MEMBRANE ATPASE OF BACILLUS MEGATERIUM .1. PROPERTIES OF MEMBRANE ATPASE AND ITS SOLUBILIZED FORM

A large part of the membrane ATPase [EC 3.6.1.3] of Bacillus megaterium was solubilized by dialysis and mild treatment with alkali. The membrane ATPase was activated by Mg++ or Ca++ and stable in the cold, while the solubilized ATPase was remarkably activated by Ca++ and inactivated by the cold. The optimum pH for the enzyme activity varied depending on the ratio of ATP to Mg++ or Ca++. The solubilized ATPase activity was distinctly stimulated by SO3--. The effects of various compounds on the enzymatic activity were studied and several differences between the properties of the membrane-bound and the solubilized ATPase were observed. Some distinct differences were also seen between the effects of dithionite, pentachlorophenol, ethanol, gramicidine, and ADP on the Mg-and Ca-ATPase activities. © 1969 BY THE JOURNAL OF BIOCHEMISTRY.