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[[Image:ATP chemical structure.png|thumb|[[Adenosine triphosphate]]]]

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==Overview==
'''ATPases''' are a class of [[enzyme]]s that [[catalysis|catalyze]] the [[decomposition]] of [[adenosine triphosphate]] (ATP) into [[adenosine diphosphate]] (ADP) and a free [[phosphate]] [[ion]].  This [[dephosphorylation]] reaction releases [[energy]], which the enzyme (in most cases) harnesses to drive other [[chemical reaction]]s that would not otherwise occur.  This process is widely used in all known forms of [[life]].

Some such enzymes are [[integral membrane protein]]s (anchored within [[biological membrane]]s), and move [[solute]]s across the membrane.  (These are called ''transmembrane ATPases'').

==Functions==
Transmembrane ATPases import many of the metabolites necessary for [[cell (biology)|cell]] [[metabolism]] and export toxins, wastes, and solutes that can hinder cellular processes. An important example is the sodium-potassium exchanger (or [[NaKATPase|Na<sup>+</sup>/K<sup>+</sup>ATPase]]), which establishes the ionic concentration balance that maintains the [[cell potential]]. Another example is the [[hydrogen potassium ATPase]] (H<sup>+</sup>/K<sup>+</sup>ATPase or gastric proton pump) that acidifies the contents of the stomach.

Besides exchangers, other categories of transmembrane ATPase include [[co-transport]]ers and pumps (however, some exchangers are also pumps). Some of these, like the Na<sup>+</sup>/K<sup>+</sup>ATPase, cause a net flow of charge, but others do not. These are called "electrogenic" and "nonelectrogenic" transporters, respectively.

==Mechanism==
The coupling between ATP hydrolysis and transport is more or less a strict chemical reaction, in which a fixed number of solute molecules are transported for each ATP molecule that is hydrolyzed; for example, 3 Na<sup>+</sup> ions out of the cell and 2 K<sup>+</sup> ions inward per ATP hydrolyzed, for the Na<sup>+</sup>/K<sup>+</sup> exchanger. 

Transmembrane ATPases harness the chemical potential energy of ATP, because they perform mechanical work: they transport solutes in a direction opposite to their [[thermodynamic|thermodynamically]] preferred direction of movement&mdash;that is, from the side of the membrane where they are in low concentration to the side where they are in high concentration. This process is considered [[active transport]]. 

For example, the blocking of the vesicular H+-ATPAses would increase the pH inside vesicles and decrease the pH of the cytoplasm.

==ATP synthase==

The [[ATP synthase]] of [[mitochondria]] and [[chloroplast]]s is an [[Anabolism|anabolic]] enzyme that harnesses the energy of a transmembrane [[proton]] gradient as an energy source for adding an [[inorganic phosphate]] group to a molecule of [[adenosine diphosphate]] (ADP) to form a molecule of adenosine triphosphate (ATP). 

This enzyme works when a proton moves down the concentration gradient, giving the enzyme a spinning motion. This unique spinning motion bonds ADP and P together to create ATP. 

ATP synthase can also function in reverse, that is, use energy released by ATP hydrolysis to pump protons against their thermodynamic gradient.

==Classification==
There are different types of ATPases, which can differ in function (ATP synthesis and/or hydrolysis), structure (F-, V- and A-ATPases contain rotary motors) and in the type of ions they transport.

*[[F-ATPase]]s (F1F0-ATPases) in [[mitochondria]], [[chloroplast]]s and [[bacteria]]l [[plasma membrane]]s are the prime producers of ATP, using the proton gradient generated by [[oxidative phosphorylation]] (mitochondria) or [[photosynthesis]] (chloroplasts).
*[[V-ATPase]]s (V1V0-ATPases) are primarily found in eukaryotic vacuoles, catalysing ATP hydrolysis to transport solutes and lower pH in organelles.
*'''A-ATPases''' (A1A0-ATPases) are found in [[Archaea]] and function like F-ATPases.
*[[P-ATPase]]s (E1E2-ATPases) are found in bacteria and in eukaryotic plasma membranes and organelles, and function to transport a variety of different ions across membranes.
*'''E-ATPases''' are [[cell-surface]] [[enzyme]]s that hydrolyse a range of NTPs, including extracellular ATP.

===P-ATPase=== 
{{main|P-ATPase}}
[[P-ATPase]]s (sometime known as E1-E2 ATPases) are found in bacteria and in a number of eukaryotic plasma membranes and organelles. P-ATPases function to transport a variety of different compounds, including ions and phospholipids, across a membrane using ATP hydrolysis for energy. There are many different classes of P-ATPases, each of which transports a specific type of ion: H+, Na+, K+, Mg2+, [[Calcium ATPase|Ca2+]], Ag+ and Ag2+, Zn2+, Co2+, Pb2+, Ni2+, Cd2+, Cu+ and Cu2+. P-ATPases can be composed of one or two polypeptides, and can usually assume two main conformations called E1 and E2.

