earticle

영어

Various native and hydroxyethylated starch granules were reacted as substrates for a debranching enzyme, pullulanase, from Bacillus acidopullulyticus , and the kinetic mechanism was investigated in initial rate studies. The apparent K m values of the native starch hydrolysis reactions decreased in the order of rice, corn, and potato, whereas V max remained constant for all starches. Assuming that starch granules were spherical, the double reciprocal of the initial rates of the hydrolysis reactions along with the surface area of the three native starch granules could be described in a linear function. Therefore, enzymatic hydrolysis of native starches during the initial stage is mainly affected by particle size of starch granules. In case of hydroxyethylated corn starch (HES) and native corn starch, the apparent K m values of the native corn starch and HES hydrolysis reactions showed similar values, but V max of HES was higher than that of native corn starch, which was resulted from reduced activation energy of HES toward a debranching enzyme. From these results, the surface area as well as particle size of granules have important effects on the initial rate at which native starch is digested by debranching enzyme. Also, we could modulate the enzyme activity toward native starch by modifying the surface of native starches.