Pollution from plastics is a global problem that threatens the biosphere for a host of reasons, including the time scale that it takes for most plastics to degrade. Biodegradation is an ideal solution for remediating bioplastic waste as it does not require the high temperatures necessary for thermal degradation and does not introduce additional pollutants into the environment. Numerous organisms can scavenge for bioplastics, such as polylactic acid (PLA) or poly-(R)-hydroxybutyrate (PHB), which they can use as an energy source. Recently, a promiscuous PHBase from the thermophilic soil bacterium Lihuaxuella thermophila (LtPHBase) was identified. LtPHBase can accommodate many substrates, including PHB granules and films and PHB block copolymers, as well as the unrelated polymers polylactic acid (PLA) and polycaprolactone (PCL). LtPHBase uses the expected Ser-His-Asp catalytic triad for hydrolysis at an optimal enzyme activity near 70°C. Here, the 1.75 Å resolution crystal structure of apo LtPHBase is presented and its chemical stability is profiled. Knowledge of its substrate preferences was extended to different-sized PHB granules. It is shown that LtPHBase is highly resistant to unfolding, with barriers typical for thermophilic enzymes, and shows a preference for low-molecular-mass PHB granules. These insights have implications for the long-term potential of LtPHBase as an industrial PHB hydrolase and shed light on the evolutionary role that this enzyme plays in bacterial metabolism.

中文翻译：

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水解多羟基丁酸酯的载脂蛋白嗜热酯酶的结构和稳定性。


塑料污染是一个全球性问题，威胁着生物圈，原因有很多，包括大多数塑料降解所需的时间。生物降解是修复生物塑料废物的理想解决方案，因为它不需要热降解所需的高温，也不会将额外的污染物引入环境中。许多生物体可以搜刮生物塑料，例如聚乳酸 （PLA） 或聚-（R）-羟基丁酸酯 （PHB），它们可以将其用作能源。最近，鉴定出来自嗜热土壤细菌嗜热丽华雪菌 （LtPHBase） 的混杂 PHBase。LtPHBase 可以容纳许多底物，包括 PHB 颗粒和薄膜以及 PHB 嵌段共聚物，以及不相关的聚合物聚乳酸 （PLA） 和聚己内酯 （PCL）。LtPHBase 使用预期的 Ser-His-Asp 催化三联体在 70°C 附近以最佳酶活性进行水解。 本文介绍了载脂蛋白 LtPHBase 的 1.75 Å 分辨率晶体结构，并分析了其化学稳定性。对其底物偏好的了解扩展到不同大小的 PHB 颗粒。结果表明，LtPHBase 对去折叠具有很强的抵抗力，具有嗜热酶的典型屏障，并且显示出对低分子量 PHB 颗粒的偏好。这些见解对 LtPHBase 作为工业 PHB 水解酶的长期潜力具有影响，并阐明了这种酶在细菌代谢中发挥的进化作用。