Multi-Enzymatic Synthesis of Optically Pure β-Hydroxy α-Amino Acids

A novel enzymatic production system of optically pure β‐hydroxy α‐amino acids was developed. Two enzymes were used for the system: an N‐succinyl L‐amino acid β‐hydroxylase (SadA) belonging to the iron(II)/α‐ketoglutarate‐dependent dioxygenase superfamily and an N‐succinyl L‐amino acid desuccinylase (LasA). The genes encoding the two enzymes are part of a gene set responsible for the biosynthesis of peptidyl compounds found in the Burkholderia ambifaria AMMD genome. SadA stereoselectively hydroxylated several N‐succinyl aliphatic L‐amino acids and produced N‐succinyl β‐hydroxy L‐amino acids, such as N‐succinyl‐L‐β‐hydroxyvaline, N‐succinyl‐L‐threonine, (2S,3R)‐N‐succinyl‐L‐β‐hydroxyisoleucine, and N‐succinyl‐L‐threo‐β‐hydroxyleucine. LasA catalyzed the desuccinylation of various N‐succinyl‐L‐amino acids. Surprisingly, LasA is the first amide bond‐forming enzyme belonging to the amidohydrolase superfamily, and has succinylation activity towards the amino group of L‐leucine. By combining SadA and LasA in a preparative scale production using N‐succinyl‐L‐leucine as substrate, 2.3 mmol of L‐threo‐β‐hydroxyleucine were successfully produced with 93% conversion and over 99% of diastereomeric excess. Consequently, the new production system described in this study has advantages in optical purity and reaction efficiency for application in the mass production of several β‐hydroxy α‐amino acids.