Protein Phosphorylation Induced by Pyruvate Kinase M2 Inhibited Myofibrillar Protein Degradation in Post-Mortem Muscle

Abstract

Myofibrillar protein degradation is primarily related to meat tenderness through protein phosphorylation regulation. Pyruvate kinase M2 (PKM2), a glycolytic rate-limiting enzyme, is also regarded as a protein kinase to catalyze phosphorylation. The objective of this study was to investigate the relationship between myofibrillar protein degradation and phosphorylation induced by PKM2. Myofibrillar proteins were incubated with PKM2 at 4, 25, and 37 °C. The global phosphorylation level of myofibrillar proteins in the PKM2 group was significantly increased, but it was sensitive to temperature (P < 0.05). Compared with 4 and 25 °C, PKM2 significantly increased the myofibrillar protein phosphorylation level from 0.5 to 6 h at 37 °C (P < 0.05). In addition, the degradation of desmin and actin was inhibited after they were phosphorylated by PKM2 when incubated at 37 °C. These results demonstrate that phosphorylation of myofibrillar proteins catalyzed by PKM2 inhibited protein degradation and provided a possible pathway for meat tenderization through glycolytic enzyme regulation.

Acetylation and Phosphorylation Regulate the Role of Pyruvate Kinase as a Glycolytic Enzyme or a Protein Kinase in Lamb

“…However, PKM can also transfer the phosphate group from PEP to a protein substrate and act as a protein kinase . PKM inhibits myofibrillar protein degradation by phosphorylation which will regulate meat tenderization . There are more than 900 protein substrates of PKM, suggesting a wide effect of PKM on phosphorylating proteins.…”

“…The previous study showed that actin was one of the phosphorylated substrates of PKM, therefore the kinase assay on actin was performed to evaluate PKM kinase activity . The wtPKM and mutated PKMs were incubated with actin (Shanghai Yuanye Bio-Technology Co., Ltd., Shanghai, China) at 37 °C for 0.5 and 6 h in a buffer consisting of 100 mM KCl, 50 mM MgCl 2 , 1 mM DTT, 1 mM NaVO 4 , 5% glycerin, 2 mM PEP, 30 mM HEPES, pH 7.5.…”