Mechanism of the Effect of Protein Phosphorylation on Myofibril Protein Degradation

Myofibrillar proteins degradation contributes to meat tenderization during postmortem. Protein phosphorylation has been revealed to be associated with meat tenderness in recent years. This chapter aimed to investigate the effect of myofibrillar protein phosphorylation on the degradation susceptibility by μ-calpain. Protein kinase A (PKA) and alkaline phosphatase (AP) were added to myofibrillar proteins, extracted from ovine longissimus lumborum (LL) muscles, to modify the phosphorylation level for 30 min at 30 °C. The samples were then incubated with μ-calpain at 4 °C at different Ca2+ concentrations. The results showed that more degradation products of myosin heavy chain, actin, titin, desmin, and troponin T were detected with the increase of Ca2+ concentration. The protein degradation was higher in AP treated group compared to the control group. This research indicated that phosphorylation prevented proteolytic susceptibility of myofibrillar proteins to degradation by μ-calpain. Protein phosphorylation made a major contribution in meat tenderization during postmortem.