Locked ultrasound-induced active conformation of laccase in covalent organic frameworks

Improving enzyme catalytic activity is a key challenge in biocatalysis. To this end, the present study explored a simple and versatile strategy to enhance the catalytic activity of laccase (LAC). LAC was pretreated with ultrasound (US) for 20 min, and the activity of the pretreated LAC (designated as LAC_US) was increased by 2.6-fold compared with that of pristine LAC. This increase in activity was attributed to the partial depolymerization of the spatial structure of LAC during ultrasound pretreatment, leading to a shift from the α-helix structure to an irregularly coiled structure. This structural change increased enzyme flexibility and active-site (copper ions) exposure. However, the structural transition of LAC_US is unstable. The covalent organic framework COF-LZU1 was able to rapidly "lock" this unstable transient conformation, thus maintaining the high-energy enzymatic activity of LAC_US. The composites showed stable recyclability over 10 cycles. Notably, the LAC_US@COF-LZU1 composites were capable of degrading the environmental pollutant bisphenol A. This approach enables efficient enzyme catalysis with broad biocatalytic applications.