Peroxidase Activity of G-Quadruplex Hemin-Binding DNA Aptamers Determined by Electrochemical Measurement

Certain guanine-rich DNA oligomers that form a G-quadruplex structure and bind hemin inside are called hemin-binding DNA aptamers. A hemin-binding DNA aptamer with the 4c15 sequence forms a parallel G quadraplex and the PS2.M sequence folds and forms an anti-parallel structure. We propose a novel method to examine the peroxidase activity of hemin-binding DNA aptamers through electrochemical measurements. In this study, a polyA chain and thiol were introcuced to the 5´ terminal of each oligonucleotide. The peroxidase activity of hemin-binding DNA aptamers was determined after modifying a gold electrode with the aptamers. The distance to hemin from the surface of the electrode is most important to determine catalytic activity. Catalytic activity, shown as KM of the examined parallel DNA aptamers, was around 20 μM. 4c15 without a poly A linker showed the highest catalytic activity, and its KM was 19 μM. The KM of the anti-parallel aptamer was almost the same as that of the parallel aptamer.