Bifunctional enzyme containing sulfatase and alpha-L-rhamnosidase activities 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). The sulfatase specifically desulfates L-rhamnose at the 3-position and can act on the motif Rha3S-Xyl-Rha3S in an exolytic mode of action, producing Rha-Xyl-Rha3S. Also desulfates Rha3S monosaccharides, which are produced by the action of unsaturated glucuronyl hydrolases acting on ulvan oligomers (PubMed:31285597). Hydrolysis of terminal non-reducing alpha-L-rhamnose residues in alpha-L-rhamnosides. Binds 1 Ca(2+) ion per subunit. By ulvan and rhamnose. The conversion to 3-oxoalanine (also known as C-formylglycine, FGly), of a serine or cysteine residue in prokaryotes and of a cysteine residue in eukaryotes, is critical for catalytic activity. This post-translational modification is severely defective in multiple sulfatase deficiency (MSD). In the N-terminal section; belongs to the sulfatase family. In the C-terminal section; belongs to the glycosyl hydrolase 78 family. Truncated N-terminus.