Aldolase B

Aldolase B

Diagram of the catalytic mechanism of Aldolase B.

Aldolase B is an enzyme that plays a crucial role in the metabolism of fructose. It is one of the three isoenzymes of aldolase, the others being aldolase A and aldolase C. Aldolase B is primarily found in the liver, kidney, and intestine.

Function

Aldolase B catalyzes the reversible cleavage of fructose-1,6-bisphosphate and fructose-1-phosphate into dihydroxyacetone phosphate (DHAP) and glyceraldehyde. This reaction is a key step in both glycolysis and gluconeogenesis. In the context of fructose metabolism, aldolase B is essential for the conversion of fructose into intermediates that can enter the glycolytic pathway.

Structure

Aldolase B is a homotetramer, meaning it is composed of four identical subunits. Each subunit contains a TIM barrel structure, which is a common motif in enzymes that catalyze reactions involving sugar phosphates. The active site of aldolase B contains a lysine residue that forms a Schiff base with the substrate, facilitating the cleavage of the carbon-carbon bond.

Clinical significance

Deficiency of aldolase B leads to a condition known as hereditary fructose intolerance (HFI). This is an autosomal recessive disorder characterized by the accumulation of fructose-1-phosphate in the liver, leading to hypoglycemia, jaundice, and hepatomegaly. Patients with HFI must avoid dietary fructose, sucrose, and sorbitol to prevent symptoms.

Related pages

• Fructose metabolism
• Glycolysis
• Gluconeogenesis
• Hereditary fructose intolerance