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Comparative temperature dependence of (Na+ + K+)-ATPase
Physiological Chemistry and Physics
|January 1, 1976
Summary
The temperature dependence of sodium-potassium adenosine triphosphatase ((Na+ + K+)-ATPase) enzyme activity was studied across various species. Results challenge the enzyme's proposed primary role in ion pumping.
Area of Science:
- Biochemistry
- Enzymology
- Comparative Physiology
Background:
- The sodium-potassium adenosine triphosphatase ((Na+ + K+)-ATPase) is a crucial membrane protein involved in cellular ion transport.
- Its temperature-dependent activity is vital for understanding enzyme function across different physiological states and species.
- Previous studies established a specific temperature dependence for (Na+ + K+)-ATPase from rabbit kidney.
Purpose of the Study:
- To investigate the temperature dependence of (Na+ + K+)-ATPase activity in diverse vertebrate species.
- To compare the enzyme's thermal behavior across homeothermic, heterothermic (hibernating), and ectothermic species.
- To evaluate the applicability of a thermodynamic kinetic model to describe the enzyme's activity across temperatures.
Main Methods:
- Enzyme preparations were obtained from the heart and kidney of rats, hamsters, guinea pigs, ground squirrels, turtles, chickens, and ducks.
- Enzyme activity was measured across a range of temperatures, including normothermic and hibernating conditions (4°C) for hamsters and ground squirrels.
- Data were analyzed using a previously established thermodynamic kinetic model.
Main Results:
- Most species exhibited a similar temperature dependence to rabbit (Na+ + K+)-ATPase, with activity increasing above 15°C and minimal activity below.
- Turtle (Na+ + K+)-ATPase showed a broader activity curve, with reduced function at both high and low temperatures.
- The thermodynamic kinetic model successfully fitted the data for all species, including the observed high-temperature enzyme inactivation.
Conclusions:
- The temperature dependence of (Na+ + K+)-ATPase is conserved across a wide range of vertebrate species, with variations observed in turtles.
- A thermodynamic kinetic model effectively describes the enzyme's activity across different temperatures and species.
- These findings do not support the widely accepted hypothesis of a primary ion pumping role for (Na+ + K+)-ATPase.