Tilapia myosin (2.5 mg/ml) was treated by hydrostatic pressure (50-300 MPa) for 0-60 min to determine the inactivation kinetics of myosin Ca-ATPase. The process of the pressure-induced inactivation of myosin Ca-ATPase included two steps: the first one was an instantaneous pressure-induced inactivation, and the degrees of lost activities, called instantaneous pressure kill (IPK) values, increased with elevated pressure. The second one, the logarithm of residual activity of myosin ATPase, decreased smoothly during each pressure treatment for 10-60 min. However, D values (the time needed for 90% loss of the activity during a treatment at the same pressure) of Ca-ATPase decreased about 50% with per 50 MPa increase. In this study, 150 MPa was the pressure level that caused apparent myosin denaturation and the typical network structure formation with beyond 50% decrease of myosin Ca-ATPase activity.
