• ST3Gal-II exclusively uses Type III lactosamine (Galβ1,3GalNAc) substrate. Poor activity for Type I and no activity for Type-II.
• In contrast, ST3Gal-III, ST3Gal-IV, ST3Gal-V, and ST3Gal-VI use Galβ1-3/4Glc(NAc)-R substrate
• Mainly involved in the synthesis of GD1a, GM1b and GT1b in glycolipids. Mice lacking ST3Gal-II have 50% less GD1a, GT1b.
• Mice lacking ST3Gal-II/III display complete lack of these gangliosides suggesting that these are the two dominant enzymes involved in GD1a, GT1b production.
• Can act on glycoproteins e.g. fetuin and oligosaccharide substrate, though predominant role is during glycolipid biosynthesis.
• Transgenic mice show onset of cardiac dilation and enhanced cardiomyopathy.
• Mouse and the human ST3Gal-I & -II and ST6GalNAc-I & -II contain 4 residues named Kurosawa motif (Cys-Xaa70-85-Cys-Xaα2-Cys-Ala-Val-Val-Gly-Asn-Xaa120-170-Cys; Xaa denotes any amino acid residue). These enzymes commonly utilize the Galβ1,3GalNAc structure as an acceptor substrate.
• Human ST3Gal-II mRNA is tissue specific, being prominent in skeletal muscle and heart and also expressed in liver, placenta, brain, and pancreas, while that in lung and kidney is very low. Mouse ST3Gal-II is expressed in brain, liver, and striated muscle.