Abstract: The purpose of this study was to explore the cascade regulation of NO on the AMP-activated protein kinase (AMPK) activity, glycolysis and water-holding capacity (WHC) in beef during postmortem aging. Beef quadriceps femoris treated with the NO release agent DETA, the nitric oxide synthase (NOS) inhibitor L-nitro-arginine methyl ester (L-NAME) or the AMPK inhibitor DETA + compound C were tested for NO content, AMPK activity and the key enzyme activities related to glycolysis, protein solublity and WHC after 0, 6, 12, 24, 48 and 72 h of postmortem aging. The results showed that at 0, 6 and 12 h postmortem, AMPK activity was significantly lower in the L-NAME-treated group than in the control group (P < 0.05), while it was significantly higher in the DETA-treated group than in the control group (P < 0.05). The activity of hexokinase (HK) and phosphofructokinase (PFK) in the L-NAME-treated group were significantly lower than those in the control group at 6 and 12 h (P < 0.05), whereas the pH was significantly higher than that in the control group at 6, 12 and 24 h (P < 0.05). Moreover, the total protein solubility was higher than that in the control group at 6, 12, 24, 48 and 72 h (P < 0.05), while the centrifugal loss was lower than that in the control group at these time points (P < 0.05). On the other hand, there was no significant difference in any of the above indexes between the NO-promoted group and the control group (P > 0.05). However, the activity of HK and PFK in the NO-promoted + AMPK inhibited group were significantly lower than in the other three groups at 6 and 12 h (P < 0.05), while the pH was significantly higher than in the other three groups at 6, 12 and 24 h (P < 0.05); the total protein solubility was significantly higher than in the other three groups at 6, 12, 24, 48 and 72 h (P < 0.05), while the opposite was true for centrifugal loss at these times (P < 0.05). From these results, it was shown that at the early post-mortem aging stage, NO enhanced the activity of HK and PFK and glycolysis rate by activating AMPK, which thereby reduced the pH, total protein solubility and WHC of beef. This study provides a theoretical basis for revealing the endogenous factors causing postmortem deterioration of beef quality and for future studies on meat quality control.

Key words: NO; AMP-activated proteinkinase activity; glycolysis; protein solubility; water-holding capacity; beef