Some Enzymatic Properties of Ca2+-Dependent Adenosine Triphosphatase from a Calcareous Red Alga, Serraticardia maxima and Its Distribution in Marine Algae

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Abstract
A Ca2+-dependent ATPase was extracted from a calcareous red alga, S. maxima, by homogenization with Tris-HCl buffer (pH 8.2) containing KCl. Some enzymatic properties were investifated using a partially purified enzyme preparation. Optimum activity of this enzyme was approximately at pH 9.0. The enzyme was activated by several divalent metal ions, of which Ca2+ showed the highest effect. The activation of the ATPase by Ca2+, Mg2+ and Sr2+ seemed to compete mutually with the same site of this enzyme. In addition to ATP, other nucleotides such as ITP, GTP and ADP served as the substrate but with less effectiveness. In contrast to the Ca2+-dependent ATPases of animal origin, this algal ATPase was not inhibited by p-CMB [parachloromercuribenzoate] and ethacrynic acid. The Ca2+-dependent ATPase activity was detected specifically in various species of Corallinaceae but not in other calcareous and non-carcareous algae.