260 



PURIFICATION AND PROPERTIES 



and without added FMN the total activity of the enzyme at first in- 

 creases and subsequently declines with continued irradiation. It was 

 thought that this effect might be due to the destruction of riboflavin, 



I 2 



IRRADIATION TIME-HOURS 

 Fig. 2. Stimulation of luminescence by added FMN, using enzyme irradiated for 

 time intervals indicated. 



which is a potent inhibitor of the system (Table II). This was shown 

 not to be true when it was found that the stimulatory factor could be 

 produced by irradiation of the 20-^30% (NH4)oS04 fraction, which it- 

 self had no inhibitorv effect and no luciferase activity. The relation- 



TABLE II 



Inhibitors of Bacterial Luminescence in Vitro 



Inhibitor 



Concentration, molar 



Inhibition, % 



43 



58 

 47 



47 



