Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 6, 1998
Publication Date: N/A
Interpretive Summary: Inconsistency in meat tenderness has been identified as one of the major problems facing the meat industry. Difference in the rate and extent of postmortem tenderization is responsible for the variation in meat tenderness. Degradation of structural muscle proteins by u-calpain is responsible for meat tenderization during postmortem storage of meat. u-Calpain is inhibited by its endogenous inhibitor, calpastatin. Calpastatin activity at 24-h postmortem accounts for a greater proportion of the variation in beef tenderness (approximately 40%) than any other single factor. The present experiment was conducted to determine whether calpastatin inhibits only the rate, or both the rate and extent of calpain-induced degradation of muscle proteins. This was accomplished by Western blot analysis of postmortem degradation of muscle proteins in normal lamb muscle and lamb muscle with high levels of calpastatin (callipyge lamb). Levels of u-calpain did not differ between these muscles. Even after 56 days of postmortem storage, degradation of structural muscle proteins was inhibited in the callipyge muscle as compared to the control muscle. The results of this experiment indicate that calpastatin inhibits both the rate and extent of postmortem proteolysis.
Technical Abstract: The present experiment was conducted to determine whether calpastatin inhibits only the rate, or both the rate and extent of calpain-induced postmortem proteolysis. Biceps femoris from normal (n = 6) and callipyge (n = 6) lamb was stored for 56 d at 4 deg C. Calpastatin activity was higher (P < .05) in the callipyge muscle at 0 and 14 d postmortem, but not at 56 d postmortem. The activity of u-calpain did not differ between normal and callipyge biceps femoris at 0 and 56 d postmortem (P > .05), but was higher at 14 d postmortem in the callipyge muscle (P < 0.05). The activity of m-calpain was higher in the callipyge muscle (P < 0.05). Western blot analyses of titin, nebulin, dystrophin, myosin heavy chain, vinculin, alpha-actinin, desmin, and troponin-T indicated that postmortem proteolysis was less extensive in callipyge than in normal biceps femoris at all postmortem times. The results of this experiment indicate that calpastatin inhibits both the rate and extent of postmortem proteolysis.