Enzymatic glycosylation of polyphenols is a tool to improve their physicochemical properties and bioavailability. On the other hand, glycosidic enzymes can be inhibited by phenolic compounds. In this work, we studied the specificity of various phenolics (hydroquinone, hydroxytyrosol, epigallocatechin gallate, catechol and p-nitrophenol) as fructosyl acceptors or inhibitors of the β-fructofuranosidase from Xanthophyllomyces dendrorhous (pXd-INV). Only hydroquinone and hydroxytyrosol gave rise to the formation of glycosylated products. For the rest, an inhibitory effect on both the hydrolytic (H) and transglycosylation (T) activity of pXd-INV was observed. To disclose the binding mode of each compound and elucidate the molecular features determining its acceptor or inhibitor behaviour, ternary complexes of the inactive mutant pXd-INV-D80A with fructose and the different polyphenols were analyzed by X-ray crystallography. All the compounds bind by stacking against Trp105 and locate one of their phenolic hydroxyls making a polar linkage to the fructose O2 at 3.6–3.8 Å from the C2, which could enable the ulterior nucleophilic attack leading to transfructosylation. The acceptor capacity of the different polyphenols seems mediated by their ability to make flexible polar links with the protein.
Ref.: “Deciphering the molecular specificity of phenolic compounds as inhibitors or glycosyl acceptors of β fructofuranosidase from Xanthophyllomyces dendrorhous”. M. Ramirez-Escudero, N. Miguez, M. Gimeno-Perez, A.O. Ballesteros, M. Fernandez-Lobato, F.J. Plou* and J. Sanz-Aparicio* Scientific Reports 9, 17441 (2019), doi:10.1038/s41598-019-53948-y