Proteolytic potential in white muscle of sea bass (Dicentrarchus labrax L.) during post mortem storage on ice: time-dependent changes in the activity of the components of the calpain system

The variations in the amounts of milli-calpain and its specific inhibitor in the white muscle of sea bass (Dicentrarchus labrax) during storage at 4 °C for up to 7 days were determined after separation by hydrophobic chromatography on a Phenyl Sepharose gel. There was a significant decline in postslaughter m-calpain activity with an important inter-individual variability in the rate of decrease of the total activity. In contrast with the calpastatin of mammalian post mortem muscles, calpastatin remained constant within fish muscles after death. The initial levels of protease and inhibitor activities, and their behaviour through post mortem storage, are discussed and implications for the mechanism of tenderisation of fish muscle are suggested.