Regulation of extracellular proteinase production in an ectomycorrhizal fungusHebeloma crustuliniforme

Abstract

Hebeloma crustuliniforme was grown in de? fined liquid media containing different combinations of ammonium, glucose, and bovine serum albumin as sources of nitrogen and carbon for proteinase induc- tion or repression. The production of extracellular proteinase was highest in the medium containing bo? vine serum albumin as sole nitrogen source and it was not affected by the addition of ammonium at concen? trations below 3.2 mM, but higher ammonium con? centrations repressed the proteinase production. Pro? teinase synthesis required simple carbon as an energy source and was not repressed by glucose at concen? trations from 0.5 to 2%. Optimal culture pH for pro? teinase production was between 4 and 5. At pH 3, the fungus yielded biomass only 10% of that at pH 5, though proteinase production per mg dry weight of mycelium was not affected. The fungus was unable to grow and produce proteinase at pH 7 or above. The proteinase was most active at pH 2.5-3 and stable at pH 2.5-5.5. These results suggest that the regulation of extracellular acid proteinase in H. crustuliniforme involves protein induction and partial nitrogen re? pression but not carbon catabolite repression.