Effects of Different Na⁺ Concentrations on cAMP-Dependent Protein Kinase Activity in Postmortem Meat

cAMP-dependent protein kinase (PKA) activity regulates protein phosphorylation, with Na⁺ playing a crucial role in PKA activity. The aim of this study was to investigate the effects of different Na⁺ concentrations on PKA activity and protein phosphorylation level in postmortem muscle. The study consisted of two experiments: (1) NaCl of 0, 20, 100, 200 and 400 mM was added to a muscle homogenate incubation model to analyze the effect of Na⁺ concentration on PKA activity, and (2) the same concentrations were added to pure PKA in vitro incubation models at 4 °C to verify the effect of Na⁺ on PKA activity. The PKA activity of the muscle homogenate model increased with storage time in groups with different Na⁺ concentrations. High concentrations of Na⁺ inhibited sarcoplasmic protein phosphorylation. The PKA activity at 24 h of storage and the sarcoplasmic protein phosphorylation level at 12 h of storage in the group with 200 mM Na⁺ was lower than that of the other groups. After 1 h incubation, the PKA activity of samples in the 200 mM Na⁺ group was inhibited and lower than that in the other Na⁺ groups in the in vitro incubation model. These results suggest that the Na⁺ concentration at 200 mM could better inhibit PKA activity. This study provided valuable insights for enhancing curing efficiency and improving meat quality.