298 



LIGHT AND LIFE 



TABLE 1 

 Purification of Gonyaulax Luciferase 



purified luciferase preparation in the presence of salt, light emission 

 occurs. The light intensity is a measure of the velocity of the reaction. 

 Light intensity increases linearly with increasing enzyme concentra- 

 tion, whereas luciferin shows a typical substrate saturation curve 

 with increasing concentration (5) . 



These facts make it possible to represent the reaction by using a 



modification of Harvey's (3) scheme for bioluminescent reactions 



(Fig. 4) . A reduced luciferin molecule (LH2) is oxidized enzymati- 



cally to yield an excited molecule, L*, which falls to the ground state 



with the emission of a quantum of light. 



The side reactions shown are based upon several observations. 

 Hot water extracts rapidly lose luciferin activity. After 24 hours 

 the activity remaining is usually less than 10 per cent of the original. 

 First of all, the loss of activity can be prevented by the exclusion of 

 oxygen. Thus, a nonenzymatic nonluminescent oxidation is indicated. 

 Second, treatment of nonenzymatically inactivated preparations with 

 reducing agents, such as cysteine, or hydrogen in the presence of 

 platinized asbestos, will i^artially restore activity. This is not ob- 

 served with enzymatically oxidized luciferin. Third, the total light 

 yield is much greater at higher enzyme concentrations. This may be 

 explained in terms of a competition for reduced luciferin. At higher 

 enzyme concentrations a greater percentage of the LHo is channeled 

 through the enzymatic pathway. Fourth, the addition of crystalline 



