Quantitative N-Glycomic and N-Glycoproteomic Profiling of Peach [ Prunus persica (L.) Batsch] during Fruit Ripening

Being part of the human diet, peach is an important fruit consumed worldwide. In the present study, a systematic first insight into the N-glycosylation of peach fruit during ripening was provided. First, N-glycome by reactive matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spec-trometry indicated that 6 of 24 N-glycans of peach were differentially expressed. Second, a comparative N-glycoproteome was characterized via 18O-tagged N-glycosylation site labeling followed by nano-liquid chromatography-electrospray ionization -tandem mass spectrometry (nLC-ESI-MS/MS). Totally 1464 N-glycosites on 881 N-glycoproteins were identified, among which 291 N-glycosites on 237 N-glycoproteins were expressed differ-entially with a fold change value of 1.5 or 0.67. The enrichment analysis of GO and KEGG revealed that four pathways including other glycan degradation, phenylpropanoid biosynthesis, amino sugar and nucleotide sugar metabolism, and protein processing in endoplasmic reticulum were mainly enriched, in which several important N-glycoproteins with dynamic change during fruit ripening were further screened out. Our findings on a large scale for N-glycosylation analysis of peach fruit during ripening may provide new molecular insights for comprehending N-glycoprotein functions, which should be of great interest to both glycobiologists and analytical chemists.