Flexible Assembly of an Enzyme Cascade on a DNA Triangle Prism Nanostructure for the Controlled Biomimetic Generation of Nitric Oxide.

Spatial organization of multiple enzymes at specific positions for a controlled reaction cascade has attracted wide attention in recent years. Here, we report the construction of a biomimetic enzyme cascade organized on DNA triangle prism (TP) nanostructures to enable the efficient catalytic production of nitric oxide (NO) on a single microbead. Two enzymes, glucose oxidase (GOx) and horseradish peroxidase (HRP), were assembled at adjacent locations on a DNA TP nanostructure by using DNA-binding protein adaptors with small interenzyme distances. In the cascade, the first enzyme, GOx, converts glucose into gluconic acid in the presence of oxygen. The produced H2 O2 intermediate is rapidly transported to the second enzyme, HRP, which oxides hydroxyurea into NO and other nitroxyl species. The pH near the surface of the negatively charged DNA nanostructures is believed to be lower than that in the bulk solution; this creates an optimal pH environment for the anchored enzymes, which results in higher yields of the NO product. Furthermore, the multienzyme system was immobilized on a microbead mediated by a DNA adaptor, and this enabled the efficient catalytic generation of gas molecules in the microreactor. Therefore, this work provides an alternative route for the biomimetic generation of NO through enzyme cascades. In particular, the dynamic binding capability of the DNA sequence enabled the positions of the protein enzyme and the DNA nanostructure to be reversed, which allowed the cascade catalysis to be modulated.