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

J Biochem. 1980 Jun;87(6):1721-7. doi: 10.1093/oxfordjournals.jbchem.a132916.

Abstract

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.

MeSH terms

  • Adenosine Diphosphate* / pharmacology
  • Animals
  • Binding, Competitive
  • Calcium / pharmacology
  • Calcium-Transporting ATPases / antagonists & inhibitors*
  • Kinetics
  • Magnesium / pharmacology
  • Muscles / enzymology
  • Phosphates*
  • Rabbits
  • Sarcoplasmic Reticulum / enzymology*
  • Sodium-Potassium-Exchanging ATPase / antagonists & inhibitors*

Substances

  • Phosphates
  • Adenosine Diphosphate
  • Calcium-Transporting ATPases
  • Sodium-Potassium-Exchanging ATPase
  • Magnesium
  • Calcium