A new protein inhibitor of trypsin and activated hageman factor from pumpkin (Cucurbita maxima) seeds

作者：Ramaswamy Krishnamoorthi, YuXi Gong, Michael A. Richardson · 发表于：FEBS Letters · 年份：1990 · DOI：10.1016/0014-5793(90)81075-y · 被引用次数：64 · 研究领域：Insect Resistance and Genetics、Biochemical and Structural Characterization、Coagulation, Bradykinin, Polyphosphates, and Angioedema

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.