Unique Ca(2+)-activated ATPase in the nervous ganglia of Phyllocaulis soleiformis (Mollusca).
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.
Da Silva
Rosane Souza
RS
Laboratório de Pesquisa Bioquímica, Departamento de Ciências Fisiológicas, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul, Avenida Ipiranga, 6681, Caixa Postal 1429, 90619-900, Porto Alegre, RS, Brazil.
de Paula Cognato
Giana
G
Bogo
Maurício Reis
MR
da Graça Fauth
Maria
M
Fin
Cyntia Alencar
CA
Thomé
José Willibaldo
JW
Bonan
Carla Denise
CD
Dutra Dias
Renato
R
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism; D004795:Enzyme Stability; D005724:Ganglia / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D008974:Mollusca / Q000201:enzymology*; D009994:Osmolar Concentration; D013379:Substrate Specificity; D013696:Temperature
D004791:Enzyme Inhibitors; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium