ABSTRACT
Beta-amylase was prepared in a 33.4% yield from the homogenate of healthy, nongerminated sweet potato tubers. Beta-amylase in the cell-free extract was precipitated by ammonium sulfate fractionation [30-40%], chromatography on DEAE-cellulose and further purified by filtration on Sephadex-G 100. It has a specific activity of 1593.2 U/mg protein. No alpha-amylolytic activity was detected. The enzyme was active with starch, while being inactive towards sucrose, lactose and maltose. The Km value for beta-amylase was 2.63%. Optimal conditions for the action of potato amylase on soluble starch were at pH 5.5 and temperature 35-40C. The activity was completely inactivated by Fe 2+, Mg 2+ but EDTA, Ca 2+, Zn 2+, Cu 2+ and Co 2+ increase the activity of the enzyme by 2.1, 1.85, 1.75, 1.54, 1.51 fold, respectively. The molecular weight of the enzyme was estimated by gel filtration to be 64,000. The enzyme was relatively heat-stable, heating for 15 minutes at 40C resulted 14% loss of its activity