Ilian M A, Morton J D, Kent M P, Le Couteur C E, Hickford J, Cowley R, Bickerstaffe R
Animal and Food Sciences Division, Lincoln University, Canterbury, New Zealand.
J Anim Sci. 2001 Jan;79(1):122-32. doi: 10.2527/2001.791122x.
The biochemistry of intermuscular variation in tenderness is not fully understood. To investigate the role of the calpains in this process we performed two experiments using bovine and ovine species. In the bovine experiment, two distinct muscles, longissimus thoracis et lumborum (LT) and psoas major (PM), were used. In the ovine experiment, four muscles, LT, PM, semimembranosus (SM), and semitendinosus (ST), were used. Muscles were sampled at death for the determination of the steady-state mRNA level of calpains and calpastatin and the activities of calpain 1, 2, and calpastatin. Muscles were also sampled to determine the temporal changes in pH, tenderness, and the activity of the ubiquitous calpain system during postmortem aging. The results of the relative rate of tenderization in both species was found to be related to muscle type; LT had the highest value in both species. Within species, the mRNA steady-state levels of calpain 1 and calpastatin were similar in various bovine and ovine muscles. Bovine calpain 2 mRNA level was significantly lower in the LT than in the PM. Ovine calpain 2 mRNA level was lower, but not significantly different, in the LT compared to the other muscles. The mRNA level of bovine calpain 3 was significantly higher in the LT muscle than in the PM. In the ovine, the mRNA level of calpain 3 was highest in the LT, followed by SM, PM, and ST. Results on the activity of the ubiquitous calpain system in various muscles at death were dependent on muscle type and species. Temporal changes in the activity of calpains and calpastatin during the first 24 h of postmortem aging were similar in the muscles studied: calpain 1 and calpastatin declined significantly and calpain 2 remained relatively unchanged. The temporal changes in muscle pH in both experiments indicated that the extent and rate of pH decline during aging was related to muscle type. Correlation analysis between the relative rate of tenderization and mRNA expression of calpains revealed a strong relationship with calpain 3 in both species.
肌肉间嫩度差异的生物化学机制尚未完全明确。为研究钙蛋白酶在这一过程中的作用，我们使用牛和羊进行了两项实验。在牛的实验中，选用了两块不同的肌肉，即胸腰最长肌（LT）和腰大肌（PM）。在羊的实验中，选用了四块肌肉，即LT、PM、半膜肌（SM）和半腱肌（ST）。在动物死亡时采集肌肉样本，用于测定钙蛋白酶和钙蛋白酶抑制蛋白的稳态mRNA水平以及钙蛋白酶1、2和钙蛋白酶抑制蛋白的活性。还采集肌肉样本以确定宰后成熟过程中pH值、嫩度以及普遍存在的钙蛋白酶系统活性的时间变化。结果发现，两个物种的嫩化相对速率均与肌肉类型有关；在两个物种中，LT的嫩化相对速率值最高。在同一物种内，不同牛和羊肌肉中钙蛋白酶1和钙蛋白酶抑制蛋白的mRNA稳态水平相似。牛的LT中钙蛋白酶2的mRNA水平显著低于PM。与其他肌肉相比，羊的LT中钙蛋白酶2的mRNA水平较低，但差异不显著。牛的LT肌肉中钙蛋白酶3的mRNA水平显著高于PM。在羊中，钙蛋白酶3的mRNA水平在LT中最高，其次是SM、PM和ST。不同肌肉在死亡时普遍存在的钙蛋白酶系统活性结果取决于肌肉类型和物种。在所研究的肌肉中，宰后成熟最初24小时内钙蛋白酶和钙蛋白酶抑制蛋白活性的时间变化相似：钙蛋白酶1和钙蛋白酶抑制蛋白显著下降，而钙蛋白酶2相对保持不变。两项实验中肌肉pH值的时间变化表明，成熟过程中pH值下降的程度和速率与肌肉类型有关。嫩化相对速率与钙蛋白酶mRNA表达之间的相关性分析表明，在两个物种中均与钙蛋白酶3有很强的关系。
