Engineered GalNAc-T glycosyltransferases were used to incorporate a chemically modified GalNAc analog into the glycoproteins on the cell surface of K-562 cells. The chemical modification included a bioorthogonal alkyne tag that allowed for introduction of a clickable, acid-cleavable biotin-picolyl-azide. Glycoproteins were enriched using Streptavidin, and on-bead digestion yielded a peptide fraction that was analysed by mass spectrometry.