E. NEWTON HARVEY 143 



in absence of oxygen and, upon admitting air and adding luciferase> 

 obtain light. As luciferase is only found in luminous animals it does 

 not seem likely that a coluciferase would be widespread but we do 

 know that a reducing enzyme occurs in milk and tissue extracts — is, 

 in fact, widespread. It seems more logical to interpret the above 

 experiments as due to the reduction of an oxyluciferin to luciferin 

 rather than the conversion of a proluciferin to luciferin. 



Indeed, we can reduce oxyluciferin by means which do not involve 

 the use of animal extracts and consequently are free from the ob- 

 jection that "coluciferase" may be responsible for the result, but 

 which, nevertheless, are perfectly well known reducing methods. 

 Perhaps the best of these is reduction by palladium black and sodium 

 hypophosphite. The latter is oxidized in presence of palladium and 

 nascent hydrogen is set free.^" The nascent hydrogen reduces any 

 easily reducible substance which may be present, such as methylene 

 blue or oxyluciferin. Oxyluciferin is not reduced by palladium 

 alone or hypophosphite alone but methylene blue is reduced by palla- 

 dium black alone. 



If hydrogen sulfide is passed through a solution of methylene blue 

 the dye is very quickly reduced and becomes colorless. If the H2S 

 is driven off by boiling the colorless methylene blue solution, the blue 

 color again returns on cooling. Oxyluciferin can also be reduced to a 

 certain extent by H2S. Sulfur dioxide or oxides of nitrogen (prepared 

 by the action of HNO3 on Cu) had no reducing action on either 

 methylene blue or oxyluciferin. 



Dilute acid favors the reduction of oxyluciferin. If one saturates 

 an oxyluciferin solution with CO2 or adds a little dilute acetic acid 

 and allows the solution to stand for 24 hours, a certain amount of 

 reduction will occur. No reduction occurs if the solution is saturated 

 with pure hydrogen and allowed to stand 24 hours. If one adds some 

 Mg powder to oxyluciferin and then dilute acetic acid in successive 

 additions as the acetic acid is used up in formation of Mg acetate, 

 the oxyluciferin will be reduced relatively quickly. Nascent hydro- 

 gen is produced in the reaction and is no doubt the active reducing 

 agent, while the acid accelerates the reduction. Soured milk also has 



16 Bach, Ber. chem. Ges., 1909, xlii, 4463. 



