A Mechanistic Understanding of the Activity-Stability Trade-off in PETase

Enzymatic degradation of poly(ethylene terephthalate) (PET) has garnered considerable interest in plastic recycling efforts. Despite numerous descriptions of both natural and engineered enzymes, the fundamental mechanism underlying PETase-catalyzed PET depolymerization at the solid-liquid interface remains elusive. This lack of understanding hampers the rational design of highly efficient depolymerases. Here, we employ multiscale simulations and experiments to elucidate the complete catalytic pathway of IsPETase, from enzyme adsorption at the interface to PET fragment capture, conformational refinement, and ester bond cleavage. Both endo- and exo-cleavage modes of the enzyme are identified, indicating its capacity for endo- and exo-lytic activities. We discover that the trade-off between the activity and stability of IsPETases PET-capturing pliers brings compromises to its PET depolymerization performance. Reshaping the loop dynamics of the enzyme can break this trade-off and enhance its stability and activity simultaneously, as demonstrated by the evolved variant HotPETase. Overall, our study offers comprehensive details into how PETase functions at the interface and provides valuable insights for engineering efficient plastic-degrading enzymes.