title: Colorimetric Assays of Na,K-ATPase.
abstract: The Na,K-ATPase is a plasma membrane enzyme that catalyzes active ion transport by the hydrolysis of ATP. Its activity in vivo is determined by many factors, particularly the concentration of intracellular sodium ions. It is the target of the cardiac glycoside class of drugs and of endogenous regulators. Its assay is often an endpoint in the investigation of physiological processes, and it is a promising drug target. As described in this unit, its enzymatic activity can be determined in extracts from tissues by test tube assay using a spectrophotometer or (32)P-ATP. The protocols in this chapter measure inorganic phosphate as the end product of hydrolysis of ATP.
authors.affiliation: Laboratory of Membrane Biology, Massachusetts General Hospital, Edwards 4, 55 Fruit Street, Boston, MA, 02114, USA. sweadner@helix.mgh.harvard.edu.
authors.forename: Kathleen J
authors.initials: KJ
authors.lastname: Sweadner
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D002301:Cardiac Glycosides / Q000737:chemistry / Q000627:therapeutic use; D003124:Colorimetry / Q000379:methods*; D006801:Humans; D006868:Hydrolysis; D010710:Phosphates / Q000737:chemistry / Q000378:metabolism*; D012964:Sodium / Q000737:chemistry / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D002301:Cardiac Glycosides; D010710:Phosphates; D000255:Adenosine Triphosphate; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase
keywords: ATP hydrolysis; Activity assay; Cardiac glycosides; Drug assay; Na,K-ATPase