Contribution of β-Glucuronidase to the Degradation of Chondroitin 4-Sulfate by Canine Liver Lysosomal Enzymes

Oligosaccharides derived from chondroitin 4-sulfate (Ch4-S) and chondroitin were digested by canine liver lysosomes under acidic conditions. The degree of digestion of Ch4-S by hyaluronidase and β-glucuronidase was examined on the basis of types of the digestion products. Tetradeca- and dodecasaccharides derived from Ch4-S and chondroitin were first digested by hyaluronidase, while the octasaccharide was hydrolyzed by β-glucuronidase. Decasaccharide was degraded by both hyaluronidase and β-glucuronidase. The results showed that decasaccharide from Ch4-S served as the largest-molecular-weight substrate for β-glucuronidase in the degradation of Ch4-S by the enzymes of lysosomes in contrast to the results of the digestion studies of hyaluronic acid (HA). The contribution of β-glucuronidase to the depolymerization of chondroitin and HA by hyaluronidase was examined in the presence of saccharo-l, 4-lactone, a specific inhibitor of β-glucuronidase, in the reaction mixture. The depolymerization of chondroitin by hyaluronidase was significantly reduced by the addition of saccharo-1, 4-lactone. From the results, it is suggested that β-glucuronidase contributes to the degradation of the evennumbered oligosaccharides which inhibit the action of hyaluronidase in the depolymerization of Ch4-S.