O-linked β-N-acetylglucosamine (O-GlcNAc) modification sites are present in a vast number of proteins, including antibodies, and play important roles in very different biological processes like transcription, translation, protein turnover and regulation in hyperglycemia.
Enzymatic modification of O-GlcNAc sites can be achieved using UDP-GalNAz and a modified glycosyl-transferase (e.g. GalT(Y289L)) or a glycosynthase (e.g. EndoS(D233A/Q)) in combination with Copper-free Strain-promoted Azide-Alkyne Click-labeling (SPAAC).
Many such molecules are available which gives significant flexibility and makes it possible to find a labelling molecule for your experiment. Such molecules enable the
Figure 1: Chemo-enzymatic labeling of antibodies. Azide labeling of glycosylated serine or threonine residues by modified enzymes like GalT(Y289L) or EndoS(D233A/Q) opens the possibility to specifically mark antibodies using copper-free Strain-promoted Azide-Alkyne Click-labeling (SPAAC). Afterwards antibodies easily can be screened or sorted by fluorescence, for example.
 Yang et al. (2017) Protein O-GlcNAcylation: emerging mechanisms and functions.” Nature reviews. Molecular cell biology 18 (7):452.
 Ma et al. (2019) O-GlcNAc Site Mapping by Using a Combination of Chemoenzymatic Labeling, Copper-Free Click Chemistry, Reductive Cleavage, and Electron-Transfer Dissociation Mass Spectrometry. Anal. Chem. 91 (4):2620.
 Huang et al. (2012) Chemoenzymatic glycoengineering of intact IgG antibodies for gain of functions. J. Am. Chem. Soc. 134 (29):12308.
 Walsh et al. (2021) Site-selective modification strategies in antibody-drug conjugates. Chem. Soc. Rev. 50 (2):1305.
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