Screening of microorganisms for enzyme-inhibiting activities.

In the course of a screening for extracellular inhibitors of 8 different proteinases 140 actinomycete and 150 mould strains were examined. 130 fungal and 50 actinomycete strains were similarly tested for the production of extracellular inhibitors of dihydrofolate reductase (DHFR) and alkaline phosphatase (APh). Most of the inhibitors found in the culture media of the actinomycete and mould strains were specific against serine proteinases. Inhibitors of DHFR were discovered in the culture media of different actinomycetes and moulds. Inhibiting activities towards APh were found mainly in the fermentation filtrates of the mould strains. The approximate molecular sizes of the active substances were determined by using membrane filtration.