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Mitochondrial pyruvate consumption decreases glycolytic flux in postmortem muscleColor, water-holding capacity and tenderness are important aspects of meat quality that are impacted by pH. The pH of meat is primarily determined by the amount of anaerobic glycolysis that occurs postmortem. As glycogen is degraded, it will produce ATP, pyruvate and hydrogen ions that acidify the meat, and this acidification process is essential for proper meat quality development. In the absence of oxygen, pyruvate is converted to lactate to restore NAD+ necessary for further glycolysis. In this state of anoxia, mitochondria are often ignored due to their reliance on oxygen to produce ATP. However, mitochondrial enzymes continue to function and may compete for pyruvate, causing decreased lactate and NAD+ production. This may limit glycolytic flux and slow the rate of pH decline. The purpose of this study was to investigate the impact of mitochondria on pH decline. To achieve this, we inhibited two key mitochondrial enzymes involved in pyruvate metabolism, pyruvate dehydrogenase and pyruvate carboxylase, with CPI-613 and avidin in an in vitro system. We hypothesized that inhibition of pyruvate dehydrogenase and pyruvate carboxylase would increase the rate of glycolysis. The increased rate of glycolysis in treated samples would indicate that the consumption of pyruvate by mitochondria decreases glycolytic flux. Pre-rigor pork muscle tissue was added to an in vitro system that mimics postmortem metabolism. Each tube was treated with inhibitors or control and analyzed for pH, glycogen, glucose, glucose-6-phosphate and lactate. Treated samples had lower pH (P < 0.05) as well as increased lactate production and glycogen degradation (P < 0.05). Glucose and glucose-6-phosphate concentrations were higher in the treated tubes (P < 0.05), indicating increased glycolytic flux. Collectively, these data suggest that inhibition of pyruvate dehydrogenase and pyruvate carboxylase increases the rate of glycolysis in meat, and mitochondria may play a role in modulating postmortem glycolysis.

Publisher

Utah State University

Publication Date

12-10-2020

Disciplines

Life Sciences | Nutrition

Mitochondrial Pyruvate Consumption Decreases Glycolytic Flux in Postmortem Muscle

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