Aldolase B

Aldolase B

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

Function

Aldolase B catalyzes the reversible cleavage of fructose-1-phosphate into dihydroxyacetone phosphate (DHAP) and glyceraldehyde. This reaction is a key step in the fructose metabolism pathway, allowing the conversion of fructose into intermediates that can enter glycolysis or gluconeogenesis.

Structure

Aldolase B is a homotetramer, meaning it is composed of four identical subunits. Each subunit contains a catalytic site that binds to the substrate, fructose-1-phosphate. The enzyme's active site includes a lysine residue that forms a Schiff base with the substrate, facilitating the cleavage reaction.

Catalytic Mechanism

The catalytic mechanism of aldolase B involves the formation of a Schiff base intermediate between the enzyme and the substrate. The lysine residue in the active site forms a covalent bond with the carbonyl group of fructose-1-phosphate, creating an imine. This intermediate is then cleaved to produce dihydroxyacetone phosphate and glyceraldehyde.

The catalytic mechanism of aldolase B.

Clinical Significance

Deficiency of aldolase B is associated with hereditary fructose intolerance (HFI), a genetic disorder that results in the accumulation of fructose-1-phosphate in the liver, leading to hypoglycemia, jaundice, and liver damage. Individuals with HFI must avoid dietary fructose to prevent symptoms.

Related Enzymes

• Aldolase A
• Aldolase C

Related Pages

• Fructose metabolism
• Glycolysis
• Gluconeogenesis
• Hereditary fructose intolerance