Nucleophilic α-Functionalization of Benzyl Amines Using an Engineered Threonine Aldolase

Area of Science:

• Biocatalysis and Enzyme Engineering
• Organic Synthesis
• Medicinal Chemistry

Background:

• Chiral amines are essential building blocks in pharmaceuticals and agrochemicals.
• Threonine aldolases offer stereoselective synthesis of chiral amines but are limited to small amino acids.
• Expanding the substrate scope of aldolases is crucial for broader synthetic applications.

Purpose of the Study:

• To engineer a threonine aldolase for the α-functionalization of benzylamines.
• To broaden the substrate scope of threonine aldolases for synthesizing diverse chiral amines.
• To elucidate the mechanistic basis for the engineered enzyme's novel function.

Main Methods:

• Directed evolution of threonine aldolase.
• Biocatalytic synthesis using engineered enzymes.
• Mechanistic studies and X-ray crystallography.

Main Results:

• An engineered threonine aldolase efficiently catalyzes the α-functionalization of a wide range of benzylamines.
• The enzyme accepts diverse aldehydes, yielding single-enantiomer 1,2-amino alcohols with high yield and diastereoselectivity.
• Crystallographic and mechanistic data explain the enzyme's expanded substrate scope and novel function.

Conclusions:

• Engineered threonine aldolases can overcome previous substrate limitations, enabling the synthesis of complex chiral amines.
• The developed biocatalytic approach offers a powerful tool for accessing valuable chiral amine building blocks.
• The identified beneficial mutations demonstrate generality and can be transferred to related enzymes.