Bee Giuseppe, Anderson Abbey L, Lonergan Steven M, Huff-Lonergan Elisabeth
Department of Animal Science, Iowa State University, 2278 Kildee Hall, Ames, IA 50011, United States.
Meat Sci. 2007 Jun;76(2):359-65. doi: 10.1016/j.meatsci.2006.12.004. Epub 2007 Feb 5.
The objective of this study was to determine the extent to which early postmortem (PM) pH decline influences proteolysis of the intermediate filament protein desmin, the costameric proteins vinculin and talin and autolysis of μ-calpain in the longissimus muscle (LM) of pigs from two genetic lines. Based on the LM 3h pH (H=3h pH of LM>6.0; L=3h pH of LM pH<5.7) PM, 10 carcasses per line and pH group were selected. The average 3h pH within pH group was 6.23 (H) and 5.44 (L). The LM samples were collected 24, 48, 72, and 120h PM and percent drip loss was measured after 1, 2, and 4d of storage. Samples collected at 24, 48, 72, and 120h PM were used to monitor desmin, vinculin, and talin degradation and samples collected at 24h PM were used to determine the extent of μ-calpain autolysis by immunoblotting. Higher (P<0.01) pH values at 45min, 6h, and 24h PM and lower (P<0.01) drip losses after 1, 2, and 4d of storage were recorded in the H-compared to the L-group. Abundance of the 76kDa μ-calpain autolysis product was greater (P<0.01), proteolysis of talin at all measured time points and proteolysis of desmin after 24 and 48h PM was greater (P⩽0.03) in the H-group than in the L-group. The current findings indicate activation rate of μ-calpain may be associated with proteolysis of desmin and talin and could play a role in the development of drip loss. The rate of early PM pH decline can partly explain the variation of desmin and talin degradation by affecting the activation of μ-calpain.
本研究的目的是确定宰后早期（PM）pH值下降对两个遗传品系猪的背最长肌（LM）中中间丝蛋白结蛋白、粘着斑蛋白纽蛋白和踝蛋白的蛋白水解以及μ-钙蛋白酶自溶的影响程度。根据宰后3小时背最长肌pH值（H =宰后3小时背最长肌pH值>6.0；L =宰后3小时背最长肌pH值<5.7），每个品系和pH组选择10头胴体。pH组内的平均3小时pH值分别为6.23（H）和5.44（L）。宰后24、48、72和120小时采集背最长肌样本，并在储存1、2和4天后测量滴水损失百分比。宰后24、48、72和120小时采集的样本用于监测结蛋白、纽蛋白和踝蛋白的降解，宰后24小时采集的样本用于通过免疫印迹法确定μ-钙蛋白酶自溶的程度。与L组相比，H组在宰后45分钟、6小时和24小时的pH值更高（P<0.01），在储存1、2和4天后的滴水损失更低（P<0.01）。H组中76kDaμ-钙蛋白酶自溶产物的丰度更高（P<0.01），在所有测量时间点踝蛋白的蛋白水解以及宰后24和48小时结蛋白的蛋白水解均比L组更大（P⩽0.03）。目前的研究结果表明，μ-钙蛋白酶的激活率可能与结蛋白和踝蛋白的蛋白水解有关，并可能在滴水损失的发展中起作用。宰后早期pH值下降速率可以通过影响μ-钙蛋白酶的激活来部分解释结蛋白和踝蛋白降解的差异。
