Studies in Mice on the Isolation and Characterization of Growth Inhibitors from Soybeans

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Abstract
The pH 4.4 supernatant from raw (unheated) soybean meal was separated into five fractions on a Sephadex G-25 column in efforts to isolate the animal growth inhibitors present in soybeans. Each fraction was added to the diet of weanling mice, and growth inhibitor activity was determined by comparing their growth rates to growth rates achieved when an autoclaved soybean meal diet was fed. Fractions 1 and 2 contained 37 to 45% and 40 to 50% of the growth inhibitor activity, respectively, with a trace in fraction 3 and none in fractions 4 and 5. Only fraction 1 contained trypsin inhibitor and caused pancreas enlargement. Fraction 1 was further separated into two fractions (G-50-1-a and G-50-1-b) on a Sephadex G-50 column. Fractions G-50-1-a and G-50-1-b both contained growth inhibitor activity, whereas only fraction G-50-1-b contained trypsin inhibitors and caused pancreas enlargement. Fraction 2 (approximately 1,200 molecular weight) was further separated into two fractions (PC-2-a and PC-2-b) using a phosphocellulose column eluted with a KCl gradient. Fractions PC-2-a and PC-2-b both contained growth inhibitor activity although specific activity (units/g) was highest in PC-2-b. PC-2-a, but not PC-2-b, contained polysac-charide whereas both contained peptides. Amino acid analysis of G-25-2 showed that it contained all major amino acids, with only a trace of cystine and low levels of methionine.