Genus Nostoc a source of novel trypsin inhibitors
Drápalová, Petrastys; Lukešová, Alena; Kopecký, Jiří
In extracts from fifty newly-isolated strains of the genus Nostoc, numerous new molecules showing a capacity for protease inhibition were identified. The production conditions of the most active molecule, found in the Nostoc sp., strain Lukešová 30/93, were studied in detail and the optimal physiological parameters (growth phase, light intensity and culture temperature) examined. The highest active compound concentration was usually found 3 days after inoculation in cultures grown under optimum conditions (light intensity 70 W .m-2 and temperature 25°C). Similar observations seemed to be found for the other strains examined in the study. As far as the trypsin-inhibiting secondary metabolites are concerned, we may thus conclude that we have found no dependency on cell growth phase, light intensity or temperature other than that leading to optimum growth conditions. We propose that the production of the trypsin inhibitor is coincident with conditions under which the colony of the microorganism mostly prospers. The possibility that these compounds serve an anti-grazing function, prominent at a time of expansion, is logical and consistent with previous observations. The trypsin inhibitor examined in detail is a cyclic oligopeptide containing non-coded amino acids. As such this compound is highly interesting: both from the point of view of pharmacology - probably not degradable by ordinary proteinases - and from the point of view of the mechanism of inhibition.