A new class of compounds, namely highly substituted diaminocyclopentane-l-lysine adducts, have been discovered as potent inhibitors of O-GlcNAcase, an enzyme crucial for protein de-O-glycosylation. These inhibitors exhibit exceptional selectivity and reversibility and are the first example of human O-GlcNAcase inhibitors that are structurally related to the transition state of the rate-limiting step with the "aglycon" still in bond-length proximity. The ease of their preparation, remarkable biological activities, stability, and non-toxicity make them promising candidates for the development of anti-tau-phosphorylation agents holding significant potential for the treatment of Alzheimer's disease.

• MeSH
• beta-N-Acetylhexosaminidases antagonists & inhibitors   metabolism   MeSH
• Cyclopentanes chemistry   pharmacology   chemical synthesis   MeSH
• Enzyme Inhibitors * chemistry   pharmacology   chemical synthesis   MeSH
• Humans MeSH
• Lysine * chemistry   pharmacology   MeSH
• Molecular Structure MeSH
• Dose-Response Relationship, Drug MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH

YKL-40, also known as human cartilage glycoprotein-39 (HC-gp39) or CHI3L1, shares structural similarities with chitotriosidase (CHIT1), an active chitinase, but lacks chitinase activity. Despite being a biomarker for inflammatory disorders and cancer, the reasons for YKL-40's inert chitinase function have remained elusive. This study reveals that the loss of chitinase activity in YKL-40 has risen from multiple sequence modifications influencing its chitin affinity. Contrary to the common belief associating the lack of chitinase activity with amino acid substitutions in the catalytic motif, attempts to activate YKL-40 by creating two amino acid mutations in the catalytic motif (MT-YKL-40) proved ineffective. Subsequent exploration that included creating chimeras of MT-YKL-40 and CHIT1 catalytic domains (CatDs) identified key exons responsible for YKL-40 inactivation. Introducing YKL-40 exons 3, 6, or 8 into CHIT1 CatD resulted in chitinase inactivation. Conversely, incorporating CHIT1 exons 3, 6, and 8 into MT-YKL-40 led to its activation. Our recombinant proteins exhibited properly formed disulfide bonds, affirming a defined structure in active molecules. Biochemical and evolutionary analysis indicated that the reduced chitinase activity of MT-YKL-40 correlates with specific amino acids in exon 3. M61I and T69W substitutions in CHIT1 CatD diminished chitinase activity and increased chitin binding. Conversely, substituting I61 with M and W69 with T in MT-YKL-40 triggered chitinase activity while reducing the chitin-binding activity. Thus, W69 plays a crucial role in a unique subsite within YKL-40. These findings emphasize that YKL-40, though retaining the structural framework of a mammalian chitinase, has evolved to recognize chitin while surrendering chitinase activity.

• MeSH
• Chitin * metabolism   chemistry   MeSH
• Chitinases metabolism   genetics   chemistry   MeSH
• Exons MeSH
• Hexosaminidases metabolism   chemistry   genetics   MeSH
• Catalytic Domain MeSH
• Humans MeSH
• Evolution, Molecular MeSH
• Chitinase-3-Like Protein 1 * metabolism   genetics   chemistry   MeSH
• Amino Acid Sequence MeSH
• Amino Acid Substitution MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH

The addition of O-linked β-N-acetylglucosamine (O-GlcNAc) to proteins (referred to as O-GlcNAcylation) is a modification that is crucial for vertebrate development. O-GlcNAcylation is catalyzed by O-GlcNAc transferase (OGT) and reversed by O-GlcNAcase (OGA). Missense variants of OGT have recently been shown to segregate with an X-linked syndromic form of intellectual disability, OGT-linked congenital disorder of glycosylation (OGT-CDG). Although the existence of OGT-CDG suggests that O-GlcNAcylation is crucial for neurodevelopment and/or cognitive function, the underlying pathophysiologic mechanisms remain unknown. Here we report a mouse line that carries a catalytically impaired OGT-CDG variant. These mice show altered O-GlcNAc homeostasis with decreased global O-GlcNAcylation and reduced levels of OGT and OGA in the brain. Phenotypic characterization of the mice revealed lower body weight associated with reduced body fat mass, short stature and microcephaly. This mouse model will serve as an important tool to study genotype-phenotype correlations in OGT-CDG in vivo and for the development of possible treatment avenues for this disorder.

• MeSH
• beta-N-Acetylhexosaminidases metabolism   MeSH
• Phenotype MeSH
• Glycosylation MeSH
• Intellectual Disability * genetics   MeSH
• Disease Models, Animal * MeSH
• Brain pathology   metabolism   MeSH
• Mice MeSH
• N-Acetylglucosaminyltransferases * metabolism   genetics   deficiency   MeSH
• Neurodevelopmental Disorders pathology   genetics   enzymology   MeSH
• Body Weight MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural 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.

