850 15. EFFECTS OF VARIOUS FACTORS ON INHIBITION 



luminescent intensity of Photohacterium pJiosphoreuni is increased, that of 

 Achromobacter fiscJieri is unaffected except at high pressures, and that of 

 Achromohacter harveyi is depressed (Brown et al., 1942). It might be that 

 the responsible enzymes in these organisms are qualitatively different, but 

 it would seem more reasonable that other factors are the basis for the varying 

 responses. Also the very marked effects of the temperature on the response 

 to high pressures would point to controlling factors more complex than a 

 single enzyme. Work with bacterial extracts has led to the following pro- 

 visional scheme for the sequence of reactions: 



(1) (2) (4) X 



X^A^B-^D^ (15-119) 



^^'' m\ 



C + heat C + heat 



(1) XHa + DPN+ ^ X + DPNH + H+ 



(2) DPNH + FMN + H+ ^ DPN+ + FMNH^ 



(3) FMNH^ + 1/2 O2 -^ FMN + H^O 



OH 



(4) FMXH2 + O2 + R-CHO-E -> FMN + E-R-C^OOH 



^H 

 OH 



(5) E-R-C^OOH + FMNH2 -> E-R-CHO-FMN* 



^H 

 OH 



(6) E— R— C^OOH + Y — ^ nonluminescent products 



^H 



XHg represents electron donors, FMN is flavin mononucleotide, 



OH 

 E-R-C^OOH 

 ^H 



is an aldehyde-peroxide addition complex, and the asterisks indicate the 

 photochemically activated molecules. The R-CHO is a long-chain aldehyde 

 originally obtained from renal cortex and later shown to be palmitic al- 

 dehyde. The enzyme, E, might be considered as the equivalent of luciferase, 

 but the other reactions are also enzymic. It might also be pointed out that 

 the level of DPN+ would be determined by reactions unrelated to the 

 luminescence sequence. The reduction of FMN by DPNH is perhaps the 

 limiting step under certain circumstances but in the living cell it is difficult 

 to know if this is always true. In any event, the effects of pressure may be 



