tailieunhanh - Báo cáo khoa học: Properties of purified gut trypsin from Helicoverpa zea, adapted to proteinase inhibitors

Pest insects such asHelicoverpaspp. frequently feed on plants expressing protease inhibitors. Apparently, their digestive system can adapt to the presence of protease inhibitors. To study this, a trypsin enzymewas purified from the gut of insects that were raised on an inhibitor-containing diet. The amino-acid sequence of this enzyme was analysed by tandem MS, which allowed assignment of 66% of the mature protein amino acid sequence. This trypsin, called HzTrypsin-S, corresponded to a known cDNA sequence fromHelicoverpa. . | Eur. J. Biochem. 270 10-19 2003 FEBS 2003 doi Properties of purified gut trypsin from Helicoverpa zea adapted to proteinase inhibitors Mariateresa Volnicella1. Luigi R. Ceci2. Jan Cordewener3 Twan America3 Raffaele Gallerani1 . Wolfram Bode4 Maarten A. Jongsma3 and Jules Beekwilder3 1 Dipartimento di Biochimica e Biologia Molecolare Universita di Bari Italy 2Centro di Studio sui Mitocondri e Metabolismo Energetico . Sezione di Trani Italy 3Plant Research International Wageningen the Netherlands 4Max-Planck-Institut fur Biochemie Munchen Germany Pest insects such as Helicoverpa spp. frequently feed on plants expressing protease inhibitors. Apparently their digestive system can adapt to the presence of protease inhibitors. To study this a trypsin enzyme was purified from the gut of insects that were raised on an inhibitor-containing diet. The amino-acid sequence of this enzyme was analysed by tandem MS which allowed assignment of 66 of the mature protein amino acid sequence. This trypsin called HzTrypsin-S corresponded to a known cDNA sequence from Helicoverpa. The amino acid sequence is closely related 76 identical to that of a trypsin HzTrypsin-C which was purified and identified in a similar way from insects raised on a diet without additional inhibitor. The digestive properties of HzTrypsin-S and HzTrypsin-C were compared. Both trypsins appeared to be equally efficient in degrading protein. Four typical plant inhibitors were tested in enzymatic measurements. HzTrypsin-S could not be inhibited by 1000-fold molar excess of any of these. The same inhibitors inhibited HzTrypsin-C with apparent equilibrium dissociation constants ranging from 1 nM to 30 nM. Thus HzTrypsin-S seems to allow the insect to overcome different defensive proteinase inhibitors in plants. Keywords gut Helicoverpa inhibitor insect trypsin. Larvae of the lepidopteran insect species Helicoverpa are a pest in Asia Australia and the Americas. They cause yield .