Identification of plum and peach seed proteins by nLC-MS/MS via combinatorial peptide ligand libraries

Plum (Prunus domestica L.) and peach (Prunus persica (L.) Batsch) seed proteins are a source of bioactive peptides. These seeds, though, are usual residues produced during canning and beverage preparation that, in most cases, are irreversibly lost. The recovery and identification of these proteins might be of importance in human nutrition. This work employs the combinatorial peptide ligand libraries (CPLLs) technology as a tool to reduce the proteins dynamic concentration range. The most suitable extraction and CPLL capture conditions have been obtained and applied for the comprehensive identification of seed proteins. The analysis of recovered species by nLC-MS/MS has allowed the identification of 141 and 97 unique gene products from plum and peach seeds, respectively. It was possible to identify 16 proteins belonging to the Prunus genus. Moreover, a high number of histones and seed storage proteins were identified. Additionally, 21 and 14 bioactive peptides previously identified were found within protein sequences in plum and peach seeds, respectively.

Plums and peaches seeds are cheap sources of proteins that are irretrievably lost after canning and beverage production. Although this kind of residues has been used in animal feed or production of biofuel, they are usually incinerated or sent to landfills, wasting their huge potential. In order to exploit this, it is important to comprehensively study proteins present in plum and peach seeds. Nevertheless, since proteomics analysis is in most cases handicapped by the presence of high-abundance proteins masking the detection of the low-abundance ones, it is important to overcome this challenge. In this sense, combinatorial peptide ligand libraries (CPLLs) have been used in this work to reduce the dynamic protein concentration range to enable the identification of a higher amount of proteins than employing conventional methods. In this work, the better extracting conditions have been optimized and up to 141 and 97 unique gene products from plum and peach seeds have been found, respectively. Moreover, 21 and 14 peptides previously identified as bioactive peptides were ascertained within protein sequences in plum and peach seeds, respectively. For that reason, this research takes the first step in the recovery of these valuable proteins and in the extraction of bioactive peptides, which could be successfully adopted in human nutrition.