Hydrolysis of Maltose by Taka-amylase A*

Publisher Website
Google Scholar
Abstract
1. Maltose was found to be hydrolyzed at pH5.3 and 25°C by Taka-amylase A [EC 3.2.1.1] preparation which was crystallized three times and which was proved to be of single protein component by electrophoretic and ultracentrifugal analyses. 2. The Michaelis constant Km for the hydrolysis of maltose was found to be numerically equal to the competitive inhibitor constant Kt of maltose for the hydrolysis of p-nitrophenyl α-maltoside catalyzed by Taka-amylase A. 3. This Km value for maltose is one hundred times larger than the Km. value for the hydrolysis of maltose catalyzed by Taka-maltase [EC 3.2.1.20] or Taka-amylase B [EC 3.2.1.3] preparation. 4. A treatment of Taka-maltase at pH8.8 and 37°C for 2hr decreases its specific activity towards maltose, but the same treatment of the crystalline Taka-amylase A preparation causes no loss of specific activity towards maltose. On the other hand, a treatment with 1% HgCl2 solution at pH6.8 and room temperature for 24hr for crystalline Takaamylase A preparation decreases its specific activity towards maltose, but the same treatment for Taka-amylase B causes no loss of specific activity towards maltose. 5. From the results, it was concluded that the observed hydrolysis of maltose was caused by the action of Taka-amylase A itself and not by Taka-maltase or Taka-amylase B which might be contaminated in the crystalline preparation of Taka-amylase A. 6. The Michaelis constant Km for the hydrolysis of maltose catalyzed by Taka-amylase A was determined to be 9.6×10−2M and its breakdown rate constant k+2 of ES complex was determined to be 0.019 sec−1.

This publication has 0 references indexed in Scilit: