Abstract
Midgut trypsins from 12 species of tabanids were fractionated by Sephadex G-100 gel nitration and DEAE-cellulose chromatography. Two trypsins, with molecular weights of approximately 15,000–26,000 and 45,000–60,000 were found in Chtysops excitans Walker, Chrysops frigidus Osten Sacken, Chrysops furcatus Walker, Haematopota americana Osten Sacken, and 6 species of Hybomitra [ H. affinis (Kirby), H. arpadi (Szilady), H. frontalis (Walker), H. illota (Osten Sacken), H. lasiophthalma (Macquart), H. nuda (McDunnough)]. Only 1 trypsin was found in Hybomitra pediontis (McAlpine) and in Hybomitra typhus (Whitney). In H. affinis high molecular weight trypsin appears first; low molecular weight trypsin appears 24 hr after ingestion of a blood meal. Both high and low molecular weight trypsins have pH optimum of 7.7 to 8.0 and are inhibited by tosyl-L-lysine chloromethyl ketone (TLCK) and phenylmethane sulphonylfluoride (PMSF). The Km for benzoyl-DL-arginine paranitroanilide (BAPNA) is higher for low molecular weight trypsins than it is for high molecular weight trypsins.
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