Galectins are small human proteins participating in inflammation processes, immune response, and cancerogenesis. Tandem-repeat galectins comprising Gal-4, Gal-8, and Gal-9 are a vital yet less studied part of the galectin fingerprint in cancer-related processes. The present work studies a library of prepared multivalent neo-glycoproteins decorated with poly-N-acetyllactosamine and human-milk-type oligosaccharides as ligands of this underexplored family of tandem-repeat galectins. A thorough binding evaluation by ELISA and biolayer interferometry was complemented with a detailed epitope mapping both from the galectin and the glycoconjugate viewpoints by nuclear magnetic resonance. The found interactions in the galectin binding site were correlated to in silico data from molecular modeling. The present work reveals pioneer information on the binding of tandem-repeat galectins to multivalent glycoconjugates carrying complex carbohydrate ligands and represents an invaluable starting point for the development of new high-affinity tailored ligands of tandem-repeat galectins, needed both for diagnosis and therapy.

• MeSH
• galektiny * chemie   metabolismus   MeSH
• glykoproteiny * chemie   metabolismus   MeSH
• lidé MeSH
• ligandy MeSH
• mateřské mléko * chemie   MeSH
• oligosacharidy * chemie   metabolismus   MeSH
• tandemové repetitivní sekvence MeSH
• vazebná místa MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• galektiny * MeSH
• glykoproteiny * MeSH
• ligandy MeSH
• oligosacharidy * MeSH
• poly-N-acetyllactosamine MeSH Prohlížeč
• polysacharidy MeSH

INTRODUCTION: The immunosuppressive roles of galectin-3 (Gal-3) in carcinogenesis make this lectin an attractive target for pharmacological inhibition in immunotherapy. Although current clinical immunotherapies appear promising in the treatment of solid tumors, their efficacy is significantly weakened by the hostile immunosuppressive tumor microenvironment (TME). Gal-3, a prominent TME modulator, efficiently subverts the elimination of cancer, either directly by inducing apoptosis of immune cells or indirectly by binding essential effector molecules, such as interferon-gamma (IFNγ). METHODS: N-(2-Hydroxypropyl)methacrylamide (HPMA)-based glycopolymers bearing poly-N-acetyllactosamine-derived tetrasaccharide ligands of Gal-3 were designed, synthesized, and characterized using high-performance liquid chromatography, dynamic light scattering, UV-Vis spectrophotometry, gel permeation chromatography, nuclear magnetic resonance, high-resolution mass spectrometry and CCK-8 assay for evaluation of glycopolymer non-toxicity. Pro-immunogenic effects of purified glycopolymers were tested by apoptotic assay using flow cytometry, competitive ELISA, and in vitro cell-free INFγ-based assay. RESULTS: All tested glycopolymers completely inhibited Gal-3-induced apoptosis of monocytes/macrophages, of which the M1 subtype is responsible for eliminating cancer cells during immunotherapy. Moreover, the glycopolymers suppressed Gal-3-induced capture of glycosylated IFNγ by competitive inhibition to Gal-3 carbohydrate recognition domain (CRD), which enables further inherent biological activities of this effector, such as differentiation of monocytes into M1 macrophages and repolarization of M2-macrophages to the M1 state. CONCLUSION: The prepared glycopolymers are promising inhibitors of Gal-3 and may serve as important supportive anti-cancer nanosystems enabling the infiltration of proinflammatory macrophages and the reprogramming of unwanted M2 macrophages into the M1 subtype.

