Peptidomics analysis of potato protein hydrolysates: post-translational modifications and peptide hydrophobicity

Post-translational modifications (PTMs) often occur in proteins and play a regulatory role in protein function. However, the role of PTMs in food-derived peptides remains largely unknown. The shotgun peptidomics strategy was employed to identify PTMs in peptides from potato protein hydrolysates. Various hydrophobicity-inducing PTMs were found to be located in different potato peptides, e.g. acetylation of lysine, N-terminal of proteins and peptides, C-terminal amidation, asparagine/glutamine deamidaiton, methylation and trimethylation, methionine oxidation, and N-terminal pyro-glutamate formation. Some of the PTMs are likely formed by chemical reactions that occur during isolation and proteolytic processing of potato proteins. The PTMs enhance peptide hydrophobicity, which can improve bioactivity, decrease solubility and increase the bitterness of peptides. This is the first report that food-derived peptides are widely modified by various PTMs associated with hydrophobicity-inducing structural changes. This finding will enhance understanding of the behaviour of bioactive peptides in biological matrices.