaccharide ring size, a type of isomerism, is still challenging due to the high flexibility of the five-membered ring (also called furanose). Galactose is a monosaccharide that can be naturally found in furanose configuration in plant and bacterial polysaccharides.
View Article and Find Full Text PDFImidazo[4,5-b]pyridines are amongst the oldest known heteroaromatic derivatives. Their structural similarity with purine basis has however aroused the curiosity of biologists and resulted in the developments of innovative bioactive compounds. This review thus firstly describes the main synthetic ways currently used to produce imidazo[ 4,5-b]pyridine derivatives, and secondly gives examples of their potential, especially focusing on protein inhibition abilities, thus opening the way to applications as anti-cancer or antimicrobial agents.
View Article and Find Full Text PDFCarbohydrates are ubiquitous in nature but are among the least conserved biomolecules in life. These biopolymers pose a particular challenge to analytical chemists because of their high diversity and structural heterogeneity. In addition, they contain many isomerisms that complicate their structural characterization, notably by mass spectrometry.
View Article and Find Full Text PDFNatural compounds isolated from macroalgae are promising, ecofriendly, and multifunctional bioinoculants, which have been tested and used in agriculture. Ulvans, for instance, one of the major polysaccharides present in spp. cell walls, have been tested for their plant growth-promoting properties as well as their ability to activate plant immune defense, on a large variety of crops.
View Article and Find Full Text PDFThe synthesis of disaccharides, particularly those containing hexofuranoside rings, requires a large number of steps by classical chemical means. The use of glycosidases can be an alternative to limit the number of steps, as they catalyze the formation of controlled glycosidic bonds starting from simple and easy to access building blocks; the main drawbacks are the yields, due to the balance between the hydrolysis and transglycosylation of these enzymes, and the enzyme-dependent regioselectivity. To improve the yield of the synthesis of β-d-galactofuranosyl-(1→X)-d-mannopyranosides catalyzed by an arabinofuranosidase, in this study we developed a strategy to mutate, then screen the catalyst, followed by a tailored molecular modeling methodology to rationalize the effects of the identified mutations.
View Article and Find Full Text PDFMarine polysaccharides are part of the huge seaweeds resources and present many applications for several industries. In order to widen their potential as additives or bioactive compounds, some structural modifications have been studied. Among them, simple hydrophobization reactions have been developed in order to yield to grafted polysaccharides bearing acyl-, aryl-, alkyl-, and alkenyl-groups or fatty acid chains.
View Article and Find Full Text PDFSequencing glycans is demanding due to their structural diversity. Compared to mammalian glycans, bacterial glycans pose a steeper challenge because they are constructed from a larger pool of monosaccharide building blocks, including pyranose and furanose isomers. Though mammalian glycans incorporate only the pyranose form of galactose (Gal), many pathogens, including and , contain galactofuranose (Gal) residues in their cell envelope.
View Article and Find Full Text PDFNature offers a huge diversity of glycosidic derivatives. Among numerous structural modulations, the nature of the ring size of hexosides may induce significant differences on both biological and physicochemical properties of the glycoconjugate of interest. On this assumption, we expect that small disaccharides bearing either a furanosyl entity or a pyranosyl residue would give a specific signature, even in the gas phase.
View Article and Find Full Text PDFArabinogalactan proteins (AGPs) encompass a diverse group of plant cell wall proteoglycans, which play an essential role in plant development, signaling, plant-microbe interactions, and many others. Although they are widely distributed throughout the plant kingdom and extensively studied, they remain largely unexplored in the lower plants, especially in seaweeds. Ulva species have high economic potential since various applications were previously described including bioremediation, biofuel production, and as a source of bioactive compounds.
View Article and Find Full Text PDFBiological functionality of isomeric carbohydrates may differ drastically, making their identifications indispensable in many applications of life science. Because of the large number of isoforms, structural assignment of saccharides is challenging and often requires a use of different orthogonal analytical techniques. We demonstrate that isomeric carbohydrates of any isoforms can be distinguished and quantified using solely the library-based method of 2D ultraviolet fragmentation spectroscopy-mass spectrometry (2D UV-MS) of cold ions.
