Date of this Version
J. Biol. Chem. 1942 142: 693-696.
Some time ago we observed that a sulfuric acid hydrolysate of zein prepared in an autoclave at 165˚ did not support growth in young rats when it was supplemented with certain amino acids, even though the same amino acids, added to a hydrolysate prepared by refluxing, permitted moderate growth. Since the optical rotation of the autoclaved hydrolysate was lower than that of the refluxed, either destruction or racemization of essential constituents, or both, might have occurred. Loss of amino nitrogen and production of extra ammonia upon prolonged autoclaving of proteins with acids have been noted by Van Slyke (1912) and others, but simultaneous observations on optical rotation have apparently never been made. To determine whether racemization also takes place, hydrolysates of zein prepared under conditions differing widely with respect to sulfuric acid concentration, temperature, and time were examined for optical rotation, amino nitrogen content, and in some cases for ammonia content.