The effect of pressure on the catalytic properties of glutamate racemase from Aquifex pyrophilus, an extremophilic bacterium, was investigated. The activation volume for the overall reaction $({Delta}V^{ eq})$ and catalysis $({{Delta}V_{cat}}^{ eq})$ was -96.97 ml/mol and 4.97 ml/mol, respectively, while the reaction volume for the substrate binding (${Delta}V_{K_m^-1}$) was -101.94 ml/mol. The large negative ${Delta}V^{ eq}$ 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 ${Delta}V_{K_m^-1}$ for the substrate binding. The negative value of ${Delta}V_{K_m^-1}$ 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 ${{Delta}V_{cat}}^{ eq}$suggested that the pressure did not affect the glutamate racemase catalysis after the substrate binding.