A multi-enzymatic cascade reaction for the stereoselective production of γ\gamma-oxyfunctionalyzed amino acids

A stereoselective three-enzyme cascade for synthesis of diasteromerically pure $\gamma$-oxyfunctionalized $\alpha$-amino acids was developed. By coupling a dynamic kinetic resolution (DKR) using an $\it N$-acylamino acid racemase (NAAAR) and an L-selective aminoacylase from $\textit {Geobacillus thermoglucosidasius}$ with a stereoselective isoleucine dioxygenase from $\textit {Bacillus thuringiensis,}$ diastereomerically pure oxidized amino acids were produced from racemic $\it N$-acetylamino acids. The three enzymes differed in their optimal temperature and pH-spectra. Their different metal cofactor dependencies led to inhibitory effects. Under optimized conditions, racemic $\it N$-acetylmethionine was quantitatively converted into L-methionine-$\textit {(S)}$-sulfoxide with 97% yield and 95% $\textit {de.}$ The combination of these three different biocatalysts allowed the direct synthesis of diastereopure oxyfunctionalized amino acids from inexpensive racemic starting material