Levels of calpain and calpastatin in meat subjected to high pressure.

The levels of μ-, m-calpain and calpastatin were assayed in pressurized rabbit muscle. The crude calpain level from the pressurized muscle at 100 MPa was almost the same with that of control. Above 100 MPa, the level of calpain decreased rapidly with increased pressure. At 300 MPa, the calpain level was almost inactivated. When the crude extract was pressurized, the calpain level followed the same tendency as that in the pressurized muscle. When the extracts from control or pressurized muscle were subjected to DEAE-Sephacel column chromatography, μ- and m-calpains and calpastatin lost their activity with increasing pressure, but the degree of loss was different for each. Calpains resisted changes in pressurization at 200 MPa and were inactivated over 200 MPa. Inactivation of calpastatin at 100 MPa was faster than that of calpains. From the results, it was concluded that calpain levels remained in muscle pressurized up to 200 MPa, whereas calpastatin levels were decreased by the pressurization. Thus the total activities of calpains in pressurized muscle appear to have been increased by the pressure treatment and this may result in tenderization of meat.