View Article and Find Full Text PDFSelective glycosylation of the C-6 fluorinated galactofuranosyl acceptor 2 was studied with four galactofuranosyl donors. It was highlighted that this electron-withdrawing atom strongly impacted the behavior of the acceptor, thus leading to unprecedented glycosylation pathways. Competition between expected glycosylation of 2, ring expansion of this acceptor and furanosylation, and intermolecular aglycon transfer was observed.
View Article and Find Full Text PDFBackground: The chemotherapeutic arsenal available to treat visceral leishmaniasis is currently limited, in view of many drawbacks such as high cost, toxicity or emerging resistance. New therapeutic strategies are particularly needed to improve the management and the outcome in immunosuppressed patients. The combination of an immunomodulatory drug to a conventional anti-Leishmania treatment is an emerging concept to reverse the immune bias from Th2 to Th1 response to boost healing and prevent relapses.
View Article and Find Full Text PDFLaminaran, a β-(1→3)-glucan extracted from Laminaria digitata, is a known elicitor of plant defenses, but provides only low level of disease control in vineyard trials. In this context, laminaran was partly hydrophobized by grafting from 1.6 to 7.
View Article and Find Full Text PDFColloids Surf B Biointerfaces
November 2019
Preventing microorganism colonization on a surface is a great challenge in the conception of medical, food and marine devices. Here, we describe the formation of carbohydrate functionalized glass surfaces with D-glucose, D-galactose and D-mannose and how they efficiently affected the bacterial attachment. The carbohydrate entities were covalently attached to the pre-functionalized surface by click chemistry thanks the copper catalysed alkyl-azide cycloaddition.
View Article and Find Full Text PDFDespite the crucial role of the rare galactofuranose (Galf) in many pathogenic micro-organisms and our increased knowledge of its metabolism, there is still a lack of recombinant and efficient galactofuranoside hydrolase available for chemo-enzymatic synthetic purposes of specific galactofuranosyl-conjugates. Subcloning of the Galf-ase from JHA 19 Streptomyces sp. and its further overexpression lead us to the production of this enzyme with a yield of 0.
View Article and Find Full Text PDFHexoses are mainly found in nature in the pyranose form (6-membered ring). Yet, furanose forms (5-membered ring) are observed in some rare polysaccharides. Using IRMPD spectroscopy (InfraRed Multiple Photon Dissociation), we propose a straightforward diagnostic of the ring-size of N-acetyl galactosamine ions.
View Article and Find Full Text PDFKoenigs-Knorr glycosylation of acceptors with more than one free hydroxyl group by 2,3,5,6-tetrabenzoyl galactofuranosyl bromide was performed using diphenylborinic acid 2-aminoethyl ester (DPBA) as inducer of regioselectivity. High regioselectivity for the glycosylation on the equatorial hydroxyl group of the acceptor was obtained thanks to the transient formation of a borinate adduct of the corresponding 1,2-cis diol. Nevertheless formation of orthoester byproducts hampered the efficiency of the method.
View Article and Find Full Text PDFTwo fluorescent galactofuranosides were synthesized and their biological activities evaluated on non-infected and Leishmania infected macrophages. Both tagged scaffolds were able to penetrate macrophages. Compared to the activity of the parent octyl galactofuranoside used as a reference, the fluorescein-conjugate showed altered biological properties while the rhodamine 6G one synergistically acted with the lipid chain to significantly increase antiparasitic activity.
View Article and Find Full Text PDFFisher glycosylation, the oldest but efficient reaction towards alkyl glycosides, suffers nonetheless from lack of selectivity, especially when dealing with pentoses. In this case, a mixture of the four isomers, namely the furanosides and the pyranosides, is formed. According to previous studies, the rate and selectivity of the reaction depend greatly on the reaction time and the temperature.
View Article and Find Full Text PDFTransglycosylation reactions biocatalyzed by the native arabinofuranosidase Araf51 and using d-galactosyl, d-fucosyl and 6-deoxy-6-fluoro-D-galactosyl derivatives as donors and acceptors provided di-to pentahexofuranosides. The immunostimulatory potency of these compounds, and more especially their ability to induce production of TNF-α, was evaluated on the murine macrophage cell line, Raw 264.7.
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