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Published on: June 13, 2022
Reprogramming Imine Reductases for Enantioselective Reduction of Electron-Rich Enamides
Xiao-Qi Liu1,2, Ru Li1,2, Jun-Liang Chen1,2
1Key Laboratory of Drug-Targeting and Drug Delivery System of the Education Ministry and Sichuan Province, Sichuan Engineering Laboratory for Plant-Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, Department of Biopharmaceutics, West China School of Pharmacy, Sichuan University, Chengdu 610041, China.
Abstract:
Imine reductases (IREDs) are powerful biocatalysts to afford valuable enantioenriched amines via the stereoselective reduction of imines. While significant progress has been made in expanding their catalytic capabilities, direct reduction of electron-rich alkenes by IREDs remains a formidable challenge and is unprecedented in biology. Here, we report the reprogramming of an IRED from Sinorhizobium (SinIRED) to catalyze the enantioselective reduction of enamides. Through directed evolution, the final optimized SinIRED-V5 variant is able to reduce a variety of enamides and deliver diverse protected chiral amines in up to 97% yield and >99:1 enantiomeric ratio (e.r.). Mechanistic studies suggest a novel synergistic pathway involving enamine-imine tautomerization followed by NADPH-mediated hydride transfer process. This work expands the catalytic versatility of IREDs and provides the first known example of IRED-catalyzed reduction of electron-rich enamides.
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