Identifying Sialylation Linkages at the Glycopeptide Level by Glycosyltransferase Labeling Assisted Mass Spectrometry (GLAMS)

Abstract

<p class="first" id="P4">Precise assignment of sialylation linkages at the glycopeptide level is of importance in bottom-up glycoproteomics and an indispensable step to understand the function of glycoproteins in pathogen–host interactions and cancer progression. Even though some efforts have been dedicated to the discrimination of <i>α</i>2,3/ <i>α</i>2,6-sialylated isomers, unambiguous identification of sialoglycopeptide isomers is still needed. Herein, we developed an innovative glycosyltransferase labeling assisted mass spectrometry (GLAMS) strategy. After specific enzymatic labeling, oxonium ions from higher-energy C-trap dissociation (HCD) fragmentation of <i>α</i>2,3-sailoglycopeptides then generate unique reporters to distinctly differentiate those of <i>α</i>2,6-sailoglycopeptide isomers. With this strategy, a total of 1236 linkage-specific sialoglycopeptides were successfully identified from 161 glycoproteins in human serum. </p><p id="P5"> <div class="figure-container so-text-align-c"> <img alt="" class="figure" src="/document_file/09ba6d51-204e-4c82-85f5-1ece22106aab/PubMedCentral/image/nihms-1651430-f0001.jpg"/> </div> </p>