ON DEPOSITION AND UTILIZATION OF INORGANIC PYROPHOSPHATE IN TETRAHYMENA PYRIFORMIS

1. 1. Tetrahymena pyriformis deposit calcium magnesium pyrophosphate in spherical granules which appear to be surrounded by membranes. 2. 2. The deposition of granules occurs in the stationary phase and is greatly augmented by elevated levels of phosphate, Ca2+ and Mg2+ in the medium; the presence of two divalent cations is essential for this process. The granules disappear rapidly during phosphate deprivation. 3. 3. Associated with the granules is a pyrophosphatase activity which hydrolyses specifically the pyrophosphate of the granules. 4. 4. Phosphotransferase activity involving pyrophosphate could not be demonstrated in Tetrahymena and we conclude that the function of these deposits is that of phosphate storage. © 1969.