AbstractThe activity of ATP‐ase activity in bean roots homogenate was tested by following the release of32Pi from γ‐labelled ATP. It was found that most of the enzymatic activity resides in the soluble fraction. The soluble enzyme requires Mg or Ca for activity and is further highly stimulated by some monovalent cations. The enzyme is compared with the “transport” ATP‐ase located in membranes of various animal tissues and with other enzymatic systems which