aldolázy

Aldolases are enzymes that catalyze aldol cleavage and aldol addition reactions. These reactions are crucial in many metabolic pathways, particularly in carbohydrate metabolism. Specifically, aldol cleavage involves the breaking of a carbon-carbon bond in a beta-hydroxy carbonyl compound, producing two smaller carbonyl compounds. This is the reverse of the aldol addition reaction, where two carbonyl compounds combine to form a beta-hydroxy carbonyl compound.

In biochemistry, aldolases are most famously known for their role in glycolysis, the breakdown of glucose for energy. Aldolase B, for example, cleaves fructose-1,6-bisphosphate into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. This step is essential for continuing the glycolytic pathway. Other aldolases are involved in gluconeogenesis, the synthesis of glucose, and in the synthesis of various other organic molecules.

Aldolases are classified based on the mechanism they employ. Class I aldolases use a Schiff base intermediate formed between a lysine residue in the enzyme's active site and the carbonyl group of the substrate. Class II aldolases, on the other hand, utilize a divalent metal ion, typically zinc, to activate the carbonyl group. The specific aldolase present in an organism or tissue often reflects its primary metabolic needs. Defects in aldolase enzymes can lead to serious metabolic disorders.