对苯二甲酸单羟乙酯水解酶结构与功能的研究进展

Advances in the structure and function of MHETase

摘要:

聚对苯二甲酸乙二醇酯(polyethylene terephthalate, PET)作为目前广泛使用的塑料之一，其废弃物对全球环境造成了严重污染。PET降解酶(polyethylene terephthalate hydrolase, PETase)的发现为处理PET废弃物提供了一种绿色环保的途径。尽管PETase降解PET会产生中间产物，抑制水解酶的进一步降解，影响酶的催化效率，但对苯二甲酸单羟乙酯水解酶[mono(2-hydroxyethyl) terephthalate hydrolase, MHETase]通过与PETase协同作用，将PETase水解产生的中间产物MHET高效降解为乙二醇(ethylene glycol, EG)和对苯二甲酸(terephthalic acid, TPA)。MHETase对MHET表现出极高的特异性，是完全降解PET的关键酶。本文全面梳理了MHETase的三维结构、底物结合模式以及催化反应机理等，介绍了该酶降解活性的结构特征和关键残基，以及酶工程改造的研究进展。同时，对基于MHETase支架结合PETase开发定制的酶促PET降解系统进行了展望，为设计和开发更加高效的PET水解酶体系提供了参考。

关键词:聚对苯二甲酸乙二醇酯(PET);对苯二甲酸单羟乙酯水解酶(MHETase);双酶系统;塑料降解;生物降解

Abstract:

Polyethylene terephthalate (PET) is one of the widely used plastics, but its waste pollution has become a global environmental issue. The discovery of polyethylene terephthalate hydrolase (PETase) has provided a green and environmentally friendly approach for PET degradation. However, PETase produces intermediate products that inhibit the enzyme’s further activity, leading to a decrease in enzyme efficiency. Mono(2-hydroxyethyl) terephthalate hydrolase (MHETase) works synergistically with PETase to further degrade the intermediate product MHET into ethylene glycol (EG) and terephthalic acid (TPA). MHETase exhibits extremely high specificity for MHET and is crucial for the complete degradation of PET. This article comprehensively reviews MHETase from various perspectives, including its three-dimensional structure, substrate binding, and catalytic mechanism. It demonstrates the structural features and key residues associated with the enzyme’s degrading activity and discusses the progress in enzyme engineering modifications. Additionally, the study envisions the development of a two-enzyme PET degradation system by combining MHETase with PETase, aiming to provide valuable references for designing and developing more efficient PET hydrolytic enzyme systems.

Key words:polyethylene terephthalate (PET);mono (2-hydroxyethyl) terephthalate hydrolase (MHETase);two-enzyme system;plastic degradation;biodegradation