SYNTHESIS AND ACTIVITY OF NITROGENASE IN THE CYANOBACTERIUM PLECTONEMA-BORYANUM

The synthesis and activity of nitrogenase was studied in the filamento us cyanobacterium Plectonema boryanum 465 under different conditions o f incubation and enzyme assay. It was shown that this species did not synthesize nitrogenase under photoautotrophic conditions. However, syn thesis of the enzyme was observed in cells incubated in the light on n itrogen-free medium containing fructose, glucose, ribose, or lactate. The maximal nitrogenase synthesis was achieved under an illumination o f 200 Ix. At Light intensities above 600 Ix or under anaerobic conditi ons in the dark, nitrogenase was not produced. The activity of nitroge nase was also dependent on the light intensity and reached its maximum at 200 Ix. Nitrogenase was also found to be synthesized and active at higher illuminations (1200-2000 Ix) when the photosynthetic O-2 relea se was inhibited by diuron. The formation of nitrogenase in P. boryanu m 465 was blocked in the presence of ammonium or nitrate in the medium . However, these compounds, as well as glutamine and asparagine, did n ot inhibit the activity of nitrogenase.