Unsaturated glucuronyl hydrolase involved in ulvan degradation (PubMed:31285597). Ulvan is the main polysaccharide component of the Ulvales (green seaweed) cell wall. It is composed of disaccharide building blocks comprising 3-sulfated rhamnose (Rha3S) linked to D-glucuronic acid (GlcA), L-iduronic acid (IduA), or D-xylose (Xyl) (Probable). Unsaturated glucuronyl hydrolase catalyzes the cleavage of the unsaturated 4-deoxy-L-threo-hex-4-enopyranosiduronic acid (deltaUA) at the non-reducing end of ulvan oligomers, thus forming 5-dehydro-4-deoxy-D-glucuronate (PubMed:31285597). Belongs to the glycosyl hydrolase 88 family.