Purification and Characterization of Two β-d-Glucosidases from an Aspergillus Niger Enzyme Preparation: Affinity and Specificity Toward Glucosylated Compounds Characteristic of the Processing of Fruits

Autor: Patrice Pellerin, Marie-Paule Le Traon-Masson
Rok vydání: 1998
Předmět:
Zdroj: Enzyme and Microbial Technology. 22:374-382
ISSN: 0141-0229
Popis: Two β- d -glucosidases were purified to homogeneity from an Aspergillus niger enzyme preparation. Their respective molecular weights (118 kDa for β- d -glucosidase A and 109 kDa for β- d -glucosidase B) and pH and temperature properties were in the range of values reported for fungal β- d -glucosidases. They were competitively inhibited by glucose, gluconolactone, and deoxynojirimycin. Their substrate specificities (specific activities, affinity and catalytic constants) were determined on three glucosylated compounds corresponding to the technological applications of β- d -glucosidases in the processing of fruits; malvidin-3-glucoside (decolorization), geranyl-β- d -glucoside (aroma enhancing), and cellobiose (cellulolysis); in comparison with the activity on p-nitrophenyl-β- d -glucoside. β- d -Glucosidase A presented similar affinities toward the four substrates (Km in the range 0.43–0.5 m m ) but displayed very different activities. Cellobiose and geranyl-β- d -glucoside were degraded with respective catalytic constants of 200 μmol min−1 mg−1 and 28 μmol min−1 mg−1, whereas the degradation of malvidin-3-glucoside was very slow (kcat ∼ 1 μmol min−1 mg−1). On the contrary, β- d -glucosidase B displayed its maximum activity toward malvidin-3-glucoside (Km ∼ 0.11 m m , kcat ∼ 50 μmol min−1 mg−1) and had no significant activity on geranyl-β- d -glucoside and cellobiose (Km ∼ 0.25 m m , kcat ∼ 0.4 μmol min−1 mg−1); thus, the two enzymes presented different potential applications to the fruit juice industry, aroma enhancing and liquefaction/maceration with β- d -glucosidase A, and decolorization with β- d -glucosidase B.
Databáze: OpenAIRE
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