Localization and cation dependence of a Ca2+- or Mg2+-ATPase from electrocytes of Electrophorus electricus, L.
J Histochem Cytochem
; 37(7): 953-9, 1989 Jul.
Article
em En
| MEDLINE
| ID: mdl-2525141
Electrocyte membranes of Electrophorus electricus exhibit high ATPase activity, as demonstrated by cytochemical and biochemical techniques. This activity is visualized as electron-dense deposits in electron micrographs, and appears to be localized only at the innervated face of the electrocyte. ATP hydrolysis can be detected cytochemically or biochemically only in the presence of calcium or magnesium. The effects of Ca or Mg on ATPase activity can be described by Michaelis-like functions with similar apparent Km values for Ca and Mg (0.41 mM and 0.23 mM, respectively). Vmax, however, is fivefold higher in the presence of Mg. The effects of the two cations are not additive, and pH dependence of ATP hydrolysis is identical in the presence of Ca or Mg (maximal at pH 8-9). Therefore, it can be concluded that Ca and Mg activate the same enzyme, the differences in Vmax being attributable to influences in kcat.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Cloreto de Cálcio
/
Electrophorus
/
ATPase de Ca(2/) e Mg(2/)
/
ATPases Transportadoras de Cálcio
/
Órgão Elétrico
/
Magnésio
Limite:
Animals
Idioma:
En
Revista:
J Histochem Cytochem
Assunto da revista:
HISTOCITOQUIMICA
Ano de publicação:
1989
Tipo de documento:
Article
País de afiliação:
Brasil
País de publicação:
Estados Unidos