BENT LEY GLASS 851 



water extract is an oxyliuileriii, wliich is recliued l)y the pyridine 

 niKieotide to the active substrate, kuilerin. He emphasizes several 

 differences between the iiingal system and that found in luminous 

 bacteria: (i) the fiuigal system tloes not respond to reduced flavin 

 mononucleotide; (ii) there is no requirement in the fungal system 

 for a long-chain aldehyde; and (iii) the emission maximum in the 

 hmiinous mold (in vivo) is at 530 m^i., whereas in the bacteria it is 

 at 480 niyn, and consequently the excitation energy required for the 

 latter is greater than for the former. 



7he report by W. D. McElroy and H. H. Seliger reviews and ex- 

 tends present knowledge of the bioluminescent system of the North 

 American fireflies. The general scheme of the firefly's luciferin-luci- 

 ferase reaction system is reproduced in Fig. 5, from which it may be 

 seen that luciferin (LH^) , reacting through its carboxyl group with 

 ATP in the presence of luciferase, yields an enzyme-bound luciferin 

 adenylate (E-LH2-AMP) plus pyrophosphate (PP) . It is for this 

 step that the magnesium ion is required. The enzyme-bound luciferin 

 adenylate may undergo either of two reactions, one a simple non- 

 radiative separation of the enzyme and the luciferin adenylate, the 

 other an oxidation by molecular oxygen with the emission of light. 

 The immediate product of the luminous reaction is enzyme-bound 

 oxyluciferin adenylate (E-L-AMP) . This product acts as a strong 

 inhibitor of the luminous reaction by typing up the enzyme, to which 

 L-AMP is tightly bound. 



A study of the kinetics of the luminous reaction reveals two parts 

 to the decay of the light intensity from the maximum flash height. 



E + LH2-AMP 

 E + LH2 + ATP ^ * F- LH2 AMP + PP 



O2 



LIGHT 



E H- L -4- ATP ^ ' F-I-AMP-I- PP 



E+ L-AMP 



Fig. 5. Summary of the reactions concerned with light emission in firefly extracts. 

 LH„, luciferin; ATP, adenosine triphosphate; PP, pyrophosphate; E, luciferase; L, 

 oxyluciferin; LH3-AMP and LAMP, luciferyl and oxyluciferyl adenylic acid, re- 

 spectively. 



