Antimicrobial and Phytochemical Properties of Alstonia Boonei Extracts

Abstract

Publisher Summary The sodium- and potassium-dependent adenosinetriphosphatase Na+, K+-ATPase (ATP phosphohydrolase) is a plasma membrane protein, which has been identified as the enzymatic expression of the sodium pump. Na+, K+-ATPase serves two functions—the extrusion of sodium out of the intracellular compartment and the accumulation of potassium into the same compartment. The cell devotes a large fraction (2–40%) of its ATP production for this single function. In the most extreme cases (epithelial cells), up to 70% of the oxydative metabolism can be coupled to obtain sensitive sodium and potassium transport. Therefore, this process plays a critical role in the homeostasis of sodium and potassium not only in the intracellular but also in the extracellular milieu. In all cells, Na+, K+-ATPase maintains a high intracellular K+ concentration required for the macromolecule biosynthesis machinery. In epithelial cells, Na+, K+-ATPase is one of the major factors allowing transcellular salt transport, thereby controlling the osmolarity of the extracellular compartment. Epithelia are, therefore, able to create and maintain a large hydro osmotic gradient between the extracellular space and the external environment.