Syringate and vanillate are the major metabolites of lignin biodegradation. In Sphingobium sp. strain SYK-6, syringate is O demethylated to gallate by consecutive reactions catalyzed by DesA and LigM, and vanillate is O demethylated to protocatechuate by a reaction catalyzed by LigM. The gallate ring is cleaved by DesB, and protocatechuate is catabolized via the protocatechuate 4,5-cleavage pathway. The transcriptions of desA, ligM, and desB are induced by syringate and vanillate, while those of ligM and desB are negatively regulated by the MarR-type transcriptional regulator DesR, which is not involved in desA regulation. Here, we clarified the regulatory system for desA transcription by analyzing the IclR-type transcriptional regulator desX, located downstream of desA. Quantitative reverse transcription (RT)-PCR analyses of a desX mutant indicated that the transcription of desA was negatively regulated by DesX. In contrast, DesX was not involved in the regulation of ligM and desB. The ferulate catabolism genes (ferBA), under the control of a MarR-type transcriptional regulator, FerC, are located upstream of desA. RT-PCR analyses suggested that the ferB-ferA-SLG_25010-desA gene cluster consists of the ferBA operon and the SLG_25010-desA operon. Promoter assays revealed that a syringate- and vanillate-inducible promoter is located upstream of SLG_25010. Purified DesX bound to this promoter region, which overlaps an 18-bp inverted-repeat sequence that appears to be essential for the DNA binding of DesX. Syringate and vanillate inhibited the DNA binding of DesX, indicating that the compounds are effector molecules of DesX.

中文翻译：

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鞘氨醇单胞菌 SYK-6丁香酸O-脱甲基酶基因受DesX调控，这与其他由DesR调控的香草醛和丁香酸分解代谢基因不同。

丁香酸酯和香草酸酯是木质素生物降解的主要代谢产物。在鞘氨醇中。菌株SYK-6，通过DesA和LigM催化的连续反应将丁香酸酯O脱甲基化为没食子酸酯，通过LigM催化的反应将香草醛O脱甲基化为原儿茶酸酯。没食子酸酯环被DesB切割，而原儿茶酸通过原儿茶酸的4，5-裂解途径分解代谢。的转录DESA，LIGM，和desB由丁香和诱导香草，而那些的LIGM和desB由马尔型转录调节DESR，这是不参与负调节DESA规。在这里，我们明确了监管体系德萨通过分析ICLR型转录调节转录DESX，位于下游的德萨。定量逆转录（RT）-PCR的一个分析DESX突变体指出的转录DESA呈负由DESX调节。相反，DesX不参与ligM和desB的调控。的分解代谢阿魏基因（ferBA），一个马尔型转录调节，FERC的控制下，分别位于上游的DESA。RT-PCR分析表明，在小佛-费拉-SLG_25010- DESA基因簇由的ferBA操纵子和SLG_25010- DESA操纵子。启动子分析显示，可从丁香酸酯和香草酸酯诱导的启动子位于SLG_25010的上游。纯化的DesX结合到该启动子区域，该启动子区域与18bp的反向重复序列重叠，该序列似乎对DesX的DNA结合至关重要。丁香酸酯和香草酸酯抑制了DesX的DNA结合，表明该化合物是DesX的效应分子。