Purification and properties of an inulin fructotransferase (depolymerizing) from Arthrobacter sp. H65-7

Abstract

Arthrobacter sp. H65-7 produced inulin fructotransferase (depolymerizing) which converts inulin into di- d-fructofuranose 1, 2′ : 2, 3′ dianhydride (DFA III) and small amounts of oligosaccharides. The enzyme was purified 8-fold with a yield of 13% from a culture supernatant by ammonium sulfate precipitation followed by DEAE-Toyopearl 650 M column chromatography. The purified enzyme gave a single band on polyacrylamide gel electrophoresis. The molecular weight of the enzyme was estimated to be 49,000 by SDS-polyacrylamide gel electrophoresis, and 100,000 by gel filtration. The isoelectric point of the enzyme was determined to be pH 4.7. The optimal pH and temperature for the enzyme reaction were 5.5, and 60°C, respectively. The enzyme was stable with a pH range of 4.5 to 9.0, and at up to 70°C. After exhaustive digestion of inulin by this enzyme, nystose and 1-F-fructofuranosyl-nystose were produced in addition to DFA III.