Galf-Specific Neolectins: Towards Promising Diagnostic Tools.

In the absence of naturally available galactofuranose-specific lectin, we report herein the bioengineering of GalfNeoLect, from the first cloned wild-type galactofuranosidase (Streptomyces sp. strain JHA19), which recognises and binds a single monosaccharide that is only related to nonmammalian species, usually pathogenic microorganisms. We kinetically characterised the GalfNeoLect to confirm attenuation of hydrolytic activity and used competitive inhibition assay, with close structural analogues of Galf, to show that it conserved interaction with its original substrate. We synthetised the bovine serum albumin-based neoglycoprotein (GalfNGP), carrying the multivalent Galf units, as a suitable ligand and high-avidity system for the recognition of GalfNeoLect which we successfully tested directly with the galactomannan spores of Aspergillus brasiliensis (ATCC 16404). Altogether, our results indicate that GalfNeoLect has the necessary versatility and plasticity to be used in both research and diagnostic lectin-based applications.

Lectin Analysis of SARS-CoV-2-Positive Nasopharyngeal Samples Using GLYcoPROFILE® Technology Platform.

Nasopharyngeal samples are currently accepted as the standard diagnostic samples for nucleic acid amplification testing and antigenic testing for the SARS-CoV-2 virus. In addition to the diagnostic capacity of SARS-CoV-2-positive crude nasopharyngeal samples, their qualitative potential for direct glycan-specific analysis, in order to uncover unique glycol profiles, was assessed. In this study we provide glycan characterization of SARS-CoV-2-positive and -negative nasopharyngeal samples directly from lectin interactions. Although with limited throughput, this study evaluated the clinical sensitivity and specificity of the GLYcoPROFILE® technology platformon45crude nasopharyngeal samples collected between November 2020 and April 2022. Each GLYcoPROFILE® of 39 SARS-CoV-2-positive samples was compared toglycoprofiling on a panel of 10 selected lectins and the results were paralleled with SARS-CoV-2-negative samples' results. The GLYcoPROFILE® showed a clear distinction between positive and negative samples with WFA, GSL-II, PHA-L (GlcNAc-specific) and BPA (GalNAc-specific) highlighted as relevant lectins in SARS-CoV-2-positive samples. In addition, a significant, positive statistical correlation was found for these lectins (p < 0.01).

Galactofuranose-Related Enzymes: Challenges and Hopes.

Galactofuranose is a rare form of the well-known galactose sugar, and its occurrence in numerous pathogenic micro-organisms makes the enzymes responsible for its biosynthesis interesting targets. Herein, we review the role of these carbohydrate-related proteins with a special emphasis on the galactofuranosidases we recently characterized as an efficient recombinant biocatalyst.

Galactofuranosidase from JHA 19 Streptomyces sp.: subcloning and biochemical characterization.

Despite 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 0.5 mg/L of culture. It exhibits substrate specificity exclusively towards pNP ß-d-Galf, giving a KM value of 250 µM, and the highest enzymatic efficiency ever observed of 14 mM-1  s-1. It proved to be stable to temperature up to 60 °C and to at least 4 freeze-thaw's cycles. Thus, Galf-ase demonstrated to be an efficient and stable biocatalyst with greatly improved specificity toward the galactofuranosyl entity, thus paving the way to the further development of transglycosylation and thioligation reactions.

Mannosylated N-aryl substituted 3-hydroxypyridine-4-ones: synthesis, hemagglutination inhibitory properties, and molecular modeling.

Structural alterations of the aglycon portions of α-mannosides influence their inhibitory potency toward type 1-fimbriated Escherichia coli. The aim of our work was to prepare and explore inhibitory properties of novel mannosylated N-aryl-substituted 3-hydroxypyridine-4-ones because they possess needed structural characteristics as possible FimH antagonists. Hemagglutination inhibitory tests showed that the examined 3-hydroxypyridine-4-one α-mannosides exhibited better inhibitory activity than methyl α-d-mannopyranoside used as a reference compound. Molecular modeling studies revealed the specific interactions responsible for the observed binding activities toward the mannose-specific FimH lectin. The activity depends on the substituent in p-position on the aglycon aromatic ring.