MIDGUT PROTEINASE ACTIVITIES IN LARVAE OF ANOPLOPHORA-GLABRIPENNIS (COLEOPTERA, CERAMBYCIDAE) AND THEIR INTERACTION WITH PROTEINASE-INHIBITORS

The major proteinase activities in the larval midgut of a common popla r tree borer, Anoplophora glabripennis, were characterised. Overall di gestive capacity, as measured by casein hydrolysis, showed a pH optimu m between 10 and 11.5, suggestive of serine endopeptidase activity. Tr ypsin, chymotrypsin, and chymotrypsin-like activities were detected us ing specific p-nitroanilide synthetic substrates and by use of specifi c serine endopeptidase inhibitors. These activities also showed pH opt ima in the extreme alkaline range. The absence of cysteine, aspartic, and metallo-endopeptidases were confirmed using class specific protein ase inhibitors. The dominant exopeptidase in the midgut is leucine ami nopeptidase with a pH optimum of 7-9. Carboxypeptidase a and b activit y were barely detectable. A large range of serine endopeptidase inhibi tors were screened and were found to vary widely in their ability to i nhibit casein hydrolysis. Potato proteinase inhibitor 1 (a chymotrypsi n inhibitor) and wheatgerm trypsin inhibitor 1 inhibited particularly effectively in tandem and represent possible candidates for gene trans formation to produce plants tolerant to this pest. (C) 1996 Wiley-Liss , Inc.