A strong inhibitor of chymotrypsin/elastase is highly antimetabolic to Helicoverpa armigera larvae

Chymostatin is a small non-protein poly-amino acid that specifically inhibits chymotrypsin-like enzymes by covalently binding to their active site. It is therefore a model for tight-binding proteinaceous protease inhibitors of chymotrypsin/elastase specificity. The Lepidopteran Helicoverpa armigera was raised on an artificial diet containing 0.03% chymostatin. After 14 days the experimental animals were approximately twentyfold smaller than the controls, although there was no increase in mortality. The RNA expression levels of the main trypsin gene group were found to decrease while that of the chymotrypsin/elastase gene group increased. Changes in activity of the midgut protease enzymes did not correlate to these changes in RNA expression.