An oxidatively damaged G-quadruplex/hemin DNAzyme.
International audience; Oxidative damage of guanine to 8-oxoguanine triggers a partial and variable loss of G-quadruplex/hemin DNAzyme activity and provides clues to the mechanistic origins of DNAzyme deactivation, which originates from an interplay between decreased G-quadruplex stability, lower hemin affinity and a modification of the nature of hemin binding sites.
The noncovalent dimerization of a G-quadruplex/hemin DNAzyme improves its biocatalytic properties.
While many protein enzymes exert their functions through multimerization, which improves both selectivity and activity, this has not yet been demonstrated for other naturally occurring catalysts. Here, we report a multimerization effect applied to catalytic DNAs (or DNAzymes) and demonstrate that the enzymatic efficiency of G-quadruplexes (GQs) in interaction with the hemin cofactor is remarkably enhanced by homodimerization. The resulting non-covalent dimeric GQ–DNAzyme system provides hemin with a structurally defined active site in which both the cofactor (hemin) and the oxidant (H2O2) are activated. This new biocatalytic system efficiently performs peroxidase- and peroxygenase-type biot…
How Proximal Nucleobases Regulate the Catalytic Activity of G-Quadruplex/Hemin DNAzymes
International audience; G-quadruplexes (G4s) are versatile catalytic DNAs when combined with hemin. Despite the repertoire of catalytically competent G4/hemin complexes studied so far, little is known about the detailed catalytic mechanism of these biocatalysts. Herein, we have carried out an in-depth analysis of the hemin binding site within the G4/hemin catalysts, providing the porphyrinic cofactor with a controlled nucleotidic environment. We intensively assessed the position-dependent catalytic enhancement in model reactions and found that proximal nucleobases enhance the catalytic ability of the G4/hemin complexes. Our results allow for revisiting the mechanism of the G4/hemin-based ca…
A Thermophilic Tetramolecular G-Quadruplex/Hemin DNAzyme.
International audience; The quadruplex-based DNAzyme system is one of the most useful artificial enzymes or catalysts; their unique properties make them reliable alternatives to proteins for performing catalytic transformation. The first prototype of a thermally stable DNAzyme system is presented. This thermophilic DNAzyme is capable of oxidizing substrates at high temperatures (up to 95 degrees C) and long reaction times (up to 18 h at 75 degrees C). The catalytic activity of the DNAzymes were investigated with the standard peroxidase-mimicking oxidation of 2,2'-azino-bis(3-ethylbenzothiozoline-6-sulfonic acid) (ABTS) by H2O2. The step-by-step design of this unique heat-activated G-quadrup…
The catalytic properties of DNA G-quadruplexes rely on their structural integrity
International audience; The influence of the G-quartet structural integrity on the catalytic activity of the G-quadruplex (G4) was investigated by comparing the G4-DNAzyme performances of a series of G4s with a G-vacancy site and a G-triplex (G-tri). The results presented herein not only confirm that the structural integrity of the 3’-end G-quartet is necessary for G4s to be catalytically competent but also show how to remediate G-vacancy-mediated catalytic activity losses via the addition of guanine surrogates in an approach referred to as G-vacancy complementation strategy that is applicable to parallel G4s only. Furthermore, this study demonstrates that the terminal G-quartet could act a…
A Push-Pull Mechanism Helps Design Highly Competent G-Quadruplex-DNA Catalysts
International audience; Massive efforts are currently being invested to improve the performance, versatility, and scope of applications of nucleic acid catalysts. G-quadruplex (G4)/hemin DNAzymes are of particular interest owing to their structural programmability and chemical robustness. However, optimized catalytic efficiency is still bottleneck and the activation mechanism is unclear. Herein, we have designed a series of parallel G4s with different proximal cytosine (dC) derivatives to fine-tune the hemin-binding pocket for G4-DNAzymes. Combining theoretical and experimental methods, we have assessed the dependence of catalytic enhancement on the electronic properties of proximal dCs and…