Identification of a Hotdog Fold Thioesterase Involved in the Biosynthesis of Menaquinone in Escherichia coli
Identification of a Hotdog Fold Thioesterase Involved in the Biosynthesis of Menaquinone in Escherichia coli
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DOI：
10.1128/jb.00141-13
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发表时间：
2013-06-01
影响因子：
3.2
通讯作者：
Guo, Zhihong
中科院分区：
文献类型：
--
作者：
Chen, Minjiao;Ma, Xinyu;Guo, Zhihong
大肠杆菌被用作阐明甲萘醌生物合成的模式生物，其中从1，4-二羟基-2-萘甲酰辅酶A（DHNA-CoA）到1，4-二羟基-2-萘甲酸的水解步骤仍然是未知的。最近，热狗折叠硫酯酶已被证明催化叶绿醌生物合成中的这种转化，这表明其最接近的同系物，大肠杆菌中的YbgC，可能是甲基萘醌生物合成中的DHNA-CoA硫酯酶。然而，由于YbgC参与Tol-CoA系统，并且完全缺乏对DHNA-CoA的水解活性，因此排除了这种可能性。为了鉴定水解酶，我们对所有9种大肠杆菌热狗折叠硫酯酶进行了基于活性的筛选，发现YdiI对DHNA-CoA具有高水平的水解活性，具有高底物特异性，而另一种来自铁载体生物合成的硫酯酶EntH表现出中等的、低得多的DHNA-CoA硫酯酶活性。从细菌基因组中删除ydiI基因导致甲基萘醌产量显著降低，这在Delta ybgC和Delta entH突变体中几乎没有影响。这些结果支持YdiI是参与模型细菌中甲基萘醌生物合成的DHNA-CoA硫酯酶的观点。
Escherichia coli is used as a model organism for elucidation of menaquinone biosynthesis, for which a hydrolytic step from 1,4-dihydroxy-2-naphthoyl-coenzyme A (DHNA-CoA) to 1,4-dihydroxy-2-naphthoate is still unaccounted for. Recently, a hotdog fold thioesterase has been shown to catalyze this conversion in phylloquinone biosynthesis, suggesting that its closest homolog, YbgC in Escherichia coli, may be the DHNA-CoA thioesterase in menaquinone biosynthesis. However, this possibility is excluded by the involvement of YbgC in the Tol-Pal system and its complete lack of hydrolytic activity toward DHNA-CoA. To identify the hydrolytic enzyme, we have performed an activity-based screen of all nine Escherichia coli hotdog fold thioesterases and found that YdiI possesses a high level of hydrolytic activity toward DHNA-CoA, with high substrate specificity, and that another thioesterase, EntH, from siderophore biosynthesis exhibits a moderate, much lower DHNA-CoA thioesterase activity. Deletion of the ydiI gene from the bacterial genome results in a significant decrease in menaquinone production, which is little affected in Delta ybgC and Delta entH mutants. These results support the notion that YdiI is the DHNA-CoA thioesterase involved in the biosynthesis of menaquinone in the model bacterium.