Preparation and Characterization of a Trypsin Inhibitor from Glycine max (L.) merr

A trypsin inhibitor with thermal and pH stability, designated Mercine, was prepared from seeds of Glycine max (L.) merr. The preparation procedure involved ammonium sulfate precipitation, ion-exchange chromatography on CM-Sephadex C-50, affinity chromatography on Affi-gel blue gel. The 20 N-terminal amino acid sequences were determined to be DEYSKPCCDLCMCTRRMPPQ, demonstrating highly homologies with the sequence of Bowman-Birk type trypsin inhibitors. The molecular mass and isoelectric point of the inhibitor were estimated by SDS-PAGE and isoelectric focusing to be 17.9 kD and 4.6, respectively. Trypsin could be completely inhibited by Mercine when the molar ratio was 8.0. The inhibitory activity of Mercine was unaffected after exposure to temperatures up to 80C, or within the pH range 2-12. Besides inhibiting trypsin-chymotrypsin, the inhibitor Mercine demonstrated additional antifungal activity toward the species of Alternaria alternate, Fusarium oxysporum, Pythium aphanidermatum, Physalospora piricola and Botrytis cinerea.