Characterization of a new α-l-fucosidase isolated from Fusarium proliferatum LE1 that is regioselective to α-(1 → 4)-l-fucosidic linkage in the hydrolysis of α-l-fucobiosides

Abstract

Here, we report the biochemical characterization of a novel α-l-fucosidase with broad substrate specificity (FpFucA) isolated from the mycelial fungus Fusarium proliferatum LE1. Highly purified α-l-fucosidase was obtained from several chromatographic steps after growth in the presence of l-fucose. The purified α-l-fucosidase appeared to be a monomeric protein of 67 ± 1 kDa that was able to hydrolyze the synthetic substrate p-nitrophenyl α-l-fucopyranoside (pNPFuc), with K_m = 1.1 ± 0.1 mM and k_cat = 39.8 ± 1.8 s^-1. l-fucose, 1-deoxyfuconojirimycin and tris(hydroxymethyl)aminomethane inhibited pNPFuc hydrolysis, with inhibition constants of 0.2 ± 0.05 mM, 7.1 ± 0.05 nM, and 12.2 ± 0.1 mM, respectively. We assumed that the enzyme belongs to subfamily A of the GH29 family (CAZy database) based on its ability to hydrolyze practically all fucose-containing oligosaccharides used in the study and the phylogenetic analysis. We found that this enzyme was a unique α-l-fucosidase that preferentially hydrolyzes the α-(1 → 4)-L-fucosidic linkage present in α-L-fucobiosides with different types of linkages. As a retaining glycosidase, FpFucA is capable of catalyzing the transglycosylation reaction with alcohols (methanol, ethanol, and 1-propanol) and pNP-containing monosaccharides as acceptors. These features make the enzyme an important tool that can be used in the various modifications of valuable fucose-containing compounds.

Keywords: Fusarium proliferatum; Translycosylation; α-(1 → 4)-l-fucosidic linkage; α-l-fucobiosides; α-l-fucosidase.