Cucurbit[7]uril as a Supramolecular Artificial Enzyme for Diels-Alder Reactions.

The ability to mimic the activity of natural enzymes using supramolecular constructs (artificial enzymes) is a vibrant scientific research field. Herein, we demonstrate that cucurbit[7]uril (CB[7]) can catalyse Diels-Alder reactions for a number of substituted and unreactive N-allyl-2-furfurylamines under biomimetic conditions, without the need for protecting groups, yielding powerful synthons in previously unreported mild conditions. CB[7] rearranges the substrate in a highly reactive conformation and shields it from the aqueous environment, thereby mimicking the mode of action of a natural Diels-Alderase. These findings can be directly applied to the phenomenon of product inhibition observed in natural Diels-Alderase enzymes, and pave the way toward the development of novel, supramolecular-based green catalysts.

Covalent Probes for Carbohydrate-Active Enzymes: From Glycosidases to Glycosyltransferases.

Covalent probes for glycosidases and glycosyltransferases are of great interest as tool compounds for chemical biology. For glycosidases, a sizable number of such probes have been developed from covalent glycosidase inhibitors. We review selected recent examples and highlight different design strategies, including probes based on photoaffinity labels and mechanism-based inhibitors, as well as their applications in biology and for activity-based protein profiling. In contrast to glycosidases, only a limited number of covalent probes have been reported to date for glycosyltransferases. We describe a new class of covalent probes for the retaining α-1,4-galactosyltransferase LgtC from Neisseria meningitidis. On the basis of these probes, we have developed an operationally simple two-step protocol for the fluorescent labeling of recombinant LgtC both in purified form and in cell lysates. In principle, our approach is also applicable to other bacterial glycosyltransferases. Among other applications, our protocol may therefore be particularly useful for imaging of the differential expression of these enzymes in different bacterial species and strains.