Defosforüülaasid

Defosforüülaasid are enzymes that catalyze the removal of a phosphate group from a molecule through phosphorolytic cleavage. This process involves the introduction of a phosphate group to break a bond, distinct from hydrolysis where water is used for cleavage. Defosforüülaasid are a class of enzymes that play important roles in various metabolic pathways, particularly in carbohydrate metabolism and nucleic acid metabolism.

In carbohydrate metabolism, defosforüülaasid are involved in the breakdown of glycogen and starch. For example, glycogen phosphorylase is a key defosforüülaas that releases glucose-1-phosphate from glycogen stores, providing a readily available energy source for cells. This phosphorolytic cleavage allows for the efficient release of glucose units without requiring ATP.

In nucleic acid metabolism, defosforüülaasid are involved in the degradation of RNA and DNA. Enzymes like RNA phosphorylase can break down RNA molecules by cleaving phosphodiester bonds using inorganic phosphate. This process is important for RNA turnover and recycling of nucleotides within the cell. The mechanism of action for defosforüülaasid typically involves an active site that binds both the substrate and inorganic phosphate. The phosphate then acts as a nucleophile, attacking the bond to be cleaved, leading to the formation of a phosphorylated substrate intermediate and the release of the dephosphorylated product and inorganic phosphate. Their function is crucial for maintaining cellular homeostasis and energy balance.