Isolation and characterization of trypsin inhibitors from wheat germ

Trypsin inhibitors were isolated from wheat germ and two major inhibitors (trypsin inhibitors I and II) were purified by various chromatographies including ion-exchange chromatographies on DEAE-Sephadex and CM-Sephadex as well as gel filtration on Bio-gel and Sephadex. Both inhibitors were polypeptides composed solely of amino acids. In the presence of 1% SDS, inhibitor I showed a single symmetrical sedimentation boundary of 1.6 S and a single band in SDS-gel electrophoresis, but in the absence of SDS, it tended to aggregate. Inhibitor II was found to be homogeneous in gel electrophoresis and velocity sediemntation with or without SDS in the solutions. The molecular weights of inhibitors I and I were approxiamtely 16,000 and 10,000, respectively, by SDS-gel electrophoresis. Some other properties of the two inhibitors, including specific inhibitory activities, amino acid compositions and UV spectral properties are presented.