Glucuronidase-assisted Transglycosylation for the Synthesis of Highly Functional Disaccharides: β-D-Glucuronyl 6-O-Sulfo-β-D-Gluco- and -β-D-Galactopyranosides

Abstract

The substrate specificity of snail (Helix pomatia and Helix aspersa), limpet (Patella vulgata), and bovine glucuronidases was examined by using p-nitrophenyl glucuronide (GlcA-O-pNP) and p-nitrophenyl 6-O-sulfo-β-D-glycopyranosides as the glycosyl donor and acceptors, respectively. When the donor was treated with these enzymes in the absence of the acceptors, β (1 → 3) glucuronyl disaccharides were obtained as the major products together with β (1 → 2) isomers as the result of an enzymatic “self-transglycosylation” reaction. When p-nitrophenyl 6-O-sulfo-β-D-glucopyranosides (6-O-sulfo-Glc-O-pNP and 6-O-sulfo-Glc-S-pNP) were applied as acceptor substrates, every glucuronidase transferred the GlcA residue to either the O-3 or O-2 position in 6-O-sulfo-Glc to yield a mixture of GlcAβ (1 → 3)- and GlcAβ (1 → 2)-linked disaccharides in a ratio of 12:1 ∼ 1:1. On the other hand, when p-nitrophenyl 6-O-sulfo-β-D-galactopyranosides (6-O-sulfo-Gal-O-pNP and 6-O-sulfo-Gal-S-pNP) were applied, limpet and bovine glucuronidases gave a GlcAβ (1 → 3)-linked disaccharide regioselectively, while the snail enzymes showed no reactivity.