Ulvan lyase involved in ulvan degradation (PubMed:22009751, PubMed:28327560). 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). Ulvan lyase catalyzes the endolytic cleavage of the glycosidic bond between Rha3S and the uronic acids GlcA or IduA, producing oligosaccharides that have unsaturated 4-deoxy-L-threo-hex-4-enopyranosiduronic acid (deltaUA) at the non-reducing end. This results eventually in the degradation of the ulvan polysaccharide into deltaUA-Rha3S disaccharides and deltaUA-Rha3S-Xyl-Rha3S tetrasaccharides (PubMed:22009751). Optimum pH is 9. Optimum temperature is 50 degrees Celsius. Secreted via the type IX secretion system (T9SS). The ulvan-binding domain binds strongly to ulvan, it does not bind other polymers like alginate, heparin, dextran sulfate or iota carrageenan. Presumably it serves to anchor the enzyme at the substrate, thus improving catalysis. Notably, the catalytic domain alone is more active than the full-length enzyme with the binding domain attached. Possibly, the ulvan-binding domain helps the enzyme to act on ulvan in its insoluble form embedded in the algal cell wall. Belongs to the polysaccharide lyase 28 family.