Biochemical characterization of the α-Amylase inhibitor in mungbeans and its application in inhibiting the growth of callosobruchus maculatus

• Main Authors: Anussorn Wisessing, Arunee Engkagul, Arunee Wongpiyasatid, Klattawee Choowongkomon
• Other Authors: Mahidol University
• Format: Article
• Published: 2018
• Subjects: Agricultural and Biological Sciences; Chemistry
• Online Access: https://repository.li.mahidol.ac.th/handle/123456789/28530

The insect Callosobruchus maculatus causes considerable damage to harvested mungbean seeds every year, which leads to commercial losses. However, recent studies have revealed that mungbean seeds contain α-amylase inhibitors that can inhibit the protein C. maculatus, preventing growth and development of the insect larvae in the seed, thus preventing further damage. For this reason, the use of α-amylase inhibitors to interfere with the pest's digestion process has become an interesting alternative biocontrolling agent. In this study, we have isolated and purified the a-amylase inhibitor from mungbean seeds (KPSl) using ammonium sulfate precipitation, gel filtration chromatography and reversed phase HPLC. We found that the αa-amylase inhibitor, isolated as a monomer, had a molecular weight of 27 kDa. The α-amylase inhibitor was purified 750-fold with a final yield of 0.4 mg of protein per 30 g of mungbean seeds. Its specific activity was determined at 14.5 U (mg of protein) -1 . Interestingly, we found that the isolated α-amylase inhibitor inhibits C. maculatus a-amylase but not human salivary α-amylase. After preincubation of the enzyme with the inhibitor, the mungbean α-amylase inhibitor inhibited C. maculatus α-amylase activity by decreasing Vmaxwhile increasing the Km constant, indicating that the mungbean α-amylase is a mix noncompetitive inhibitor. The in vivo effect of α-amylase inhibitor on the mortality of C. maculatus shows that the α-amylase inhibitor acts on C. maculatus during the development stage, by reducing carbohydrate digestion necessary for growth and development, rather than during the end laying/ hatching stage. Our results suggest that mungbean α-amylase inhibitor could be a useful future biocontrolling agent. © 2010 American Chemical Society.