Transfer of sialic acid in α2-6 linkage to mannose in Man β1-4GlcNAc and Man β1-4GlcNAc β1-4GlcNAc by the action of Gal β1-4GlcNAc αa2-6-sialyltransferase

Abstract

The disaccharide Man beta1-4GlcNAc and the trisaccharide Man beta1-4GlcNAc beta1-4GlcNAc were each incubated with CMPNeuAc and rat liver alpha2-6-sialyltransferase (CMP-NeuAc: Gal beta1-4GlcNAc alpha2-6-N-acetylneuraminyl transferase). The resulting mixtures were fractionated by HPLC on Partisil 10 SAX, and the fractions obtained were investigated by TLC, GLC (monosaccharide analysis) and 500-MHz 1H-NMR spectroscopy. The followingproducts were identified: NeuAc alpha2-6Man beta1-4GlcNAc and NeuAc alpha2-6Man beta1-4GlcNAc beta1-4GlcNAc in yields of 4% and 27%, respectively. The sialylation of Man beta-4GlcNAc-R by Gal beta-4GlcNAc alpha2-6-sialyltransferase contrasts the reported high specificity of this enzyme for the structural element Gal beta1-4GlcNAc of N-linked carbohydrate chains of glycoproteins and related oligosaccharides.