Uremic toxins (UTs) are microbiota-derived metabolites that accelerate the progression of kidney damage in patients with chronic kidney disease (CKD). One of the major UTs involved in CKD progression is p-cresol-sulfate (PCS), derived from dietary l-tyrosine (l-Tyr). Here, we engineered a probiotic strain of Escherichia coli Nissle 1917, to convert l-Tyr to the nontoxic compound p-coumaric acid via tyrosine ammonia lyase (TAL). First, a small metagenomic library was assessed to identify the TAL with the greatest whole-cell activity. Second, accessory genes implicated in the import of l-Tyr and export of PCA were overexpressed to enhance l-Tyr degradation by 106% and 56%, respectively. Last, random mutagenesis coupled to a novel selection and screening strategy was developed that identified a TAL variant with a 25% increase in whole-cell activity. Taken together, the final strain exhibits a 183% improvement over initial whole-cell activity and provides a promising candidate to degrade l-Tyr mediated PCS accumulation.

中文翻译：

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大肠杆菌 Nissle 1917 作为活生物治疗剂的合理工程可降解尿毒症毒素前体

尿毒症毒素（UT）是微生物群衍生的代谢物，可加速慢性肾病（CKD）患者肾脏损伤的进展。参与 CKD 进展的主要 UT 之一是对甲酚硫酸盐 (PCS)，源自膳食l -酪氨酸 ( l -Tyr)。在这里，我们设计了一种大肠杆菌 Nissle 1917益生菌菌株，通过酪氨酸氨裂解酶 (TAL)将l -Tyr转化为无毒化合物对香豆酸。首先，对一个小型宏基因组文库进行评估，以确定具有最大全细胞活性的 TAL。其次，与l -Tyr输入和 PCA 输出相关的辅助基因被过度表达，分别使l -Tyr 降解增强 106% 和 56%。最后，开发了随机诱变与新的选择和筛选策略相结合的方法，该策略鉴定出全细胞活性增加 25% 的 TAL 变体。总而言之，最终菌株的全细胞活性比最初的全细胞活性提高了 183%，并为降解l -Tyr 介导的 PCS 积累提供了有希望的候选菌株。