The activities of ribosome-degrading enzymes and of a proteinase inhibitor in Tetrahymena pyriformis during starvation

Abstract

1. 1. In starved Tetrahymena acid RNase decreased but acid proteinase and a heat-stable proteinase inhibitor both increased. 2. 2. A greater proportion of proteinase than RNase was released from the lysosomes of growing cells by homogenization, but progressively less proteinase was released during starvation. 3. 3. Inhibitors of protein synthesis enhanced the decrease in RNase and prevented the increase in proteinase and proteinase inhibitor. Chloroquine caused a large increase in both enzymes. 4. 4. Proteinase and RNase may be located in different lysosomes which together participate in ribosome destruction, but this process is unlikely to be limited by the total amount of these lysosomal hydrolases.