Functional proteomics analysis of Triticum durum germ

Wheat germ has been shown to contain a wide range of bioactive molecules with beneficial effects on human health. The identification of specific biomarkers could be effective in assessing the wheat germ content of wheat-based products. To date, wheat germ agglutinin (WGA), a lectin predominantly found in the germ tissue of wheat kernels, has been evaluated as a biomarker of whole-grain wheat. In this study, we performed a detailed investigation of the protein composition of wheat germ isolated from Triticum durum (Italian cultivar Svevo) with the aim of expanding the inventory of the wheat germ proteome. Wheat germ proteins were extracted and large-scale proteomics was performed using a bottom-up shotgun approach, including rough quantification using intensity Based Absolute Quantification (iBAQ). Overall, 1353 proteins were identified and functionally classified by gene ontology enrichment analysis. The predominant enzymatic fraction (280 gene products) was represented by hydrolases, including peptidases and glycosylases. Metallopeptidases were the most abundant peptidases, while the most represented glycosidases were chitinase followed by β-amylase. The identification of WGA was carried out only by a dedicated experiment based on Western blotting coupled to gel-based mass spectrometry analyses, as shotgun proteomics did not reveal this protein among those identified. This result provided a basis for a more in-depth study of the proteome in the dormant state of the germ, but also enabled to pinpoint the abundant proteins in germ that can be used as potential biomarkers as alternative to WGA.