Enantioselective nitrile hydratases and amidases from different bacterial isolates

Abstract

Different enrichment cultures were performed using various nitriles as sole source of nitrogen, succinate or a mixture of sugars as carbon sources and soil samples as inocula. It was attempted to obtain a relationship between the selective nitrogen source and the enzyme systems which were synthesized by the isolates, the enzyme specificities, and enzyme enantioselectivities. Various strains were obtained which harbored enantioselective nitrilases, nitrile-hydratases or amidases. The enantioselective amidase from the isolate Rhodococcus erythropolis MP50 and the enantioselective nitrile hydratase from Agrobacterium tumefaciens d3 were studied in greater detail. The purified amidase from R. erythropolis MP50 hydrolysed 2-phenylpropionamide, naproxen amide and ketoprofen amide with enantiomeric excesses (ee)>99% up to 49% conversion of the respective substrates. In the presence of hydroxylamine, the amidase also formed the corresponding hydroxamates enantioselectively. These chiral hydroxamates could be chemically converted by a Lossen rearrangement into chiral amines. The partially purified nitrile hydratase from A. tumefaciens d3 converted 2-phenylbutyronitrile and ketoprofen nitrile to the corresponding S-amides with ee values>90% at 30% conversion of the respective substrate.