Characterization of Minor N-linked Glycans on Antibodies Using Endo H Release and MALDI-Mass Spectrometry

A MALDI mass spectrometry method using Bruker Daltonic's LIFT technology for MS/MS analysis has been developed for profiling and characterizing low abundant N-glycans from recombinant immunoglobulin G (IgG) antibodies. In this method, Endoglycosidase H (Endo H) released N-glycans are derivatized at their reducing end with 2-aminobenzamide (2-AB) and separated by normal phase chromatography. Endo H hydrolyses the bond between the two GlcNAc residues of the trimannosyl core of high mannose and hybrid N-linked glycans, leaving the core GlcNAc attached to the protein. High mannose and hybrid type N-glycans are released from the glycoprotein whereas the more abundant, complex biantennary type oligosaccharide structures are unaffected. Analysis of Endo H treated glycan moieties by MALDI mass spectrometry identified several minor species of high mannose and hybrid type glycans. Subsequent MALDI TOF MS/MS analysis of the resulting products yielded information about structural features of the high mannose and hybrid type glycans. This study involving Endo H treatment followed by MALDI mass spectrometry coupled with LIFT technology for MS/MS analysis offers a specific and sensitive technique for visualizing, and characterizing minor glycan species.