MILTOX I. CORMIER 



279 



centrations, and that the response obtained with ADP is somewhat 

 less than that with AMP. The higher efficiency of ATP at lower 

 concentrations is also shown by calculation of the apparent Michaelis 

 constant, which, for the ATP reaction, is approximately one-fifth 

 that of the ADP- or AMP-stimulated reactions. Since generating 

 systems are frequently more efficient than substrate levels of a re- 

 actant, the higher efficiency of ATP could be explained on the basis 

 that it acts as a generating system for ADP and AMP. 



Requirement for Liiciferin and Oxygen 



Since other bioluminescence systems require an oxidizable sub- 

 strate, termed luciferin, for luminescence, an attempt was made to 

 demonstrate the necessity for luciferin in this system. The require- 

 ment for an additional factor became apparent by studying lumines- 

 cence decay as a function of time. Fig. 2 shows that, at the end of 

 approximately 70 minutes, the luminescence rate decays to a negligi- 

 ble value that is not affected by the addition of nucleotides. Al- 

 though ADP A\as added in this experiment, ATP and AMP are also 

 without eflfect. Nucleotides are required, however, to bring about the 

 luminescence decay. For example, an extract incubated 70 minutes 



125- 



100- 



z 



UJ 



I 

 O 



2 5- 



Add 



boiled extract 



120 



TIME (min.) 

 Fig. 2. Effect of boiled extract on luminescence after luminescence decay. 



