Ligand-Directed Chemistry on Glycoside Hydrolases - A Proof of Concept Study.

Selective covalent labelling of enzymes using small molecule probes has advanced the scopes of protein profiling. The covalent bond formation to a specific target is the key step of activity-based protein profiling (ABPP), a method which has become an indispensable tool for measuring enzyme activity in complex matrices. With respect to carbohydrate processing enzymes, strategies for ABPP so far involve labelling the active site of the enzyme, which results in permanent loss of activity. Here, we report in a proof of concept study the use of ligand-directed chemistry (LDC) for labelling glycoside hydrolases near - but not in - the active site. During the labelling process, the competitive inhibitor is cleaved from the probe, departs the active site and the enzyme maintains its catalytic activity. To this end, we designed a building block synthetic concept for small molecule probes containing iminosugar-based reversible inhibitors for labelling of two model ß-glucosidases. The results indicate that the LDC approach can be adaptable for covalent proximity labelling of glycoside hydrolases.

New lectin ligands: Testing of Amadori rearrangement products with a series of mannoside-specific lectins.

1-(N-Phenyl)amino-1-deoxy-α-D-manno-hept-2-ulose (2) and two multivalent BSA-based structures 7 and 8, d-manno-configured C-glycosyl-type compounds derived from an Amadori rearrangement, were evaluated as ligands for mannoside-specific lectins of various sources. The determination of the concentration corresponding to 50% of inhibition (IC50) is described. Multivalency turned out to effectively influence ligand selectivity and lectin binding.