Phosphatase

Phosphatases catalyze the hydrolysis of a phosphomonoester, removing a phosphate moiety from the substrate. Water is split in the reaction, with the -OH group attaching to the phosphate ion, and the H+ protonating the hydroxyl group of the other product. The net result of the reaction is the destruction of a phosphomonoester and the creation of both a phosphate ion and a molecule with a free hydroxyl group. Studies reveal that so called "docking interactions" play a significant role in substrate binding. Docking interactions can also allosterically regulate phosphatases and thus influence their catalytic activity. == Functions ==

In contrast to kinases, phosphatase enzymes recognize and catalyze a wider array of substrates and reactions. For example, in humans, Ser/Thr kinases outnumber Ser/Thr phosphatases by a factor of ten. Two notable protein phosphatases are PP2A and PP2B. PP2A is involved in multiple regulatory processes, such as DNA replication, metabolism, transcription, and development. PP2B, also called calcineurin, is involved in the proliferation of T cells; because of this, it is the target of some drugs that seek to suppress the immune system. Nucleotidases are essential for cellular homeostasis, because they are partially responsible for maintaining a balanced ratio of nucleotides to nucleosides. Some nucleotidases function outside the cell, creating nucleosides that can be transported into the cell and used to regenerate nucleotides via salvage pathways. Inside the cell, nucleotidases may help to maintain energy levels under stress conditions. A cell deprived of oxygen and nutrients may catabolize more nucleotides to boost levels of nucleoside triphosphates such as ATP, the primary energy currency of the cell. In gluconeogenesis Phosphatases can also act on carbohydrates, such as intermediates in gluconeogenesis. Gluconeogenesis is a biosynthetic pathway wherein glucose is created from noncarbohydrate precursors; the pathway is essential because many tissues can only derive energy from glucose. Each cleaves a phosphate group from a six-carbon sugar phosphate intermediate. == Classification ==

Within the larger class of phosphatase, the Enzyme Commission recognizes 104 distinct enzyme families. Phosphatases are classified by substrate specificity and sequence homology in catalytic domains. == See also ==