title: A new protein inhibitor of trypsin and activated Hageman factor from pumpkin (Cucurbita maxima) seeds.
abstract: A protein inhibitor (CMTI-V; Mr 7106) of trypsin and activated Hageman factor (Factor XIIa), a serine protease involved in blood coagulation, has been isolated for the first time from pumpkin (Cucurbita maxima) seeds by means of trypsin-affinity chromatography and reverse phase high performance liquid chromatography (HPLC). The dissociation constants of the inhibitor complexes with trypsin and Factor XIIa have been determined to be 1.6 x 10(-8) and 4.1 x 10(-8) M, respectively. The primary structure of CMTI-V is reported. The protein has 68 amino acid residues and one disulfide bridge and shows a high level of sequence homology to the Potato I inhibitor family. Furthermore, its amino terminus consists of an N-acetylates Ser. The reactive site has been established to be the peptide bond between Lys44-Asp45. The modified inhibitor which has the reactive site peptide bond hydrolyzed inhibits trypsin but not the Hageman factor.
authors.affiliation: Department of Biochemistry, Kansas State University, Manhattan 66506.
authors.forename: R
authors.initials: R
authors.lastname: Krishnamoorthi
authors.forename: Y X
authors.initials: YX
authors.lastname: Gong
authors.forename: M
authors.initials: M
authors.lastname: Richardson
mesh_terms: D000595:Amino Acid Sequence; D005174:Factor XII / Q000037:antagonists & inhibitors*; D008969:Molecular Sequence Data; D011480:Protease Inhibitors / Q000302:isolation & purification*; D012639:Seeds / Q000032:analysis*; D012689:Sequence Homology, Nucleic Acid; D014361:Trypsin Inhibitors / Q000302:isolation & purification*
chemical_list: D011480:Protease Inhibitors; D014361:Trypsin Inhibitors; D005174:Factor XII