Unique Ca(2+)-activated ATPase in the nervous ganglia of Phyllocaulis soleiformis (Mollusca)

• Published in: Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology Biochemistry & molecular biology, 2002-01, Vol.131 (1), p.55-61
• Main Authors: Da Silva, Rosane Souza, de Paula Cognato, Giana, Bogo, Maurício Reis, da Graça Fauth, Maria, Fin, Cyntia Alencar, Thomé, José Willibaldo, Bonan, Carla Denise, Dutra Dias, Renato
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Animals; Calcium - metabolism; Calcium-Transporting ATPases - antagonists & inhibitors; Calcium-Transporting ATPases - metabolism; Enzyme Inhibitors - metabolism; Enzyme Stability; Ganglia - enzymology; Hydrogen-Ion Concentration; Mollusca - enzymology; Osmolar Concentration; Substrate Specificity; Temperature
• ISSN: 1096-4959
• DOI: 10.1016/S1096-4959(01)00475-4

Nucleotide-metabolizing enzymes play important roles in the regulation of intracellular and extracellular nucleotide levels. We studied ATPase activity in the nervous ganglia of Phyllocaulis soleiformis, a terrestrial slug. The ATPase was divalent cation-dependent, with a maximal rate for ATP hydrolysis at pH 6.0 and 7.2 in the presence of Ca(2+) (5 mM). Mg(2+)-ATPase activity was only 26% of the activity observed in the presence of Ca(2+) (5 mM). ZnCl2 (10 mM) produced a significant inhibition of 70%. Ca(2+)-ATPase activity was insensitive to the classical ATPase inhibitors ouabain, N-ethylmaleimide, orthovanadate and sodium azide. Levamisole, an inhibitor of alkaline phosphatase, was ineffective. Among nucleotides, ATP was the best substrate. The apparent K(m) ((ATP)) for Ca(2+)-ATPase was 348+/-84 microM ATP and the V(max) was 829+/-114 nmol Pi min(-1) mg(-1) protein. The P. soleiformis ganglial ATPase does not appear to fit clearly into any of the previously described types of Ca(2+)-ATPases.