Tuning of peroxidase activity by covalently tethered DNA oligonucleotides.

We report on the modulation of the peroxidase activity of hybrid catalysts, comprising short DNA oligonucleotides and heme enzymes by means of sequence variation of tethered oligonucleotides. In particular, binary mixtures of native heme (protophorphyrin IX) and single-stranded DNA oligonucleotides as well as the analogous covalent heme-oligonucleotide conjugates were compared with DNA-enzyme conjugates, prepared by reconstitution of apo-myoglobin or apo-horseradisch peroxidase, using the aforementioned covalent heme-oligonucleotide conjugates. In all systems, it was clearly evident that the implemented oligonucleotides markedly influence the catalytic activity in a sequence-dependent matter. Greater than 100-fold changes in catalytic constants were observed, depending on which oligonucleotide was incorporated in the hybrid catalyst. We also observed that the tethered oligomers affect the inhibition of HRP-mediated peroxidation by means of small molecule inhibitors. On the basis of the quantitative description of this phenomenon and consideration of the current state of knowledge, we hypothesize that distinct interactions, such as hydrogen bonding or electrostatic contacts, occur between the oligonucleotides and the heme-containing catalyst, which account for the effects observed.