Delgado E F, Geesink G H, Marchello J A, Goll D E, Koohmaraie M
Roman L. Hruska US Meat Animal Research Center, USDA, ARS, Clay Center, Nebraska 68933-0166, USA.
J Anim Sci. 2001 Feb;79(2):398-412. doi: 10.2527/2001.792398x.
Activities of mu- and m-calpain and of calpastatin were measured at four different times during postmortem storage (0, 1, 3, and 10 d) in three muscles from either callipyge or noncallipyge (normal) sheep. The weights of two muscles, the biceps femoris and the longissimus, are greater in the callipyge phenotype, whereas the weight of the infraspinatus is not affected. The activity of m-calpain was greater (P < 0.05) in the biceps femoris and longissimus from callipyge than in those from normal sheep, but it was the same in the infraspinatus in the two phenotypes. The extractable activity of m-calpain did not change (biceps femoris and infraspinatus) or decreased slightly (longissimus) during postmortem storage. Extractable activity of mu-calpain decreased to zero or nearly zero after 10 d postmortem in all muscles from both groups of sheep. The rate of decrease in mu-calpain activity was the same in muscles from the callipyge and normal sheep. At all time points during postmortem storage, calpastatin activity was greater (P < 0.05) in the biceps femoris and longissimus from the callipyge than from the normal sheep, but it was the same in the infraspinatus from callipyge and normal sheep. Calpastatin activity decreased (P < 0.05) in all three muscles from both phenotypes during postmortem storage; the rate of this decrease in the callipyge biceps femoris and longissimus and in the infraspinatus from both the callipyge and normal sheep was slow, especially after the first 24 h postmortem, whereas calpastatin activity in the biceps femoris and longissimus from the normal sheep decreased rapidly. During postmortem storage, the 125-kDa calpastatin polypeptide was degraded, but the 80-kDa subunit of mu-calpain was cleaved only to 76- and 78-kDa polypeptides even though extractable mu-calpain activity declined nearly to zero. Approximately 50 to 60% of total mu-calpain became associated with the nonextractable pellet after 1 d postmortem. The myofibril fragmentation index for the biceps femoris and longissimus from normal sheep increased significantly during postmortem storage. The fragmentation index for the infraspinatus from the callipyge and normal sheep increased to an intermediate extent, whereas the index for the biceps femoris and longissimus from the callipyge did not change during 10-d postmortem storage. The results suggest that postmortem tenderization is related to the rate of calpastatin degradation in postmortem muscle and that calpastatin inhibition of the calpains in postmortem muscle is modulated in some as yet unknown manner.
在死后储存的四个不同时间点（0、1、3和10天），对来自臀肌肥大或非臀肌肥大（正常）绵羊的三块肌肉中的μ-钙蛋白酶、m-钙蛋白酶和钙蛋白酶抑制蛋白的活性进行了测定。臀肌肥大表型的两块肌肉，即股二头肌和背最长肌的重量更大，而冈下肌的重量不受影响。与正常绵羊的股二头肌和背最长肌相比，臀肌肥大绵羊的股二头肌和背最长肌中m-钙蛋白酶的活性更高（P < 0.05），但两种表型的冈下肌中m-钙蛋白酶的活性相同。死后储存期间，m-钙蛋白酶的可提取活性没有变化（股二头肌和冈下肌）或略有下降（背最长肌）。两组绵羊所有肌肉在死后10天后，μ-钙蛋白酶的可提取活性降至零或几乎为零。臀肌肥大绵羊和正常绵羊肌肉中μ-钙蛋白酶活性的下降速率相同。在死后储存的所有时间点，臀肌肥大绵羊的股二头肌和背最长肌中钙蛋白酶抑制蛋白的活性均高于正常绵羊（P < 0.05），但臀肌肥大绵羊和正常绵羊的冈下肌中钙蛋白酶抑制蛋白的活性相同。死后储存期间，两种表型的所有三块肌肉中钙蛋白酶抑制蛋白的活性均下降（P < 0.05）；臀肌肥大绵羊的股二头肌和背最长肌以及臀肌肥大和正常绵羊的冈下肌中钙蛋白酶抑制蛋白活性的下降速率较慢，尤其是在死后的头24小时之后，而正常绵羊的股二头肌和背最长肌中钙蛋白酶抑制蛋白的活性下降迅速。死后储存期间，125 kDa的钙蛋白酶抑制蛋白多肽被降解，但尽管可提取的μ-钙蛋白酶活性几乎降至零，μ-钙蛋白酶的80 kDa亚基仅被切割为76 kDa和78 kDa的多肽。死后1天，约50%至60%的总μ-钙蛋白酶与不可提取的沉淀结合。正常绵羊股二头肌和背最长肌的肌原纤维断裂指数在死后储存期间显著增加。臀肌肥大和正常绵羊冈下肌的断裂指数增加到中等程度，而臀肌肥大绵羊的股二头肌和背最长肌在10天的死后储存期间断裂指数没有变化。结果表明，死后嫩化与死后肌肉中钙蛋白酶抑制蛋白的降解速率有关，并且死后肌肉中钙蛋白酶抑制蛋白对钙蛋白酶的抑制作用以某种未知方式受到调节。
