Derepressible proteolytic activity in homokaryotic hyphae ofSchizophyllum commune

Proteolytic activity produced bySchizophyllum commune homokaryons was derepressed upon starvation of plate-grown cultures for nitrogen. Decreasing thel-asparagine concentration in the growth medium resulted in slower growth (as total protein), alteration of colonial morphology, and an increase in mycelial and extracellular protease specific activity against hide-powder azure. In comparisons between colonies grown on minimal medium (1 g/literl-Asn), 0.1 ×l-Asn, 0.01 ×l-Asn, and Nol-Asn medium, mycelial proteolytic specific activity increased 2- to 8-fold. Mycelial specific activity also generally increased as the colonies aged. In addition, substantial increases, up to 100-fold, in extracellular protease specific activity occurred under conditions of nitrogen deprivation. This derepression could result in increased mycelial protein turnover and, potentially, proteolysis of extracellular substrates.