Investigations on the identity of the light-emitting molecule in Photobacterium phosphoreum

1. 1. Filtration of a bacterial lysate over Sephadex G-25 results in either a total or partial inactivation of the luciferase. 2. 2. The filtrate contains a non-protein fraction that stimulates the light reaction in vitro, evoked by addition of FMNH2 to a diluted, palmital-containing, luciferase preparation. Besides, a fraction inhibiting the light reaction is found. 3. 3. None of the fractions of the Sephadex filtrate shows a clear fluorescence peak at the wavelength of maximum luminescence (about 470 mμ). 4. 4. Addition of FMNH2 to a bacterial enzyme preparation results in the formation of some compound which is transformed by irradiation with ultraviolet light (366 mμ) into a fluorescent substance with a fluorescence maximum around 470 mμ. The time during which the first compound is formed is of the same order of magnitude as the time of duration of the light reaction in the complete reaction mixture. Its formation is not enzymic. 5. 5. The compound is suggested to be a precursor of the light-emitting molecule in bacterial luminescence