In an erythrocyte undergoing glycolysis, what would be the effect of a sudden increase in the concentration of a. ATP? b. AMP? c. fructose-1,6-bisphosphate? d. fructose-2,6-bisphosphate? e. citrate? f. glucose-6-phosphate?

Sourav PanApril 23, 2025

Answered

• a. ATP​

  • ATP acts as an allosteric inhibitor of phosphofructokinase-1 (PFK-1), a key regulatory enzyme in glycolysis.​

  • An increase in ATP concentration signals sufficient energy availability, leading to decreased PFK-1 activity and a subsequent slowdown in glycolytic flux.​

  • This negative feedback mechanism helps maintain energy homeostasis within the cell.​

• b. AMP​

  • AMP serves as an allosteric activator of PFK-1.​

  • Elevated AMP levels indicate low cellular energy status, prompting an upregulation of glycolysis to generate more ATP.​

  • This positive feedback ensures rapid response to energy demands.​

• c. Fructose-1,6-bisphosphate (F-1,6-BP)​

  • F-1,6-BP is an intermediate in glycolysis that acts as an allosteric activator of pyruvate kinase (PK), enhancing the conversion of phosphoenolpyruvate to pyruvate.​

  • An increase in F-1,6-BP concentration accelerates the latter stages of glycolysis, promoting efficient energy production.​

• d. Fructose-2,6-bisphosphate (F-2,6-BP)​

  • F-2,6-BP is a potent allosteric activator of PFK-1 and an inhibitor of fructose-1,6-bisphosphatase.​

  • Elevated levels of F-2,6-BP enhance glycolysis by increasing PFK-1 activity and simultaneously inhibit gluconeogenesis.​

  • This dual regulation ensures a coordinated control of glucose metabolism.​

• e. Citrate​

  • Citrate functions as an allosteric inhibitor of PFK-1.

  • An increase in citrate concentration reflects a high level of biosynthetic precursors, signaling to downregulate glycolysis.​

  • This inhibition prevents excessive accumulation of metabolic intermediates.​

• f. Glucose-6-phosphate (G6P)​

  • G6P acts as an allosteric inhibitor of hexokinase, the enzyme catalyzing the first step of glycolysis.​

  • Elevated G6P levels indicate a bottleneck in downstream glycolytic steps, leading to feedback inhibition of glucose phosphorylation.​

  • This regulation prevents unnecessary consumption of glucose when glycolytic flux is impeded.