Pb²⁺ as a Substrate and a Cofactor of a Porphyrin Metalation DNAzyme

Abstract

We herein report a DNAzyme named T30695 (sequence: (G3T)4) that can catalyze Zn2+ insertion into three different porphyrins in the presence of Pb2+ as a cofactor. Meanwhile, T30695 with Pb2+ alone was found to cause a shift in both the fluorescence and UV‐vis spectra of protoporphyrin IX (PPIX), thus suggesting that metalation of Pb2+ was also achieved at room temperature. From kinetic measurements, the reaction required two Pb2+ ions; this is consistent with one being a cofactor and the other being a substrate. No previous reports inserted Pb2+ into porphyrins by using DNAzymes or protein‐based enzymes. This reaction was most significantly inhibited in the presence of K+ followed by Na+ and Li+, suggesting the importance of the Pb2+‐stabilized G‐quadruplex. When Pb2+ is inserted into PPIX, its emission blue shifts from 635 to 590 nm, thus allowing simple ratiometric fluorescent sensing with a detection limit of 1.2 nM Pb2+.

Zn2+‐Dependent DNAzymes: From Solution Chemistry to Analytical, Materials and Therapeutic Applications

“…Metal complexes, such as hemin, can serve as key cofactors in DNAzyme catalysis [29] . Finally, metal ions can also be a substrate for DNAzymes, as seen in porphyrin metalation reactions [30–33] …”

“…[29] Finally, metal ions can also be a substrate for DNAzymes, as seen in porphyrin metalation reactions. [30][31][32][33] Zn 2 + is a highly important metal in biology for enzyme catalysis, structural regulation, and signaling. [34,35] Using Zn 2 + in assisting DNAzymes has been extensively carried out, especially for the DNA/RNA cleavage reactions.…”