Studies On The Activity Differences, Types And Mechanism Of Debranching Enzyme In Wheat Grains

DBE is one of the key enzymes, which plays an important role in the formation of amylopectin. Under the optimized conditions for the enzyme extracting and activity analysis, we compared the changes of DBE activity during different stages among different wheat.cultivars. Furthermore, DBE was purified and its characterization was studied for the first time. This will establish theoretical foundation for further research on the mechanism of amylopectin formation in endosperms of wheat in the future. The main results are as follows:1 Optimization of conditions for extracting and activity analysis of DBEUsing potato amylopectin as substrate, the conditions for extracting and activity analysis of DBE in the endosperms of wheat were studied. The results indicated that the amount of 2-BE had great impact on DBE activity when the enzyme was extracted. With the amount of 2-BE increasing, the enzyme activity had the trend to ascend. It attained maximum when the amount of 2-BE was equal to 50-60mmol/L. the results also showed that DBE activity was affected by different buffers and pH value. As pH value rose to 6.5, DBE activity increased to max, and then decreased. Under the same pH value, enzyme activity was the highest with MES-NaOH buffer. It was found that the enzymatic reaction was stable at 30℃within 120min. In a word, the extracting conditions of DBE were that the amount of 2-BE should be to 50-60mmol/L that of using MES-NaOH (pH6.5) as extracting buffer. The enzymatic reaction should be performed at 30℃within 120min and the testing wavelength ought to be 540nm.2 Changes of DBE activity during different stages among different cultivarsThe changes of DBE activity among four wheat cultivars, named Nuomai 1, Guandong 107, Jinan 16 and Lumai 21, were investigated in the paper. As a result, during different stages of filling, the changes of DBE activity were similar among the four cultivars. From 14 to 21d, the enzyme activity preserved rather high then decreased rapidly from 35d to mature. It hinted that...