^^g Comparative Animal Physiology 



since there is a conspicuous similarity in the general properties of biolumi- 

 nescence, wherever it occurs. 



The photogenic materials show a certain degree of group-specificity. Lu- 

 minescence will result only when the luciferin and luciferase from the same 

 or from two rather closely related species are mixed, as for example with two 

 genera of fireflies, or two genera of ostracods. No light results on the mixing 

 of these substances obtained from two widely separated genera in the same 

 subphvlum, as for example, the ostracod, Cypridina, and the decapod, Acan- 

 thephyra. Similarly no light results when the two materials come from dif- 

 ferent phvla. 



Very little is known as to the chemical nature of luciferin and luciferase. 

 All studies indicate luciferase to be non-dialyzable and to show a number 

 of properties characteristic of a protein. Such properties include heat lability; 

 precipitation by alcohols, saturated ammonium sulfate, and alkaloidal rea- 

 gents: destruction by proteinase; and induction of an anti-luciferase on in- 

 jection into a rabbit.-^-^ Furthermore, careful study of the reaction kinetics 

 of Cypridina luciferase shows it to have characteristics of a typical enzyme, 

 although it will not oxidize an unlimited quantity of luciferin. The enzyme 

 gradually becomes denatured. 



Luciferin appears definitely to be non-protein. It is dialyzable, indicating 

 relatively small molecular weight. Cypridina luciferin is readily oxidized 

 by numerous oxidizing agents, but yields light only when oxidized in the 

 presence of luciferase' (see exception below). Crude luciferin extracts are 

 readily and rapidly oxidized without luminescence in strong light, appar- 

 endy by a photochemical reaction. This non-luminescent reaction is not 

 observed in solutions of more carefully purified luciferin and luciferase, 

 therefore it probablv requires the presence of photosensitizers for its oc- 

 currence. 



Just as there has been disco\ered no oxidizing agent which Vv'ill, in the 

 presence of Cypridina luciferin, produce light, so also has no substrate ex- 

 cept luciferin yet been found which, on oxidation in the presence of luci- 

 ferase, yields light. 



The kinetics of the Cypridina luciferin-luciferase reaction have been care- 

 fullv investigated.'- The reaction appears monomolecular. There is also 

 a rather high temperature coefficient (Qk,) having an average value in the 

 functional range of 2.74. lower at the lower end of the temperature range 

 and higher at the higher end. The velocity constant of the reaction is pro- 

 portional to the luciferase concentration. The total light emitted is propor- 

 tional to the quantitv of luciferin, other conditions being ecjual. However, 

 the total amount of light is also influenced b\ the amount and type of salt 

 content of the extract, the pFL and the temperature of the medium. The ef- 

 ficiency of light production in terms of units of luciferin decreases as the tem- 

 perature rises from 18 to 28° C. 



When luciferin and luciferase are first mixed in an oxygenated medium 

 there is an initial flash of light, too intense to fit smoothly with the general 

 curve of decay of the luminescent reaction which follows. The time re- 

 quired for the intensity of the flash to reach a maximum is longer (0.03 sec.) 

 when luciferin and luciferase are mixed in an oxygenated medium than when 

 oxygen is added to an oxygen-free and hence non-luminescing mixed solu- 



