Order of release of ADP and Pi from phosphoenzyme with bound ADP of Ca2+-dependent ATPase from sarcoplasmic reticulum and of Na+, K+-dependent ATPase studied by ADP-inhibition patterns.
The inhibition of Ca2+-dependent ATPase from SR [EC 3.6.1.3] by ADP was of mixed type under both low Ca2+ and high Mg2+ concentration and high Ca2+ and low Mg2+ concentrations. On the other hand, the inhibition of Na+, K+-dependent ATPase [EC 3.6.1.3] by ADP was of competitive type in the presence of low and high K+ concentrations. These results suggest that ADP is released before Pi from the phosphoenzyme with bound ADP (EPADP) in the case of Ca2+-ATPase, but that Pi is released before ADP in the case of Na+, K+-ATPase.
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009132:Muscles / Q000201:enzymology; D010710:Phosphates; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*
D010710:Phosphates; D000244:Adenosine Diphosphate; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D002118:Calcium