Скачать или смотреть Regulation of Glycolysis | Part 10 Carbohydrate Foundations | Macronutrients Lecture 56

Phosphofructokinase catalyzes the committed step in glycolysis and is regulated by the energy status of the cell. Subscribe to Nourishable at    / nourishable  

This video is part 10 of the Carbohydrate Foundations module within a lecture series on the nutrition science of macronutrients.


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References
Chapter 5 Carbohydrates in Wardlaw’s Perspectives in Nutrition, 2019 (Editors: Byrd-Bredbenner, Moe, Berning and Kelley, 11th edition)
Chapter 2 - Carbohydrates in Modern Nutrition in Health and Disease, 2014 (Editors: Ross, Caballero, Cousins, Tucker and Ziegler; 11 edition)

The enzyme phosphofructokinase catalyzes the committed step in glycolysis. Abbreviated as PFK, it uses ATP to add a phosphate to fructose-6-phosphate to yield fructose-2,6,-bisphoshate and ADP. Since it is catalyzing the committed step in glycolysis, PFK is heavily regulated based on the energy status of the cell. PFK is inhibited by a high concentration of ATP - this makes sense because if we already have a high concentration of energy in the cell then we don’t need to send more glucose through glycolysis into the Krebs cycle. Similarly, citric acid also inhibits PFK. This makes sense because it is the first step in the Krebs cycle. The citric acid concentration would be high when we’re already sending lots of acetylCoA into the Krebs cycle, so we shouldn’t send more towards the Krebs cycle. Fructose-2,6,-bisphosphate will undergo a rearrangement and then will split into two separate 3-carbon compounds: dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. These two compounds can be interconverted with one another. Glyceraldehyde-3-phosphate will go through a series of reactions to yield phosphoenolpyruvate (or PEP), which is converted to pyruvate by pyruvate kinase in an energy-producing reaction that yields ATP. Finally, pyruvate will be converted to acetylCoA - which can get shuttled into the Krebs cycle or other directions depending on the energy status of the cell.