Study on the catalytic mechanism of polypeptide-based polyethylene terephthalate mimics

Abstract

Polyethylene terephthalate (PET) is a polyethylene plastic with a large amount. Due to its good heat resistance, plasticity, toughness and other advantages, PET is widely used in various fields. However, due to the stability of its polymer structure, PET plastic waste is difficult to degrade naturally, resulting in a large amount of plastic waste accumulation, which poses a serious threat to human health and the ecological environment. Enzymatic degradation means that the enzyme molecule binds to the binding site of the PET molecule to form the enzyme-host complex to achieve the purpose of decomposing PET. Enzymatic degradation, as a green and sustainable method, has brought a new idea to solve the environmental pollution caused by waste plastics. However, the preparation process of natural enzymes is complicated, the production cost is high, the stability is poor, the reaction medium is strict and other conditions limit their wide application. In this experiment, PETase, a natural enzyme with high PET degradation activity, was used as the simulated object. Based on the structural and catalytic characteristics of the natural enzyme, PET degradation enzyme was constructed with polypeptides. The structure of the simulated enzyme was characterized by CD, TEM and THT methods. The catalytic activity of PET degradation by simulated enzyme was studied by HPLC. Molecular docking was used to simulate the interaction between enzymes and substrates. The experimental results showed that the simulated enzyme could self-assemble to form β-folded secondary structure, and had good stability under high temperature conditions. The simulated enzyme can effectively catalyze PET degradation at a temperature of 65 ℃ and PH of 9, and the degradation products are TPA and MEHT. Further through molecular docking, it was found that the simulated enzyme interacts with the substrate mainly through hydrogen bonding and hydrophobic interaction. The simulated enzyme constructed in this experiment can provide a theoretical reference for the degradation of industrial and daily waste plastics.