Purification and properties ofβ-fructofuranosidase from Aspergillus japonicus

β-Fructofuranosidase fromAspergillus japonicus, which produces 1-kestose (O-β-D-fructofuranosyl-(2→1)-β-D-fructofuranosyl α-D-glucopyranoside) and nystose (O-β-D-fructofuranosyl-(2→1)-β-D-fructofuranosyl-(2→1)-β-D-fructofuranosyl α-D-glucopyranoside) from sucrose, was purified to homogeneity by fractionation with calcium acetate and ammonium sulphate and chromatography with DEAE-Cellulofine and Sephadex G-200. Its molecular size was estimated to be about 304,000 Da by gel filtration. The enzyme was a glycoprotein which contained about 20% (w/w) carbohydrate. Optimum pH for the enzymatic reaction was 5.5 to 6. The enzyme was stable over a wide pH range, from pH 4 to 9. Optimum reaction temperature for the enzyme was 60 to 65°C and it was stable below 60°C. The Km value for sucrose was 0.21M. The enzyme was inhibited by metal ions, such as those of silver, lead and iron, and also byp-chloromercuribenzoate.