Utilization by Chicks of Half-Cystine from Native and Denatured Proteinase Inhibitor Protein from Potatoes 1

Summary

In a proteinase inhibitor protein fraction obtained from the soluble proteins of Russet Burbank potatoes, over 78% of the total half-cystine rich proteins are inhibitors of the pancreatic proteases, trypsin, chymotrypsin, and carboxypeptidase A. This protein fraction was utilized to supplement a half-cystine limited chick diet to determine the availability of half-cystine residues in native and autoclaved (denatured) inhibitor proteins. Chicks fed diets supplemented with native inhibitor protein showed a severe growth depression. Weight gain of chicks fed autoclaved inhibitor protein were equivalent to chicks whose diets were supplemented with half-cystine. The experiments indicated that high protein potato selections based on high inhibitor contents should provide nutritionally available half-cystine, provided the potatoes are cooked before consumption.