title: Characterization of a highly stable trypsin-like proteinase inhibitor from the seeds of Opuntia streptacantha (O. streptacantha Lemaire).
abstract: A trypsin inhibitor from Opuntia streptacantha Lemaire (Prickly pear) seeds was purified and characterized. Of several proteases tested, this inhibitor showed specificity to trypsin-like enzymes. The major inhibitor present in these seeds showed distinctive characteristics, most notably a low molecular weight of 4.19 kDa, as determined by MALDI TOF, and an unusually high thermal stability, retaining most of the activity after heating the sample 1h to 120 degrees C with a pressure of 1 kg/cm(2). Its complete amino acid sequence was obtained through mass spectrometry, this establishing presence a blocked N-terminal region. When comparing its sequence in the MEROPS database for peptidases and peptidase inhibitors, it showed 34.48% identity with a serine-proteinase inhibitor from the I15 family.
authors.affiliation: Centro de Investigación y de Estudios Avanzados del I.P.N., Unidad Irapuato, Km. 9.6, Libramiento Norte Carr., Irapuato-León A. P. 629, Irapuato, Gto. 36821, Mexico.
authors.forename: J A
authors.initials: JA
authors.lastname: Torres-Castillo
authors.forename: C
authors.initials: C
authors.lastname: Mondragón Jacobo
authors.forename: A
authors.initials: A
authors.lastname: Blanco-Labra
mesh_terms: D000595:Amino Acid Sequence; D013058:Mass Spectrometry; D008970:Molecular Weight; D029747:Opuntia / Q000201:enzymology*; D012639:Seeds / Q000201:enzymology; D017385:Sequence Homology; D015842:Serine Proteinase Inhibitors; D013696:Temperature; D014361:Trypsin Inhibitors / Q000737:chemistry / Q000302:isolation & purification*
chemical_list: D015842:Serine Proteinase Inhibitors; D014361:Trypsin Inhibitors