title: Vanadate inhibition of Na+K+. ATPase and K+-dependent p-nitrophenylphosphatase: a kinetic analysis.
abstract: Vanadate in redox state +5 inhibited the Na+K+-activated ATPase as well as the potassium-stimulated p-nitrophenylphosphatase (p-NPPase) activities of plasma membrane fragments prepared from rat brain. Vanadate exhibited a mixed type inhibition on the Na+K+-ATP-ase activity. The same type of inhibition was observed when the p-NPPase activity of the enzyme preparation was measured either in the presence of 20 mM K+ or with 5 mM Na+ + 1 mM K+. When the reaction mixture contained 50 microM ATP, 5 mM Na+ and 1 mM K+, inhibition of p-NPP hydrolised by vanadate displayed a noncompetitive character. Higher noradrenalin concentration was required for counteracting, the inhibition of p-NPPase by vanadate in the presence of ATP than in its absence.
mesh_terms: D009597:4-Nitrophenylphosphatase / Q000037:antagonists & inhibitors*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002462:Cell Membrane / Q000201:enzymology; D007700:Kinetics; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors*; D011188:Potassium / Q000502:physiology; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology*
chemical_list: D014639:Vanadium; D014638:Vanadates; D000255:Adenosine Triphosphate; D010744:Phosphoric Monoester Hydrolases; D009597:4-Nitrophenylphosphatase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium