An Ion‐stimulated Adenosine Triphosphatase from Bean Roots

A soluble ATP‐ase from bean roots was discovered. The enzyme was assayed by measuring the release of inorganic P from 32 P‐labelled ATP. The enzyme is strongly stimulated by hoth sodium and potassium ions, in the alkaline pH range. Its characteristics are compared to that of the animal membrnnal ATP‐ase which is presumably involved in the transport of ions in animal tissues.