• Klíčová slova
• carbohydrate, galectin-3, glycopolymer, interferon-gamma, monocyte, tumor microenvironment,
• MeSH
• akrylamidy chemie   farmakologie   MeSH
• apoptóza účinky léků   MeSH
• galektin 3 * antagonisté a inhibitory   MeSH
• interferon gama * metabolismus   MeSH
• lidé MeSH
• makrofágy účinky léků   MeSH
• monocyty * účinky léků   MeSH
• nádorové mikroprostředí účinky léků   MeSH
• polymery * chemie   farmakologie   MeSH
• protinádorové látky * farmakologie   chemie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• akrylamidy MeSH
• galektin 3 * MeSH
• galektiny MeSH
• interferon gama * MeSH
• krevní proteiny MeSH
• LGALS3 protein, human MeSH Prohlížeč
• polymery * MeSH
• protinádorové látky * MeSH

Galectins are carbohydrate-binding lectins that modulate the proliferation, apoptosis, adhesion, or migration of cells by cross-linking glycans on cell membranes or extracellular matrix components. Galectin-4 (Gal-4) is a tandem-repeat-type galectin expressed mainly in the epithelial cells of the gastrointestinal tract. It consists of an N- and a C-terminal carbohydrate-binding domain (CRD), each with distinct binding affinities, interconnected with a peptide linker. Compared to other more abundant galectins, the knowledge of the pathophysiology of Gal-4 is sparse. Its altered expression in tumor tissue is associated with, for example, colon, colorectal, and liver cancers, and it increases in tumor progression, and metastasis. There is also very limited information on the preferences of Gal-4 for its carbohydrate ligands, particularly with respect to Gal-4 subunits. Similarly, there is virtually no information on the interaction of Gal-4 with multivalent ligands. This work shows the expression and purification of Gal-4 and its subunits and presents a structure-affinity relationship study with a library of oligosaccharide ligands. Furthermore, the influence of multivalency is demonstrated in the interaction with a model lactosyl-decorated synthetic glycoconjugate. The present data may be used in biomedical research for the design of efficient ligands of Gal-4 with diagnostic or therapeutic potential.

• Klíčová slova
• blood-group antigen, galectin-4, inhibitor, multivalency, oligosaccharide, transglycosylation,
• MeSH
• galektin 4 * MeSH
• galektiny chemie   MeSH
• lidé MeSH
• ligandy MeSH
• nádory * MeSH
• oligosacharidy chemie   MeSH
• sacharidy MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• galektin 4 * MeSH
• galektiny MeSH
• ligandy MeSH
• oligosacharidy MeSH
• sacharidy MeSH

β-N-Acetylhexosaminidase from Talaromyces flavus (TfHex; EC 3.2.1.52) is an exo-glycosidase with dual activity for cleaving N-acetylglucosamine (GlcNAc) and N-acetylgalactosamine (GalNAc) units from carbohydrates. By targeting a mutation hotspot of the active site residue Glu332, we prepared a library of ten mutant variants with their substrate specificity significantly shifted towards GlcNAcase activity. Suitable mutations were identified by in silico methods. We optimized a microtiter plate screening method in the yeast Pichia pastoris expression system, which is required for the correct folding of tetrameric fungal β-N-acetylhexosaminidases. While the wild-type TfHex is promiscuous with its GalNAcase/GlcNAcase activity ratio of 1.2, the best single mutant variant Glu332His featured an 8-fold increase in selectivity toward GlcNAc compared with the wild-type. Several prepared variants, in particular Glu332Thr TfHex, had significantly stronger transglycosylation capabilities than the wild-type, affording longer chitooligomers - they behaved like transglycosidases. This study demonstrates the potential of mutagenesis to alter the substrate specificity of glycosidases.

• Klíčová slova
• Pichia pastoris, Talaromyces flavus, site-directed mutagenesis, site-saturation mutagenesis, substrate specificity, β-N-acetylhexosaminidase,
• MeSH
• acetylgalaktosamin metabolismus   MeSH
• acetylglukosamin * metabolismus   MeSH
• acetylglukosaminidasa MeSH
• beta-N-acetylhexosaminidasy * metabolismus   MeSH
• kinetika MeSH
• mutace MeSH
• substrátová specifita MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• acetylgalaktosamin MeSH
• acetylglukosamin * MeSH
• acetylglukosaminidasa MeSH
• beta-N-acetylhexosaminidasy * MeSH

