Fructose-bisphosphatase

Fructose-bisphosphatase (FBPase) is an enzyme that plays a critical role in gluconeogenesis, the metabolic pathway that leads to the generation of glucose from non-carbohydrate substrates. It catalyzes the hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate and inorganic phosphate, which is a key step in the regulation of glucose synthesis. This enzyme is found in the liver, kidney, and other gluconeogenic tissues.

Function

Fructose-bisphosphatase is crucial for maintaining blood glucose levels, especially during fasting or periods of low carbohydrate intake. By reversing part of the glycolytic pathway, it facilitates the production of glucose, ensuring a continuous energy supply to the body, particularly to the brain and red blood cells, which rely heavily on glucose for energy.

Structure

The enzyme is a protein composed of multiple subunits, which may vary among different species. Its activity is regulated by several factors, including the concentration of its substrate, fructose 1,6-bisphosphate, and the presence of allosteric effectors such as adenosine monophosphate (AMP) and fructose 2,6-bisphosphate.

Regulation

Fructose-bisphosphatase is regulated by a balance between phosphorylation and dephosphorylation, mediated by various hormones such as insulin and glucagon. Insulin inhibits gluconeogenesis, including the action of fructose-bisphosphatase, while glucagon promotes it. This regulation ensures that glucose production is increased during fasting or stress when it is needed most and decreased when glucose is abundant.

Clinical Significance

Deficiencies in fructose-bisphosphatase can lead to metabolic disorders, including Fructose-bisphosphatase deficiency, a rare inherited condition. This disorder is characterized by impaired gluconeogenesis, leading to symptoms such as hypoglycemia, lactic acidosis, and ketosis. Early diagnosis and management are crucial for preventing severe metabolic crises.

See Also

• Gluconeogenesis
• Fructose 1,6-bisphosphate
• Fructose 6-phosphate
• Metabolic pathway