This study reexamines the mechanism of rigor mortis, a characteristic phenomenon observed during postmortem changes in skeletal muscle of livestock and poultry, by focusing on the influence of imidazole dipeptides, which are abundantly present in skeletal muscle tissue. Previous studies on rigor mortis have largely overlooked the presence of low-molecular-weight compounds other than calcium and magnesium. Imidazole dipeptides possess pH-buffering and antioxidant properties and play an important role in maintaining the homeostasis of skeletal muscle tissue. With a focus on these compounds, we investigated their effects on the ATP-degrading activity (ATPase activity) of actomyosin in the postmortem skeletal muscle environment. Under acidic conditions, actomyosin ATPase activity decreased; however, the addition of imidazole dipeptides restored this activity. Furthermore, this recovery was suggested to involve an increased affinity between myosin and ATP mediated by imidazole dipeptides. Overall, these findings indicate that, even under acidic conditions that develop in postmortem skeletal muscle tissue, the presence of imidazole dipeptides allows actomyosin to retain sufficient ATPase activity. This sustained activity promotes muscle contraction and thereby contributes to the progression of rigor mortis.

Read the full article in the Journal of Animal Science.