A Hemin/G-Quadraplex Acts as an NADH Oxidase and NADH Peroxidase Mimicking DNAzyme

摘要

Appropriately ordered guanosine bases in DNA chains form G-quartets stabilized by interbase hydrogen bonds. These G-quartets are further stacked, in the presence of ions, into a G-quadruplex structure. Different organic molecules are known to interact with G-quadruplex structures. Specifically, hemin was found to bind to a G-quadruplex, and the resulting complex revealed horseradish peroxidise mimicking activities. For example, the hemin/G-quadruplex catalyzes the H2O2-mediated oxidation of the 2,2'-azino-bis(3-ethyl-benzthiazoline-6-sulfonate dianion) (ABTS~(2-)) to the colored product ABTS~(·-) or leads to the generation of chemilumi-nescence in the presence of H2O2/luminol. Also, the hemin/ G-quadruplex structure linked to electrodes was reported to act as an electrocatalyst for the reduction of H2O2, and the hemin/G-quadruplex associated with semiconductor quantum dots was found to quench the luminescence of the quantum dots. These properties enabled the use of the hemin/G-quadruplex as a versatile label for numerous sensors including enzyme-, DNA-, and aptamer-based sensors. In the present study, we demonstrate that the hemin/G-quadruplex acts not only as a horseradish peroxidase mimicking DNAzyme, but, also, as an NADH oxidase and NADH peroxidase mimicking DNAzyme. The regeneration of the nicotinamide adenine dinucleotide, NAD~+, cofactor attracted substantial interest for biotechnological applications, and NAD~+-depen-dent enzymes have been widely used for chemical transformations. Our results pave the way to use the hemin/G-quadruplex as a biocatalyst for the regeneration of the NAD~+ cofactor and to apply the DNAzyme as a catalyst for enzyme-driven transformations.