Comparative Site-Specific N-Glycosylation Analysis of Lactoperoxidase from Buffalo and Goat Milk Using RP-UHPLC–MS/MS Reveals a Distinct Glycan Pattern

The N-glycan pattern of lactoperoxidase (LPO) from buffalo and goat milk was analyzed with the corresponding site of attachment. The enzyme was purified from whey on cation exchange chromatography, proteolyzed using chymotrypsin, and the resulting (glyco)peptides were directly analyzed on reverse phase ultrahigh performance liquid chromatography coupled to ESI-Q-TOF MS in tandem mode. N-Glycans such as high mannose, complex, and hybrid types were identified in buffalo and goat LPO. Among sialylated complex and hybrid types, the terminal Neu5Ac linked to either LacNAc/LacdiNAc found exclusively in buffalo, whereas Neu5Gc linked to LacdiNAc was predominant in goat LPO. N-Glycans at Asn6 and Asn349 in buffalo LPO were completely core fucosylated, while these sites in goat LPO showed differential fucosylation. Differential occupancy was observed at Asn112 with or without nonfucosylated complex and hybrid types, whereas mainly high mannose glycans were found in Asn222 in both of the LPOs. The presence of glyca...