Investigation of Sample Preparation Artifacts Formed during the Enzymatic Release of N-Linked Glycans prior to Analysis by Capillary Electrophoresis

In the biotechnology industry, highly sensitive and accurate methods are required for monitoring glycosylation of therapeutic recombinant monoclonal antibodies (rMAbs) due to possible effects on bioactivity. At Genentech, a method employing PNGase F digestion, fluorescent labeling of released glycans, and analysis by capillary electrophoresis (CE) is used for routine monitoring of N-linked glycosylation during process development and quality control of therapeutic glycoproteins. In our laboratory, capillary electrophoresis-mass spectrometry (CE-MS) technology was developed to identify minor glycan species in assay and it revealed several unidentified isomeric species. Additional studies indicate that these species (1−10% total glycans) are sample preparation artifacts caused by base-catalyzed epimerization of N-acetylglucosamine (GlcNAc) at the reducing terminus by following the use of commercially available PNGase F and the supplied incubation buffer (pH 7.5). As these isomeric species directly impact th...