Cereal Chem 47:597 - 606.  |  VIEW ARTICLE
Heterogeneity of Soybean Trypsin Inhibitor. I. Chromatographic Fractionation and Polyacrylamide-Gel Electrophoresis.

T. Obara, M. Kimura-Kobayashi, T. Kobayashi, and Y. Watanabe. Copyright 1970 by the American Association of Cereal Chemists, Inc. 

A soybean trypsin inhibitor (TI) fraction which contained all trypsin and chymotrypsin inhibitor activities of water-extractable soybean protein was obtained by Sephadex G-75 gel filtration. Eleven electrophoretic protein bands were obtained by polyacrylamide-gel electrophoresis of the inhibitor fraction. Ten bands had TI activity. The soybean TI fraction was fractionated by DEAE-cellulose chromatography into eight fractions. Seven of these (I, I-1, II, III, IV-1, IV-2, and V) were TI-active. Fractions I, I-1, II, and III were classified as cystine-poor inhibitors (less than 2% half-cystine) and were electrophoretically heterogeneous. Fractions I, I-1, and II were trypsin inhibitors with essentially no chymotrypsin-inhibitor activity. Fraction III had the highest TI activity. Fractions IV-1 and IV-2 were cystine-rich inhibitors (more than 8% half- cystine) and had relatively high chymotrypsin-inhibitor activity. Fraction V was identified as the Kunitz inhibitor and SBTIA-2. The major components of III, IV-1, and IV-2, respectively, corresponded to SBTIB-1, SBTIB-2, and SBTIA-1 of Rackis and Anderson. The N-terminal amino acid of II, III, IV-1, IV- 2, and V was aspartic acid.