Measurement of Plasma Membrane CalciumCalmodulin-Dependent ATPase (PMCA) Activity

The plasma membrane calcium–calmodulin-dependent ATPase (PMCA) is a calcium-extruding enzymatic pump that ejects calcium from the cytoplasm to the extracellular compartment. Although in excitable cells such as skeletal and cardiac muscle cells PMCA has been shown to play only a minor role in regulating global intracellular calcium concentration, increasing evidence points to an important role for PMCA in signal transduction, in particular in the nitric oxide signaling pathway. Moreover, recent evidence has shown the functional importance of PMCA in mediating cardiac contractility and vascular tone. Here we describe a method in determining PMCA activity in the microsomal membrane preparation from cultured cells that overexpress specific isoform of PMCA by using modified coupled enzyme assay.