156 



CARNEGIE INSTITUTION OF WASHINGTON. 



In the firefly, for instance, it is possible that reduction occurs in the period 

 between flashes, while we know that oxidation occurs during the flash of 

 light. Dilute alkali favors oxidation and dilute acid favors the reduction. 



So far as I have been able to determine, luciferin and oxyluciferin have 

 identical chemical properties. Neither are digested by the enzymes: malt 

 diastase, ptyalin, yeast, inveHase, pepsin, trypsin, steapsin, amylopsin, 

 rennin, erepsin, urease, o" enzymes occurring in the water-extracts of dried 

 spleen, kidney, or liver. Of the above enzymes tried, luciferase is destroyed 

 only by pepsin (probably), trypsin, erepsin, and something in spleen and 

 liver extract. Further properties of Cypridina luciferin and Cypridina luci- 

 ferase may be noted from the following table: 



Table 2. — Properties of photogenic substances. 



Property. 



Luciferase. 



Luciferin. 



Alkaloidal reagents: 

 Phosphotungstic acid. 



Completely precipitated . 



Phosphotungstic and acetic acid 

 Phosphotungstic acid and HCl . 

 Formic acid 



Nearly precipitated. 



Formic and acetic acid 



Formic acid and HCl 



Picric acid 



Picric and acetic acid 



Picric acid and HCl 



K4Fe(CN)6 and acetic acid. 

 Heavy metal salts: 



Basic lead acetate 



Neutral lead acetate 



Nearly completely precipi'd 



Completely precipitated . . . , 

 Nearly completely precipi- 

 tated. 



Neutral lead acetate and ace- 

 tic A. 



Mercuric chloride 



Mercuric chloride and acetic A. 

 Uranyl nitrate and acetic acid . 

 Acids and alkalies: 



KOH 



NH4OH 



Acetic acid 



Carbonic acid 



Trichloracetic acid 



Not precipitated . 



Not precipitated . 



Do 



Do 



Do 



Do 



Very nearly completely pre- 

 cipitated. 



Do. 

 Completely precipitated. 

 Nearly completely precipi- 

 tated. 



Do. 



Do. 

 Not precipitated. 



Do. 



Do. 



Do. 



Not completely precipitated, 

 Do. 



Do. 



Do. 



Almost completely prec. 

 Not completely prec. 



Not precipitated. 

 Do. 

 Do. 

 Do. 

 Do. 



There is no doubt that luciferase is a protein. All its properties agree with 

 those of the albumins. 



Luciferin, on the other hand, is not digested by proteolytic enzymes is 

 dialyzable, almost but not completely precipitated by saturation with 

 (NH4)2S04, and is soluble in absolute alcohol, acetone, and some other 

 organic solvents, but not in the strictly fat-solvents like ether, chloroform, and 

 benzol. There are, however, certain CO-NH hnkages which are not attacked 

 by proteolytic enzymes and some peptones soluble in absolute alcohol, so that 

 these two characteristics do not bar it from the group of proteins. Luciferin, 

 in fact, has many properties in common with the proteoses and peptones and 

 may be provisionally placed in a new g 'oup of natural proteins on the border- 

 land between the proteoses and peptones. 



