title: Isolation and some properties of a trypsin inhibitor from seeds of Schizolobium parahyba (Vell.) Toledo.
abstract: A trypsin inhibitor was isolated as a homogenous protein from the seeds of guapuruvu-tree (Schizolobium parahyba (Vell.) Toledo). In addition to its strong inhibitory activity against trypsin the purified inhibitor presented a lesser activity against alpha-chymotrypsin. The purification of the protein inhibitor was achieved from the crude extract of deffated seeds through ammonium sulphate salting-out, successive chromatographies on Sephadex G-75 and DEAE-Sephadex A-50 columns followed by preparative polyacrylamide-slab electrophoresis. The following properties were presented by the purified inhibitor: molecular weight of 12,000 daltons, as estimated by gel filtration; isoelectric point at pH 5.0 - 5.2, by electrofocusing; combining molar ratio of 1:1 (mole trypsin/mole inhibitor), on the basis of inhibition assay and the molecular weight of 29,800 daltons found for the trypsin-inhibitor complex; A1%1-cm = 4.35, at 275 nm and pH 7.0. The inhibitor presents a high content of cystine (14 cystinyl residues per molecule) and is entirely devoid of methionine, tryptophan and free sulhydryl groups. The fluorescence spectra are typical for tyrosine with a strong quenching of emission indicated by the quantum yield. The circular dichroism spectra suggest a predominantly unordered structure for the inhibitor molecule.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D002848:Chromatography, DEAE-Cellulose / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D007887:Fabaceae / Q000032:analysis / Q000201:enzymology*; D010946:Plants, Medicinal; D011506:Proteins / Q000032:analysis; D012639:Seeds / Q000032:analysis / Q000201:enzymology*; D014361:Trypsin Inhibitors / Q000302:isolation & purification*
chemical_list: D000596:Amino Acids; D011506:Proteins; D014361:Trypsin Inhibitors