Enzymatic synthesis is an elegant biocompatible approach to complex compounds such as human milk oligosaccharides (HMOs). These compounds are vital for healthy neonatal development with a positive impact on the immune system. Although HMOs may be prepared by glycosyltransferases, this pathway is often complicated by the high price of sugar nucleotides, stringent substrate specificity, and low enzyme stability. Engineered glycosidases (EC 3.2.1) represent a good synthetic alternative, especially if variations in the substrate structure are desired. Site-directed mutagenesis can improve the synthetic process with higher yields and/or increased reaction selectivity. So far, the synthesis of human milk oligosaccharides by glycosidases has mostly been limited to analytical reactions with mass spectrometry detection. The present work reveals the potential of a library of engineered glycosidases in the preparative synthesis of three tetrasaccharides derived from lacto-N-tetraose (Galβ4GlcNAcβ3Galβ4Glc), employing sequential cascade reactions catalyzed by β3-N-acetylhexosaminidase BbhI from Bifidobacterium bifidum, β4-galactosidase BgaD-B from Bacillus circulans, β4-N-acetylgalactosaminidase from Talaromyces flavus, and β3-galactosynthase BgaC from B. circulans. The reaction products were isolated and structurally characterized. This work expands the insight into the multi-step catalysis by glycosidases and shows the path to modified derivatives of complex carbohydrates that cannot be prepared by standard glycosyltransferase methods.

• Klíčová slova
• enzymatic synthesis, glycosidase, human milk oligosaccharide, mutagenesis,
• MeSH
• Bifidobacterium bifidum * metabolismus   MeSH
• glykosidhydrolasy metabolismus   MeSH
• glykosyltransferasy metabolismus   MeSH
• lidé MeSH
• mateřské mléko * metabolismus   MeSH
• novorozenec MeSH
• oligosacharidy chemie   MeSH
• substrátová specifita MeSH
• Check Tag
• lidé MeSH
• novorozenec MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• glykosidhydrolasy MeSH
• glykosyltransferasy MeSH
• oligosacharidy MeSH

The monolayer character of two-dimensional materials predestines them for application as active layers of sensors. However, their inherent high sensitivity is always accompanied by a low selectivity. Chemical functionalization of two-dimensional materials has emerged as a promising way to overcome the selectivity issues. Here, we demonstrate efficient graphene functionalization with carbohydrate ligands-chitooligomers, which bind proteins of the lectin family with high selectivity. Successful grafting of a chitooligomer library was thoroughly characterized, and glycan binding to wheat germ agglutinin was studied by a series of methods. The results demonstrate that the protein quaternary structure remains intact after binding to the functionalized graphene, and that the lectin can be liberated from the surface by the addition of a binding competitor. The chemoenzymatic assay with a horseradish peroxidase conjugate also confirmed the intact catalytic properties of the enzyme. The present approach thus paves the way towards graphene-based sensors for carbohydrate-lectin binding.

• Klíčová slova
• 2D materials, carbohydrate, graphene, sensor, wheat germ agglutinin,
• MeSH
• grafit chemie   MeSH
• křenová peroxidasa MeSH
• kvarterní struktura proteinů MeSH
• lektiny analýza   metabolismus   MeSH
• polysacharidy chemie   metabolismus   MeSH
• vazba proteinů MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• grafit MeSH
• křenová peroxidasa MeSH
• lektiny MeSH
• polysacharidy MeSH

The interaction of multi-LacNAc (Galβ1-4GlcNAc)-containing N-(2-hydroxypropyl) methacrylamide (HPMA) copolymers with human galectin-1 (Gal-1) and the carbohydrate recognition domain (CRD) of human galectin-3 (Gal-3) was analyzed using NMR methods in addition to cryo-electron-microscopy and dynamic light scattering (DLS) experiments. The interaction with individual LacNAc-containing components of the polymer was studied for comparison purposes. For Gal-3 CRD, the NMR data suggest a canonical interaction of the individual small-molecule bi- and trivalent ligands with the lectin binding site and better affinity for the trivalent arrangement due to statistical effects. For the glycopolymers, the interaction was stronger, although no evidence for forming a large supramolecule was obtained. In contrast, for Gal-1, the results indicate the formation of large cross-linked supramolecules in the presence of multivalent LacNAc entities for both the individual building blocks and the polymers. Interestingly, the bivalent and trivalent presentation of LacNAc in the polymer did not produce such an increase, indicating that the multivalency provided by the polymer is sufficient for triggering an efficient binding between the glycopolymer and Gal-1. This hypothesis was further demonstrated by electron microscopy and DLS methods.

