Several topics concerning Na, K-ATPase

Abstract

Publisher Summary This chapter discusses several topics concerning Na, K-ATPase. Na, K-ATPase is an entity that exchanges Na+ and K+ ions across the cell membrane against an electrochemical gradient, which is accompanied by ATP hydrolysis. This enzyme has many characteristics, some of which are specific for this enzyme. The enzyme binds ATP at a ratio of 1:1. The binding is not affected by the presence of Mg or Na, but K increases the dissociation constant and Na antagonizes the effect of K. The binding site is closely related to the active site according to Post, but there have been some experiments suggesting that ATP also acts aliosterically with Na on p-NPase activity. In the presence of a small amount of magnesium ion, or with NEM-treated enzyme, an ADP-ATP exchange react ion is observed and the reaction is accelerated by Na. The fact that cardiac glycosides specifically inhibit both cation active transport and Na, K-ATPase has been taken as strong evidence for the physiological entity of the enzyme in the active cation transport. The ratio between maximum binding of ouabain and the E-P in the presence of Na and Mg is 1:1.