EFFECTS ON VARIOUS METABOLIC SYSTEMS 497 



showed that it requires 500 times the concentration of toluquinone to in- 

 hibit streptococcal growth compared to inhibition of Achromobacter fisckeri 

 light emission, whereas various antibiotics do not show this specificity and 



K ' (Dao for: 



uinone , , 



(mv) 



Luminescence Respiration 



usually inhibit growth more effectively. Bacterial extracts luminesce when 

 NAD is added and this is appreciably inhibited by 1,2-naphthoquinone and 

 menadione at 0.0001 mM, around 50% at 0.01 mM, and completely at 

 0.1 mM (Strehler and Cormier, 1953). This could be interpreted either as 

 an oxidation of luciferin or a block between NAD and luciferin. 



McElroy and Kipnis (1947) objected to the luciferin oxidation mechanism 

 on the basis that respiration is also quite well inhibited by the quinones 

 and that cyanide does not reverse the inhibition when glucose is present 

 — arguments which do not seem to be completely valid — and preferred to 

 assume that luciferin is reduced by some factor X between cytochrome b 

 and cytochrome c, luciferin actually competing with the cytochrome c 

 for electrons. The naphthoquinones are assumed to act between cytochrome 

 b and X, thereby inhibiting both luminescence and respiration; the effect 

 on the latter may be less because another pathway for glucose oxidation 

 exists. The modern scheme of bacterial luminescence (see page 1-850) 

 involves NAD in the reduction of FMN to FMNHg, which reacts with the 

 aldehyde and the enzyme to form an excited complex, and it could well 

 be that the quinones oxidize FMNHg to prevent the formation of this com- 

 plex, but no recent work has been done on this point. It would also be in- 

 teresting to know if luciferase is inhibited by the quinones. The luciferase 

 of Renilla reniformis is not inhibited at all by menadione at 0.1 mM, but 

 neither is the light emission, and thus the luminescent system in the sea 

 pansy must be quite different from that in bacteria (Cormier, 1960). Like- 

 wise, the luciferase of Odontosyllis phosphorea, a polychaete annelid, is 

 inhibited only 15% by 0.5 mM menadione (Shimomura et al, 1963). 



