Glycosidases of Aspergillus niger

Abstract

Abstract A highly purified preparation of 1,2-α-l-fucosidase, free of β-galactosidase and β-N-acetylglucosaminidase activities, has been obtained from a commercial preparation of Aspergillus niger by a simple isolation procedure involving ammonium sulfate precipitation, pressure dialysis, repeated gel filtration on Sephadex G-150, and chromatography on diethylaminoethyl Sephadex A-50. The enzyme has a pH optimum of 3.8 ± 0.2 and Km and Vmax values of 8.3 x 10-5 m and 16.0 µmoles per mg per hour, respectively, at 37° for methyl 2-O-α-l-fucopyranosyl-β-d-galactoside as substrate. The detailed specificity studies indicate that it is highly specific for nonreducing terminal l-fucose residues linked to d-galactose residues by 1 → 2-α linkage. It hydrolyzes fucose residues quantitatively from 2-O-α-l-fucopyranosyl-d-galactose, 2-O-α-l-fucosyllactose, and lacto-N-fucopentaose I. It does not split p-nitrophenyl-α-l-fucoside, 2-O-, 3-O-, and 4-O-α-l-fucopyranosylfucoses, and 3-O- and 4-O-α-l-fucopyranosyl-d-galactoses. It also does not release any focuse from oligosaccharides of human milk such as lacto-N-fucopentaose II, lacto-N-fucopentaose III, and 3'-O-α-l-fucosyllactose. The enzyme liberates 80 to 90% of fucose residues from porcine and canine submaxillary mucins. It has no action on orosomucoid, human chorionic gonadotropin, and fucan sulfate. The enzyme is extremely active against human blood group substance H, destroying virtually all of the detectable activity.