Activation of Lysozyme with Robust Flavoenzyme Activity by Amyloid Fibrillation.

The intrinsic disadvantages of natural enzymes limit their practical applications. How to achieve artificial enzymes with a green process, low cost, high stability, robust catalytic activity, and excellent biocompatibility remains a great challenge. Amyloid fibrils deserve particular attention in electron transfer and biocatalysis due to their unique biochemical properties and long-range ordered structure. Inspired by the relationship between the structure and function of natural flavoenzymes, we report that lysozyme amyloid fibril (LAF) binds cofactor flavin mononucleotide (FMN) and forms a stable nanofibril complex (FMNLAF) through noncovalent interactions. Interestingly, FMNLAF exhibits NADH oxidase activity (Km, 55.3 μM; Kcat, 0.65 min-1) to generate NAD+ under physiological conditions. Possessing exceptional structural stability, FMNLAF shows enhanced activity at high temperature (60 °C) and tolerates organic solvents. In addition, FMNLAF also exhibits strong Fe3+-cyt c reductase-like activity in aerated environments. This work provides a convenient and rational strategy for designing metal-free biocatalytic systems through amyloid fibrillation, which converts a protein into an artificial enzyme.