title: Micro-calpain is essential for postmortem proteolysis of muscle proteins.
abstract: The objective of this investigation was to test the hypothesis that -calpain is largely responsible for postmortem proteolysis of muscle proteins. To accomplish this objective, we compared proteolysis of known muscle proteins in muscles of wild type and micro-calpain knockout mice during postmortem storage. Knockout mice (n = 6) were killed along with control mice (n = 6). Hind limbs were removed and stored at 4 degrees C. Muscles were dissected at 0, 1, and 3d postmortem and subsequently analyzed for degradation of nebulin, dystrophin, metavinculin, vinculin, desmin, and troponin T. In a separate experiment, hind limb muscles from knockout (n = 4) and control mice (n = 4) were analyzed at 0, 1, and 3 d postmortem using casein zymography to confirm that mu-calpain activity was knocked out in muscle and to determine whether or not m-calpain is activated in murine postmortem muscle. Cumulatively, the results of the first experiment indicated that postmortem proteolysis was largely inhibited in micro-calpain knockout mice. The results of the second experiment established the absence of micro-calpain in the muscle tissue of knockout mice and confirmed the results of an earlier study that m-calpain is active in postmortem murine muscle. The results of the current study show that even in a species in which m-calpain is activated to some extent postmortem, micro-calpain is largely responsible for postmortem proteolysis. This observation excludes a major role for any of the other members of the calpain family or any other proteolytic system in postmortem proteolysis of muscle proteins. Therefore, understanding the regulation of micro-calpain in postmortem muscle should be the focus of further research on postmortem proteolysis and tenderization of meat.
authors.affiliation: CCL Research, Veghel, The Netherlands NL-5462.
authors.forename: G H
authors.initials: GH
authors.lastname: Geesink
authors.forename: S
authors.initials: S
authors.lastname: Kuchay
authors.forename: A H
authors.initials: AH
authors.lastname: Chishti
authors.forename: M
authors.initials: M
authors.lastname: Koohmaraie
mesh_terms: D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002154:Calpain / Q000502:physiology*; D006614:Hindlimb; D051379:Mice; D018345:Mice, Knockout; D009124:Muscle Proteins / Q000032:analysis / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000737:chemistry / Q000201:enzymology*; D011180:Postmortem Changes; D012034:Refrigeration; D013997:Time Factors
chemical_list: D009124:Muscle Proteins; D002154:Calpain