Effects of hydrostatic pressure on the quaternary structure and enzymatic activity of a large peptidase complex from Pyrococcus horikoshii.

While molecular adaptation to high temperature has been extensively studied, the effect of hydrostatic pressure on protein structure and enzymatic activity is still poorly understood. We have studied the influence of pressure on both the quaternary structure and enzymatic activity of the dodecameric TET3 peptidase from Pyrococcus horikoshii. Small angle X-ray scattering (SAXS) revealed a high robustness of the oligomer under high pressure of up to 300 MPa at 25°C as well as at 90°C. The enzymatic activity of TET3 was enhanced by pressure up to 180 MPa. From the pressure behavior of the different rate-constants we have determined the volume changes associated with substrate binding and catalysis. Based on these results we propose that a change in the rate-limiting step occurs around 180 MPa.