Isolation of trypsin isozymes from the mosquito Aedes aegypti (L.)

Trypsin has been isolated from midgut homogenates of blood-fed females of Aedes aegypti by a simple two-step purification procedure: ion-exchange chromatography followed by affinity chromatography. The resulting mosquito trypsin contains a number of isozymes, among which 5 major SDS-PAGE bands are recognized with molecular weights of 26.7, 28.5, 29.7, 31.0 and 32.0 kdaltons, as are some minor bands above and below this range. The isozymic pattern is comparable to that in crude homogenates. Isoelectric focussing of purified trypsin however, revealed over 20 tryptic isozymes, demonstrating that several isozymes segregate into subforms. A high correlation between TAME-active fractions and their DFP equivalent was demonstrated by using ³H-labelled DFP as a marker for trypsin on native acrylamide gels.The purification factor and the specific activities are discussed with respect to the unusual amounts of protein of dietary origin present in the midgut homogenates. Interference of blood-borne coagulation factors of a tryptic nature is unlikely.