Glycosidases are a large, evolutionary conserved enzyme family that catalyze the hydrolysis of glycosidic linkages of glycopolymers. These enzymes are involved in many (patho)physiological... Show moreGlycosidases are a large, evolutionary conserved enzyme family that catalyze the hydrolysis of glycosidic linkages of glycopolymers. These enzymes are involved in many (patho)physiological processes and they are applied in the glycopolymer assembly and biotechnological industry. The research described in this Thesis aims to develop inhibitors (mechanism-based and competitive) and activity-based probes for glycosidases using the naturally occurring molecule cyclophellitol as template. Different cyclophellitol derivatives have been synthesized and they could be used to study the role of glycosidases in different (patho)physiological and biotechnological processes. Show less
Glycoconjugates (a carbohydrate connected to a lipid, protein or other carbohydrate) play a key role in great variety of biological processes. The synthesis of these constructs is tightly regulated... Show moreGlycoconjugates (a carbohydrate connected to a lipid, protein or other carbohydrate) play a key role in great variety of biological processes. The synthesis of these constructs is tightly regulated by enzymes. Defects in these enzymes may result in an impaired degradation of the glycoconjugate. Consequently, the levels of glycoconjugates are increased and this may eventually lead to storage disorders such as Gaucher disease. The research described in this thesis focuses on the synthesis of chemical tools (activity-based probes, ABPs) to study the enzymes involved in the degradation of glycoconjugates. Using these probes, it was demonstrated that the activity of peptide N-glycanase (the enzyme that is responsible for the hydrolysis of N-linked glycoproteins)inhibitors is determined by its reactive group. Furthermore, the activity-based protein profiling strategy was used to study degradation of glycosy lated proteins. It appeared that deglycosylation of O-GlcNAclated proteins is not a prerequisite for proteasomal degradation. To study beta-glucosidases (enzymes that catalyze the hydrolysis of O-glycosidic linkages), ABPs based on cyclophellitol have been developed. Especially fluorescently labeled probes bind efficiently and selectively to beta-glucosidases. These probes have been used to investigate Gaucher disease. Both wild-type and mutant forms of the enzyme could be labeled in vitro and in living cells which allowed rapid identification activity of this glucosidase. Show less
