MECHANISMS OF HIOLUMINESCENT REACTIONS 

 ^V. D. McELRcn AND H. H. Seligf.r 



Dt'Jxnliiient of Biology and McCollum-Pratl Institulc 

 Johns Hopkins University, Baltimore, Maryland 



Introduction 



Bioluminescence is an enzyme-catalyzed chemiluminescence in which 

 oxygen acts as an electron acceptor. The enzyme effectively channels 

 the oxidative events so that light is emitted with a high efficiency as 

 compared with ordinary chemiluminescence (8) . So far as we can 

 determine, the requirements for chemiluminescence and biolumines- 

 cence are an ionizable substrate which can form a peroxide addi- 

 tion, molecular oxygen, and presumably a fluorescent product mole- 

 cule. These requirements appear to be fulfilled for both the firefly 

 and the bacterial systems. In the examination of these light-emitting 

 processes we have been concerned with the isolation and purification 

 of the components of the reactions, the identification of end-products 

 and possible intermediates, and the mechanism of the conversion of 

 the chemical energy into light energy. 



In chemiluminescence in aqueous media, hydrogen peroxide or 

 the formation of a peroxide appears to be a necessary factor for the 

 production of light. On this basis a number of workers have sug- 

 gested that an organic peroxide radical is the important intermediate 

 in bioluminescence, particularly since oxygen is essential for light 

 emission (19). 



The enzyme molecule must therefore be able to bind the substrate 

 molecule in such a manner that a catalyzed peroxide addition can 

 occur at the proper ionizable site, and further must be able to 

 protect the excited state from non-luminescent quenching interactions. 

 In this respect the configuration of the substrate on the enzyme mole- 

 cule appears to be extremely important for intramolecular energy 

 transfer which will determine the efficiency of light emission, and in 

 some cases, the color. 



In the present paper we shall sunnnarize the data available on the 

 chemical and physical properties of the firefly and the bacterial bio- 



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