A uronic acid analogue of isofagomine lactam as a nanomolar glucuronidase inhibitor

Substituent Position of Iminocyclitols Determines the Potency and Selectivity for Gut Microbial Xenobiotic-Reactivating Enzymes

Selective inhibitors of gut bacterial β-glucuronidases (GUSs) are of particular interest in the prevention of xenobiotic-induced toxicities. This study reports the first structure-activity relationships on potency and selectivity of several iminocyclitols (2-7) for the GUSs. Complex structures of Ruminococcus gnavus GUS with 2-7 explained how charge, conformation, and substituent of iminocyclitols affect their potency and selectivity. N1 of uronic isofagomine (2) made strong electrostatic interactions with two catalytic glutamates of GUSs, resulting in the most potent inhibition (K_i ≥ 11 nM). C6-propyl analogue of 2 (6) displayed 700-fold selectivity for opportunistic bacterial GUSs (K_i = 74 nM for E. coli GUS and 51.8 μM for RgGUS). In comparison with 2, there was 200-fold enhancement in the selectivity, which was attributed to differential interactions between the propyl group and loop 5 residues of the GUSs. The results provide useful insights to develop potent and selective inhibitors for undesired GUSs.

Carbohydrate-Processing Enzymes of the Lysosome: Diseases Caused by Misfolded Mutants and Sugar Mimetics as Correcting Pharmacological Chaperones

Lysosomal storage diseases are hereditary disorders caused by mutations on genes encoding for one of the more than fifty lysosomal enzymes involved in the highly ordered degradation cascades of glycans, glycoconjugates, and other complex biomolecules in the lysosome. Several of these metabolic disorders are associated with the absence or the lack of activity of carbohydrate-processing enzymes in this cell compartment. In a recently introduced therapy concept, for susceptible mutants, small substrate-related molecules (so-called pharmacological chaperones), such as reversible inhibitors of these enzymes, may serve as templates for the correct folding and transport of the respective protein mutant, thus improving its concentration and, consequently, its enzymatic activity in the lysosome. Carbohydrate-processing enzymes in the lysosome, related lysosomal diseases, and the scope and limitations of reported reversible inhibitors as pharmacological chaperones are discussed with a view to possibly extending and improving research efforts in this area of orphan diseases.