• MeSH
• Acetylgalactosamine metabolism   MeSH
• Acetylglucosamine * metabolism   MeSH
• Acetylglucosaminidase MeSH
• beta-N-Acetylhexosaminidases * metabolism   MeSH
• Kinetics MeSH
• Mutation MeSH
• Substrate Specificity MeSH
• Publication type
• Journal Article MeSH

We developed potent and selective aminocyclopentane-derived inhibitors of human O-N-acetyl-β-D-glucosaminidase (OGA) implicated in Alzheimer's disease. For example compound 13 was a nanomolar OGA inhibitor with 92 000-fold selectivity over human HexB. It was non-toxic and increased protein O-GlcNAcylation in the culture of murine neural cells, showing new alternatives in the treatment of tauopathies.

• MeSH
• Acetylglucosaminidase MeSH
• Alzheimer Disease * drug therapy   metabolism   MeSH
• beta-N-Acetylhexosaminidases MeSH
• Phosphorylation MeSH
• Enzyme Inhibitors pharmacology   MeSH
• Humans MeSH
• Mice MeSH
• tau Proteins metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

Concerned by the urgent need to explore new approaches for the treatment of Alzheimer's disease, we herein describe the synthesis and evaluation of new multitarget molecules. In particular, we have focused our attention on modulating the activity of cholinesterases (AChE, BuChE) in order to restore the levels of the neurotransmitter acetylcholine, and of O-GlcNAcase (OGA), which is associated with hyperphosphorylation of tau protein, in turn related to the formation of neurofibrillary tangles in the brain. Specifically, we considered the possibility of using carbohydrate-fused 1,3-selenazolines, decorated with a 2-alkylamino or 2-alkoxy moieties. On the one hand, the presence of a selenium atom might be useful in modulating the intrinsic oxidative stress in AD. On the other hand, such bicyclic structure might behave as a transition state analogue of OGA hydrolysis. Moreover, upon protonation, it could mimic the ammonium cation of acetylcholine. The lead compound, bearing a propylamino moiety on C-2 position of the selenazoline motif, proved to be a good candidate against AD; it turned out to be a strong inhibitor of BuChE (IC50 = 0.46 μM), the most prevalent cholinesterase in advanced disease stages, with a roughly 4.8 selectivity index in connection to AChE (IC50 = 2.2 μM). This compound exhibited a roughly 12-fold increase in activity compared to galantamine, one of the currently marketed drugs against AD, and a selective AChE inhibitor, and virtually the same activity as rivastigmine, a selective BuChE inhibitor. Furthermore, it was also endowed with a strong inhibitory activity against human OGA, within the nanomolar range (IC50 = 0.053 μM for hOGA, >100 μM for hHexB), and, thus, with an outstanding selectivity (IC50(hHexB)/IC50(hOGA) > 1887). The title compounds also exhibited an excellent selectivity against a panel of glycosidases and a negligible cytotoxicity against tumor and non-tumor cell lines. Docking simulations performed on the three target enzymes (AChE, BuChE, and OGA) revealed the key interactions to rationalize the biological data.

• MeSH
• Acetylcholine MeSH
• Acetylcholinesterase metabolism   MeSH
• Alzheimer Disease * drug therapy   metabolism   MeSH
• beta-N-Acetylhexosaminidases * antagonists & inhibitors   MeSH
• Cholinesterase Inhibitors * chemistry   MeSH
• Cholinesterases * metabolism   MeSH
• Humans MeSH
• Nootropic Agents pharmacology   MeSH
• Carbohydrates MeSH
• Molecular Docking Simulation MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH

Inhibition of the human O-linked β-N-acetylglucosaminidase (hOGA, GH84) enzyme is pharmacologically relevant in several diseases such as neurodegenerative and cardiovascular disorders, type 2 diabetes, and cancer. Human lysosomal hexosaminidases (hHexA and hHexB, GH20) are mechanistically related enzymes; therefore, selective inhibition of these enzymes is crucial in terms of potential applications. In order to extend the structure-activity relationships of OGA inhibitors, a series of 2-acetamido-2-deoxy-d-glucono-1,5-lactone sulfonylhydrazones was prepared from d-glucosamine. The synthetic sequence involved condensation of N-acetyl-3,4,6-tri-O-acetyl-d-glucosamine with arenesulfonylhydrazines, followed by MnO2 oxidation to the corresponding glucono-1,5-lactone sulfonylhydrazones. Removal of the O-acetyl protecting groups by NH3/MeOH furnished the test compounds. Evaluation of these compounds by enzyme kinetic methods against hOGA and hHexB revealed potent nanomolar competitive inhibition of both enzymes, with no significant selectivity towards either. The most efficient inhibitor of hOGA was 2-acetamido-2-deoxy-d-glucono-1,5-lactone 1-naphthalenesulfonylhydrazone (5f, Ki = 27 nM). This compound had a Ki of 6.8 nM towards hHexB. To assess the binding mode of these inhibitors to hOGA, computational studies (Prime protein-ligand refinement and QM/MM optimizations) were performed, which suggested the binding preference of the glucono-1,5-lactone sulfonylhydrazones in an s-cis conformation for all test compounds.

