Preparation and characterization of phosphopeptides derived from egg yolk granules

Phosphorylated peptides derived from egg yolk phosvitin (PPP) have been reported with various physiological functions such as mineral absorption promoting, antioxidant, antimicrobial and anti-inflammatory activities. However, the animal/clinical study and commercial application of PPP was hampered by the difficulties in phosvitin purification and peptide fragmentation. This study introduced a new approach to prepare phosphopeptides from egg yolk granules to avoid difficulties obtaining purified phosvitin. The egg yolk granules were first dephosphorylated by 0.2 N NaOH for 0.5 h and then hydrolyzed by eight enzymes, respectively. Pancreatin produced the highest degree of hydrolysis of 24.2% with a protein recovery of 41.8% and nitrogen to phosphorus atomic ratio of 19.1, which is comparable to commercial casein phosphopeptides. In the pancreatin hydrolysate 15 peptide sequences were characterized from three phosvitin domains: AKTSSSSSSASSTATSSSSSSASSPN (PV 9-34), DEEENDQV (PV 40-47) and SGHLEDDSSSSSSSSVLSKIWG (PV 190-211). In addition, 54 peptides were characterized from lipovitellins, and 26 of them were phosphorylated. This experiment suggests that it is feasible to produce phosphopeptides from granules instead of purified phosvitin.