Characterization of recombinant human glucuronyltransferase I involved in the biosynthesis of the glycosaminoglycan-protein linkage region of proteoglycans

We characterized the recombinant glucuronyltransferase I (GlcAT-I) involved in the glycosaminoglycan-protein linkage region biosynthesis. The enzyme showed strict specificity for Galβ1-3Galβ1-4Xyl, exhibiting negligible incorporation into other galactoside substrates including Galβ1-3Galβ1-O-benzyl, Galβ1-4GlcNAc and Galβ1-4Glc. A comparison of the GlcAT-I with another β1,3-glucuronyltransferase involved in the HNK-1 epitope biosynthesis revealed that the two β1,3-glucuronyltransferases exhibited distinct and no overlapping acceptor substrate specificities in vitro. Nevertheless, the transfection of the GlcAT-I cDNA into COS-1 cells induced the significant expression of the HNK-1 epitope. These results suggested that the high expression of the GlcAT-I gene rendered the cells capable of synthesizing the HNK-1 epitope. Copyright (C) 1999 Federation of European Biochemical Societies.