Preparation of an Active Monomer from Sweet Potato Tetrameric .BETA.-Amylase in the Presence of .ALPHA.-Cyclodextrin.

The active monomer of sweet potato tetrameric β-amylase prepared by modification with periodate-oxidized maltohexaose was a labile molecule. However, the stability of the active monomer was found to be very enhanced at pHs lower than 5 and higher than 9, and also at 60°C in the presence of α-cyclodextrin. The monomer, therefore, was prepared by the same modification in the presence of α-cyclodextrin. The specific activity of the resulting active monomer was 2700 units per mg protein while that of the original tetrameric enzyme was 3000, and the yield of the monomer was about 50% by weight of protein. Both the specific activity and yield of the active monomer were greatly improved comparing with those of the active monomer obtained in the absence of α-cyclodextrin. Also, the stabilization with α-cyclodextrin was observed for the original tetrameric enzyme.