title: Purification and characterization of a strictly specific beta-D-fucosidase from Aspergillus phoenicis.
abstract: Although beta-D-fucosidase (beta-D-fucohydrolase, EC 3.2.1.38) has been isolated from various sources, all those enzymes were associated with a high activity of beta-D-galactosidase and/or beta-D-glucosidase. We have purified a specific beta-D-fucosidase in electrophoretically homogeneous form from crude extracts of Aspergillus phoenicis by polyethyleneglycol 8000-phosphate buffer aqueous two-phase separation, and successive chromatography on DEAE-Sephadex A-50, hydroxyapatite, and Sephadex G-100 columns. The molecular weight of the enzyme was estimated to be 57,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 50,000 to 60,000 by gel filtration on Sephadex G-100. The enzyme showed optimum activity at pH 6.0 and 40 degrees C; it was stable in the pH range 5.5-6.5 and below 35 degrees C. The Km and the Vmax values for pNP-beta -D-fucoside were 2.4 mM, and 12.8 mumol.min-1.mg-1, respectively. The enzyme was strongly inhibited by sulfhydryl group reagents, p-chloromercuribenzoate, n-ethylmaleimide, and iodoacetate. It was also inhibited by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, diethyl pyrocarbonate, and N-bromosuccinimide. Thus, -SH and -COOH groups and histidyl and tryptophyl residues were essential for enzyme activity. The purified beta-D-fucosidase showed high specificity toward p-nitrophenyl-beta-D-fucoside. The enzyme was inhibited by D-fucose and D-fucono-gamma-lactone, but not by D-galactose, D-galactono-gamma-lactone, D-glucose, or D-glucono-gamma-lactone; the latter compounds are specific inhibitors of beta-D-galactosidase and beta-D-glucosidase, respectively. Thus, this enzyme is the most strictly specific beta-D-fucosidase when compared with those previously reported.
authors.affiliation: Institute of Microbiology, Academia Sinica, Beijing, China.
authors.forename: Y C
authors.initials: YC
authors.lastname: Zeng
authors.forename: Y T
authors.initials: YT
authors.lastname: Li
authors.forename: Y J
authors.initials: YJ
authors.lastname: Gu
authors.forename: S Z
authors.initials: SZ
authors.lastname: Zhang
mesh_terms: D001230:Aspergillus / Q000201:enzymology*; D002845:Chromatography; D005656:Fungal Proteins / Q000302:isolation & purification / Q000378:metabolism; D008970:Molecular Weight; D013379:Substrate Specificity; D005644:alpha-L-Fucosidase / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; C028219:beta-D-fucosidase; D005644:alpha-L-Fucosidase