ATPase is used to liberate inorganic phosphorus from ATP. ATPase, from porcine cerebral cortex, has been used in inhibition assays of Na/K-ATPase activity .
This membrane enzyme hydrolyzes ATP to ADP and orthophosphate. The hydrolysis is coupled with the exchange of sodium and potassium ions across the plasma membrane. The enzyme is present in almost all tissues of higher organisms, but it is most abundant in the kidney where it reabsorbs sodium ions from the glomerular filtrate. Na+,K+-ATPase is affected by changes in intracellular calcium. It is also sensitive to ouabain and inhibited by vanadate, and (in vitro) by SPAI-1, a peptide isolated from porcine duodenum. It has been reported to be regulated by phosphorylation by protein kinase A (PKA). Bufalin, and other cardiotonic steroids, may inhibit Na+/K+-ATPase activity and induce the differentiation of HL60, U937, and ML1 cells .
