REGULATION OF NEUTRAL PROTEASE ACTIVITY THROUGH THE LIFE-CYCLE OF TETRAHYMENA-PYRIFORMIS

Substantial fluctuations in the intracellular specific activity of neutral proteases, as assayed at pH 8 with azocasein as substrate, occur during the life cycle of the protozoan Tetrahymena pyriformis. Specific activity increases during growth in 2% proteose peptone, despite slow secretion into the medium. The most rapid increase occurs during late stationary phase and appears to be a response to one or more low molecular weight (less than 10 000), heatstable, trypsin-insensitive, polar molecules secreted into the medium. In contrast, intracellular specific activity drops by a factor of 2-5 within the first 2-3 h after transfer to non-nutritive medium. The decrease in activity under these conditions results from an enhanced rate of secretion and the cessation of net synthesis. Its kinetics are unaffected by cycloheximide and concanavalin A. © 1979.