Comparison of denaturing agent effects in enzymatic N-glycan release for human plasma N-glycan analysis

Glycosylation is an essential posttranslational modification observed in the living proteome. Glycosylation profiles in glycoproteins can change in commonly observed diseases such as cancer. Identifying these changes is crucial in discovering new biomarkers for the early diagnosis of cancer. One of the main steps of N-glycan analysis is to release N-glycans from glycoproteins by specific enzymes. The study compares common denaturing agent combinations used in N-glycan release methods. In the study, human plasma was used to test the release methods of N-glycans containing different detergent combinations. The released N-glycans were labeled with the procainamide tag, purified using cellulose-containing solid-phase extraction cartridges, and analyzed by high-performance liquid chromatography-hydrophilic interaction liquid chromatography equipped with fluorescence detection (HPLC-HILIC-FLD). The results showed that the sodium dodecyl sulfate and sodium deoxycholate (SDS + SDC) detergent combination provided the highest average FLD signal areas and intensities in the N-glycan analysis. The protocol with SDS resulted in more reproducible average FLD signal areas and intensities. It was also found that the average signal FLD signal areas and intensities of the detected N-glycans were reduced when SDS and SDC were used with 1,4-dithiothreitol (DTT) reducing agents. In addition, deglycosylation of glycoproteins with various denaturing agents resulted in relatively minor variation in human plasma N-glycosylation profiles.