Enzyme toolbox: novel enantiocomplementary imine reductases

Area of Science:

• Biocatalysis
• Organic Chemistry
• Enzymology

Background:

• Enzymatic reductions are key for chiral compound synthesis in the fine-chemical industry.
• While enzymatic reduction of C=O and C=C bonds is established, stereoselective reduction of C=N bonds (imines) is less developed.
• Recent discovery of imine-reducing enzymes has opened new avenues for asymmetric synthesis.

Purpose of the Study:

• To expand the range of available imine-reducing enzymes through bioinformatics analysis.
• To identify novel imine reductases with diverse enantiopreferences and catalytic functionalities.
• To characterize the catalytic activity and potential of newly discovered imine reductases.

Main Methods:

• Database mining to identify uncharacterized protein sequences with potential imine reductase activity.
• Bioinformatic analysis to predict enzyme function and enantiopreference.
• Experimental validation of identified enzymes through the reduction of a pharmaceutically relevant imine (2-methylpyrroline).

Main Results:

• Identification of three novel imine reductases with complementary enantiopreference.
• Characterization of amino acid residues crucial for enzyme catalysis.
• Demonstration of high catalytic efficiency and selectivity in the reduction of 2-methylpyrroline, comparable to or exceeding previously known enzymes.
• Successful whole-cell biotransformation of 2-methylpyrroline using the novel enzymes.

Conclusions:

• The discovery significantly broadens the enzymatic toolbox for stereoselective imine reduction.
• These novel imine reductases show great potential for industrial applications in chiral synthesis.
• The findings pave the way for further development of biocatalytic routes for complex molecule synthesis.