Ouabain-Sensitive Mg++-ATPase, K+-ATPase and Na+-ATPase Activities Accompanying a Highly Specific Na+-K+-ATPase Preparation

Abstract

1. An Na+-K+-ATPase [EG 3.6.1.3] preparation obtained from pig cerebrum microsomes by Nal-treatment has been shown to hy-drolyse ATP in the presence of either K+ alone (K+-ATPase) or Na+ alone (Na+-ATPase) when the assay pH was low for the former and high for the latter. 2. K+-ATPase activity had the optimum pH at 5.3 when K+ concentration was 1 mM. Na+-ATPase activity was near maximum when the assay pH was between 7.7 and 9.0 at Na+-concentration of 10 mM. 3. Ouabain-sensitive Mg++-ATPase activity has been detected with the optimum pH which was nearly the same as that of K+-ATPase activity but with a pH-activity curve broader toward alkalinity than that for the latter.