An improved method for the purification of eggplant trypsin inhibitor

The trypsin inhibitor in eggplant, Solanum melongena L., was isolated and purified by the improved method with the techniques of dialysis using acetylated cellulose tube and ion-exchange chromatography on DEAE-Sephadex. The final preparation was found to be homogeneous by disc and SDS-polyacrylamide gel electrophoresis. This inhibitor had the molecular weight of about 6,200, the pI value of 4.7, and furthermore characteristic amino acid composition lacking in tryptophan, histidine, valine and methionine. The trypsin inhibition data indicated that the purified inhibitor combined with bovine trypsin [EC 3.4.21.4] in the molar ratio of 1:1. These properties of this inhibitor were in agreement with those of the dialyzable eggplant trypsin inhibitor previously purified, indicating that the dialyzable and non-dialyzable inhibitors in eggplant are identical.