Fructose-1,6-bisphosphatase

Definition

Fructose-1,6-bisphosphatase is a key enzyme in the gluconeogenesis pathway that catalyzes the hydrolysis of fructose-1,6-bisphosphate to fructose-6-phosphate, an important step in the regulation of blood glucose levels.

5 Must Know Facts For Your Next Test

1. Fructose-1,6-bisphosphatase is a rate-limiting enzyme in the gluconeogenesis pathway, making it a key regulatory point in the control of blood glucose levels.
2. The enzyme catalyzes the hydrolysis of fructose-1,6-bisphosphate to fructose-6-phosphate, an important step in the conversion of non-carbohydrate precursors to glucose.
3. Fructose-1,6-bisphosphatase is allosterically inhibited by fructose-2,6-bisphosphate, a potent activator of the glycolytic enzyme phosphofructokinase-1.
4. The activity of fructose-1,6-bisphosphatase is regulated by hormones, such as glucagon and insulin, which modulate its expression and phosphorylation state.
5. Deficiencies in fructose-1,6-bisphosphatase can lead to hypoglycemia and lactic acidosis, highlighting its importance in maintaining glucose homeostasis.

Review Questions

• Explain the role of fructose-1,6-bisphosphatase in the catabolism of triacylglycerols and the fate of glycerol.
  • During the catabolism of triacylglycerols, the glycerol backbone is released and can be used as a substrate for gluconeogenesis. Fructose-1,6-bisphosphatase plays a key role in this process by catalyzing the conversion of fructose-1,6-bisphosphate to fructose-6-phosphate, an important intermediate in the gluconeogenic pathway. This allows the glycerol to be converted to glucose, which can then be used to maintain blood glucose levels or provide energy for the body.
• Describe how the activity of fructose-1,6-bisphosphatase is regulated in the context of carbohydrate biosynthesis and gluconeogenesis.
  • The activity of fructose-1,6-bisphosphatase is tightly regulated to control the rate of gluconeogenesis and maintain blood glucose homeostasis. The enzyme is allosterically inhibited by fructose-2,6-bisphosphate, a potent activator of the glycolytic enzyme phosphofructokinase-1. This regulatory mechanism ensures that gluconeogenesis and glycolysis are balanced, preventing futile cycling between the two pathways. Additionally, the expression and phosphorylation state of fructose-1,6-bisphosphatase are modulated by hormones, such as glucagon and insulin, which further fine-tune its activity in response to the body's energy needs.
• Analyze the significance of fructose-1,6-bisphosphatase in the overall regulation of glucose metabolism and energy homeostasis in the body.
  • Fructose-1,6-bisphosphatase is a critical enzyme in the regulation of glucose metabolism and energy homeostasis. As a rate-limiting enzyme in the gluconeogenesis pathway, it plays a pivotal role in maintaining blood glucose levels, especially during periods of fasting or low carbohydrate availability. By catalyzing the conversion of fructose-1,6-bisphosphate to fructose-6-phosphate, fructose-1,6-bisphosphatase controls the flux of glucose precursors into the gluconeogenic pathway, allowing the body to synthesize glucose from non-carbohydrate sources. This regulatory function is essential for preventing hypoglycemia and ensuring a stable supply of glucose to meet the body's energy demands. The dysregulation of fructose-1,6-bisphosphatase activity can lead to metabolic disorders, underscoring its importance in the overall maintenance of glucose homeostasis and energy balance.

Related terms

Gluconeogenesis: The metabolic pathway that synthesizes glucose from non-carbohydrate precursors, such as amino acids, lactate, and glycerol, to maintain blood glucose levels.

Fructose-1,6-bisphosphate: An intermediate in both glycolysis and gluconeogenesis that is converted to fructose-6-phosphate by the enzyme fructose-1,6-bisphosphatase.

Glycerol Kinase: An enzyme that catalyzes the phosphorylation of glycerol to glycerol-3-phosphate, an important step in the conversion of glycerol to glucose during gluconeogenesis.