Membrane Adenosine Triphosphatase from Streptococcus faecalis

Abstract

Abstract The membrane adenosine triphosphatase from Streptococcus faecalis has been purified by heat treatment, gel filtration through Agarose, and repeated chromatography on diethylaminoethyl cellulose. The purified ATPase appears to be homogeneous as judged from gel electrophoresis and sedimentation velocity studies. Sedimentation equilibrium studies, which are presented in the succeeding paper, also indicate that the purified preparation is homogeneous. Both products of the ATPase reaction, ADP and inorganic phosphate, are competitive inhibitors of the enzyme with Ki values of 0.7 and 10 mm, respectively, and the two have synergistic inhibitory effects. The purified enzyme does not catalyze an ADP-ATP exchange, and no evidence for a phosphorylated enzyme intermediate could be found. No cooperative homotropic effect of ATP on the purified enzyme could be observed over the range of substrate concentrations tested.