Cupin‐Type Dimethylsulfoniopropionate Lyase from Pelagibacter ubique (DddKPu) Catalyzes Aza‐Michael Addition of Primary and Secondary Amines to Acrylic Acid

The formation of carbon─nitrogen (C─N) bonds is a cornerstone of organic synthesis, underpinning the production of amines, imines, and nitriles found in numerous active ingredients. Among the methods for C─N bond formation, the aza-Michael addition stands out as a powerful and versatile approach. Herein, we present a biocatalytic strategy for the efficient aza-Michael addition of primary and secondary amines to acrylic acid, i.e., aza-Michaelase activity, leveraging the promiscuity of dimethylsulfoniopropionate (DMSP) lyase from Pelagibacter ubique HTCC1062 (DddKPu). In vivo DddKPu catalyzes the β-elimination of DMSP to sodium acrylate and dimethylsulfide (i.e., a retro sulfa-Michael reaction). Here, we screened DddKPu against a diverse library of 30 primary and 44 secondary amines. The wild-type enzyme achieved 90%-100% conversion and 40%-86% isolated yields of N,N-disubstituted-β-amino acids with secondary amines. For primary amines, the W26G variant proved optimal, furnishing 50%-100% conversion and 43%-81% isolated yields of N-substituted-β-amino acids. Notably, the enzyme exhibited remarkable chemoselectivity: for pyrrolidin-2-ylmethanamine, the reaction occurred exclusively at the secondary amine, while for piperidin-2-ylmethanamine, it reacted selectively at the primary amine. These findings highlight DddKPu as a versatile biocatalyst for the selective synthesis of β-amino acids, expanding the toolbox for C─N bond formation.