Whether the wobbling W156 is a pre-requisite for efficient PET biodegradation by IsPETase

Abstract

IsPETase displayed great potential for mitigating PET contamination under moderate temperatures attributed to its specific high activity towards PET, while rapid activity loss limited its commercial viability. Herein, a thermostable S92P/D157A variant (Tm=70.8 °C) was constructed, enabling a 109.3-fold increase in products released from amorphous PET depolymerization at 40 °C. Further depolymerization of untreated post-consumer PET in a 360-times expanded reaction system obtained 20.09 mM products (95.0% TPA). Crystal structure characterized the “wobbling” W156 residue fixed at substrate-binding conformation in S92P/D157A variant, which stabilized the enzyme structure and could provide steady interaction with the substrate. Further MD simulations cement the importance of conformation selection and the contribution of W156. The different structure-function relationship observed raised the question of “whether the wobbling W156 is a pre-requisite for efficient PET biodegradation”. Especially, the S92P/D157A variant could serve as a starting point for further engineering and a potential candidate for industrial PET depolymerization processes.