In Vitro Properties of Protease in the Midgut of the Adult Horn Fly, Haematobia irritans L. : Diptera : Muscidae

Abstract

Some properties of protease in the midgut of the adult horn fly, Haematobia irritans L., were clarified and compared with those of the stable fly, Stomoxys calcitrans L. In the horn fly the protease was most active at 45°C and pH 8.5, while in the stable fly it was most active at 45°C and pH 9.5. The proteases of both species were inhibited by more cations at pH 9.5 than at pH 8.5 or 8.0. The activities of trypsin-like enzyme were suppressed only by Hg⁺⁺ and Zn⁺⁺, while those of aminopeptidase were inhibited by various cations including Mg⁺⁺, cysteine and ascorbic acid.