Purification of a toxic substance from defatted soy bean flour.

Investigations undertaken to elucidate the mechanism whereby concentrates of the soy bean trypsin inhibitor depress growth have indicated that an inhibition of intestinal proteolysis is not the only factor involved (l-3). In a previous paper (4), it was shown that a concentrate of the soy bean trypsin inhibitor, which had been treated so as to destroy its antitryptic activity, still retained the ability to inhibit the growth of weanling rats when administered by intraperitoneal injection. Evidence was presented for the existence in such a concentrate of a heat-labile, non-dialyzable toxic principle which appeared to be different from the trypsin inhibitor. A high degree of purification of this toxic substance has now been achieved. During the course of its purification a loss in antitryptic activity and an increase in hemagglutinating activity have been observed.