title: Identification and characterization of digestive serine proteases from inhibitor-resistant Helicoverpa zea larval midgut.
abstract: Protease inhibitors mediate a natural form of plant defence against insects, by interfering with the digestive system of the insect. In this paper, affinity chromatography was used to isolate trypsins and chymotrypsins from Helicoverpa zea larvae, which had been raised on inhibitor-containing diet. Sensitivity of the fractions to inhibition by plant proteinase inhibitors was tested, and compared to the sensitivity of proteinases found in insects raised on diet to which no inhibitor had been added. The isolated chymotrypsin activity was found to be less sensitive to plant protease inhibitors. The sensitivity of the isolated trypsin activity was found to be intermediate between completely sensitive trypsins and completely insensitive forms that have been previously described. Mass spectrometry was used to identify one trypsin and two chymotrypsins in the partially purified protease fraction. The sequence features of these proteases are discussed in relation to their sensitivity to inhibitors. The results provide insight in the enzymes deployed by Helicoverpa larvae to overcome plant defence.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Bari, Via Amendola 165/A, 70126 Bari, Italy. m.volpicella@biologia.uniba.it
authors.forename: Mariateresa
authors.initials: M
authors.lastname: Volpicella
authors.forename: Jan
authors.initials: J
authors.lastname: Cordewener
authors.forename: Maarten A
authors.initials: MA
authors.lastname: Jongsma
authors.forename: Raffaele
authors.initials: R
authors.lastname: Gallerani
authors.forename: Luigi R
authors.initials: LR
authors.lastname: Ceci
authors.forename: Jules
authors.initials: J
authors.lastname: Beekwilder
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D041981:Gastrointestinal Tract / Q000201:enzymology*; D007525:Isoelectric Focusing; D007814:Larva / Q000201:enzymology*; D007915:Lepidoptera / Q000201:enzymology* / Q000254:growth & development; D013058:Mass Spectrometry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D012697:Serine Endopeptidases