O-Glycans / O-Linked Glycosylation

Galβ1-3GalNAc/(O-glycans) = Substrate for ST6GalNAc I, ST6GalNAc II, ST6GalNAc III, ST6GalNAc IV Sialyltransferases

are ubiquituously found on cells and are particularly secreted into the extracellular matrix or into the lumen of internal organs.
Rodrigues Mantuano et al. 2020

Mucin-type O-linked oligosaccharide structures = constituents of many secreted & membrane-bound proteins in higher eukaryotes
Freire et al. 2003

see also:
Glycans