General features to enhance enzymatic activity of poly(ethylene terephthalate) hydrolysis

Poly(ethylene terephthalate) (PET) is the most abundant polyester plastic and a major contributor to plastic pollution. IsPETase, from the PET-assimilating bacterium Ideonella sakaiensis, is a unique PET-hydrolytic enzyme that shares high sequence identity to canonical cutinases, but shows substrate preference towards PET and exhibits higher PET-hydrolytic activity at ambient temperature. Structural analyses suggest that IsPETase harbours a substrate-binding residue, W185, with a wobbling conformation and a highly flexible W185-locating β6-β7 loop. Here, we show that these features result from the presence of S214 and I218 in IsPETase, whose equivalents are strictly His and Phe, respectively, in all other homologous enzymes. We found that mutating His/Phe residues to Ser/Ile could enhance the PET-hydrolytic activity of several IsPETase-like enzymes. In conclusion, the Ser/Ile mutations should provide an important strategy to improve the activity of potential PET-hydrolytic enzymes with properties that may be useful for various applications.