Effects of alkali metal cations on phospho-enzyme levels and [3H] ouabain binding to (Na+ + K+)-ATPase.
Biochim Biophys Acta
; 429(3): 993-1005, 1976 May 13.
Article
em En
| MEDLINE
| ID: mdl-131582
ABSTRACT
The effects of several alkali metal cations on the relationship between steady state phospho-enzyme levels and initial velocity and equilibrium levels of [3H]-ouabain binding to (Na+ + K+)-ATPase (ATP phosphohydrolase EC 3.6.1.3.) were examined. Only Na+ increased both phospho-enzyme and [3H] ouabain binding levels above those observed in the presence of Mg2+ alone. While Na+ stimulated phosphorylation with an apparent Km of about 1 mM, its stimulation of [3H] ouabain binding was biphasic, the lower Km for stimulation corresponding to the Km for formation of phospho-enzyme. Among the other alkali metal cations, potassium, rubidium and lithium were at least eight times more effect in reducing phospho-enzyme levels than in reducing [3H] ouabain binding. This discrepancy is not due to the stability of the enzyme-ouabain complex, nor to any action on the rates of formation or dissociation of the enzyme-ouabain complex. The data thus suggest that [3H] ouabain interacts with the K+, Rb+ or Li+ -enzyme complexes. For Li+, this hypothesis is further supported by the observation that Li+ can cirectly increase the equilibrium level of [3H] ouabain binding to this enzyme under certain conditions.
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Base de dados:
MEDLINE
Assunto principal:
Ouabaína
/
Cátions Monovalentes
/
Adenosina Trifosfatases
Limite:
Animals
Idioma:
En
Ano de publicação:
1976
Tipo de documento:
Article