Cutinase fused with C-terminal residues of α-synuclein improves polyethylene terephthalate degradation by enhancing the substrate binding

Environmental-friendly treatment of poly (ethylene terephthalate) (PET) is important for the circular plastic economy, and enzymatic degradation provided a promising approach. However, enzyme binding toward the PET surface is a rate-limiting factor in PET hydrolysis. Thus, a 16-residue peptide (αSP) from the C-terminal sequence of α-synuclein was used to fuse to the C-terminal of a variant (ICCG) of the leaf-branch compost cutinase, and supposed to serve as an anchor peptide for PET degradation. The fusion enzyme (ICCG-αSP) was characterized to keep the same secondary and tertiary structures as ICCG, but enhanced enzyme binding onto bis(2-hydroxyethyl) terephthalate and PET, respectively. Moreover, αSP-fusion enhanced enzyme expression by over 50%, and increased the catalytic efficiency of p -nitrophenyl butyrate by 20% without compromising the enzyme stability. For PET degradation, ICCG-αSP was 3.89 times more active than ICCG by 3-h reaction at 50°C, and exhibited 1.05 to 1.45 times higher degradation activity than ICCG in 4-d reaction at 50°C to 70°C, and pH 7.0 to pH 9.0, respectively. Furthermore, αSP-fusion lowered the optimal long-term degradation temperature from 65°C to 50°C at pH 8.0. Therefore, αSP-fusion was effective to increase the hydrolytic efficiency of PET hydrolases by increasing the degradation efficiency and decreasing the degradation temperature. • C-terminal residues of α-synuclein (αSP) was fused to the ICCG variant of cutinase. • αSP-fusion enhanced enzyme adhesion on PET but did not affect enzyme stability. • αSP-fusion improved PET degradation performance at 50-70°C, up to 3.7-fold. • αSP-fusion decreased the optimal PET degradation temperature from 65°C to 50°C.