Synthesis of β-hydroxy-α-amino acids with a reengineered alanine racemase

The Y265A mutant of alanine racemase (alrY265A) was evaluated as a catalyst for the synthesis of β-hydroxy-α-amino acids. It promotes the PLP-dependent aldol condensation of glycine with a range of aromatic aldehydes. The desired products were obtained with complete stereocontrol at Cα (ee > 99%, D) and moderate to high selectivity at Cβ (up to 97% de). The designed enzyme is thus similar to natural d-threonine aldolases in its substrate specificity and stereoselectivity. Moreover, its ability to utilize alanine as an alternative donor suggests an expanded scope of potential utility for the production of biologically active compounds.