Thermostable inulin fructotransferase (DFA III-producing) from Arthrobacter sp. L68-1

An inulin fructotransferase (DFA III-producing) [EC 2.4.1.93] from Arthrobacter sp. L68-1 was purified and characterised. The enzyme was purified from culture supernatant of the microorganism 54.2-fold with a yield of 16.0% using DEAE-Toyopearl chromatography (repeated twice) and Super Q-Toyopearl chromatography. The enzyme showed maximum activity at pH 5.5–6.0 and 55 °C. The enzyme activity was stable up to 80 °C after 1 h heat treatment. This heat stability was the highest of the inulin fructotransferases (DFA III-producing) reported to date. The molecular mass of the enzyme was estimated to be 43 kDa by SDS-PAGE and 73 kDa by gel filtration, and was considered to be a dimer. The N-terminal amino acid sequence (18 amino acid residues) was determined as AEETKGGPFNSPNAYDVT.