| Calcium ATPase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 Calcium ATPase[1] | |||||||||
| Identifiers | |||||||||
| EC no. | 7.2.2.10 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDBPDBePDBsum | ||||||||
| |||||||||
Ca2+ ATPase is a form ofP-ATPase that transferscalcium after amuscle has contracted. The three kinds of calcium ATPase are:[2]
Calcium ATPases belong to a family ofP-type primary ion transport ATPases that form anaspartyl phosphate intermediate.[3]
Plasma membrane Ca2+ ATPase (PMCA) is atransport protein in theplasma membrane ofcells that serves to removecalcium (Ca2+) from the cell. It is vital for regulating the amount of Ca2+ within cells.[4]In fact, the PMCA is involved in removing Ca2+ from alleukaryotic cells.[3]There is a very large transmembraneelectrochemical gradient of Ca2+ driving the entry of theion into cells, yet it is very important for cells to maintain lowconcentrations of Ca2+ for propercell signalling; thus it is necessary for the cell to employion pumps to remove the Ca2+.[5]The PMCA and thesodium calcium exchanger (NCX) are together the main regulators ofintracellular Ca2+ concentrations.[3]Since it transports Ca2+ into the extracellular space, the PMCA is also an important regulator of the calcium concentration in theextracellular space.[6]
The PMCA is expressed in a variety oftissues, including thebrain.[7]
In myocytes (muscle cells) Ca2+ is normally sequestered (isolated) in a specialized form ofendoplasmic reticulum (ER) calledsarcoplasmic reticulum (SR). It is a Ca2+ ATPase that transfers Ca2+ from thecytosol of the cell to thelumen of the SR at the expense ofATP hydrolysis during muscle relaxation. In the skeletal muscles the calcium pump in the sarcoplasmic reticulum membrane works in harmony with similar calcium pumps in the plasma membrane. This ensures that the cytosolic concentration of free calcium in resting muscle is below 0.1 μM. The sarcoplasmic and endoplasmic reticulum calcium pumps are closely related in structure and mechanism, and both are inhibited by the tumor-promoting agentthapsigargin, which does not affect the plasma membrane Ca2+ pumps.
