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

摘要

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 introduced 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 K_M of the examined parallel DNA aptamers, was around 20 μM. 4c15 without a poly A linker showed the highest catalytic activity, and its K_M was 19 μM. The K_M of the anti-parallel aptamer was almost the same as that of the parallel aptamer.