Engineered phenylalanine dehydrogenase in organic solvents: homogeneous and biphasic enzymatic reactions

Abstract

The use of engineered phenylalanine dehydrogenase N145A supported on Celite for the reductive amination of phenylpyruvic acid in homogeneous and biphasic aqueous–organic solvents is reported. The results indicate that the immobilised biocatalyst is remarkably robust, even in the presence of high concentrations of polar or non-polar organic solvents such as acetone, methanol, n-hexane, toluene and methylene chloride. Cofactor regeneration with alcohol dehydrogenase from Saccharomyces cerevisiae and ethanol was successfully explored. Application to the non-natural poorly water-soluble 2-oxo acid p-NO₂-phenylpyruvic acid was successfully performed, resulting in the biocatalytic synthesis of p-NO₂-phenylalanine. In all cases 100% stereoselectivity for the production of the amino acid was retained.