Application of Post-Glycosylation Modifying Enzymes for Mass Spectrometry Imaging of Modified N-Glycans In Situ

Glycans are essential components of cells involved in numerous biological processes, and changes in glycan profiles are often correlated with disease progression. Glycans are comprised of various monosaccharides linked together at different positions with varied stereochemistry. The structural diversity and complexity present unique analytical challenges that can limit understanding of their functional role. In addition, glycans are frequently decorated with a diverse set of chemical modifications, termed post-glycosylation modifications (PGMs). Characterization of PGMs is essential for a thorough understanding of the glycome; however, the technical challenges and low throughput of current methodologies limit our understanding of PGMs. Here, we demonstrate a novel approach for rapid visualization of specific PGMs present in tissue N-glycans by applying PGM-targeting enzymes to matrix-assisted laser desorption ionization-based mass spectrometry imaging. The method enables in situ investigation of PGMs, allowing identification of the modified sugar residue, while visualizing the spatial distribution of each modified N-glycan. As the repertoire of PGM-targeting enzymes expands, we anticipate that this approach will improve our understanding of PGM distributions within the dynamic N-glycome, providing new biological insights into the identification of novel disease biomarkers.