Properties of purified gut trypsin from Helicoverpa zea, adapted to proteinase inhibitors.
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.
Volpicella
Mariateresa
M
Dipartimento di Biochimica e Biologia Molecolare, Università di Bari, Italy.
Ceci
Luigi R
LR
Cordewener
Jan
J
America
Twan
T
Gallerani
Raffaele
R
Bode
Wolfram
W
Jongsma
Maarten A
MA
Beekwilder
Jules
J
D000595:Amino Acid Sequence; D000818:Animals; D002846:Chromatography, Affinity; D004032:Diet; D004064:Digestive System / Q000201:enzymology*; D019476:Insect Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D007814:Larva / Q000187:drug effects / Q000502:physiology; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009036:Moths / Q000502:physiology*; D010940:Plant Proteins / Q000494:pharmacology*; D011480:Protease Inhibitors / Q000494:pharmacology*; D017386:Sequence Homology, Amino Acid; D014357:Trypsin / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D014360:Trypsin Inhibitor, Kunitz Soybean / Q000494:pharmacology; D014361:Trypsin Inhibitors / Q000378:metabolism / Q000494:pharmacology*
D019476:Insect Proteins; D010940:Plant Proteins; D011480:Protease Inhibitors; D014361:Trypsin Inhibitors; D014360:Trypsin Inhibitor, Kunitz Soybean; D014357:Trypsin