To be active all known arylsulfatases undergo a unique post-translational modification leading to the conversion of an active site residue (serine or cysteine) into a C-alpha-formylglycine. Although deprived of sulfatase activity, Escherichia coli K12 can efficiently mature heterologous Cys-type sulfatases. Three potential enzymes (AsIB, YdeM and YidF) belonging to the anaerobic sulfatase maturating enzyme family (an SME) are present in its genome. Here we show that E. coli could mature Cys-type sulfatases only in aerobic conditions and that knocking-out of aslB, ydeM and yidF does not impair Cys-type sulfatase maturation. These findings demonstrate that these putative anSME are not involved in Cys-type sulfatase maturation and strongly support the existence of a second, oxygen-dependent and Cys-type specific sulfatase maturation system among prokaryotes.