Aminopeptidases as potential targets for the control of the Australian sheep blowfly, Lucilia cuprina

A series of experiments were carried out to investigate the role of protein ase enzymes in the growth of larvae of the sheep blowfly, Lucilia cuprina. First, instar larvae were incubated on an artificial growth media in the pr esence of various concentrations of inhibitors of all the major proteinase classes. Inhibitors of serine proteinases and aminopeptidases were found to cause significant growth inhibition and in some cases death of the larvae within 24 h, suggesting that these enzymes were the major classes involved in protein digestion in the gut of the insect. A second group of experiment s analysed the effects of two inhibitors from the same or different protein ase classes in the growth media. Synergistic inhibition of larval growth wa s observed with the incorporation of inhibitors of serine proteinases and a minopeptidases. The results suggest that these classes of proteinases are b oth central to protein digestion in this insect, probably in the gut, and t hat the inhibition of both types of activity leads to an almost complete bl ockade of digestion. Testing in vivo gave similar results with infections o n sheep skin inhibited by either serine proteinase or aminopeptidase enzyme inhibitors and the combination of both stopped the infection process. The role of aminopeptidases in larval metabolism and as potential targets for b lowfly control agents is examined. (C) 1999 Australian Society for Parasito logy Inc. Published by Elsevier Science Ltd. All rights reserved.