Effect of pressure on catalytic properties of glutamate racemase from Aquifex pyrophilus, an extremophilic bacteria

Abstract

The effect of pressure on the catalytic properties of glutamate racemase from Aquifiex pyrophilus, an extremophilic bacterium, was investigated. The activation volume for the overall reaction (DeltaV(not equal)) and catalysis (DeltaV(cat)(not equal)) was -96.97 ml/ mol and 4.97 mt/mol, respectively, while the reaction volume for the substrate binding (DeltaV(km)(-1)) was - 101.94 ml/mol. The large negative DeltaV(not equal) for the overall reaction indicated that the pressurization of glutamate racemase resulted in enhanced catalytic efficiencies. In addition, this value was also due to the large negative DeltaV(km)(-1) for the substrate binding. The negative value of DeltaV(km)(-1) implied that the conformational changes in the enzyme molecule occurred during the substrate binding process, thereby increasing the degree of hydration. The small value of DeltaV(cat)(not equal) suggested that the pressure did not affect the glutamate racemase catalysis after the substrate binding.