Digestive processes of hematophagous insects. IX. Some properties of two trypsins from female horse flies and deer flies (Diptera: Tabanidae).

Mid-gut trypsins from 12 species of tabanids were fractionated by Sephadex G-100 gel filtration and DEAE-cellulose chromatography. Two trypsins with molecular weights of about 15 000-26 000 and 45 000-60 000 were found in Chrysops excitans Wlk., C. frigidus Osten Sacken, C. furcatus Wlk., Haematopota americana O.-S. and 6 species of Hybomitra. Only 1 trypsin was found in H. pediontis (McAlpine) and H. typhus (Whitney). In H. affinis (Kby.), the trypsin with the high molecular weight appeared first, and that with the low weight 24 h after ingestion of a blood-meal. Both trypsins had an optimum pH of 7.7-8 and were inhibited by tosyl-L-lysine chloromethyl ketone and phenylmethanesulfonyl fluoride. The Km for benzoyl-DL-arginine p-nitroanilide is higher for trypsins with low molecular weights than for those with high ones.