ATPase

ATPases are enzymes that catalyze the hydrolysis of ATP into ADP and inorganic phosphate, releasing energy that powers a wide range of cellular processes. By coupling the chemical energy of ATP to mechanical work, transport, or biochemical reactions, ATPases act as energy transducers. They are diverse in structure and function, found in many cellular membranes and in soluble compartments.

Several major families are distinguished by mechanism and function. P-type ATPases form a transient aspartyl phosphate during phosphorylation and dephosphorylation cycles, driving active transport of ions such as Na+, K+, Ca2+, and H+. Na+/K+-ATPase and Ca2+-ATPase are classic examples, maintaining ion gradients and cellular signaling.

F-type and V-type ATPases couple ATP hydrolysis and proton translocation. F-type ATPases (F1F0-ATP synthases) use the proton motive force to synthesize ATP in mitochondria, chloroplasts, and bacteria, and can operate in reverse to hydrolyze ATP. V-type ATPases hydrolyze ATP to pump protons into organelles, acidifying vacuoles and endosomes; some subtypes can work in reverse under special conditions.

ABC transporters are ATPases that use ATP hydrolysis to move substrates across membranes, encompassing many pumps that contribute to nutrient uptake, toxin efflux, and drug resistance. In addition, cytosolic ATPases include motor proteins such as myosin, which convert ATP hydrolysis into mechanical force for muscle contraction and cellular transport. ATPases thus serve as central energy transducers in biology.