title: A trypsin inhibitor from Cassia obtusifolia seeds: isolation, characterization and activity against Pieris rapae.
abstract: A trypsin inhibitor was isolated from Cassia obtusifolia by ammonium sulfate precipitation, Sepharose 4B-trypsin affinity and Sephadex G-75 chromatography. The inhibitor consisted of a single polypeptide chain with a molecular mass of 19, 812.55 Da. It was stable from pH 2 to 12 for 24 h, whereas it was unstable either above 70 degrees C for 10 min or under reduced conditions. The inhibitor, which inhibited trypsin activity with an apparent Ki of 0.3 microM, had one reactive site involving a lysine residue. The native inhibitor was resistant to pepsin digestion, whereas the heated inhibitor produced 40% degree of susceptibility. The disulfide linkage and lysine residue were important in maintaining its conformation. Partial amino acid sequence of the purified protein showed a high degree of homology with various members of the Kunitz inhibitor family. Moreover, the inhibitor showed significant inhibitory activity against trypsin-like proteases present in the larval midgut on Pieris rapae and could suppress the growth of larvae.
authors.affiliation: College of Life Science, Sichuan University, Chengdu, China.
authors.forename: Hai
authors.initials: H
authors.lastname: Liao
authors.forename: Wei
authors.initials: W
authors.lastname: Ren
authors.forename: Zhuang
authors.initials: Z
authors.lastname: Kang
authors.forename: Jia-Hong
authors.initials: JH
authors.lastname: Jiang
authors.forename: Xiao-Jun
authors.initials: XJ
authors.lastname: Zhao
authors.forename: Lin-Fang
authors.initials: LF
authors.lastname: Du
mesh_terms: D000818:Animals; D002080:Butterflies / Q000187:drug effects* / Q000502:physiology*; D002366:Cassia / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D010572:Pest Control, Biological / Q000379:methods*; D010936:Plant Extracts / Q000008:administration & dosage / Q000737:chemistry; D014361:Trypsin Inhibitors / Q000008:administration & dosage* / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D010936:Plant Extracts; D014361:Trypsin Inhibitors