Fluorimetric analysis of phospholipase activity in Tetrahymena pyriformis GL

The unicellular Tetrahymena enzymatically split the synthetic phosphodiester, 4-methylumbelliferyl phosphocholine substrate. The enzyme activity was completely blocked in vitro and drastically inhibited in vivo by G-protein activating fluorides (NaF; AIF4- and BeF3-). The phospholipase A2 inhibitor, quinacrine, and the protein phosphatase inhibitor, neomycin, inhibited the enzyme activity in vitro and activated it in vivo. Another phospholipase A2 inhibitor 4-bromo phenacyl bromide was ineffective in vivo and in vitro alike, as well as the cyclooxygenase inhibitor indomethacin. Results of these experiments indicate that some treatments could be specific for a well defined activity (e.g., phospholipase A2, G-protein) but subject to influence by other enzymes (e.g., phospholipase C, sphingomyelinase). The experiments call attention to the differences in the results of the in vivo and in vitro studies.