NaKATPasepomp

NaKATPasepomp, commonly known as the sodium-potassium pump or Na+/K+-ATPase, is a membrane-bound enzyme that uses energy from ATP to exchange intracellular sodium ions for extracellular potassium ions. It maintains the steep Na+ and K+ concentration gradients across the plasma membrane that are essential for many cellular processes, including electrical excitability, nutrient transport, and cell volume control.

The pump operates with a stoichiometry of three Na+ ions exported for every two K+ ions imported per ATP hydrolyzed. It is a P-type ATPase that cycles between conformations. In the E1 state, the enzyme binds three Na+ from the cytosol. ATP-dependent phosphorylation converts it to the E2-P state, releasing Na+ to the outside. The enzyme then binds two K+ from the outside, dephosphorylates, and returns to the E1 state, releasing K+ inside. This cycle creates an outward current of positive charges and helps stabilize the resting membrane potential.

Structureally, the pump is a heteromer consisting mainly of an alpha subunit (catalytic) and a beta subunit (essential for proper maturation and function); some tissues also express regulatory gamma/FXYD subunits that modulate kinetics. In humans, multiple alpha and beta isoforms exist (for example ATP1A1–A4 and ATP1B1–B3), allowing tissue-specific regulation.

In physiology, NaKATPasepomp supports nerve and muscle function, renal Na+ reabsorption, and overall cellular homeostasis. It can be inhibited by cardiac glycosides such as ouabain and digoxin, which increase intracellular Na+ and affect Ca2+ handling in cardiac cells. The pump was first described by Jens Christian Skou in 1957, a discovery that earned a Nobel Prize.