0005, 0.005, 0.001). To determine the pattern of midgut proteinase activity with respect to pH in fifth instar nymphs of T. brasiliensis the wide-ranging proteinase substrate gelatine was used. Gelatinase activity of electrophoretic separated proteins led to a degradation of the gelatine matrix and appeared in colorless, non-stainable areas in the gel. Only fresh midgut content samples showed proteolytic

activity, samples stored at −20 °C lost the major part of their activity and could not be visualized by the methodology used in the present study (data not shown). Both, the small intestine content ( Fig. 5) and the small intestine tissue samples (data not shown) showed up to four distinct bands of proteolytic degradation, although the see more activity of the gut content was Selleck GSK3 inhibitor always more intense. Stomach content of unfed fifth instar nymphs never generated proteolytic activity bands (data not shown). Content of small intestine at 5 daf produced three broad proteolytic activity bands corresponding to the molecular weights of cysteine proteinases (about 28–35 kDa), showing the maximum intensity at pH 4.5. Therefore further experiments were carried out at this pH value. Also among the other tested conditions proteolytic degradation of gelatine became visible (Fig. 5A). Only at a pH 3.5 and 4.0 an additional band of about

45 kDa was visible in T. brasiliensis samples. In small intestine homogenates of T. infestans this 45 kDa band remained visible also in all tested pH values in a similar intensity (data not shown). The other activity band detected in the small intestine of T. infestans slightly differed in their molecular weight from those of T. brasiliensis ( Fig. 5B). Using specific proteinase inhibitors, the analysis revealed that the midgut activity contained cysteine like enzymes in small intestine samples at 5 daf (Fig. 5B). E-64 fully inhibited all proteinase

activity bands of T. brasiliensis after 30 min incubation at room temperature, while in T. infestans a residual activity of the 45 kDa band remained ( Fig. 5B). After incubation with the specific cathepsin B inhibitor CA-074, in T. infestans 22.9% and in T. brasiliensis 72.5% of remaining activity was detected. After incubation with E-64 at 4 °C a residual activity was visible in T. brasiliensis Alanine-glyoxylate transaminase small intestine samples, indicating a minor affinity of the inhibitor to the enzyme at low temperatures (data not shown). Cathepsin activity was detected in unfed insects and at 3, 5 and 10 daf, at 15 daf no activity was observed. Proteolytic activity increased at 3 daf and reached its maximum at 5 daf (Fig. 5C). To verify the zymography results of intestinal triatomine cathepsins, the midgut content samples were separated by SDS–PAGE and analyzed by immuno blotting using specific antibodies to Helicoverpa armigera cathepsin L. H. armigera mature cathepsin L amino acid sequence has an identity of 70.0 and 69.6% with that of TBCATL-1 and TBCATL-2, respectively.