抄録
An amylase was purified from tubers of ichoimo, a cultivar of yam (Dioscorea batatas), and its basic properties were investigated. The enzyme was purified by acid treatment of crude extracts at pH 4.5, DEAE-Toyopearl 650S ion-exchange chromatography, and hydrophobic chromatography using Butyl-Toyopearl 650S to a state showing a single band on SDS polyacrylamide gel electrophoresis (PAGE). The purified enzyme had a specific activity of 161 U/mg protein. It has a molecular mass of 60, 000 Da on SDS-PAGE, optimum pH of 6.0, optimum temperature of 55°C, and a stable pH range of 4.3 to 8.5. On isoelectric focusing PAGE it gave two protein bands with pi's of 5.0 and 5.2. It produced maltose as a sole low molecular weight product from soluble starch and did not act on cyclodextrins. The anomeric form of the maltose was identified as the β-form. These results confirmed that the purified enzyme is a β-amylase.
