R. I.. AllilH 



265 



+ BPA 



180 



240 



60 120 



TIME - SECONDS 

 Fig 2. Effect of crystalline bovine plasma addition on fimgal bioUiminescence in 

 vitro. Luciferase (6-75% (NH,),SO, fraction) 3.:") mg: lucifcrin. 0.20 ml; DPNH, 

 0.55 M"ioles; 0.05 M K-POj buffer, pH 7.45, containing 10 ' M \ersene + 10'' M 

 mercaptoethajiol to bring the final volume to .H.O ml. 



milliliter. Fig. 3 indicates that luciferase can be titrated with crystal- 

 line bovine plasma albumin. The luciferase preparation was com- 

 pletely inactive until the albumin was added. Both the maximum 

 light intensity and the change in the initial rate have been plotted, 

 and, on the whole, these two characteristics of the system behave 

 in a similar fashion. It has been found, in regard to both light 

 emission and the rate of increase in light emission, that an albumin 

 to enzyme-protein ratio of about 5 gives optimal activity. Ratios 

 greater than 5 tend to inhibit the reaction. The above could be ex- 

 plained on the basis of adsorption by the plasma albumin of an 

 inhibitor from the reaction mixture. 



The source of this inhibitor could be the hot water extract or 

 the enzyme preparation or both. Attempts to verify such an inter- 

 pretation of the data and the source of the presumed inhibitor have 

 been indecisive. Heating the albumin to 100°C for 3 minutes before 

 use completely eliminates its stimulatory effect. Preincubation with 

 the luciferin has no effect, and subsequent boiling of this preincuba- 

 tion mixture necessitates further addition of the albumin for stimu- 

 lation. This latter case is inconclusive, however, for, if a protein 

 inhibitor complex is formed during preincubation, it may be broken 

 down during subsequent heating. Likewise, preincubation of the 

 albumin and luciferase gives no data indicative of the adsorption 



