Biochemical characterization of digestive amylase of wheat bug, Eurygaster maura (Hemiptera: Scutelleridae)

Abstract

Biochemical characterization of

-amylase in the midgut and salivary glands of Eurygaster maura was conducted. Results showed that -amylase activities were present in the salivary glands and gut. The activity of -amylase in the midgut and in the salivary glands was 0.098 and 0.057 U/ml, respectively. The pH of salivary glands and the gut was determined to be in the range of 5- 5.5 (for the salivary glands) and in the range of 6-6.5 (for the gut), using staining indicator. The optimum pH and temperature for salivary glands and midgut amylase activity was 6-7 and 35-40ºC, respectively. The stability of amylase was highest in the acidic pH (4-5). Ethylenediamine tetraacetic acid (EDTA), urea, sodium dodecyl sulfate (SDS) and Mg2+ inhibited the enzyme activity but, NaCl and KCl enhanced enzyme activity. Based on linear regression analysis of reciprocal starch concentration versus reciprocal amylase activity Km and Vmax were 0.11% and 0.04 mM maltose/min for midgut amylase and 0.298% and 0.071 mM maltose/min for salivary amylase, respectively. Sodium dodecyl sulfate electrophoresis (SDS-PAGE) showed that both midgut and salivary glands contain isozymes.