M. I). Mcelroy and h. h. seliger 



233 



10 20 30 40 

 TIME - MIN. 

 Fig. 11. Effect of cysteine on oxyluciferyl-CoA fluorescence. The formation of 

 L-CO.\ is indicated by the initial decrease in fluorescence. Cysteine was added 

 at 12 minutes. 



The evidence presented above indicates that in the firefly system, 

 kiciferase catalyzes the interaction of luciferin and ATP to form 

 the enzyme luciferyl-adenylate complex. The luciferyl-adenylate- 

 enzyme complex in the presence of oxygen leads to the formation 

 of the enzyme-oxyluciferyl-adenylate complex and the emission of 

 light. The dissociation constant for the luciferase-oxyluciferyl- 

 adenylate complex indicates that the latter is very stable, thus ac- 

 coimting for the rapid product inhibition of luminescence. The 

 knowledge of the dissociation constant for the luciferase-oxyluciferyl- 

 adenylate complex, together with the equilibrium constant for the 

 activation of oxyluciferin, has made it possible to calculate the stand- 

 ard free energy of hydrolysis of oxyluciferyl-adenylate as being — 13.1 

 kilocalories per mole. The stimulation of luminescence by pyro- 

 phosphate can be explained by its reaction with the complex to pro- 

 duce free luciferase, ATP, and oxyluciferin. The luciferase then 

 reacts again with luciferin and ATP to give more light production. 



