Aptamer-Assisted Bioconjugation of Tyrosine Derivatives with hemin/G-quadruplex (hGQ) DNAzyme Nucleoapzyme Nanostructures

Hemin/G-quadruplex (hGQ) DNAzymes are horseradish peroxidase-mimicking catalysts capable of the oxidation of a variety of substrates. We now implement aptamer-functionalized hGQ DNAzymes, also known as nucleoapzymes, to achieve increased bioconjugation of N-methyl luminol to tyrosine-containing residues and peptides. We found that the presence of a tyrosinamide-binding aptamer leads to a 12-fold increase in the catalytic rate constant (kcat), and the saturation kinetics curves that were obtained provide evidence for the involvement of the substrate binding site in the reaction. The application of the best performing nucleoapzymes for the modification of Tyr-containing peptides reveals that (i) the aptamer also recognizes the ligand structure when this is embedded in a larger peptide structure, and (ii) distant residues in the peptide substrate can influence the conversion. As such, we show that nucleoapzymes display enzyme-like features and provide an additional tool in the toolbox of bioconjugation chemistry.