• Klíčová slova
• HPMA copolymer, galectin, glycomimetic, glycopolymer, inhibition, molecular recognition, multivalency,
• MeSH
• akrylamidy chemie   farmakologie   MeSH
• elektronová kryomikroskopie MeSH
• galektin 1 chemie   genetika   MeSH
• galektiny chemie   genetika   MeSH
• krevní proteiny chemie   genetika   MeSH
• lidé MeSH
• ligandy MeSH
• methakryláty chemie   farmakologie   MeSH
• polymery chemie   farmakologie   MeSH
• sacharidy chemie   MeSH
• vazba proteinů účinky léků   MeSH
• vazebná místa účinky léků   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• akrylamidy MeSH
• galektin 1 MeSH
• galektiny MeSH
• hydroxypropyl methacrylate MeSH Prohlížeč
• krevní proteiny MeSH
• LGALS1 protein, human MeSH Prohlížeč
• LGALS3 protein, human MeSH Prohlížeč
• ligandy MeSH
• methacrylamide MeSH Prohlížeč
• methakryláty MeSH
• polymery MeSH
• sacharidy MeSH

Fungal β-N-acetylhexosaminidases, though hydrolytic enzymes in vivo, are useful tools in the preparation of oligosaccharides of biological interest. The β-N-acetylhexosaminidase from Talaromyces flavus is remarkable in terms of its synthetic potential, broad substrate specificity, and tolerance to substrate modifications. It can be heterologously produced in Pichia pastoris in a high yield. The mutation of the Tyr470 residue to histidine greatly enhances its transglycosylation capability. The aim of this work was to identify the structural requirements of this model β-N-acetylhexosaminidase for its transglycosylation acceptors and formulate a structure-activity relationship study. Enzymatic reactions were performed using an activated glycosyl donor, 4-nitrophenyl N-acetyl-β-d-glucosaminide or 4-nitrophenyl N-acetyl-β-d-galactosaminide, and a panel of glycosyl acceptors of varying structural features (N-acetylglucosamine, glucose, N-acetylgalactosamine, galactose, N-acetylmuramic acid, and glucuronic acid). The transglycosylation products were isolated and structurally characterized. The C-2 N-acetamido group in the acceptor molecule was found to be essential for recognition by the enzyme. The presence of the C-2 hydroxyl moiety strongly hindered the normal course of transglycosylation, yielding unique non-reducing disaccharides in a low yield. Moreover, whereas the gluco-configuration at C-4 steered the glycosylation into the β(1-4) position, the galacto-acceptor afforded a β(1-6) glycosidic linkage. The Y470H mutant enzyme was tested with acceptors based on β-glycosides of uronic acid and N-acetylmuramic acid. With the latter acceptor, we were able to isolate and characterize one glycosylation product in a low yield. To our knowledge, this is the first example of enzymatic glycosylation of an N-acetylmuramic acid derivative. In order to explain these findings and predict enzyme behavior, a modeling study was accomplished that correlated with the acquired experimental data.

• Klíčová slova
• Glide docking, Talaromyces flavus, muramic acid, non-reducing carbohydrate, substrate specificity, transglycosylation, β-N-acetylhexosaminidases,
• MeSH
• beta-N-acetylhexosaminidasy chemie   metabolismus   MeSH
• glykosidy metabolismus   MeSH
• glykosylace MeSH
• kinetika MeSH
• konformace proteinů MeSH
• molekulární modely MeSH
• oligosacharidy metabolismus   MeSH
• substrátová specifita MeSH
• Talaromyces enzymologie   MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• beta-N-acetylhexosaminidasy MeSH
• glykosidy MeSH
• oligosacharidy MeSH