Biochemical characterization of alpha -amylase of the Sunn pest, Eurygaster integriceps.

摘要

The alpha -amylase in the midgut and salivary glands of Eurygaster integriceps was isolated and characterized. The specific activity of alpha -amylase in the midgut was 1.77 U/mg protein and in the salivary glands was 1.65 U/mg protein. Sodium dodecylsulfate electrophoresis showed that both midgut and salivary glands contain isozymes. Only a trace amount of alpha -amylase activity was detected in the first nymphal stage (0.19 U/mg protein), whereas alpha -amylase activity was highest in the third nymphal stage (1.21 U/mg protein). The results show that alpha -amylase activity in the immature stages increase constantly to the third instar stage. There was no significant difference in enzyme activity between the third, fourth and fifth nymphal stages and adults. The optimum pH and temperature for the enzyme activity was determined to be 6.5 and 35 degrees C, respectively. The enzyme activity was inhibited by addition of ethylenediaminetetraacetic acid, urea, sodium dodecylsulfate and Mg2+, but NaCl and KCl enhanced enzyme activity..