212 LIGHT AND LIFE 



The Cyf)riclina system appears to be the simplest of the three, 

 involving only an oxidizable siil)strate aiui enzyme catalyst, in addi- 

 tion to water and molecular oxygen. Anderson (3) demonstrated 

 the non-luminescent auto-oxidation designated above by k^.^■, and found 

 that it could be induced by ferricyanide and certain other agents. The 

 product is inactive in light emission, and decomposes on standing, 

 but can be initially reduced to active luciferin (CLHo) by NaoS204 

 and certain other reductants. The changes in absorption spectrum 

 of fairly well-purified luciferin (48) indicate that the product of 

 reactions k,.r, and A',, is the same, although no one has succeeded in 

 regenerating, by the action of reducing agents or other means, any 

 very considerable amounts of active luciferin after it has undergone 

 a luminescent oxidation (k,) in presence of luciferase. The similarity 

 in absorption spectra of the products of oxidation is therefore some- 

 what puzzling, and is possibly indicative of impurities in the luciferin 

 solution, or else the seeming irreversibility of the luminescent reac- 

 tion is to be attributed to catalysts other than luciferase in the 

 relatively crude enzyme solution. 



The kinetics of light emission may be profoundly influenced by 

 the proportion of CLH2 and CL in equilibrium with each other at 

 the start of the reaction with luciferase. Moreover, false "cross- 

 reactions" may occur with enzymes of other systems when the luci- 

 ferase solution contains appreciable amounts of reversibly oxidized 

 luciferin which undergoes reduction and then a light-emitting oxi- 

 dation by its own specific enzyme. This circumstance is the most 

 likely explanation for the fact that, in cross-reactions between the 

 systems of different fireflies or different kinds of Cypridina which 

 have different emission spectra (23) , the color of the light is associated 

 with the enzyme preparation. 



Crystalline preparations of Cypridina luciferin, with a light-emitting 

 potency some 40,000 times that of the starting material (whole 

 dried organisms) , have been obtained (42) and their properties 

 studied. The active luciferin is yello^\' in color, and gives a yellow 

 fluorescence in idtraviolet light. On standing in solution exposed to 

 air, the color changes to red, and three substances can be isolated by 

 chromatogra]>hy, namely, an inactive red substance, plus two colorless, 

 blue-fluorescent substances which have been designated oxyluciferin A 

 and B, respectively. The former of these t^\•o substances separates 

 from ammoniacal solution in the form of yellow crystals, l)ut the 

 latter has not been crystallized. The empirical formula adduced for 

 luciferin (.32) is C2iH280oN,;.2HCl, and on the basis of various lines 



