Fig. 1.
Synthesis of the common O-glycan core structures 1 to 4. C1GalT and C3GnT both act on GalNAc-substrates to synthesize core 1 and core 3, respectively. Core 1 is branched by either C2GnT1 or C2GnT2 to form core 2. Core 3 is branched only by C2GnT2 to form core 4. Core 1–4 structures can be extended and terminated in many different ways.