304 



LIGHT AND LIFE 



From this it may be inferred that an appreciable change in the 

 configuration of the protein occurs in the presence of salt at ambient 

 temperatures, and it is possible that this change might be related 

 to the concomitant increase in enzymatic activity. Such an effect upon 

 the catalytic activity might be mediated either via general changes in 



0.2- 



ENZYME WITH 

 Na CI 



I'ig 8. Data for heat inactivation of luciferase plotted according to ilie Arrhenius 

 equation. On the ordinate are plotted on a log scale the \elocity constants for 

 enzyme inactixation. and on the abcissa the reciprocal of absoUite temperature. 

 From the slope of the line, the enthalpy of activation may be calculated to be 

 about 62,000 calories, both for enzyme in the presence of NaCl and for enzyme 

 in the absence of salt. 



the conformation or tertiary structure of the protein, or via effects 

 upon the dissociation of groups at, or near, the active center (1, 

 7, II). The relatively nonspecific ion activation is consistent with 

 effects of this nature. 



It can also be shown that luciferin itself, in the absence of enzyme, 

 imdergoes the nonenzymatic oxidation more rapidly in the presence 

 of salt (Fig. 9) . This effect is concentration- and temperature- 



