262 



PURIFICATION AND PROPERTIES 



other enzymatic pathways for the utihzation of flavin may exist. This 

 aspect of the problem has not been clarified. 



It is important to emphasize that aldehyde destruction occurs only 

 under conditions where luminescence appears, i.e., the enzyme prep- 

 aration will not destroy aldehyde unless both DPNH and FMN are 

 present. We agree, however, that the aldehyde accelerates the oxida- 

 tion of FMNHo. It does not, however, accelerate the oxidation of 

 DPNH. Apparently the rate-limiting step is the reduction of FMN by 

 DPNH. 



ML OODECYL ALDEHYDE 



Fig. 5. Effect of varying amount of aldehyde added to reaction mixture upon 

 total light emitted during the reaction (McElroy and Green, unpubUshed). 



The effect of various inhibitors is shown in Table II. The inhibition 

 by p-chloro Hg benzoate is reduced from 58% to 17% by 2 X 10" ^ M 

 glutathione. Although the earlier indication that iron was involved in 

 the system ( McElroy, Hastings, Sonnenfeld, and Coulombre, 1954 ) 

 has not been confirmed, the effect of cyanide and versene suggests 

 that some metal may be functional in the reaction. 



In spite of the fact that the peak of bacterial emission is at a 

 shorter wavelength than is riboflavin fluorescence, there is good rea- 

 son (Strehler, Harvey, Chang, and Cormier, 1954) to suppose that 

 FMN is the light emitter in the bacterial reaction. Moreover, on the 

 basis of its probable role as light emitter, the above authors designate 

 FMN as bacterial luciferin. On the other hand, we have proposed that 

 aldehyde be classified as bacterial luciferin, since it is destroyed during 

 light emission. Although a complete evaluation of the roles of FMN 

 and aldehyde must await additional experimental studies, the question 

 of the criteria by which luciferin may be defined is raised. 



