The subcellular distribution of calpain-1 and -2 and the proteolytical activity of myofibril-bound calpains in pork were investigated during 12 days cold storage. The content of sarcoplasmic calpain-1 decreased during storage while myofibril-bound calpain-1 content first increased (P < 0.05) to 17% of that of 12 h-sarcoplasmic calpain-1 on day 6 followed by a gradual decrease with subsequent storage, suggesting that calpain-1 gradually translocated from sarcoplasm to myofibrils during the initial 6 days of postmortem storage. Intact desmin decreased (P < 0.05) after incubation of myofibrils with 0.05 mM Ca²⁺, and this was more pronounced with 5 mM Ca²⁺ (P < 0.05). Ca²⁺ titration curves of day 6 myofibrils showed two distinct proteolytic activities becoming activated in the range 0.03 to 0.06 mM and 0.4 to 0.8 mM Ca²⁺, respectively. The results suggest that both calpain-1 and calpain-2 binds to myofibrils during storage and subsequently degrade structural proteins including desmin.

在冷藏 12 天期间，研究了猪肉中 calpain-1 和 -2 的亚细胞分布以及与肌原纤维结合的钙蛋白酶的蛋白水解活性。储存期间肌浆 calpain-1 的含量降低，而与肌原纤维结合的 calpain-1 含量 在第 6 天首先增加（P < 0.05）至 12 h-sarcoplasmic calpain-1 的 17%，然后随着随后的储存逐渐减少，这表明 calpain-1 在死后储存的最初 6 天内逐渐从肌浆转移到肌原纤维。 将肌原纤维与 0.05 mM Ca ²⁺温育后，完整的结蛋白减少 ( P < 0.05) ，而这在 5 mM Ca ^{2+ 中}更为明显( P  < 0.05)。钙²⁺第 6 天肌原纤维的滴定曲线显示两种不同的蛋白水解活性分别在 0.03 至 0.06 mM 和 0.4 至 0.8 mM Ca ²⁺范围内被激活。结果表明 calpain-1 和 calpain-2 在储存过程中都与肌原纤维结合，随后降解包括结蛋白在内的结构蛋白。