Regulation of chitin synthase activity inSaccharomyces cerevisiae: Effect of the inhibition of cell division and of synthesis of RNA and protein

The effect of pronase and trypsin on the activation or deactivation (degradation?) of chitin synthase ofSaccharomyces cerevisiae occurs faster in membranous preparations than in toluene-treated cells. When the temperature is raised, the former preparation is deactivated earlier than the latter one. The activity found in growing cells is not modified after inhibition of protein synthesis by cycloheximide or amino acid starvation or by the inhibition of RNA synthesis. It was possible to activate the chitin synthase ofS. cerevisiae cdc 25 grown at 23°C by means of pronase, whereas trypsin had no effect. After the cells were grown at 37°C, chitin synthase could not be activated either with trypsin or with pronase. This effect occurred independently of protein synthesis but did not take place when the cells were toluenized prior to the transfer at 37°C. These results suggest that the low catalytic levels and stability of the chitin synthase found in actively growing cells ofS. cerevisiae may be due to the restrictions introduced in the system by its membrane location.