[Competitive inhibition of Ca-ATPase in the sarcoplasmic reticulum by sodium fluoride].

Effect of NaF and AlCl3 the activity of the sarcoplasmic reticulum Ca-ATP-ase has been investigated. NaF (mM) completely inhibits the Ca-ATP-ase activity in presence of 0.02% tween-20. The inhibition is time- and NaF-concentration-dependent and increases as affected by AlCl3 (microM). The potentiated action of AlCl3 depends on the NaF concentration. AlCl3 without NaF does not change the Ca-ATP-ase activity. NaF inhibits the Ca-ATP-ase competitively with respect to ATP, but NaF plus AlCl3 make the inhibition combined. The affinity of the Ca-ATP-ase to the NaF + AlCl3 complex, but not to NaF decreases by 5 mM with an increase of the Pi concentration. NaF probably interacts with the ATP-binding site and the NaF + AlCl3 complex interacts with the phosphate-binding site of the ATP-ase.