Comparative Glycomics of Fat Globule Membrane Glycoconjugates from Buffalo (Bubalus bubalis) Milk and Colostrum

The health-promoting effects of milk fat globule membrane (MFGM) glycoconjugates has attracted curiosity especially with regard to the challenges encountered to unravel the glycan complexities of MFGM glycoproteins and glycosphingolipids. In this context, we characterized glycans present in buffalo milk and colostrum fat globule membranes by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS analysis by adopting chemoselective glycoblotting technique. Unlike human and bovine MFGM glycoproteins, the variations were obvious with respect to their number, size, heterogeneity, and abundance among the samples analyzed. Among N-linked glycans, mono-, di-, and trisialyl glycans were apparent in colostrum, while MFGM predominantly contained mono- and disialyl glycans, in addition to neutral and high-mannose glycoforms. The structural assignments of major glycans were confirmed by TOF/TOF analysis. Core 1 O-glycans were more common in both samples, and the major glycosphingolipids were GM3 and GD3 irrespective of the samples analyzed. The colostrum N-glycans, being effective antibacterials against human pathogens, established the structure-function relationship of oligosaccharides in early milk in providing innate protection to the newborn.