268 LIGHT AND LIFE 



tial for light emission, or (d) a combination of the above three. 

 There is no a priori reason for assuming that the hot water extract 

 contains luciferin. For example, this fraction could be oxyluciferin 

 and the function of the reduced pyridine nucleotide to reduce it to 

 luciferin. On the other hand, the pyridine nucleotide requirement 

 may be for the reduction of some component other than oxyluciferin. 

 Experimental evidence for selecting between these two possibilities 

 is lacking. The experiments with albumin strongly suggest that not 

 only is possibility (a) or (c) taking place but also that the enzyme 

 preparation is inhiliited also. The results presented in Fig. 4 may 

 be explained in the following manner. When bovine plasma albumin 

 is present during the entire course of the reaction, the intensity 

 of light emission is determined by some factor other than the amount 

 of active luciferase. The results of curve A conform to the following 

 interpretation. The reactions leading to components necessary for 

 light emission are not affected by albumin, and they proceed at 

 the same rate either in its presence or absence. However, the reac- 

 tion catalyzed by luciferase and leading to light emission is rate- 

 limiting due to enzyme inhibition, and hence the unknown com- 

 ponents accumulate. The secondary addition of bovine plasma al- 

 bumin effectively increases the concentration of the luciferase by 

 reacting with the presumed inhibitor and consequently there is an 

 immediate increase in light intensity. If this suggestion is valid, 

 curve A indicates that the time necessary for the adsorption of the 

 inhibitor is comparatively short. In subsequent experiments similar 

 results have been obtained upon the secondary addition of the 

 enzyme preparation. These residts are amenable to the same inter- 

 pretation. In this case more luciferase is being added to the reaction 

 mixture. Postulation of rate limitation in the presence of albumin 

 to unknown reactions previous to light emission is preferred since 

 the velocity constants of all known luciferin-luciferase reactions are 

 extremely rapid, thus accounting for the "flash" of light seen on 

 mixing these reactants. If enzymes other than luciferase are involved 

 in light emission from these jireparations, they are not separable 

 by the purification procedure outlined above. 



The nature of the albumin response is somewhat comparable to 

 that found in the reduction of cytochrome c by cytochrome c reductase. 

 Nason et al. (10) ioinid that the addition of a-tocopherol stimulated 

 cytochrome c reduction in a manner similar to crystalline bovine 

 serum albumin. .Addition of bovine plasma albinnin, isooctane-ex- 

 tracted in ;i ni;inner similar to that described by Nason (10), to the 



