A new protein inhibitor of trypsin and activated hageman factor from pumpkin (Cucurbita maxima) seeds
Open Access
- 29 October 1990
- journal article
- Published by Wiley in FEBS Letters
- Vol. 273 (1-2) , 163-167
- https://doi.org/10.1016/0014-5793(90)81075-y
Abstract
A protein inhibitor (CMTI‐V; M r 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 × 10−8 and 4.1 × 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.Keywords
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