New insights into site‐specific N‐glycosylation profiling differences of serum proteomes between colostrum and mature breast milk

Abstract

AbstractN‐glycosylation has important implications for the physicochemical properties and biochemical activity of breast milk proteins. However, an in‐depth characterization of site‐specific N‐glycans in breast milk serum proteins is lacking. In this study, 875 site‐specific N‐glycans attached to 114 serum glycoproteins from breast colostrum (BC) and 427 site‐specific N‐glycans attached to 60 serum glycoproteins from breast mature milk (BM) were identified and quantified using label‐free site‐specific glycoproteomics. Among them, 24 site‐specific N‐glycans mapping to 11 N‐glycosites on 9 glycoproteins were significantly increased, and 76 site‐specific N‐glycans mapping to 19 N‐glycosites on 13 glycoproteins were significantly decreased. Gene ontology annotation analysis showed that BC and BM serum N‐glycoproteins were mainly enriched in complement activation, classical pathway, extracellular exosome part, and immunoglobulin receptor binding. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed that BC and BM serum N‐glycoproteins were mainly involved in the PI3K‐Akt signaling pathway. Additionally, breast milk serum N‐glycoproteins carried fucosylated core structures as well as Lewis and sialylated branch structures that may contribute to neonatal retinal homeostasis. These results provide a molecular basis for understanding the unique biological activities of breast milk serum N‐glycoproteins.