10-23 DNAzyme is a catalytic DNA molecule from in vitro selection, the 15-mer catalytic core was investigated for more DNAzyme variants by block deletions. DNAzyme DZM01 was selected with metal ion dependence of Pb2+ ≫ Mn2+, with no activity in the presence of Mg2+ (20 mM), Ca2+ (20 mM), Zn2+ (20 mM, pH 6). The unique binding properties of Pb2+ with nucleic acids might be responsible for the formation of the catalytic core, which is different from that of other divalent metal ions. More DNAzyme variants are expected to be derived for specific metal ion dependence by various nucleobase sequences and modifications.