Higher-Order Human Telomeric G-Quadruplex DNA Metalloenzymes Enhance Enantioselectivity in the Diels-Alder Reaction

Short human telomeric (HT) DNA sequences form single G-quadruplex (G(4)) units and exhibit structure-based stereocontrol for a series of reactions. However, for more biologically relevant higher-order HT G(4)-DNAs (beyond a single G(4) unit), the catalytic performances are unknown. Here, we found that higher-order HT G(4)-DNA copper metalloenzymes (two or three G(4) units) afford remarkably higher enantioselectivity (>90% ee) and a five- to sixfold rate increase, compared to a single G(4) unit, for the Diels-Alder reaction. Electron paramagnetic resonance (EPR) and enzymatic kinetic studies revealed that the distinct catalytic function between single and higher-order G(4)-DNA copper metalloenzymes can be attributed to different Cu-II coordination environments and substrate specificity. Our finding suggests that, like protein enzymes and ribozymes, higher-order structural organization is crucial for G(4)-DNA-based catalysis.