Construction,expression and characterization of fusion enzyme from <Emphasis Type="Italic">Arthrobacter oxydans</Emphasis> dextranase and <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> amylase

An artificial fusion protein of Arthrobacter oxydans dextranase and Klebsiella pneumoniae α-amylase was constructed and expressed in Escherichia coli. Most of the expressed protein existed as an insoluble fraction, which was solubilized with urea. The purified fusion enzyme electrophoretically migrated as a single protein band; M = 137 kDa, and exhibited activities of both dextranase (10.8 U mg⁻¹) and amylase (7.1 U mg⁻¹), which were lower than that of reference dextranase (13.3 U mg⁻¹) and α-amylase (103 U mg⁻¹). The fusion enzyme displayed bifunctional enzyme activity at pH 5–7 at 37°C. These attributes potentially make the fusion enzyme more convenient for use in sugar processing than a two-enzyme system.