Glucuronidase-catalyzed transglycosylation was examined by using 4-nitrophenyl β-D-glucuronide (D-GlcA-O-pNP) as the glycosyl donor; when pNP 6-O-sulfo-β-D-gluco- and D-galacto-pyranosides were used as the acceptors, a bovine enzyme was found to construct β-D-GlcA-(1–3)-linkages with the 6-O-sulfo-sugars in both a site- and β-selective way.