Catalyzes the hydrolysis of oligosaccharides with unsaturated glucuronyl residues at the non-reducing terminal, to a sugar or an amino sugar, and an unsaturated D-glucuronic acid (GlcA), which is nonenzymatically converted immediately to alpha-keto acid. beta-D-Delta(4)-GlcA-(1->4)-beta-D-Glc-(1->4)-alpha-L-Rha-(1->3)-D-Glc + H2O = 5-dehydro-4-deoxy-D-glucuronate + beta-D-Glc-(1->4)-alpha-L-Rha-(1->3)-D-Glc Partially inhibited by divalent metal ions such as calcium, copper, iron and mercury. kcat is 14.1 sec(-1) with unsaturated chondroitin (delta0S). kcat is 54.9 sec(-1) with unsaturated chondroitin disaccharide sulfated at C-6 position of GalNAc residue (delta6S). Optimum pH is 6.0-6.5. Optimum temperature is 45 degrees Celsius. Monomer. Belongs to the glycosyl hydrolase 88 family.