N-Glycosylation Plays an Essential and Species-Specific Role in Anti-Infection Function of Milk Proteins Using <i>Listeria monocytogenes</i> as Model Pathogen

Abstract

The released milk <i>N</i>-glycome has been found to possess antipathogenic activity. Natively, they are covalently linked onto proteins. Whether the conjugated <i>N</i>-glycans still have antipathogenic properties and how the glycosylation influences the antipathogenic activity of proteins remain unclear. Herein, we compared the quantitative differences of milk protein N-glycosylation and the antilisterial differences of native milk proteins, released <i>N</i>-glycan pools, and deglycosylated proteins between human and bovine milk. N-glycosylation exhibited to be quantitatively species-specific. The entire growth inhibitory activity and the majority of the antiadhesive activity against <i>Listeria monocytogenes</i> of milk whey proteins, although not as high as the released <i>N</i>-glycans, are attributed to N-glycosylation. Moreover, all <i>N</i>-glycan-bearing samples from human milk showed better growth inhibitory activities than those from bovine milk. Generally, N-glycosylation significantly contributes to the antilisterial function of milk proteins and to the functional differences between species. This gives novel insights into the role of these glycoconjugates in nature.