BIOLOGY OF LIGHT PRODUCTION — MALUF 389 



capable of a marked truly anaerobic metabolism and that their 

 luminescent reactions partake of this phase of their metabolism. 



2. The mechanism of bioluminescent reactions. — Unlike the oxidation 

 of foodstuffs, the oxidation of luciferin does not appear to result in an 

 evolution of C0 2 , or, at least not enough C0 2 is produced (pH determi- 

 nations by means of a sensitive potentiometer) during luminescence to 

 saturate the proteins in solution since "the acidity of the luciferin solu- 

 tion, luciferase solution, and the two after mixing was found to be the 

 same, pH 9.04" (Harvey, 1931). Good evidence that the luciferin- 

 oxyluciferin change is a dehydration-hydrogenation reaction is pre- 

 sented by the fact that dry oxyluciferin, when first exposed to atomic 

 hydrogen, produces light upon the addition of a solution of luciferase; 

 otherwise, dry oxyluciferin plus a solution of luciferase does not pro- 

 duce light. Evidently atomic hydrogen is capable of adequately re- 

 ducing oxyluciferin to luciferin. 



The luciferase is not merely a catalyst in the reaction but evidently 

 supplies molecules which may be excited to emit light by the energy 

 released upon the oxidation of luciferin. These activated molecules 

 may thus return to their initial state (Harvey, 1932, 1935). This 

 is indicated by the fact that when the luciferin from one animal can 

 be energized to produce luminescence with the luciferase of a closely 

 related species, the species (or sex) supplying the luciferase determines 

 the color of the resulting luminescence and by the fact that Cypridina 

 luciferin, when oxidized alone in aqueous solution, never emits light 

 even though the velocity of its oxidation may be greater than in the 

 presence of luciferase. The decay curve of light intensity in a luci- 

 ferin-luciferase solution is monomolecular, indicating that only one 

 molecule of luciferin is being transformed (Amberson, 1922). The 

 entire scheme may be expressed thus (Harvey, 1935, 1935a): 



(Luciferase accelerates) 



(a) Luciferin (LH 2 ) + 1/2 2 > oxyluciferin (Z/) + H a O 



(b) L' + luciferase (A) > L+A' 



(c) A' ► A + hv (light quanta) 



The prime (') indicates the excited molecules. 



The reaction somewhat resembles that of the reduction of methy- 

 lene blue: 



MRff 2 + l/2 2 t MB+H 2 



(reduced methylene blue) (reductants) 



Aluminum, zinc, magnesium powders, or other inorganic reducing 

 agents will reduce oxyluciferin to luciferin as they will reduce methy- 

 lene blue to the colorless compound. In both cases the reactions are 

 reversible. Further evidence that the reaction is similar to the oxi- 

 dation of a leuco-dye, rather than to the oxidation of a substance like 



