Presence of Two Different Membrane-bound, KCl-stimulated Adenosine Triphosphatase Activities in Maize Roots

Abstract
Recent publications have indicated that a KCl-stimulated ATPase from cereal roots is specifically associated with plasmalemma-enriched membrane fractions. However, in previous work we found that relatively high specific activities of this enzyme were also associated with a membrane fraction which did not contain plasmalemma. In an attempt to clarify this discrepancy, we have investigated the effect of density gradient composition upon the association of the enzyme with different membrane fractions isolated from the roots of Zea mays L. (WF9 × M14).