Post-translational modifications (PTMs) play important roles in regulating endogenous protein functions. There is an increasing interest in the use of food protein-derived peptides as bioactive compounds. Peptides are chemically reactive and highly susceptible to modifications during food processing. To date, the occurrence of PTMs and their influence on the structure, behaviour and function of food peptides remain largely unknown. The shotgun-based peptidomics workflow was applied in this study to analyze protein hydrolysates generated with pepsin, involving LC-MS/MS analysis followed by a comprehensive database search and peptide/PTM identification. After analyzing 3,972 peptides generated from 560 proteins, a total of 609 PTMs were found in many peptides, including lysine and N-terminal acetylation, C-terminal amidation, asparagine/glutamine deamidation, methylation, trimethylation, methionine oxidation, and pyroglutamylation. Although PTMs occur as a part of natural processes, most of the modifications observed in this study originated from the process used to generate the peptides. Using model peptides, pyroglutamylation at the N-terminal glutamine/glutamate residues significantly altered the solubility, molecular and surface hydrophobicities, isoelectric point, and enzyme inhibitory activities of the peptides, on the basis of in vitro and molecular modeling analyses. This work demonstrates that processing of proteins to produce bioactive peptides can lead to structural modifications that alter the peptide properties. This finding is critical for developing peptide-based functional foods, and in understanding the structure-bioavailability-function relationships of bioactive peptides.

Processing-induced modification on food peptide structure and function

256th National Meeting (2018)

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