Amylolytic enzymes from the digestive tract of the giant cricket Brachytrupes membranaceus (Orthoptera: Gryllidae): enzymatic profiles and biochemical characteristics of activities

The activity of a crude enzyme preparation extracted from hepatopancreas in the digestive tract of the giant cricket Brachytrupes membranaceus (Drury) was assayed for amylase and α-glucosidase. Amylase- and α-glucosidase-specific activities were estimated to be 3.31 and 13.02 UI/mg, respectively. The zymogram analysis of the crude enzymatic extract showed the existence of two isoforms of amylase. For α-glucosidase, the zymogram analysis showed one form only. Both the amylolytic activities exhibited optimum pH at 6.6 and 7.0, respectively, for amylase and α-glucosidase. As for optimum temperature, values were estimated at 55 and 40 °C for amylase and α-glucosidase activities, respectively. Amylase activity was found to be stable at pH 6.6–7.6 and temperatures up to 55 °C. The corresponding values for α-glucosidase were pH 6–7 and up to 40 °C. Amylolytic enzymes of B.membranaceus were activated by Ca2+ and Ba2+ and inhibited by chemical agents such as ethylenediaminetetraacetic acid, 4-chloromercuribenzoic acid and dithionitrobenzoic acid. The analysis of hydrolytic products after soluble starch hydrolysis by the enzyme preparation from the digestive tract of B. membranaceus by thin layer chromatography revealed that glucose and maltose were the major products. The present study showed that these amylolytic enzymes play a fundamental role in energy production for this insect.