Studies on the surface and cytoplasmic membranes of Ehrlich ascites carcinoma cells

Abstract

A membrane fraction isolated from Ehrlich ascites carcinoma microsomes contians an ATP phosphohydrolas which is strongly stimulated by K⁺ in the presence of Na⁺. The enzyme system has an absolute requirement for Na⁺ and Mg²⁺, but a number of monovalent cations can simulate K⁺. Ca²⁺, ADP and ouabain are inhibitory. The enzyme is believed to be associated with plasma membrane fragments.

The quantitative relationships between enzyme activity and reactant concentration is presented and the probable relationship between ion transport in the whole cell and the alkali-cation-sensitive ATP phosphohydrolase is discussed.