ISOLATION AND CHARACTERIZATION OF A TRYPSIN-LIKE-ENZYME FROM THE BUFFALO FLY, HAEMATOBIA-IRRITANS EXIGUA

The incorporation of soybean trypsin inhibitor (SBTI) into the diet of the buffalo fly, Haematobia irritans exigua (De Meijere), results in increased mortality and reduced fecundity. A trypsin-like enzyme which binds to SBTI was isolated by affinity chromatography on a Sepharose-SBTI column followed by ion-exchange, chromatography. The enzyme was inhibited by benzamidine, phenylmethylsulfonyl fluoride, ovomucoid, leupeptin and alpha-2 macroglobulin. The enzyme was not inhibited by EDTA or p-chloromecuribenzoic acid and had abroad pH optimum of pH 7-9. Vaccination of, sheep produced antibodies specific for the trypsin-like enzyme which inhibited enzyme activity in vitro but did not affect the survival of flies maintained in in vitro culture.