In vitro study to evaluate the degradation of bovine muscle proteins post-mortem by proteasome and μ-calpain

The degradation of bovine muscle proteins by proteasome and ubiquitous calpains was explored via 2D gel proteome analysis by inhibition of the physiological level of the proteases by specific inhibitors.The inhibition of the proteasome chymotrypsin- and trypsin-like activity results in the lack of degradation of several fragments of structural proteins such as actin, troponin T, myosin light chain and nebulin. In addition the degradation of several sarcoplasmatic proteins was eliminated when proteasome was inhibited. The inhibition of the ubiquitous calpain only resulted in minor changes in the degradation pattern, which might indicate that p94, which is not inhibited by calpastatin, is involved in the degradation post-mortem. The results of the present study indicate a sequential degradation of the structural proteins post-mortem, where calpain initiates the disruption and destabilisation of the myofibrillar structure, and thereby allows the proteasome to act.