Fructose 1,6-bisphosphatase

Fructose-1.6-bisphosphatase-pdb-3FBP

Fructose 1,6-bisphosphatase is an important enzyme in the gluconeogenesis pathway, which is the metabolic process that generates glucose from non-carbohydrate substrates. This enzyme catalyzes the conversion of fructose 1,6-bisphosphate to fructose 6-phosphate and inorganic phosphate. The reaction is a key regulatory step in gluconeogenesis and is essentially the reverse of the reaction catalyzed by phosphofructokinase in glycolysis.

Structure

Fructose 1,6-bisphosphatase is a homotetramer, meaning it consists of four identical subunits. Each subunit has a binding site for fructose 1,6-bisphosphate, and the enzyme's activity is regulated by various metabolites and hormones.

Function

The primary function of fructose 1,6-bisphosphatase is to regulate the levels of glucose in the blood. By converting fructose 1,6-bisphosphate to fructose 6-phosphate, it helps to maintain glucose homeostasis, especially during periods of fasting or intense exercise. This enzyme is crucial for the proper functioning of the liver and kidneys, where gluconeogenesis predominantly occurs.

Regulation

Fructose 1,6-bisphosphatase is tightly regulated by several mechanisms:

• **Allosteric Inhibition**: The enzyme is inhibited by AMP (adenosine monophosphate), which signals low energy levels in the cell.
• **Allosteric Activation**: It is activated by citrate, which indicates a high level of energy and building blocks for biosynthesis.
• **Hormonal Regulation**: Insulin and glucagon play significant roles in the regulation of this enzyme. Insulin inhibits its activity, while glucagon promotes it.

Clinical Significance

Deficiency in fructose 1,6-bisphosphatase can lead to a rare metabolic disorder known as Fructose 1,6-bisphosphatase deficiency. This condition can cause severe hypoglycemia, lactic acidosis, and ketosis, especially during fasting or illness. Early diagnosis and management are crucial for affected individuals.

Related Enzymes

• Phosphofructokinase
• Glucose-6-phosphatase
• Pyruvate carboxylase
• Phosphoenolpyruvate carboxykinase

See Also

• Gluconeogenesis
• Glycolysis
• Metabolism
• Enzyme regulation
• Fructose 1,6-bisphosphate

External Links

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