Asymmetric Ene-Reduction of α,β-Unsaturated Compounds by F<sub>420</sub>-Dependent Oxidoreductases A Enzymes from <i>Mycobacterium smegmatis</i>
作者:Suk Woo Kang、James Antoney、Rebecca L. Frkic、David W. Lupton、Robert Speight、Colin Scott、Colin J. Jackson
DOI:10.1021/acs.biochem.2c00557
日期:2023.2.7
The stereoselective reduction of alkenes conjugated to electron-withdrawing groups by ene-reductases has been extensively applied to the commercial preparation of fine chemicals. Although several different enzyme families are known to possess ene–reductase activity, the old yellow enzyme (OYE) family has been the most thoroughly investigated. Recently, it was shown that a subset of ene-reductases belonging to the flavin/deazaflavin oxidoreductase (FDOR) superfamily exhibit enantioselectivity that is generally complementary to that seen in the OYE family. These enzymes belong to one of several FDOR subgroups that use the unusual deazaflavin cofactor F420. Here, we explore several enzymes of the FDOR-A subgroup, characterizing their substrate range and enantioselectivity with 20 different compounds, identifying enzymes (MSMEG_2027 and MSMEG_2850) that could reduce a wide range of compounds stereoselectively. For example, MSMEG_2027 catalyzed the complete conversion of both isomers of citral to (R)-citronellal with 99% ee, while MSMEG_2850 catalyzed complete conversion of ketoisophorone to (S)-levodione with 99% ee. Protein crystallography combined with computational docking has allowed the observed stereoselectivity to be mechanistically rationalized for two enzymes. These findings add further support for the FDOR and OYE families of ene-reductases displaying general stereocomplementarity to each other and highlight their potential value in asymmetric ene-reduction.
烯还原酶可立体选择性地还原烯与电子萃取基团的共轭,这种方法已被广泛应用于精细化学品的商业制备。尽管已知有多个不同的酶家族具有烯还原酶活性,但对老黄酶(OYE)家族的研究最为深入。最近的研究表明,属于黄素/去氮黄素氧化还原酶(FDOR)超家族的烯还原酶子集表现出的对映选择性通常与 OYE 家族的对映选择性互补。这些酶属于使用不常见的脱氮黄素辅助因子 F420 的几个 FDOR 亚群之一。在这里,我们研究了 FDOR-A 亚群的几种酶,用 20 种不同的化合物鉴定了它们的底物范围和对映体选择性,确定了可以立体选择性还原多种化合物的酶(MSMEG_2027 和 MSMEG_2850)。例如,MSMEG_2027 能催化柠檬醛的两种异构体完全转化为(R)-香茅醛,ee 为 99%;MSMEG_2850 能催化酮异佛尔酮完全转化为(S)-来伏二酮,ee 为 99%。蛋白质晶体学与计算对接相结合,使观察到的两种酶的立体选择性得到了机理上的合理解释。这些发现进一步支持了 FDOR 和 OYE 系列烯还原酶显示出一般的立体互补性,并突出了它们在不对称烯还原中的潜在价值。