276 STUDIES ON BIOLUMINESCENCE. IX 



unquestionably due to their trypsin content. That the destruction 

 of luciferase is actually due to digestion and not to the injurious ac- 

 tion of amino-acids resulting from the digestion of proteins associated 

 with the luciferase is shown by adding the products of a 4 day (at 

 38°C.) tryptic digest of albumen (then boiled to destroy the trypsin) 

 to luciferase, and keeping the mixture with toluene at 38°C. for 4 

 days more. The luciferase was found to be unaffected by the amino- 

 acids present. 



These experiments all indicate that luciferase is a protein. As 

 erepsin has a digestive action one might suppose that it belongs to 

 the group of proteoses, but too great reliance cannot be placed on 

 conclusions drawn from the action of erepsin, as this enzyme is said 

 to hydrolyze histones, protamines, casein, fibrin, and nucleic acid in 

 addition to proteoses and peptones.^ Dubois finds that Pholas lucif- 

 erase is digested by tr3^sin.^ 



On the other hand, none of the enzyme preparations tested had 

 any action on luciferin. The proteolytic enzymes especially were 

 studied with great care and with the result that no digestive action 

 could be demonstrated. In one experiment not recorded in Table I 

 luciferin was mixed with a Parke Davis Co. pancreatin preparation, 

 having active proteolytic power and kept at 38° for 4 days without 

 digesting the luciferin. Erepsin also had no digestive action after 4 

 days at 38°. Merck's pancreatin (without toluene) had no digestive 

 action after 8 days at 38°C. Dried powdered CypridincB were mixed 

 with Merck's pancreatin and toluene and kept at 38° C. for 8 days. 

 This digest was found to contain no luciferase but abundant luciferin. 

 There is no doubt of the non-digestibihty of the latter. As already 

 mentioned, these digests must be carried out in absence of oxygen, 

 otherwise the luciferin undergoes spontaneous oxidation to oxy- 

 luciferin and disappears apart from any enzyme action. The oxy- 

 luciferin like luciferin itself is also undigested after 4 days action of a 

 pancreatin solution at 38°C. As all common proteins, except the 

 racemized proteins and certain very insoluble albuminoides (elastin 



"* Samuely, F., in Oppenheimer, C, Handb. Biochem. des Menschen und der 

 Tiere, Jena, 1909, i, 554. 



^Dubois, R., Ann. Soc. Linn. Lyons, 1914, xli, 161. 



