ATP synthase is an enzyme that creates the energy storage molecule adenosine triphosphate (ATP). ATP is the most commonly used "energy currency" of cells for all organisms. It is formed from adenosine diphosphate (ADP) and inorganic phosphate (Pi). The overall reaction catalyzed by ATP synthase is:
The F1 fraction derives its name from the term "Fraction 1" and FO (written as a subscript letter "o", not "zero") derives its name from being the binding fraction for oligomycin, a type of naturally-derived antibiotic that is able to inhibit the FO unit of ATP synthase. These functional regions consist of different protein subunits — refer to tables. This enzyme is used in synthesis of ATP through aerobic respiration.