Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2005
Publication Date: 7/20/2005
Citation: Geesink, G.H., Taylor, R.G., Koohmaraie, M. 2005. Calpain 3/p94 is not involved in postmortem proteolysis. Journal of Animal Science. 83:1646-1652.
Interpretive Summary: Current evidence shows that µ-calpain activity is responsible for the breakdown or degradation of structural proteins in postmortem skeletal muscle, and that this degradation is responsible for improvements in meat tenderness. µ-Calpain along with m-calpain and their specific inhibitors called calpastatins are considered ubiquitous because they have been isolated from all tissues and organs. In addition to the ubiquitous calpains there are tissue specific forms of the calpains such as skeletal muscle specific calpain known as p94 or calpain 3. Calpain 3 has never been isolated from skeletal muscle and not much is known about its properties. Based on known calpain 3 properties, one can easily exclude calpain 3 as playing a key role in postmortem proteolysis. But some have been insisting that calpain 3 indeed plays a key role in postmortem proteolysis. To directly address the potential role of calpain 3 in postmortem proteolysis and meat tenderness, we examined postmortem proteolysis in muscles from a strain of mice that had calpain 3 knocked out of its genome and compared postmortem proteolysis with that occurring in muscles from normal mice. Results indicated that absence of calpain 3 did not have a measurable effect on postmortem proteolysis. Therefore we concluded that calpain 3 does not play a key role in postmortem proteolysis and hence it does not play a key role meat tenderization.
Technical Abstract: Studies on the correlation between expression and/or autolysis of calpain and postmortem proteolysis in muscle have provided conflicting evidence regarding the possible role of calpain 3 in postmortem tenderization of meat. This paper reports the effect of postmortem storage on proteolysis and structural changes in muscle from normal and calpain 3 knockout mice. Knockout mice (n=6) were sacrificed along with control mice (n=6). Hind limbs were removed and stored at 4 deg C; muscles were dissected at 0, 1 and 3 d postmortem and analyzed individually for degradation of desmin. Pooled samples for each storage time and mouse type were analyzed for degradation of nebulin, dystrophin, vinculin, and troponin-T. In a separate experiment, hindlimb muscles from knockout (n=4) and control mice (n=4) were analyzed for structural changes at 0 and 7 d postmortem using light microscopy. As an index of structural changes, fiber detachment, cracked or broken fibers, and the appearance of space between sarcomeres were quantified. Cumulatively, the results of the first experiment indicate that postmortem proteolysis of muscle occurred similarly in control and in calpain 3 knockout mice. Desmin degradation was not different (P>0.05) and there were no indications that degradation of nebulin, dystrophin, vinculin, and troponin-T were affected by the absence of calpain 3 in postmortem muscle. Structural changes were affected by time postmortem (P<0.05), but not by the absence of calpain 3 from the muscles. In conclusion, these results indicate that calpain 3 plays a minor role, if any, in postmortem proteolysis in muscle.