Abstract

We investigated glycogen synthase and upstream regulatory proteins determining meat quality in porcine longissimus dorsi at 24 h post-mortem. The general meat quality traits of 300 muscle samples were estimated. Muscle samples were classified into two groups based on ultimate pH of meat 24 h post-mortem (pH_24h). Muscle glycogen synthase belonging to the low pH_24h group showed remarkably higher expression than that in the high pH_24h group. AMP activated protein kinase (AMPK) and glycogen synthase kinase 3 (GSK-3) as negative regulators of glycogen synthase deactivated the suppression of glycogen synthase by phosphorylating Ser485 of AMPK and Ser9 of GSK-3B. These inhibitory kinases lead to high glycogen synthase expression. These results suggest that the accumulation of glycogen by up-regulating glycogen synthase and inhibiting AMPKa and GSK-3B was rapidly converted to lactate resulting in acidic meat. This molecular clue representing acidic meat based on post-mortem muscular pH can be used to estimate meat quality via Akt-AMPK?/GSK-3?-mediated up-regulation of glycogen synthase.

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