Chapter 6 Sodium-potassium-activated adenosinetriphosphatase

Abstract

Publisher Summary This chapter focuses on the sodium-potassium-activated adenosinetriphosphatase. Most living animal cells are characterized by a high-intracellular K + concentration and a low Na + concentration, whereas the surrounding plasma and tissue fluid have a high Na + and a low K + concentration. These cation gradients, across the cell membrane, are gradually abolished upon cell death or upon inhibition of the cellular energy metabolism by cooling, withholding of glucose or application of suitable inhibitors. This suggests that the maintenance of the cation gradients requires metabolic energy. Radioisotope experiments have indicated that during steady-state conditions there is a passive influx of Na + ions and a passive efflux of K + ions. The chapter answers how this cation pump system is related to the cellular energy metabolism and what is the nature of the pump system. The findings suggest that the cation pump is not directly linked to some step in the glycolytic or oxidative phosphorylation chains, but rather that it is the adenosinetriphosphate (ATP) produced by these systems that provides the energy for cation transport. Direct evidence for this conclusion comes from experiments in which ATP is placed inside cells or cell membrane vesicles, which lack any other energy source.