The results obtained for the A. oryzae protease can likely
be explained by the fact that this enzymatic mixture should
be composed of different enzymes, which may individually
favor or hinder the release of peptides with ACE-IA.
According to the Merops database (Rawlings et al. 2010),
there are 126 types of proteases/peptidases that can be produced
by this type of fungus. In addition, the lower ACE-IA
values found for the A. oryzae protease, compared to the
B. licheniformis protease and pancreatin, may most likely be
attributable to its lower enzymatic activity (0.69 versus
5.97 U/mL and 6.22 U/mL, respectively).
The worst performing enzyme was the A. sojae protease,
and this result can be explained by the fact that it is an
exopeptidase (NC-IUBMB 2011) that produces free amino
acids that have low ACE-IA. Although no work in the literature
affirms that free amino acids do not have this inhibitory
action, according to Lopez-Fandino et al. (2006), the
peptides that inhibit ACE usually contain from 2 to 12
amino acid residues. Moreover, this enzyme had the lowest
activity (0.63 U/mL) among all the enzymes used in the
current study.