FUNCTION Catalyzes a step in lysosomal heparan sulfate degradation.CATALYTIC ACTIVITY N-sulfo-D-glucosamine + H2O = D-glucosamine + sulfateCOFACTOR Binds 1 Ca(2+) ion per subunit.INTERACTION 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.DISEASE The disease is caused by variants affecting the gene represented in this entry.SIMILARITY Belongs to the sulfatase family.