Role of AMP‐activated protein kinase in the glycolysis of postmortem muscle

Abstract

AbstractAMP‐activated protein kinase (AMPK) is a newly identified kinase controlling energy metabolism in vivo. The objective of this study was to show the role of AMPK in postmortem glycolysis. Rapid and excessive postmortem glycolysis is directly related to the incidence of PSE (pale, soft and exudative) meat in pork, chicken and turkey, while insufficient glycolysis leads to dark cutters in beef and lamb, which causes significant loss to the meat industry. A total of 24 two‐month‐old C57BL/6J mice were assigned to three treatments: (1) wild‐type mice without pre‐slaughter treatment; (2) wild‐type mice with a 2 min swim before slaughter; and (3) wild‐type mice intraperitoneally injected with AICAr (50 mg kg−1), a specific activator of AMPK, to stimulate the activity of AMPK. In addition, 16 two‐month‐old C57BL/6J mice with AMPK knockout were assigned to two treatments: (4) AMPK knockout mice without pre‐slaughter treatment; and (5) AMPK knockout mice with a 2 min swim before slaughter. The longissimus dorsi muscle was sampled at 0, 1 and 24 h postmortem for pH and enzyme activity measurements. Results showed that AMPK activity had a major role in determining the ultimate muscle pH. Pre‐slaughter stress induced by swimming significantly accelerated the glycogenolysis in postmortem muscle through activating glycogen phosphorylase. AMPK is important for maintaining the activity of glycogen phosphorylase and pyruvate kinase, and glycogenolysis/glycolysis in postmortem muscle. Thus, AMPK has an important role in the control of postmortem glycolysis and is crucial for a lower ultimate pH in postmortem muscle. However, the activation of AMPK cannot fully account for the initial rapid glycogenolysis/glycolysis induced by stress and another mechanism must exist for the accelerated glycolysis induced by pre‐slaughter stress. Copyright © 2005 Society of Chemical Industry