Urinary endo-β-galactosidase capable of depolymerizing polylactosaminoglycans

Human urine was found to contain and endo-β-galactosidase capable of depolymerizing sulfated and non-sulfated polylactosaminoglycans. Using 0.05 M sodium phosphate buffer, pH 7.0, this enzyme was not retained by DEAE-Sephadex A-50 or concanavalin A-Sepharose. The urinary endo-β-galactosidase liberated a disaccharide with chromatographic mobility identical to 6-O-sulfo-GlcNAcβ1→3Gal as one of the major products from keratan sulfates isolated from whale nasal cartilage, bovine cornea, and human costal cartilage. It also liberated GlcNAcβ1→3Gal as one of the major oligosaccharides from erythroglycan. The oligosaccharide profiles produced from various keratan sulfates and erythroglycan by the action of urinary endo-β-galactosidase are quite similar to those produced by Escherichia freundii endo-β-galactosidase. The presence of urinary endo-β-galactosidase indicates the existence of a new catabolic pathway for polylactosaminoglycans. This pathway involves the cleavage of internal β-galactosyl linkages of the glycan chain.