Characterization of a novel mucin sulphotransferase activity synthesizing sulphated O-glycan core 1,3-sulphate-Gal beta 1-3GalNAc alpha-R.

A novel sulphotransferase (sulpho-T) activity from rat colonic mucosa was characterized using O-glycan core 1 substrate, Gal beta 1-3GalNAc alpha-benzyl. Derivatives of Gal beta 1-3GalNAc- were used to demonstrate that the 3- and 4-hydroxyl of Gal and the 2-acetamido group of the GalNAc residue of Gal beta 1-3GalNAc alpha-benzyl substrates were important for activity. Sulphated product using Gal beta 1-3GalNAc alpha-benzyl as substrate was analysed by ion spray mass spectrometry, methylation analysis, high-pH anion-exchange chromatography and beta-galactosidase digestion. The results suggested that sulphate was added to the 3-position of the Gal residue. The synthesis of core 2 from core 1 by UDP-GlcNAc: Gal beta 1-3GalNAc beta 6-GlcNAc-transferase was inhibited by sulphation of the Gal residue, indicating that GlcNAc beta 1-6 branching has to precede sulphation in the O-glycan core 1 processing pathway. These data demonstrate several novel pathways in the synthesis of sulphated mucin-type oligosaccharides.