Peptidomic analysis of hydrolyzed oat bran proteins, and their in vitro antioxidant and metal chelating properties

Peptide profiles of hydrolyzed oat proteins and the susceptibility of their polypeptides to proteolytic cleavages were determined using peptidomic analysis. In addition, antioxidant activities were also measured. Proteins isolates were first extracted with carbohydrases, Viscozyme or Cellulase and then hydrolyzed with proteases (Alcalase, Papain, Protamex, Flavourzyme). Amongst the eight hydrolysates, Viscozyme-proteins hydrolyzed with Papain showed the highest ability to quench ABTS(center dot+) radicals (866.9 +/- 10.6 mu M TE/g) and to chelate ferrous ions (75 +/- 0.4%) while displaying the second strongest activity for ROO' radicals (396.7 +/- 14.0 mu M TE/g). Peptidomics analysis showed that the higher activity of papain hydrolysate in most assays was related to its greater proteolytic action on main proteins (avenin, 11S- and 12S-globulins) compared to other proteases. In addition, the number of peptides identified in the Papain digest of proteins extracted with Viscozyme was about half relative to the number in proteins from bran treated with Cellulase and digested with the same protease. This was likely because the carbohydrases differently affected polypeptide secondary structures.