Ca2+-stimulated, Mg2+-independent ATP hydrolysis and the high affinity Ca2+-pumping ATPase. Two different activities in rat kidney basolateral membranes.
Biochim Biophys Acta
; 778(3): 481-8, 1984 Dec 19.
Article
em En
| MEDLINE
| ID: mdl-6239653
ABSTRACT
The Mg2+-dependency of Ca2+-induced ATP hydrolysis is studied in basolateral plasma membrane vesicles from rat kidney cortex in the presence of CDTA and EGTA as Mg2+- and Ca2+-buffering ligands. ATP hydrolysis is strongly stimulated by Mg2+ with a Km of 13 microM in the absence or presence of 1 microM free Ca2+. At free Mg2+ concentrations of 1 microM and lower, ATP hydrolysis is Mg2+-independent, but is strongly stimulated by submicromolar Ca2+ concentrations (Km = 0.25 microM, Vmax = 24 mumol Pi/h per mg protein). The Ca2+-stimulated ATP hydrolysis strongly decreases at higher Mg2+ concentrations. The Ca2+-stimulated Mg2+-independent ATP hydrolysis is not affected by calmodulin or trifluoperazine and shows no specificity for ATP over ADP, ITP and GTP. In contrast, at high Mg2+ concentrations calmodulin and trifluoperazine affect the high affinity Ca2+-ATPase activity significantly and ATP is the preferred substrate. Control studies on ATP-dependent Ca2+-pumping in renal basolaterals and on Ca2+-ATPase in erythrocyte ghosts suggest that the Ca2+-pumping enzyme requires Mg2+. In contrast, a role of the Ca2+-stimulated Mg2+-independent ATP hydrolysis in active Ca2+ transport across basolateral membranes is rather unlikely.
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Base de dados:
MEDLINE
Assunto principal:
Trifosfato de Adenosina
/
Cálcio
/
ATPases Transportadoras de Cálcio
/
Rim
/
Magnésio
Limite:
Animals
Idioma:
En
Revista:
Biochim Biophys Acta
Ano de publicação:
1984
Tipo de documento:
Article