NaKATPáz

Na+/K+-ATPase, also known as the NaK-ATPase, is a membrane-bound enzyme that uses energy from ATP hydrolysis to pump sodium and potassium ions across the plasma membrane against their concentration gradients. In animal cells, it exports three Na+ ions to the extracellular space and imports two K+ ions into the cytosol for each cycle, making the pump electrogenic and helping establish the resting membrane potential and cell volume homeostasis. The pump is a heteromer composed mainly of a catalytic α subunit and a glycosylated β subunit; in vertebrates multiple α isoforms (α1, α2, α3, α4) and one or more β isoforms are expressed in tissue-specific patterns. Some auxiliary γ-subunits or FXYD proteins modulate activity.

Mechanistically, Na+/K+-ATPase belongs to the P-type ATPase family. It binds three Na+ ions on the cytoplasmic side, is phosphorylated on a conserved aspartyl residue by ATP to form E2-P, undergoes conformational changes to release Na+ outside, binds two extracellular K+, is dephosphorylated to return to the original state and release K+ inside. This cycles consumes one molecule of ATP per transport cycle and is inhibited by cardiac glycosides such as ouabain and digitoxin, which raise intracellular Na+ and indirectly increase Ca2+ via the Na+/Ca2+ exchanger.

Physiological roles include maintenance of electrochemical gradients for action potentials, driving secondary active transport, and regulating cell volume. Mutations in Na+/K+-ATPase subunits are associated with neurological and cardiac disorders, and the pump is a target for certain drugs and toxins.