THE CHEMISTRY OF LIGHT PRODUCTION 123 



natural proteose, soluble in absolute alcohol and not 

 digested by trypsin or that it belongs to some other group 

 than the proteins. The absence of a biuret reaction would 

 point in that direction and the question must await 

 further study. 



Cypridina luciferin is found in the luminous gland of 

 the animal and possibly in parts non-luminous as well as 

 in the luminous organ. This is true of the luciferin from 

 fireflies which is found throughout the body of Luciola, 

 Photuris and Photinus. 



Cypridina luciferase. — Luciferase, on the other hand, 

 has all the properties of a complex protein. It will not 

 dialyze through collodion or parchment membranes, is 

 soluble only in aqueous solvents, and hence precipitated by 

 alcohol and acetone, digested by proteolytic enzymes, 

 readily changed by contact with dilute acid and alkali and 

 irreversibly coagulated on boiling. It is completely salted 

 out of solution by saturation with (NH4)2S04 and nearly 

 completely precipitated by the alkaloidal reagents. Its 

 other properties are given in Table 8. Taken together, 

 they point to the group of albumins as the class of pro- 

 teins with which luciferase most closely agrees. 



If luciferase is not a protein it is so closely bound up 

 with protein that it cannot be separated. This is charac- 

 teristic of many enzymes and luciferase is also an enzyme. 

 "We can determine this by finding out whether luciferase 

 will accelerate the oxidation of a large amount of luciferin, 

 for such is the test of a catalytic substance. If we take 

 1 c.c. of a dilute solution of luciferase (1 Cypridina to 50 

 c.c. water) and add to it successive 1 c.c. portions of con- 

 trated luciferin (1 Cypridina to 2 c.c. solution) as soon as 

 the light from the preceding addition has disappeared, 



