An artificial fusion protein of Arthrobacter oxydans dextranase and Klebsiella pneumoniae alpha-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 alpha-amylase (103 U mg(-1)). The fusion enzyme displayed bifunctional enzyme activity at pH 5-7 at 37 degrees C. These attributes potentially make the fusion enzyme more convenient for use in sugar processing than a two-enzyme system.