Binding parameters and thermodynamics of the interaction of imino sugars with a recombinant human acid α-glucosidase (alglucosidase alfa): Insight into the complex formation mechanism

Abstract

BackgroundRecently, enzyme enhancement therapy (EET) for Pompe disease involving imino sugars, which act as potential inhibitors of acid α-glucosidases in vitro, to improve the stability and/or transportation of mutant acid α-glucosidases in cells was studied and attracted interest. However, the mechanism underlying the molecular interaction between the imino sugars and the enzyme has not been clarified yet. MethodsWe examined the inhibitory and binding effects of four imino sugars on a recombinant human acid α-glucosidase, alglucosidase alfa, by means of inhibition assaying and isothermal titration calorimetry (ITC). Furthermore, we built structural models of complexes of the catalytic domain of the enzyme with the imino sugars bound to its active site by homology modeling, and examined the molecular interaction between them. ResultsAll of the imino sugars examined exhibited a competitive inhibitory action against the enzyme, 1-deoxynojirimycin (DNJ) exhibiting the strongest action among them. ITC revealed that one compound molecule binds to one enzyme molecule and that DNJ most strongly binds to the enzyme among them. Structural analysis revealed that the active site of the enzyme is almost completely occupied by DNJ. ConclusionThese biochemical and structural analyses increased our understanding of the molecular interaction between a human acid α-glucosidase and imino sugars.