==Human genes==
* [[Na+/K+-ATPase|Na+/K+ transporting]]: {{Gene|ATP1A1}}, {{Gene|ATP1A2}}, {{Gene|ATP1A3}}, {{Gene|ATP1A4}}, {{Gene|ATP1B1}}, {{Gene|ATP1B2}}, {{Gene|ATP1B3}}, {{Gene|ATP1B4}}
* [[Calcium ATPase|Ca++ transporting]]: {{Gene|ATP2A1}}, {{Gene|ATP2A2}}, {{Gene|ATP2A3}}, {{Gene|ATP2B1}}, {{Gene|ATP2B2}}, {{Gene|ATP2B3}}, {{Gene|ATP2B4}}, {{Gene|ATP2C1}}
* Mg++ transporting: {{Gene|ATP3}}
* [[Hydrogen potassium ATPase|H+/K+ exchanging]]: {{Gene|ATP4A}}, {{Gene|ATP4B}}
* H+ transporting, mitochondrial: {{Gene|ATP5A1}}, {{Gene|ATP5B}}, {{Gene|ATP5C1}}, {{Gene|ATP5C2}}, {{Gene|ATP5D}}, {{Gene|ATP5E}}, {{Gene|ATP5F1}}, {{Gene|ATP5G1}}, {{Gene|ATP5G2}}, {{Gene|ATP5G3}}, {{Gene|ATP5H}}, {{Gene|ATP5I}}, {{Gene|ATP5J}}, {{Gene|ATP5J2}}, {{Gene|ATP5L}}, {{Gene|ATP5L2}}, {{Gene|ATP5O}}, {{Gene|ATP5S}}
* [[V-ATPase|H+ transporting, lysosomal]]: {{Gene|ATP6AP1}}, {{Gene|ATP6AP2}}, {{Gene|ATP6V1A}}, {{Gene|ATP6V1B1}}, {{Gene|ATP6V1B2}}, {{Gene|ATP6V1C1}}, {{Gene|ATP6V1C2}}, {{Gene|ATP6V1D}}, {{Gene|ATP6V1E1}}, {{Gene|ATP6V1E2}}, {{Gene|ATP6V1F}}, {{Gene|ATP6V1G1}}, {{Gene|ATP6V1G2}}, {{Gene|ATP6V1G3}}, {{Gene|ATP6V1H}}, {{Gene|ATP6V0A1}}, {{Gene|ATP6V0A2}}, {{Gene|ATP6V0A4}}, {{Gene|ATP6V0B}}, {{Gene|ATP6V0C}}, {{Gene|ATP6V0D1}}, {{Gene|ATP6V0D2}}, {{Gene|ATP6V0E}}
* Cu++ transporting: {{Gene|ATP7A}} (see also [[ATP7A]]), {{Gene|ATP7B}} (see also [[Wilson disease protein|ATP7B]])
* Class I, type 8: {{Gene|ATP8A1}}, {{Gene|ATP8B1}}, {{Gene|ATP8B2}}, {{Gene|ATP8B3}}, {{Gene|ATP8B4}}
* Class II, type 9: {{Gene|ATP9A}}, {{Gene|ATP9B}}
* Class V, type 10: {{Gene|ATP10A}}, {{Gene|ATP10B}}, {{Gene|ATP10D}}
* Class VI, type 11: {{Gene|ATP11A}}, {{Gene|ATP11B}}, {{Gene|ATP11C}}
* H+/K+ transporting, nongastric: {{Gene|ATP12A}}
*  type 13: {{Gene|ATP13A1}}, {{Gene|ATP13A2}}, {{Gene|ATP13A3}}, {{Gene|ATP13A4}}, {{Gene|ATP13A5}}

==See also==
[[AAA proteins]]

==External links==
*[http://www.biologie.uni-osnabrueck.de/biophysik/Feniouk/Home.html "ATP synthase - a splendid molecular machine"]
* {{MeshName|ATPase}}
* {{UMichOPM|families|superfamily|5}} -  Proton or sodium translocating F- and V-type ATPases
* {{UMichOPM|families|superfamily|22}} - Different conformations of P-type ATPase

{{Ion pumps}}
{{Acid anhydride hydrolases}}
{{ATPases}}
[[Category:EC 3.6.3]]
[[Category:Integral membrane proteins]]

[[es:ATPasa]]
[[fr:ATPase]]
[[ja:ATPアーゼ]]
[[pt:ATPase]]
[[vi:ATPase]]
[[zh:ATP酶]]

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