w. D. Mcelroy and j. w. Hastings 195 



restore the original steady-state level, it appears that the triphosphate 

 is effectively removing at least some of the protein essential for the 

 complexing reaction. 



Control of Firefly Luminescence 



The existence of an inactive complex as proposed above wherein 

 all the components of the system are present without appreciable 

 reaction occurring may be of some significance in considering pos- 

 sible mechanisms for controlling enzyme-catalyzed reactions. The evi- 

 dence presented suggests that such an inactive complex may be im- 

 portant in controlling the flash of the firefly. Pyrophosphate, which is 

 known to be liberated in several reactions can serve as a trigger in 

 the present reaction after the decay of the initial response to ATP. 

 The pyrophosphatase which is present in high concentrations in the 

 firefly lantern would rapidly decompose the released pyrophosphate, 

 which allows the reformation of the inactive complex leading to the 

 extinction of the light. 



The scheme in Fig. 25 illustrates one possible way in which nervous 

 stimulation could lead to the rapid liberation of inorganic pyrophos- 

 phate. Since the flash of the firefly is under nervous control this would 

 appear to be a plausible mechanism. It is suggestive that the firefly 

 lanterns contain a very high concentration of coenzyme A. 



One cannot fail to be impressed, however, with the striking re- 

 semblance between the in vitro anaerobic flash and the flash exhibited 

 by the live firefly. As mentioned previously, we believe that anaerobic 

 conditions allow the accumulation of an active intermediate from an 

 inactive one which is rapidly oxidized by molecular oxygen when air 

 is readmitted to give an excited molecule which emits light. Most 

 workers have felt that the firefly regulates flashing by liberating oxy- 

 gen into the photogenic cells. ( See Harvey, 1952, for a review of this 

 literature.) Implied in this statement and in keeping with the fact 

 that "resting" fireflies are not emitting light, is that the photogenic 

 cells are under anaerobic condition. This seems most unusual for 

 insects. Buck (personal communication, see later) has suggested that 

 the firefly must do work in order to remain dark and that only a brief 

 anaerobic period may be essential to bring about the flash response. 

 This suggestion is in keeping with all the biochemical data on the 



