1 1. I). Mi EL ROY AM) H. H. S ELI G Eli 



229 



port ol this idea was mentioned previously, namely, that when ATP 

 and Incilcrin are present in an enzyme-cataly/ed reaction there is al- 

 ways a prolonged light j^rodiu tion. in contrast to starting with the 

 LHo-AMP. riuis in some way the ATP is decreasing the inhibitory 

 effect ol LAMP and making the enzyme available to liicilerin. 



Dissociation CoiislanI of E-L-AMP 



The dissociation constant of the E-L-AMP complex may be defined 

 as follows: 



A' = 



[E]f,.., [L-AMP]f,,., 



[E-L-AMPJ 



This dissociation constant has been determined by incubating mix- 

 tiues oi lucilerase and oxyluciteryl-adenylate and determining at 

 equilibrium the concentration ol the free enzyme. The ratio of the 

 Hash height in the presence of L-AMP to the flash height in the ab- 

 sence of L-AMP is equal to the ratio of free enzyme to total enzyme. 

 This ratio has been definetl as /. Various concentrations of LAMP 

 were incubated with known concentrations of luciferase at pH 7.1, 

 and the light intensities for each mixture were measured by the addi- 

 tion of equal amounts of LH2-AMP. The total luciferase was de- 

 termined from j)rotein concentration and an estimated molecular 



6130 



f X 10" 

 Fig. 8. Dissociation of luciferase-L-AMP. / is the ratio of free enzyme to total 

 enzyme. The slope is the equivalent concentration of total enzyme, whereas the 

 intercept is A'. 



