title: Substrate inhibition of the (Na+, K+)-ATPase in the presence of excess Mg2+.
abstract: 1. High concentrations of ATP inhibit completely the activity of (Na+, K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) prepared from sheep brain. 2. The inhibition depends on the concentration of total ATP, i.e. complexed ATP+ free ATP. 3. The inhibition by high ATP concentrations persists in the absence of K+, and is then independent of the Na+ concentration between 2 and 140 mM Na+. 4. Raising the K+ concentration at 20 mM Na+ increases the ATP concentration required for the maximal hydrolysis rate. 5. The Hill number for the inhibition process is about three. 6. The inhibition by ATP is temperature-dependent, in that as the temperature is increased, higher ATP concentrations are required for inhibition.
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000201:enzymology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D008433:Mathematics; D008861:Microsomes / Q000201:enzymology; D011188:Potassium / Q000378:metabolism; D012756:Sheep; D012964:Sodium / Q000378:metabolism; D013696:Temperature
chemical_list: D000255:Adenosine Triphosphate; D012964:Sodium; D000251:Adenosine Triphosphatases; D008274:Magnesium; D011188:Potassium