Broad-specificity lyase involved in ulvan degradation (PubMed:30279430). 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) (PubMed:30279430) (Probable). 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. It is also able to degrade the glycosaminoglycans heparan sulfate and chondroitin sulfate. Not active against pectin, xanthan or alginate (PubMed:30279430). Endolytic cleavage of (1->4)-beta-galactosaminic bonds between N-acetylgalactosamine and either D-glucuronic acid or L-iduronic acid to produce a mixture of Delta(4)-unsaturated oligosaccharides of different sizes that are ultimately degraded to Delta(4)-unsaturated tetra- and disaccharides. Elimination of sulfate, appears to act on linkages between N-acetyl-D-glucosamine and uronate. Product is an unsaturated sugar. Optimum pH is 8. Optimum temperature is 40 degrees Celsius. By ulvan and rhamnose. Belongs to the polysaccharide lyase 37 family. Truncated N-terminus.