Tyrosinase from mushroom was used as a model polyphenol oxidase (PPO) enzyme to perform a systematic inactivation study using High Pressure Carbon Dioxide (HPCD). The ratio CO2/volume of enzyme (g/mL) loaded in the reactor was found to be critical. Above a critical ratio, pressure, temperature and time did not control the inactivation performance. Exposure time (2-15 min), temperature (25-45 degrees C) and pressure (5-20 MPa) allowed to show a characteristic inactivation pattern for PPO: a sudden decrease in activity (at least 75% of the total activity loss was observed within the first 2 min) was followed by a slowed decay. The experimental data were fitted into a two fraction kinetic model and the main kinetic parameters (Z(P), Z(T) activation volume and activation energy) were calculated. The fluorescence spectroscopy analysis of the samples treated with HPCD revealed significant changes in the tertiary structure of the enzyme.