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BIOCHEMISTRY OF FIREFLY LUMINESCENCE 



phosphate decreases and may, as in the purest preparations, give no 

 more than 15% of the flash obtained initially with ATP. Addition of 

 the pyrophosphatase to these preparations accelerates the complexing 

 reaction and raises the triphosphate response to as high as 85% of the 

 initial flash. This evidence is additional support for the idea that a 

 second protein is involved in the complexing of luciferase and that 

 both triphosphate and pyrophosphate accelerate the breakdown of 

 this inactive complex. The increase of the baseline level of lumines- 



80- 



05 



I 



05 10 



TIME - MINUTES 



15 



2 



Fig. 24. Light emission with successive additions of triphosphate and pyro- 

 phosphate in tlie presence of pyrophosphatase. In the reaction on the right 

 curves 1,2,3,4 show the effect of successive additions of pyrophosphate. After 

 the first pyrophosphate addition ( 1 ) the pyrophosphatase concentration was 

 doubled before additional pyrophosphate was added. Curves A, B, C show 

 tlie effect of successive additions of triphosphate. The initial response to 

 ATP was 90 light units. 



cence with triphosphate is taken as evidence for the complexing of 

 the protein with triphosphate, thus shifting tlie equilibrium between 

 active and inactive intermediate. Additional protein in this case will 

 restore the original low baseline level of luminescence. 



The fact that the triphosphate response cannot be completely 

 eliminated may be due to the fact, as mentioned above, that luciferase 

 itself may serve as the second protein in the complexing reaction. 



The results summarized above demonstrate that the rapid decrease 

 of light intensity after ATP addition to firefly extracts is due to the 



