Date of this Version
J. Biol. Chem. 1942 142: 697-704.
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