Sequence and N-glycan diversity analysis of immunoglobulin G from buffalo milk using RP-UHPLC MS/MS.

Immunoglobulin G is the abundant antibody present in the colostrum and milk of major dairy animals. In the present study, buffalo milk IgG was characterized for its amino acid sequence and glycan diversity using reverse phase liquid chromatography coupled to ESI-Q-TOF MS in tandem mode. Amino acid sequence analysis of heavy chain constant region revealed the presence of two IgG subtypes namely IgG1 and IgG3, with IgG1 being the abundant. The complete light chain constant region sequence was also determined. N-glycan sequence analysis at a highly conserved site Asn-Ser-Thr revealed the presence of mainly biantennary complex type with core fucosylation (34%), bisecting GlcNAc (19%) and sialylation with both Neu5Ac and Neu5Gc (14%). The observed glycan diversity in buffalo milk IgG is in part comparable with bovine colostrum as well as human, bovine, goat serum counterparts.