ABSTRACT
In germinating barley, the degradation of the grain reserve proteins seems to occur in some stages. The proteinase activities of extracts of germinating cereal grains, when assayed using hemoglobin, casein, or gelatin substrates, increase about 20-fold during germination for 3 to 5 days. A number of observations suggest that the general course of the mobilization of grain reserve protein in other cereals resembles that in barley. Acid serine carboxypeptidases, characterized by pH optima at 4 to 6 and complete inactivation by di-isopropyl-fluorophosphate are the best-known peptide bond hydrolyzing enzymes present in cereal grains. Neutral aminopeptidases are apparently present in the grains of all cereals. In barley grains the neutral aminopeptidases are localized in the embryo and aleurone layer. In resting barley grains the activity is localized in the living tissues like those of the neutral aminopeptidases, but it is higher and it increases in the scutellum during germination.
