Fructose-bisphosphate aldolase

Fructose-bisphosphate aldolase, also known as aldolase, is an enzyme crucial in the process of glycolysis; it catalyzes the splitting of fructose 1,6-bisphosphate into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate. This enzyme plays a pivotal role in the sugar metabolism pathway, facilitating the energy production process in cells. There are three isoforms of aldolase: A, B, and C, each encoded by a different gene and expressed in various tissues.

Function

Aldolase is a key enzyme in the glycolytic pathway, a metabolic pathway that converts glucose into pyruvate, releasing energy and producing adenosine triphosphate (ATP). Specifically, aldolase catalyzes the fourth step of glycolysis, the cleavage of fructose 1,6-bisphosphate into two three-carbon sugars, which can be further metabolized to generate energy. This reaction is reversible, allowing aldolase to also play a role in gluconeogenesis, the process of glucose synthesis from non-carbohydrate sources.

Isoforms

Aldolase A

Found predominantly in muscle tissue, aldolase A is involved in the glycolytic pathway, facilitating energy production during muscle contraction.

Aldolase B

Expressed mainly in the liver, kidney, and intestine, aldolase B is essential for fructose metabolism. Mutations in the gene encoding aldolase B are responsible for hereditary fructose intolerance (HFI), a condition that results in the inability to break down fructose, leading to serious metabolic disturbances.

Aldolase C

Aldolase C is primarily located in the brain and nervous system. Its exact function is less understood, but it is believed to play a role in the specific energy demands of the nervous system.

Structure

Aldolase is a tetramer composed of either four identical subunits (in the case of aldolase A and C) or a combination of subunits (in aldolase B). The enzyme's active site, where the catalysis occurs, binds fructose 1,6-bisphosphate. The structure of aldolase is critical for its function, as alterations can significantly affect its enzymatic activity.

Clinical Significance

Aldolase levels in the blood are sometimes measured as part of a diagnostic evaluation for muscle damage or disease. Elevated levels can indicate muscle damage or a neuromuscular disorder. Additionally, as mentioned, mutations in the aldolase B gene lead to hereditary fructose intolerance, a potentially life-threatening condition if untreated. Understanding the function and structure of aldolase can aid in the development of treatments for conditions related to this enzyme.

See Also

• Glycolysis
• Hereditary fructose intolerance
• Enzyme
• Metabolism