Contribution of beta-glucuronidase to the degradation of chondroitin 4-sulfate by canine liver lysosomal enzymes

Abstract

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 beta-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 beta-glucuronidase. Decasaccharide was degraded by both hyaluronidase and beta-glucuronidase. The results showed that decasaccharide from Ch4-S served as the largest-molecular-weight substrate for beta-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 beta-glucuronidase to the depolymerization of chondroitin and HA by hyaluronidase was examined in the presence of saccharo-1,4-lactone, a specific inhibitor of beta-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 beta-glucuronidase contributes to the degradation of the even-numbered oligosaccharides which inhibit the action of hyaluronidase in the depolymerization of Ch4-S.