NaKatpasi

Na+/K+-ATPase, often referred to as NaKATPase, is a membrane-bound enzyme found in the plasma membranes of animal cells. It uses energy from ATP hydrolysis to move sodium and potassium ions against their concentration gradients. In each transport cycle, the pump exports three Na+ ions to the extracellular space and imports two K+ ions into the cell, creating an inward-to-outward electrochemical gradient that supports various cellular functions.

The enzyme belongs to the P-type ATPase family and is composed of multiple subunits, including a catalytic α-subunit and a structural β-subunit. In mammals, several α-subunit isoforms (α1–α4) provide tissue-specific distribution and regulation. The transport mechanism involves alternating conformations, commonly described as E1 and E2. In the E1 state, three intracellular Na+ ions bind and the pump is phosphorylated from ATP. This drives a conformational change to E2, releasing Na+ outside. The pump then binds two extracellular K+ ions, is dephosphorylated, and returns to the E1 conformation to take up K+ from the outside, completing the cycle.

The Na+/K+-ATPase is essential for maintaining resting membrane potential, regulating cell volume, and supporting secondary active transport processes such as nutrient uptake and neurotransmitter reuptake. It is inhibited by cardiac glycosides (for example, ouabain and digitalis), which bind to the α-subunit and alter ion homeostasis. Mutations in ATP1A genes encoding α-subunits can be associated with neurological disorders, reflecting the pump’s broad role in physiology.