title: Purification and partial characterization of a Schizolobium parahyba chymotrypsin inhibitor.
abstract: Schizolobium parahyba seed chymotrypsin inhibitor (SPC) is a protein with M(r) of 20,000 and four half-cystine residues and no free thiol group. SPC is stable at temperatures up to 75 degrees at pH 7 but gradually loses activity when kept at 95 degrees for 1 hr and total inactivation occurs after 5 hr. Amino acid analysis shows a high content of glycine, aspartate, glutamate and alanine residues. A pI of 4.52 predicted from the amino acid content agrees with experimental results. A stable binary complex with M(r) of 45,000, Ki = 5.85 x 10(-8) M and molar ratio of 1:1 is formed between SPC and chymotrypsin. The determined single N-terminal sequence of SPC shows homology with Kunitz type soybean trypsin inhibitors.
authors.affiliation: Departamento de Biologia Celular, Universidade de Brasilia, DF, Brazil.
authors.forename: E M
authors.initials: EM
authors.lastname: Souza
authors.forename: K
authors.initials: K
authors.lastname: Mizuta
authors.forename: M U
authors.initials: MU
authors.lastname: Sampaio
authors.forename: C A
authors.initials: CA
authors.lastname: Sampaio
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D002918:Chymotrypsin / Q000037:antagonists & inhibitors*; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000302:isolation & purification*; D017386:Sequence Homology, Amino Acid; D013438:Sulfhydryl Compounds / Q000032:analysis; D014197:Trees / Q000737:chemistry*
chemical_list: D000596:Amino Acids; C096591:Chymotrypsin inhibitor protein, Schizolobium parahybum; D010940:Plant Proteins; D013438:Sulfhydryl Compounds; D002918:Chymotrypsin