The plasma membrane calcium ATPase (PMCA) is a transport protein in the plasma membrane of cells responsible for removing calcium (Ca²⁺) from the cell. This pump is vital for regulating the amount of Ca²⁺ within cells¹.

The PMCA and the sodium/calcium exchanger (NCX) are together the main regulators of intracellular Ca²⁺ concentrations².

Since it transports Ca²⁺ into the extracellular space, the PMCA is also an important regulator of the Ca²⁺ concentration in the extracellular space³.

The PMCA belongs to a family of P-type primary ion transport ATPases, and is expressed in a variety of tissues, including the brain⁴.

The pump is powered by the hydrolysis of adenosine triphosphate (ATP), with a stoichiometry of one Ca²⁺ ion removed for each molecule of ATP hydrolyzed. It binds to Ca²⁺ ions with a high affinity (a Km of 100 to 200 nM) but does not remove Ca²⁺ at a very fast rate. This is in contrast to the NCX, which has a low affinity and a high capacity. Thus, the PMCA is effective at binding Ca²⁺ even when its concentration within the cell is very low, and so is suited to maintaining Ca²⁺ at its normally very low levels. The NCX is better suited to removing large amounts of Ca²⁺ quickly, as it is needed in neurons after an action potential. Thus the activities of the two types of pump complement each other⁵.