美国加州大学伯克利分校的Ting Xu研究团队近日取得一项新成果。经过不懈努力，他们开发出用纳米分散酶可以几乎完全解聚聚酯。相关论文于2021年4月21日发表于国际顶尖学术期刊《自然》杂志上。

在这篇文章中，研究人员发现通过纳米显微镜下分散具有深层活性位点的酶，半结晶聚酯可以主要通过链端介导的具有可编程潜伏期和材料完整性的渐进解聚降解，类似于聚腺苷酸诱导的信使RNA衰减。通过工程酶-保护剂-聚合物复合物来实现具有表面暴露活性位点的酶的加工也是可行的。

含少于2％的酶的聚己内酯和聚乳酸可在几天内解聚，在标准土壤堆肥和家庭用自来水中，聚合物到小分子的转化率高达98％，从而完全消除了当前在堆肥设施中分离和掩埋其产品的需求。此外，嵌在聚烯烃中的氧化酶仍保持其活性。

然而，烃聚合物并不像聚酯聚合物那样与酶紧密结合，而且生成的活性自由基也不能对大分子宿主进行化学修饰。本研究为酶-聚合物配对和酶保护剂的选择提供了分子指导，以调节底物选择性和优化生物催化途径。研究结果还强调了固态酶学，特别是多步酶级联的深入研究的必要性，以解决化学休眠底物，而不会造成二次环境污染和/或生物安全问题。

研究人员表示，酶和生物机械与聚合物的成功连接可在塑料的制造、利用和处置过程中提供按需修饰和/或可编程降解，但需要在具有大分子底物的固体基质中进行受控的生物催化。包埋酶微粒可加快聚酯的降解速度，但会损害主体性能，并会无意中加速聚合物部分降解的微塑料的形成。

附：英文原文

Title: Near-complete depolymerization of polyesters with nano-dispersed enzymes

Author: Christopher DelRe, Yufeng Jiang, Philjun Kang, Junpyo Kwon, Aaron Hall, Ivan Jayapurna, Zhiyuan Ruan, Le Ma, Kyle Zolkin, Tim Li, Corinne D. Scown, Robert O. Ritchie, Thomas P. Russell, Ting Xu

Issue&Volume: 2021-04-21

Abstract: Successfully interfacing enzymes and biomachinery with polymers affords on-demand modification and/or programmable degradation during the manufacture, utilization and disposal of plastics, but requires controlled biocatalysis in solid matrices with macromolecular substrates1,2,3,4,5,6,7. Embedding enzyme microparticles speeds up polyester degradation, but compromises host properties and unintentionally accelerates the formation of microplastics with partial polymer degradation6,8,9. Here we show that by nanoscopically dispersing enzymes with deep active sites, semi-crystalline polyesters can be degraded primarily via chain-end-mediated processive depolymerization with programmable latency and material integrity, akin to polyadenylation-induced messenger RNA decay10. It is also feasible to achieve processivity with enzymes that have surface-exposed active sites by engineering enzyme–protectant–polymer complexes. Poly(caprolactone) and poly(lactic acid) containing less than 2 weight per cent enzymes are depolymerized in days, with up to 98 per cent polymer-to-small-molecule conversion in standard soil composts and household tap water, completely eliminating current needs to separate and landfill their products in compost facilities. Furthermore, oxidases embedded in polyolefins retain their activities. However, hydrocarbon polymers do not closely associate with enzymes, as their polyester counterparts do, and the reactive radicals that are generated cannot chemically modify the macromolecular host. This study provides molecular guidance towards enzyme–polymer pairing and the selection of enzyme protectants to modulate substrate selectivity and optimize biocatalytic pathways. The results also highlight the need for in-depth research in solid-state enzymology, especially in multi-step enzymatic cascades, to tackle chemically dormant substrates without creating secondary environmental contamination and/or biosafety concerns.

DOI: 10.1038/s41586-021-03408-3

Source: https://www.nature.com/articles/s41586-021-03408-3