Expanding the Toolbox of (R)-selective Amine Transaminases by Identification and Characterization of new Members

Amine transaminases (ATAs) are used to synthesize enantiomerically pure amines, which are building blocks for pharmaceuticals and agrochemicals. R‐selective ATAs belong to the fold type IV PLP‐dependent enzymes, and different sequence‐, structure‐ and substrate scope‐based features have been identified in the past decade. However, our knowledge is still restricted due to the limited number of characterized (R)‐ATAs, with additional bias towards fungal origin. We aimed to expand the toolbox of (R)‐ATAs and contribute to the understanding of this enzyme subfamily. We identified and characterized four new (R)‐ATAs. The ATA from Exophiala sideris contains a motif characteristic for d‐ATAs, which was previously believed to be a disqualifying factor for (R)‐ATA activity. The crystal structure of the ATA from Shinella is the first from a Gram‐negative bacterium. The ATAs from Pseudonocardia acaciae and Tetrasphaera japonica are the first characterized (R)‐ATAs with a shortened/missing N‐terminal helix. The active‐site charges vary significantly between the new and known ATAs, correlating with their diverging substrate scope.
Diversifying: The toolbox of R‐selective amine transaminases (ATAs) has been expanded by an ATA containing a motif characteristic for d‐ATAs, two ATAs with a shortened/missing N‐terminal helix and the first ATA with known structure from a Gram‐negative bacterium. Their active site charges vary significantly compared to known ATAs correlating with their diverging substrate scope.