Purification and Properties of Glutamate-phenylpyruvate Aminotransferase from the Ruminal Bacterium, Prevotella bryantii B14

Prevotella species are important in catabolic protein metabolism by the mixed ruminal microbial population. This study was conducted to purify and investigate properties of one of the enzymes involved in amino acid metabolism by Prevotella bryantii B 1 4, glutamate-phenylpyruvate aminotransferase (GPA; EC 2.6.1.64). GPA was purified 51-fold from a cell-free extract by ammonium sulfate precipitation and column chromatography with Phenyl-superose, DEAE-Toyopearl 650 M, Sephacryl S-100 HR and Sephadex G-100. The molecular mass of GPA was estimated to be 28.0 kDa by SDS-PAGE. The optimum pH was 6.5 and the activity declined above pH 9.0. GPA was reactive over a wide range of pH from 5.0 to 10.5. Maximum activity of GPA occurred at 45°C and the activity declined at temperatures over 55°C. GPA was stable below 60°C. Aminooxyacetate and phenylhydrazine were highly inhibitory, while SDS, EDTA and some heavy metal ions also inhibited activity. The purification and characterization of enzyme will help to isolate the gene and ultimately to understand the role of GPA in both anabolic and catabolic amino acid metabolism by P. bryantii B 1 4.