Passage
Glycolysis and gluconeogenesis are tightly regulated, opposing metabolic pathways that help control blood glucose levels. Glycolysis converts glucose to two pyruvate molecules, whereas gluconeogenesis consumes 6 ATP equivalents to convert two pyruvate molecules back to glucose. When glycolysis is upregulated, gluconeogenesis is downregulated, and vice versa.As shown in Figure 1, glycolysis and gluconeogenesis in the liver are largely regulated by the allosteric action of the small molecule fructose-2,6-bisphosphate (F2,6BP) on the enzymes phosphofructokinase-1 (PFK-1) and fructose-1,6-bisphosphatase (F1,6BPase) . PFK-1 is a kinase that uses ATP to phosphorylate fructose-6-phosphate (F6P) in an irreversible step of glycolysis, forming fructose-1,6-bisphosphate (F1,6BP) and ADP. During gluconeogenesis, F1,6BPase removes the phosphate group by hydrolysis.
Figure 1 Activities of (A) PFK-1 and (B) F1,6BPase in the presence (solid lines) and absence (dashed lines) of F2,6BPA bifunctional enzyme that contains a phosphofructokinase-2 (PFK-2) domain and a fructose-2,6-bisphosphatase (F2,6BPase) domain controls F2,6BP levels in the liver. The PFK-2 domain converts F6P to F2,6BP, and the F2,6BPase domain converts F2,6BP back to F6P. When blood glucose levels are low, the enzyme becomes phosphorylated. This phosphorylation event simultaneously activates the F2,6BPase domain and inactivates the PFK-2 domain. Under high blood glucose conditions, the enzyme becomes dephosphorylated, activating the PFK-2 domain and inactivating the F2,6BPase domain.
-Given the information in Figure 1, are PFK-1 and F1,6BPase activated or inhibited by F2,6BP?

Question

Passage
Glycolysis and gluconeogenesis are tightly regulated, opposing metabolic pathways that help control blood glucose levels. Glycolysis converts glucose to two pyruvate molecules, whereas gluconeogenesis consumes 6 ATP equivalents to convert two pyruvate molecules back to glucose. When glycolysis is upregulated, gluconeogenesis is downregulated, and vice versa.As shown in Figure 1, glycolysis and gluconeogenesis in the liver are largely regulated by the allosteric action of the small molecule fructose-2,6-bisphosphate (F2,6BP) on the enzymes phosphofructokinase-1 (PFK-1) and fructose-1,6-bisphosphatase (F1,6BPase) . PFK-1 is a kinase that uses ATP to phosphorylate fructose-6-phosphate (F6P) in an irreversible step of glycolysis, forming fructose-1,6-bisphosphate (F1,6BP) and ADP. During gluconeogenesis, F1,6BPase removes the phosphate group by hydrolysis.

Figure 1 Activities of (A) PFK-1 and (B) F1,6BPase in the presence (solid lines) and absence (dashed lines) of F2,6BPA bifunctional enzyme that contains a phosphofructokinase-2 (PFK-2) domain and a fructose-2,6-bisphosphatase (F2,6BPase) domain controls F2,6BP levels in the liver. The PFK-2 domain converts F6P to F2,6BP, and the F2,6BPase domain converts F2,6BP back to F6P. When blood glucose levels are low, the enzyme becomes phosphorylated. This phosphorylation event simultaneously activates the F2,6BPase domain and inactivates the PFK-2 domain. Under high blood glucose conditions, the enzyme becomes dephosphorylated, activating the PFK-2 domain and inactivating the F2,6BPase domain.
-Given the information in Figure 1, are PFK-1 and F1,6BPase activated or inhibited by F2,6BP?

Quizplus · Accepted Answer

11ecba2d_0f0d_30bf_a3bf_6316c16a9ae3_MD0008_00 Allosteric effectors are small molecules that bind to enzymes at sites other than the active site. Upon binding, allosteric effectors induce conformational changes in enzymes that alter enzyme activity. Allosteric activators increase enzymatic activity, whereas allosteric inhibitors decrease enzymatic activity. Many metabolic pathways are regulated by allosteric effectors, and an effector that activates one metabolic pathway often inhibits the opposing pathway (eg, F2,6BP in glycolysis and gluconeogenesis). Figure 1 shows that in the presence of F2,6BP, the glycolysis enzyme PFK-1 has higher activity than in the absence of F2,6BP. Conversely, the gluconeogenesis enzyme F1,6BPase has lower activity in the presence of F2,6BP than in its absence. Therefore, PFK-1 is activated by F2,6BP and F1,6BPase is inhibited. Educational objective: Metabolic pathways are commonly regulated by allosteric effectors. Allosteric effectors bind enzymes at sites other than the active site and induce conformational changes that alter enzymatic activity. A molecule that allosterically activates one pathway often allosterically inhibits the opposing pathway.

Passage Glycolysis and Gluconeogenesis Are Tightly Regulated, Opposing Metabolic Pathways That