Activity of Ribonuclease, Acid Phosphatase, and Phosphodiesterase in Tetrahymena Pyriformis during Growth

Studies on the nucleolytic activity of cell homogenates of Tetrahymena pyriformis indicated that enzyme activity was, among other factors, a function of the age of the culture (1, 2). It was shown that the specific activities of ribonuclease (RNase) (EC 2.7.7.h) and acid phosphatase (APase) (EC 3.1.3.2) in crude homogenates prepared from stationary-phase cultures were consistently higher than those from log phase by a factor of at least two (2). However, in contrast to these two enzymes, the level of a potassium-activated ribosomal phosphodiesterase (PDase) (EC 3.1.4.1) was reported to be maximal at the end of exponential multiplication (3). Our results on the level of APase in T. pyriformis GL, however, could not be reconciled with the data of Klamer and Fennel (1), who reported increased APase activity in strain W only during the exponential death phase. Therefore, it was of interest to further investigate the activity of these nucleases in more detail. In addition, we wish to report here the effect of puromycin, an inhibitor of protein synthesis, on the change in activity of RNase and APase during growth.