Converts choline-O-sulfate into choline. choline sulfate + H2O = choline + H(+) + sulfate Binds 1 Ca(2+) ion per subunit. Amine and polyamine biosynthesis; choline biosynthesis; choline from choline sulfate: step 1/1. 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. Belongs to the sulfatase family.