An 
ATPase is an 
enzyme that 
catalyzes the decomposition of 
ATP into 
ADP plus an inorganic 
phosphate ion. This 
dephosphorylation[?] is widely used in all known forms of life as a mechanism for driving energetically unfavourable reactions; as such, ATPases are rarely dedicated solely to dephosphorylating ATP, but rather couple this reaction to some other reaction and use the ATP dephosphorylation as a source of energy.
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