Intracellular Ca2+ store from rabbit brain: kinetic aspects of Ca(2+)-stimulated ATPase.

The endoplasmic reticulum of the rabbit brain manifests low but distinguishable Ca(2+)-stimulated ATPase activity with some functional peculiarities compared to the muscle isoforms. The activity is highly sensitive to the presence of detergents and optimal activatory concentration was shown to be close to the critical micellar concentration. Kinetic properties, such as (i) activation by low (K0.5 = 0.45 microM) and inhibition by high (more than 100 microM) concentration of calcium, (ii) biphasic activation with ATP and (iii) inhibition by vanadate clearly showed that the protein of Ca(2+)-ATPase is endowed with properties typical of the family of sarco/endoplasmic reticulum calcium pumps.