An Artificial Metal-Free Peroxidase Designed Using a Ferritin Cage for Bioinspired Catalysis

Developing artificial enzymes is challenging because it requires precise design of active sites with well-arranged amino acid residues. Histidine-rich oligopeptides have been recently shown to exhibit peroxidase-mimetic activities, but their catalytic function relies on maintaining unique supramolecular structures. This work demonstrates the design of a specific array of histidine residues on the internal surface of the ferritin cage to function as an active center for catalysis. The crystal structures of the ferritin mutants revealed histidine–histidine interactions, forming well-defined histidine clusters (His-clusters). These mutants exhibit peroxidase-mimetic activities by oxidizing 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. Molecular dynamics simulations further highlight the co-localization of TMB and hydrogen peroxide at the histidine-rich clusters, indicating that the confined environment of the ferritin cage enhances their interactions. This study presents a simple yet effective approach to design metal-free artificial enzymes, paving the way for innovations in bioinspired catalysis.