木薯淀粉分支酶活性测定方法比较研究

Comparison of Activity Measuring Methods of Cassava Starch Branching Enzyme

旨在找到木薯淀粉分支酶活性有效测定方法。以成熟期的木薯块根为材料,对现有的淀粉分支酶活性测定方法从酶液提取液、酶液浓度、反应体系、反应时间和酶反应终止方式作了比较和改进。木薯淀粉分支酶活性测定的有效方法:取0.5 g成熟木薯块根,加入提取液研磨成浆,离心后上清为粗酶液,粗酶液稀释后加0.5%可溶性淀粉,37℃恒温水浴中保温10 min后置沸水浴中终止反应,再加碘液显色反应10 min后测定波长660 nm处吸光度值,每降低一个百分率的碘蓝值即为木薯淀粉分支酶SBE的一个活性单位(U)。改良后的淀粉分支酶活性测定方法能很好的区分木薯不同株系淀粉分支酶活性差异,实验重复性好,操作简单、快捷。

An effective method for measuring activity of starch branching enzyme was developed in this study.Tuberous roots of mature cassava were collected as materials to study various reaction parameters of the starchbranching enzyme（SBE）, including extracting solution of enzyme, enzyme concentration, reaction system,reaction duration and termination methods. Finally, we introduced an improved method for detecting activity ofcassava starch branching enzyme. Firstly, 0.5 g root of mature cassava was ground into pulp with extractingsolution. Then, the crude enzyme solution was obtained from the supernatant after centrifugation. The crudeenzyme solution was diluted and added with 0.5% soluble starch at 37℃ water bath for 10 min. Then, thereaction was terminated by boiling water. Iodine solution and KI were added to conduct chromogenic reactionfor 10 min. The activity of enzyme was measured at 660 nm. One unit of cassava SBE activity was defined asthe amount of substrate causing 1% decrease in absorbance of iodine blue at 660 nm. The improved method issimple and rapid for measuring activity of starch branching enzyme from different cassava germplasms withexcellent repeatability.