The gut bacterium Gordonibacter urolithinfaciens DSM 27213 metabolizes ellagic acid into three polyphenol compounds, namely, urolithin M5, urolithin M6, and urolithin C, which are collectively called urolithin. The key reactions of this metabolic pathway are the dehydroxylation of the phenolic hydroxy group, i.e., conversion of urolithin M5 to urolithin M6, and successive conversion of urolithin M6 to urolithin C. By testing the effects of various electron-transferring compounds on the dehydroxylation reactions, methylviologen was found to effectively support the dehydroxylation catalyzed by the cell free extracts. The urolithin dehydroxylating enzymes were found in the soluble fraction of the cell free extracts. The urolithin dehydroxylation was found to be coupled with reduction of dicationic methylviologen to a cation radical form catalyzed by enzymes with hydrogen as an electron donor, which was also found with the soluble fraction. Further investigation of the reaction in the presence of natural cofactors with or without methylviologen and hydrogen revealed the involvement of NADPH and FAD in the electron transportation systems of the urolithin dehydroxylation.

中文翻译：

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尿单球菌DSM 27213中涉及尿石素脱羟基化的电子转移辅助因子介导酶系统的评估。

肠道细菌尿杆菌Goldonibacter urolithinfaciens DSM 27213将鞣花酸代谢为三种多酚化合物，即尿石素M5，尿石素M6和尿石素C，统称为尿石素。该代谢途径的关键反应是酚羟基的脱羟基反应，即尿石素M5向尿石素M6的转化，以及尿石素M6向尿石素C的连续转化。通过测试各种电子转移化合物对脱羟基反应的影响，发现甲基紫罗兰可以有效支持无细胞提取物催化的脱羟基反应。在无细胞提取物的可溶性部分中发现了尿石素脱羟基酶。发现尿石素脱羟基与通过氢作为电子给体的酶催化的二甲基甲基紫精还原成阳离子自由基形式有关，这也与可溶性部分一起发现。在有或没有甲基紫罗兰和氢的天然辅因子存在下对反应的进一步研究表明，NADPH和FAD参与了尿石素脱羟基的电子传输系统。