Expanding the Imine Reductase Toolbox by Exploring the Bacterial Protein-Sequence Space

Area of Science:

• Biocatalysis
• Enzyme Engineering
• Organic Chemistry

Background:

• Chiral amines are crucial building blocks in pharmaceutical synthesis.
• Imine reductases (IREDs) offer a promising biocatalytic route to chiral amines.
• Expanding the IRED toolbox is essential for broader applications.

Purpose of the Study:

• To identify and characterize novel imine reductases (IREDs).
• To evaluate the substrate scope of newly identified IREDs against cyclic imines.
• To demonstrate preparative-scale synthesis of chiral amines using selected IREDs.

Main Methods:

• Bioinformatic analysis using C-terminal domain clustering to identify novel IRED candidates.
• Enzyme characterization against nine cyclic imine model substrates.
• Preparative-scale reactions using purified IREDs for chiral amine production.

Main Results:

• Twenty new IREDs were identified and characterized.
• Enzyme activity was assessed across a range of cyclic imine substrates.
• Two IREDs, IR_20 and IR_23, produced (R)-2-methylpiperidine and (R)-1-methyl-1,2,3,4-tetrahydroisoquinoline with high enantiomeric excess (>98%) and yields (71-82%).

Conclusions:

• The study expands the repertoire of IRED biocatalysts for chiral amine synthesis.
• The characterized IREDs demonstrate potential for industrial applications in pharmaceutical manufacturing.
• Novel IREDs offer efficient and stereoselective access to valuable chiral amine intermediates.