]]'. 1). Mcelroy and h. h. seliger 221 



between liiciferin ami adenosine tripliosphate leads to the formation 

 ol an intermediate en/yme-hicileryl-adenylate complex, E-LH^-AMP, 

 and pyroj)hosphate (PP). Light is produced when, in the presence of 

 oxygen, E-LH^-AMP is oxidi/ed to the en/.ymc-oxyhiciferyl-adenylic 

 acid complex (E-L-AMP) (20, 21) . This last-named compoimd can 

 also be produced enzymatically by the reaction of ATP with oxy- 

 liiciferin. We shall review the experimental evidence for these various 

 reactions and describe some of the effects of coenzyme A and pyro- 

 phosphate on the light reaction, prior to discussing the mechanism of 

 light emission. 



The Production of Light from ATP and LH^ 



In the study of the kinetics of the light reaction the reactants are 

 delivered to a buffer solution in a 10 nnn X 75 mm test-tube with 

 a fixed geometry relative to a phototube. The reaction is then initiated 

 by injecting with a hypodermic syringe quickly, and in a reproduci- 

 ble manner, approximately 0.1 ml of an ATP solution. The light 

 intensity observed as a function of time is shown in Fig. 2 by the 

 solid circles. There is at first a rapid rise in light intensity which 

 is followed by a relatively rapid decrease for the first few seconds 

 and then a much slower decay that may last for several minutes or 

 even hours. This typical flash height curve can be separated into 

 three parts. The initial rise is due to the finite mixing time of the 

 reactants, as can be shown by separate fluorescence measmements in 

 which a fluorescent solution is injected into a tube imder similar 

 geometrical conditions. The rapid decrease is caused by the initial 

 inhibition of the enzyme because of the rapid formation of E-L-AMP 

 complexes. Thus the flash-height peak, which is the resultant of the 

 above two effects, is strongly dependent upon the method of injec- 

 tion. However, with sufficient practice in injection procedure this 

 flash-height peak is directly proportional to the reaction rate and 

 therefore is valid for Michaelis-Menten analysis. It is possible to 

 separate the decay portion into two exponential decays. For the 

 concentrations of reactants used for Fig. 2 the initial decay has a 

 half-value time of 0.25 seconds and the slow decay has a half-value 

 time of 13 seconds. Extrapolation of the first-order plot of the 

 initial decay to zero time suggests that the initial flash ideally should 

 be more than twice that observed. The slower decay has been shown 

 to be due in jxtrt to the fact that the production of pyrophosphate in 

 the initial flash is sufficient to partially reverse the enzyme inhibition 

 due to the product E-L-AMP. 