• MeSH
• Antigens, Neoplasm chemistry   metabolism   MeSH
• beta-Hexosaminidase beta Chain chemistry   metabolism   MeSH
• Histone Acetyltransferases chemistry   metabolism   MeSH
• Hyaluronoglucosaminidase chemistry   metabolism   MeSH
• Hydrazones chemical synthesis   chemistry   pharmacology   MeSH
• Enzyme Inhibitors chemical synthesis   chemistry   pharmacology   MeSH
• Lactones chemistry   MeSH
• Humans MeSH
• Molecular Conformation MeSH
• Models, Molecular MeSH
• Oxides chemistry   MeSH
• Manganese Compounds chemistry   MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH

The β-N-acetylhexosaminidase from Penicillium oxalicum (PoHex; EC 3.2.1.52) is a fungal glycosidase with an outstandingly high GalNAcase/GlcNAcase activity ratio. It has a remarkable synthetic capability and can process carbohydrates functionalized at various positions. However, the production in the native fungal host is lengthy, unselective and purification from the fungal medium is complicated and low yielding. We present here a novel production method of this enzyme in the eukaryotic host of Pichia pastoris, followed by elegant one-step purification to homogeneity. The resulting recombinant enzyme has improved biochemical and catalytic properties compared to the fungal wild type. Its good production yield (11 mg/400 mL cultivation medium) greatly expands the scope of synthetic applications. We further demonstrate the synthetic utility and broad acceptor specificity of recombinant PoHex in the glycosylation of a series of challenging acceptors with varying structural architectures, namely secondary and tertiary hydroxyl, aldoxime and a poly-hydroxylated compound.

• MeSH
• beta-N-Acetylhexosaminidases genetics   metabolism   MeSH
• Glycosylation MeSH
• Kinetics MeSH
• Hydrogen-Ion Concentration MeSH
• Penicillium enzymology   MeSH
• Pichia metabolism   MeSH
• Recombinant Proteins biosynthesis   isolation & purification   metabolism   MeSH
• Substrate Specificity MeSH
• Temperature MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Chitotriosidase (Chit1) and acidic mammalian chitinase (AMCase) have been attracting research interest due to their involvement in various pathological conditions such as Gaucher's disease and asthma, respectively. Both enzymes are highly expressed in mice, while the level of AMCase mRNA was low in human tissues. In addition, the chitinolytic activity of the recombinant human AMCase was significantly lower than that of the mouse counterpart. Here, we revealed a substantially higher chitinolytic and transglycosylation activity of human Chit1 against artificial and natural chitin substrates as compared to the mouse enzyme. We found that the substitution of leucine (L) by tryptophan (W) at position 218 markedly reduced both activities in human Chit1. Conversely, the L218W substitution in mouse Chit1 increased the activity of the enzyme. These results suggest that Chit1 may compensate for the low of AMCase activity in humans, while in mice, highly active AMCase may supplements low Chit1 activity.

• MeSH
• Chitin metabolism   MeSH
• Chitinases genetics   metabolism   MeSH
• Escherichia coli genetics   growth & development   MeSH
• Glycosylation MeSH
• Hexosaminidases genetics   metabolism   MeSH
• Humans MeSH
• Mice MeSH
• Gene Expression Regulation, Enzymologic MeSH
• Recombinant Proteins metabolism   MeSH
• Amino Acid Substitution * MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Comparative Study MeSH

β-N-Acetylhexosaminidases (CAZy GH20, EC 3.2.1.52) are exo-glycosidases specific for cleaving N-acetylglucosamine and N-acetylgalactosamine moieties of various substrates. The β-N-acetylhexosaminidase from the filamentous fungus Talaromyces flavus (TfHex), a model enzyme in this study, has a broad substrate flexibility and outstanding synthetic ability. We have designed and characterized seven glycosynthase-type variants of TfHex mutated at the catalytic aspartate residue that stabilizes the oxazoline reaction intermediate. Most of the obtained enzyme variants lost the majority of their original hydrolytic activity towards the standard substrate p-nitrophenyl 2-acetamido-2-deoxy-β-D-glucopyranoside (pNP-β-GlcNAc); moreover, the mutants were not active with the proposed glycosynthase donor 2-acetamido-2-deoxy-d-glucopyranosyl-α-fluoride (GlcNAc-α-F) either as would be expected in a glycosynthase. Importantly, the mutant enzymes instead retained a strong transglycosylation activity towards the standard substrate pNP-β-GlcNAc. In summary, five out of seven prepared TfHex variants bearing mutation at the catalytic Asp370 residue acted as efficient transglycosidases, which makes them excellent tools for the synthesis of chitooligosaccharides, with the advantage of processing an inexpensive, stable and commercially available pNP-β-GlcNAc.

• MeSH
• Enzyme Activation MeSH
• beta-N-Acetylhexosaminidases genetics   metabolism   MeSH
• Fungi enzymology   genetics   MeSH
• Hydrolysis MeSH
• Catalysis MeSH
• Molecular Conformation MeSH
• Models, Molecular MeSH
• Mutation * MeSH
• Protein Engineering MeSH
• Substrate Specificity MeSH
• Chromatography, High Pressure Liquid MeSH
• Structure-Activity Relationship MeSH
• Publication type
• Journal Article MeSH