The role of phosphoenolpyruvate

Phosphoenolpyruvate is a relatively common biochemical molecule in biological cells. At the same time, phosphoenolpyruvate is not only a product of glycolysis, but also a product of gluconeogenesis. Many people don’t know much about it. If you want to have a detailed understanding of phosphoenolpyruvate, then you can join me in introducing the following content to help us understand it.

First, in glycolysis, this molecule is produced by 2-phosphoglycerate under the catalysis of enolase and is a high-energy phosphate molecule. Phosphoenolpyruvate then enters the 10th and final step of glycolysis. In the final step of glycolysis, phosphoenolpyruvate will be catalyzed by pyruvate kinase to transfer the phosphate group originally attached to the oxygen atom to ADP, thereby generating ATP and pyruvate. This reaction releases a large amount of energy and is a difficult to reverse reaction. Its standard free energy change is 31.4 kJ/mol (in water with pH = 7 and concentration of 55.5M). In addition, this reaction also requires the participation of potassium ions and magnesium ions (or other divalent cations).

Second, because the final step of glycolysis is a difficult reaction to reverse, an alternative pathway is needed to reduce pyruvate to phosphoenolpyruvate during gluconeogenesis. First, pyruvate must consume ATP molecules and be converted into oxaloacetate under the catalysis of pyruvate carboxylase. Oxaloacetate is then converted into phosphoenolpyruvate via the catalysis of phosphoenolpyruvate carboxykinase. In this reaction, ATP is consumed and ADP and carbon dioxide are generated.

Third, unlike the previous and next reactions, the above two reactions take place in chloroplasts. In addition to the direct conversion, oxaloacetate can also use another pathway that requires more steps to produce phosphoenolpyruvate. In addition, the intermediate gluconeogenesis process from the formation of phosphoenolpyruvate to the production of fructose-1,6-bisphosphate is the reverse reaction of glycolysis.

Phosphoenolpyruvate is a common biochemical molecule in biological cells and is an intermediate product of glycolysis and gluconeogenesis. In C4 plants, phosphoenolpyruvate reacts with carbon dioxide to form oxaloacetate under the action of phosphoenolpyruvate carboxylase.