Structural insight and engineering of a plastic degrading hydrolase Ple629

Polyethylene terephthalate (PET) is one of the most abundantly produced synthetic polyesters. The vast number of waste plastics including PET has challenged the waste management sector while also posing a serious threat to the environment due to improper littering. Recently, enzymatic PET degradation has been shown to be a viable option for a circular plastic economy, which can mitigate the plastic pollution. While protein engineering studies on specific PET degradation enzymes such as leaf-branch compost cutinase (LCC), Thermobifida sp. cutinases and Ideonella sakaiensis PETase (IsPETase) have been exten-sively published, other homologous PET degrading enzymes have received less attention. Ple629 is a polyester hydrolase identified from marine microbial consortium having activity on PET and the bio-plastic polybutylene adipate terephthalate (PBAT). In order to explore its catalytic mechanism and improve its potential for PET hydrolysis, we solved its crystal structure in complex with a PET monomer analogue, and validated its structural and mechanistic similarity to known PET hydrolases. By structural comparisons, we identified some hot spot positions described in previous research on protein engi-neering of PET hydrolases. We substitute these amino acid residues in Ple629, and obtained variants with improved activity and thermo-stability. The most promising variant D226A/S279A exhibited a more than 5.5-fold improved activity on PET nanoparticles than the wild-type enzyme, suggesting its potential applicability in the biotechnological plastic recycling.(c) 2022 Elsevier Inc. All rights reserved.

Automated summary

Polyethylene terephthalate (PET) is a commonly produced synthetic polyester. The increasing amount of waste plastics, including PET, poses a serious threat to the environment and waste management. Recent research has shown that enzymatic PET degradation can be an effective solution to mitigate plastic pollution and achieve circular plastic economy. Although protein engineering studies on specific PET degradation enzymes have been extensively conducted, other homologous PET degrading enzymes have received less attention. In this study, researchers investigated a polyester hydrolase called Ple629 and its catalytic mechanism for PET degradation. By analyzing its crystal structure and making amino acid substitutions, variants with improved activity and thermo-stability were obtained. The most promising variant, D226A/S279A, exhibited significantly increased activity on PET nanoparticles, suggesting its potential application in biotechnological plastic recycling.