220 BIOCHEMISTRY OF BACTERIAL LUMINESCENCE 



to a multiplicity of factors must await its isolation for a definitive 

 answer. 



Effect of Physical and Chemical Environment 



The pH dependence of the reaction is illustrated in Fig. 7. The 

 double optima may be due to the semipurified nature of the system, 



40-1 



in 



O 



in 

 o 



20- 



z 



»- 

 z 



I 

 o 



r 



6 



7 

 pH 



8 



9 



Fig. 7. Effect of pH on dialyzed bacterial extract luminescence: Extract dia- 

 lyzed for 15 hours against distilled water at 0° C. Each vessel contained 50 

 fig DPNHo, 0.2 ml enzyme, 0.2 ml NaHo POi (0.01 M) titrated to desired 

 pH with 1 N NaOH; total volume 0.5 ml; temperature 23° C. 



but are readily duplicated with crude acetonized extracts in the 

 presence of added DPNHo. 



Temperature profoundly affects the rate of the luminescent reac- 

 tion in vitro and Fig. 8 illustrates a typical result with the crude ex- 

 tract. Particular care must be exercised in making such measurements, 

 since the instantaneous effect of temperature is somewhat different 

 from its delayed effects, even in the lower temperature range. Per- 

 haps some of this effect is due to different pool sizes of intermediates 

 if differential effects are not measured rapidly. The extremely high 

 apparent activation energies (ca. 25 to 31 kcal) observed cast some 

 doubt on the meaning of this measurement, the presence of some arti- 



