Key Laboratory of Advanced Light Conversion Materials and Biophotonics, School of Chemistry and Life Resources, Renmin University of China, Beijing 100872, China.
Inorg Chem. 2024 Jul 29;63(30):13948-13958. doi: 10.1021/acs.inorgchem.4c01263. Epub 2024 Jul 15.
Deoxypodophyllotoxin synthase (DPS), a nonheme Fe(II)/2-oxoglutarate (2OG)-dependent oxygenase, is a key enzyme that is involved in the construction of the fused-ring system in (-)-podophyllotoxin biosynthesis by catalyzing the C-C coupling reaction. However, the mechanistic details of DPS-catalyzed ring formation remain unclear. Herein, our quantum mechanics/molecular mechanics (QM/MM) calculations reveal a novel mechanism that involves the recycling of CO (a product of decarboxylation of 2OG) to prevent the formation of hydroxylated byproducts. Our results show that CO can react with the Fe-OH species to generate an unusual Fe-bicarbonate species. In this way, hydroxylation is avoided by consuming the OH group. Then, the C-C coupling followed by desaturation yields the final product, deoxypodophyllotoxin. This work highlights the crucial role of the CO molecule, generated in the crevice between the iron active site and the substrate, in controlling the reaction selectivity.
脱氧土大黄苷元合酶（DPS）是一种非血红素 Fe(II)/2-氧代戊二酸（2OG）依赖性加氧酶，是参与 (-)-鬼臼毒素生物合成中构建稠合环系统的关键酶，通过催化 C-C 偶联反应。然而，DPS 催化环形成的机制细节尚不清楚。在此，我们的量子力学/分子力学 (QM/MM) 计算揭示了一种新的机制，涉及 CO（2OG 脱羧的产物）的循环利用以防止形成羟基化副产物。我们的结果表明，CO 可以与 Fe-OH 物种反应生成不寻常的 Fe-碳酸氢盐物种。这样，通过消耗 OH 基团避免了羟基化。然后，C-C 偶联随后去饱和生成最终产物脱氧土大黄苷元。这项工作强调了 CO 分子在铁活性位点和底物之间的缝隙中产生的关键作用，它控制着反应选择性。
