THE FUNCTION OF EXTRACELLULAR ENZYMES OF DUTCH ELM DISEASE PATHOGEN

Regulation of induced cellulase synthesis in Pyrenochaeta terrestris Gorenz et al. by utilizable carbon compounds

Cellulase (Cx) synthesis was inducible by Pyrenochaeta terrestris in liquid culture. Cellulase activities on various types and amounts of cellulose reached specific maximum plateaus which were maintained indefinitely. These plateaus were reestablished when the enzyme was diluted at each substrate concentration. The maximum levels appeared related to rates of cellulolysis. Above a low threshold rate of hydrolysate liberation, maximum Cx levels are ordered inversely to cellulolytic rates. Supplementing the inducer cellulose with glucose or related compounds above 5 × 10−4 M repressed synthesis nearly to the basal level. The evidence lends credence to a hypothesis that Cx synthesis by P. terrestris is regulated by an inducer:repressor mechanism.