Biochemistry, Department of


Date of this Version



J. Biol. Chem. 1942 142: 697-704.


Copyright 1942 the authors.


In a previous paper (Borchers and Berg, 1942) we showed that

autoclaving zein with sulfuric acid longer than necessary for complete

hydrolysis causes destruction and racemization; either of

these might account for the failure of such a hydrolysate to

promote growth in young rats when substituted for a hvdrolysate,

prepared by refiuxing, in a diet which produced moderate growth.

It seemed to us that this deterioration in the dietary protein might

well be the result primarily of essential amino acid deficiencies

which could be detected and overcome by appropriate supplementation.

Because threonine is known to be present in zein in

relatively small amount1 and because its 2 asymmetric carbon

atoms might render it more susceptible to configurational modification

by racemization, a ready production of threonine deficiency

was considered likely. This was confirmed; addition of threonine

to an autoclave hydrolysate (heated with 10 per cent sulfuric acid

for 8 hours at 165°) promoted about as rapid growth as had the

reflux hydrolysate which it replaced. Longer heating at higher

temperatures produced deficiencies not fully met by threonine