ABSTRACT
A 7514-Da chymotrypsin inhibitor was isolated from the seed extract of Momordica cochinchinensis (Family Cucurbitaceae) by chromatography on chymotrypsin-Sepharose 4B and subsequently by C18 reversed-phase HPLC. This inhibitor, named MCoCl, possessed remarkable thermostability and was stable from pH 2 to 12. MCoCl also inhibited subtilisin, but had at least 50-fold lower inhibitory activity towards trypsin and elastase. Amino acid sequencing of a peptide fragment of MCoCl revealed a sequence of 23 amino acids. Comparison of this sequence and the molecular mass with those of other protease inhibitors suggests that MCoCl belongs to the potato I inhibitor family.
Subject(s)
Chymotrypsin/antagonists & inhibitors , Momordica/enzymology , Seeds/enzymology , Serine Proteinase Inhibitors/chemistry , Serine Proteinase Inhibitors/pharmacology , Amino Acid Sequence , Chromatography, Affinity , Chromatography, High Pressure Liquid/methods , Molecular Sequence Data , Molecular Weight , Pancreatic Elastase/antagonists & inhibitors , Peptide Fragments/genetics , Sequence Alignment , Serine Proteinase Inhibitors/genetics , Serine Proteinase Inhibitors/isolation & purification , Solanum tuberosum/enzymology , Subtilisins/antagonists & inhibitors , Trypsin/metabolismABSTRACT
Five trypsin inhibitors, with N-terminal sequences demonstrating homology to each other and exhibiting a molecular weight of 5100, 4800, 4400, 4100, and 3900, respectively, were isolated from Momordica cochinchinensis seeds with a protocol involving acid extraction, ion exchange chromatography on SP-Sepharose chromatography, and RP-HPLC on a C18 column. Specific inhibitory activity against trypsin was demonstrated by the trypsin isoinhibitors with Ki values ranging from 5.3 x 10(-8) to 1.8 x 10(-6) M. None of the isoinhibitors could be cleaved by trypsin.
