Characterization of an aromatic amino acid aminotransferase from Rhizobium leguminosarum biovar trifolii.

ABSTRACT

The most abundant aromatic amino acid aminotransferase of Rhizobium leguminosarum biovar trifolii was partially purified. The molecular mass of the enzyme was estimated to be 53 kDa by gel filtration. The enzyme transaminated aromatic amino acids and histidine. It used aromatic keto acids and alpha-ketoglutaric and oxalacetic acids as amino-group acceptors. The optimum temperature was 35 degrees C. Using phenylalanine and alpha-ketoglutaric acid as substrates the activation energy was 46.2 kJ.mol-1 and for the couple tryptophanalpha-ketoglutaric acid it was 70.3 kJ.mol-1. The optimum pH was different for each substrate 7.3 for phenylalanine, 7.9 for histidine and 8.7 for tryptophan.