The (R)- and (S)-enantiomers of the chiral herbicide napropamide (NAP) show different biological activities and ecotoxicities. These two enantiomers behave differently in the environment due to enantioselective catabolism by microorganisms. However, the molecular mechanisms underlying this enantioselective catabolism remain largely unknown. In this study, the genes (snaH and snpd) involved in the catabolism of NAP were cloned from Sphingobium sp. B2, which was capable of catabolizing both NAP enantiomers. Compared with (R)-NAP, (S)-NAP was much more rapidly transformed by the amidase SnaH, which initially cleaved the amide bonds of (S)/(R)-NAP to form (S)/(R)-2-(1-naphthalenyloxy)-propanoic acid [(S)/(R)-NP] and diethylamine. The α-ketoglutarate-dependent dioxygenase Snpd, showing strict stereoselectivity for (S)-NP, further transformed (S)-NP to 1-naphthol and pyruvate. Molecular docking and site-directed mutagenesis analyses revealed that when the (S)-enantiomers of NAP and NP occupied the active sites, the distance between the ligand molecule and the coordination atom was shorter than that when the (R)-enantiomers occupied the active sites, which facilitated formation of the transition state complex. This study enhances our understanding of the preferential catabolism of the (S)-enantiomer of NAP on the molecular level.

中文翻译：

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由鞘氨醇单胞菌中的对映选择性酰胺水解酶SnaH和双加氧酶Snpd介导的除草剂萘丙酰胺（S）-对映体的优先分解代谢。菌株B2。

手性除草剂萘丙酰胺（NAP）的（R）和（S）对映异构体显示出不同的生物活性和生态毒性。由于微生物的对映选择性分解代谢，这两种对映异构体在环境中的行为不同。但是，这种对映选择性分解代谢的分子机制仍是未知之数。在这项研究中，与NAP分解代谢有关的基因（snaH和snpd）是从鞘氨醇单胞菌属物种中克隆的。B2，能够分解两种NAP对映体。与（R）-NAP相比，（S）-NAP被酰胺酶SnaH更快地转化，该酶首先裂解（S）/（R）-NAP的酰胺键形成（S）/（R）-2 -（1-萘氧基）-丙酸[（S）/（R）-NP]和二乙胺。α-酮戊二酸依赖性双加氧酶Snpd，对（S）-NP表现出严格的立体选择性，进一步将（S）-NP转化为1-萘酚和丙酮酸。分子对接和定点诱变分析表明，当NAP和NP的（S）-对映体占据活性位点时，配体分子与配位原子之间的距离短于（R）-对映体占据活性位点。位点，这促进了过渡态复合物的形成。这项研究增强了我们对NAP（S）-对映异构体的优先分解代谢的分子水平的了解。这促进了过渡态络合物的形成。这项研究增强了我们对NAP（S）-对映异构体的优先分解代谢的分子水平的了解。这促进了过渡态络合物的形成。这项研究增强了我们对NAP（S）-对映异构体的优先分解代谢的分子水平的了解。