Oxidase-Mimetic Nanocatalyst Based on Geometry-Dependent Biomolecular Self-Assembly

Enzymes rely on protein folding to create functional sites essential for their catalytic activity. Reproducing enzymatic active sites in artificial systems has been difficult due to the intricate folding patterns that enzymes demonstrate. Inspired by natural systems, we developed a supramolecular copper-cluster-dependent catechol oxidase. This system is constructed through the self-assembly of flavin adenine dinucleotide (FAD) with fluorenylmethyloxycarbonyl-modified amino acids (e.g., Fmoc-lysine) and Cu2+ ions. Fmoc-amino acids self-associate through fluorenyl stacking, facilitating the formation of oxidase-mimetic copper clusters. FAD self-assembles with Fmoc-amino acids via aromatic stacking, enabling the incorporation of adenine and amino acid groups to form a coordination sphere around Cu2+. The self-assembly of FAD with Fmoc-amino acids enhances the oxidase-like activity of Cu2+ by over 100-fold. It is estimated that each copper can catalyze the transformation of ca. 80 substrate molecules within 15 min. The catalyst demonstrated thermophilic properties and excellent storage stability. When exposed to 460 nm light, the activity of the FAD/Fmoc-K/Cu2+ complex is further enhanced, potentially due to cooperative interaction between FAD and lumichrome generated from FAD photodegradation. These findings have implications for the design of advanced enzyme-mimetic catalysts.