ATPaser

ATPaser is a term sometimes used to refer to enzymes that catalyze the hydrolysis of ATP to ADP and inorganic phosphate, releasing energy that powers a variety of cellular processes. While ATPase is the more common spelling, ATPaser may appear in some texts as an informal or historical variant. The enzymes designated as ATPases span several families and differ in structure, membrane association, and biological role.

Major ATPase families include P-type ATPases, which form a covalent aspartyl-phosphate intermediate during the active transport of ions such as Ca2+ and Na+/K+; F-type and V-type ATPases, which function as rotary motors that couple ATP hydrolysis or synthesis to proton translocation across membranes; and ABC-type ATPases, which use ATP binding and hydrolysis to power substrate transport. In some contexts, ATPases function as ATP synthases (primarily F-type) that generate ATP from ADP and phosphate using a proton motive force, though they can also operate in reverse to drive transport.

Physiological roles include maintaining ion gradients essential for nerve signaling and muscle contraction (such as Na+/K+-ATPase and Ca2+-ATPases), energizing secondary transport across membranes, and acidifying intracellular compartments (lysosomes and vacuoles via V-type ATPases). In energy metabolism, mitochondrial and chloroplast F-type ATP synthases produce ATP during respiration and photosynthesis.

Structural features vary by family. P-type ATPases have transmembrane domains with cytosolic phosphorylation and actuator regions, while F- and V-type ATPases are large rotary complexes with multiple subunits. Inhibitors include vanadate for some P-type enzymes, oligomycin for F-type ATPases, and cardiac glycosides like ouabain targeting Na+/K+-ATPase.

Note on terminology: ATPase is the standard term; ATPaser is less common and may reflect informal usage or misspelling.