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A new protein inhibitor of trypsin and activated hageman factor from pumpkin ( Cucurbita maxima ) seeds
Author(s) -
Krishnamoorthi Ramaswamy,
Gong YuXi,
Richardson Michael
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)81075-y
Subject(s) - cucurbita maxima , trypsin , chemistry , kunitz sti protease inhibitor , trypsin inhibitor , serine protease , biochemistry , chymotrypsin , protease , enzyme , biology , botany
A protein inhibitor (CMTI‐V; M r 7106) of trypsin and activated Hageman factor (Factor XII a ), 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 XII a 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 Lys 44 ‐Asp 45 . The modified inhibitor which has the reactive site peptide bond hydrolyzed inhibits trypsin but not the Hageman factor.