Biochemical and Physiological Characteristics of Ca-ATPase System of Rat Liver Mitochondria with Special Attention to the Effects of pH and Temperature
Yonsei Medical Journal
; : 129-136, 1980.
Article
em En
| WPRIM
| ID: wpr-60595
Biblioteca responsável:
WPRO
ABSTRACT
The activity of Mg++-dependent, Ca++-activated adenosine triphosphatase (Ca-ATPase) of rat liver mitochondria was studied at varying medium compositions, pH and temperatures. The enzyme system was characteristically sensitive to Ca++ concentration with a KmCa of approximately 0.06 mM. The optimal concentration of Mg was about l mM, above which the enzyme activity was progressively inhibited. The inhibitory effect of high Mg++ concentrations appeared to be due to the alteration of the Mg++/ATP ratio. Variations in the Mg++/ATP ratio affected Vmax but not the KmATP. The pH optimum for enzyme activity increased as the incubation temperature decreased, but the optimal OH-/H+ ratio of the medium was constant at around 0.1, regardless of temperature. The activity of the enzyme was not affected by La# (0.01-1 mM) and Ruthenium red (2.5-10.0 microM). These results indicate that 1) the enzymatic characteristics of the Ca-ATPase system in the rat liver mitochondria is typical of those from other tissue preparations, 2) the enzyme system maintains the most effective catalytic conformation at a fixed level of OH-/H+ ratio of 0.1 when the temperature changes, and 3) the enzyme system may not play a role in the physiological transport of Ca++ in mitochondria.
Texto completo:
1
Índice:
WPRIM
Assunto principal:
Temperatura
/
Mitocôndrias Hepáticas
/
Cálcio
/
ATPases Transportadoras de Cálcio
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Ativação Enzimática
/
Concentração de Íons de Hidrogênio
/
Animais
/
Magnésio
Limite:
Animals
Idioma:
En
Revista:
Yonsei Medical Journal
Ano de publicação:
1980
Tipo de documento:
Article