A hyperthermostable protease, Tk-subtilisin, can degrade PrPSc. Scrapie-infected mouse brain homogenate ( RML strain ) was degraded by Tk-subtilisin under high-temperature condition and the degradation products were inoculated into culture cell. At high-temperature condition, Tk-subtilisin degraded PrP from RML homogenate, whereas proteinase K ( PK ) hardly degraded. In addition, Western blotting of the cell lysate inoculated the degradation product showed that the amount of PrPSc decreased significantly. Moreover, the signals of PrPSc were not observed when the concentration of Tk-subtilisin was increased. These results suggest that the combination of heat treatment and proteolysis by Tk-subtilisin is effective in reducing the infectivity titer of PrPSc.
