The Specificity of Interactions between Endoinulinase from Aspergillus ficuum and Mono-, Di-, and Polysaccharides

The aim of this study was to analyze the features of the spatial organization of the endoinulinase molecule from Aspergillus ficuum after its binding to mono-, di-, and polysaccharides. This study examined changes in volume and number of internal cavities upon binding of inulinase to mono- (glucose, fructose), di- (sucrose, mannose), and polysaccharides (inulin). Transformations in the quantity and length of tunnels and pores were described, and the reorganization of the composition and localization of charged and hydrophobic amino acid residues clusters on the surface of the enzyme molecule was analyzed. It was shown that the models of inulinase in the complex with sucrose (an alternative substrate) and mannose (an activator) exhibit the same types of internal structures. A similar pattern was found in the formation of complexes with fructose (a reaction product) and glucose (an inhibitor). In addition, it was established that both charged and hydrophobic clusters do not undergo significant changes in chemical composition after the binding of inulinase to mono-, di-, and polysaccharides, i.e., the interaction between inulinase and carbohydrates mentioned above primarily affects the internal structures of the enzyme. The specificity of the binding of inulinases to various ligands should be taken into account while developing modern industrial biocatalysts based on inulinase.