Digestive proteolytic activity in the gut and salivary glands of the predatory bug Podisus maculiventris (Heteroptera: Pentatomidae); effect of proteinase inhibitors
Bell, H.A.(Central Science Laboratory, York (United Kingdom))E-mail:[email protected] | Down, R.E.(Central Science Laboratory, York (United Kingdom)) | Edwards, J.P.(Central Science Laboratory, York (United Kingdom)) | Gatehouse, J.A.(University of Durham (United Kingdom). Dept. of Biological Sciences) | Gatehouse, A.M.R.(University of Newcastle, Newcastle upon Tyne (United Kingdom). Inst. for Research of the Environment and Sustainability)
The aim of this study was to characterise the digestive and salivary proteinases of Podisus maculiventris. The optimal pH for adult and nymph proteolysis was pH 6.0 and pH 6.5, respectively. Activity of both adult and nymphal gut extracts, detected by the hydrolysis of Z-Phe-Arg-pNA, was inhibited to less than 20% of control levels by several inhibitors (e.g. E-64 and chicken egg white cystatin) associated with the inhibition of cysteine proteinases. Proteolytic activity was due to at least four proteinases ( of ca. 30, 36, 50 and 110 kDa) which were all susceptible to E-64 inhibition. Salivary gland extracts gave maximal activity at pH 8.0 when tested for general proteolytic activity using fluorescent BODIPY-FL casein substrate, and showed moderate levels of inhibition when incubated with inhibitors of serine-, cysteine-, aspartic- and metallo-proteinases. Leupeptin and PMSF gave the highest levels of inhibition of salivary proteolytic activity.
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