Zinc N,N-bis(2-picolyl)amine Chelates Show Substitution-Dependent Cleavage of Phosphodiesters in Models as Well as of PNAzyme-RNA Bulges

TL;DR

This study explores how different zinc chelates affect the ability of artificial enzymes called PNAzymes to cut RNA, finding that certain modifications improve their activity.

Contribution

The study introduces new zinc chelating groups as active sites in PNAzymes and demonstrates their substitution-dependent cleavage activity.

Findings

Zinc complexes with 6-amino substitution showed the highest reactivity in cleaving phosphodiesters.

PNAzymes with these chelating groups exhibited cleavage activity matching the model substrate results.

The activity of PNAzymes was influenced by the size of RNA bulges in the catalyst–substrate complex.

Abstract

PNAzymes are a group of artificial enzymes which show promising results in selective and efficient cleavage of RNA targets. In the present study, we introduce a series of metal chelating groups based on N,N-bis(2-picolyl) groups (parent, 6-methyl and 6-amino substituted) as the active sites of novel PNAzymes. An improved synthetic route for the 6-amino analogues is described. The catalytic activity of the chelating groups for cleaving phosphodiesters were assessed with the model substrate 2-hydroxypropyl p-nitrophenyl phosphate (HPNPP), confirming that the zinc complexes have the reactivity order of parent < 2-methyl < 2-amino. The three ligands were conjugated to a PNA oligomer to form three PNAzymes which showed the same order of reactivity and some sensitivity to the size of the RNA bulge designed into the catalyst–substrate complex. This work demonstrates that the kinetic activity observed for the model substrate HPNPP could be translated onto the PNAzymes, but that more reactive Zn complexes are required for such PNAzymes to be viable therapeutic agents.

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