THE CHEMISTRY OF LIGHT PRODUCTION 109 



view that his co-luciferase is a reducing enzyme which 

 forms luciferin by reduction (presumably from oxidized 

 lucif erin) and no mention is made of prelucif erin. 



It is, of course, obvious that when luciferin oxidizes, 

 some oxidation products must be formed. Most observers 

 have assumed the oxidation products of luciferin to be 

 relatively simple and to represent a rather complete 

 breaking down of the luciferin molecule. Carbon dioxide 

 was mentioned by Phipson (1872) as being formed. We 

 have just seen that no carbon dioxide is formed during 

 the oxidation of Cypridina luciferin and there is evidence 

 that no fundamental change at all occurs. It is for this 

 reason that I have called the oxidation product of luciferin 

 oxyluciferin* As we shall later see, the change luciferin 

 oxyluciferin is to be compared to the oxidation of color- 

 less dyes (leuco-compounds) to the colored dye. The 

 chemical properties of oxyluciferin are similar to those of 

 luciferin and the oxyluciferin can be readily reduced 

 to luciferin again. 



Finally, we have the fluorescent substance of Pyro- 

 phorus and fireflies, which Dubois first called pyrophorin, 



* It is unfortunate that Dubois (1918 b) has used the term oxylucif- 

 erine in a quite different sense from the present use. He regards oxy- 

 luciferine as a substance still capable of giving light by autooxidation, 

 and represents the steps in luminescence as follows: 



" Co-luciferase + prelucif&ine = luieif^rine. 

 Luciffirase + luciferine ^oxy lucif erine. 

 Oxyluciferine + oxygene = lumier6." 



I should represent them as follows: 



Luciferin + oxygen ±5 oxyluciferin. 

 The reaction proceeds to right with light prodviction only in presence 

 of luciferase. 



