ALPHA-AMYLASE ACTIVITIES OF AGRICULTURAL INSECT PESTS ARE SPECIFICALLY AFFECTED BY DIFFERENT INHIBITOR PREPARATIONS FROM WHEAT AND BARLEY ENDOSPERMS

In vitro α-amylase (EC 3.2.1.1) activity from 23 agricultural insect pests, including moths, cereal aphids, pentatomids, cereal thrips, stored cereal and legume grain pests and colorado potato beetle, have been determined. Enzyme activity per unit of body weight was higher in extracts from stored cereal pests as compared with the other insect groups. Crude inhibitor preparations from the endosperms of Triticum aestivum, Hordeum vulgare and Triticum monococcum were decreasingly active in that order. The three classes of α-amylase inhibitors from T. aestivum - monomeric, dimeric and tetrameric - were differentially active against crude enzyme preparations from different insect species. This was further confirmed by testing the purified dimeric (0.19 and 0.53) and monomeric (0.28) inhibitors. The monomeric inhibitor was considerably more active against the α-amylase from Tenebrio molitor and Sitophilus oryzae than the dimeric ones, whereas the opposite situation occurs for the α-amylase from Leptinotarsa decemlineata and Oryzaephilus surinamensis. Both types of purified inhibitors were about equally active against other insect enzyme preparations tested. © 1990.