Purification and partial-characterization of a protease inhibitor from Drosophila melanogaster

A protein from Drosophila melanogaster which inhibits bovine alpha-chymotrypsin activity was purified using an extensive extraction procedure. SP-Sephadex column chromatography and affinity column chromatography. The inhibitor has an estimated molecular weight of approx. 12 000 and is extremely pH and heat stable. It did not exhibit any inhibitory activity against trypsin from numerous sources nor mosquito larval chymotrypsin but did inhibit adult mosquito chymotrypsin. Chymotrypsin-like activity has not been found in Drosophila and therefore the function of the inhibitor is unknown. Preliminary work indicates that it effectively inhibits cathepsin D activity from a nematode parasite and rabbit liver.