The Chemistry of Light-Production in Luminous Organisms. 231 



but independent of the quantity of pyrogallol, providing the pyrogallol 

 is present in excess of the quantity capable of being oxidized by per- 

 oxidase and H 2 2 . Melanin formation by tyrosinase is also propor- 

 tional to the amount of tyrosinase present (42). 



The peroxidase, therefore, transfers the O of H 2 2 to the pyrogallol 

 and the H 2 2 pyrogallol, and peroxidase are all changed i. e. } used 

 up in the reaction. If we represent the peroxidase by P and the pyro- 

 gallol by B the reaction must take place as follows : 



P +2H 2 2 = PO 2 +2H 2 O 



PO 2 + B = PO+ BO (1) 



and not as 



P +2H 2 =P0 2 +2H 2 O 



P0 2 +2B =P +2BO (2) 



Note that in the first equations the peroxidase (P) is used up and in 

 the second equations it acts as a true catalyzer and is regenerated again. 



That the peroxidase of turnip-juice is used up so far as its power to 

 cause light-production in pyrogallol is concerned is indicated in the 

 following experiment : 



If 1 c.c m/10 pyrogallol +4 c.c. H 2 O 2 (3 per cent) is mixed with 5 c.c. 

 turnip- juice heated to 80 (to destroy the catalase and weaken the 

 peroxidase), a very faint light is produced. A small amount of per- 

 oxidase is, therefore, present. The mixture is allowed to stand for 

 24 hours at 22 C. and then fresh turnip-juice is added. A good light 

 results, showing that the pyrogallol has not been changed by a small 

 amount of peroxidase when a long time has been allowed for the re- 

 action to proceed. The pyrogallol was turned a light brown by the 

 small amount of peroxidase, and this color had not deepened in 24 hours, 

 but did deepen immediately when the additional quantity of peroxidase 

 was added. A small quantity of "enzyme" can not, therefore, transform 

 an indefinite amount of pyrogallol. A similar result was obtained with 

 a weak hemoglobin solution, 0.1 per cent dried blood-extract. 



That a large quantity of peroxidase can be used up by addition of 

 successive amounts of pyrogallol i. e., by "titrating" the peroxidase 

 can be shown as follows: 



To 10 c.c. potato-juice heated to 60 C. (to destroy catalase and 

 consequent foaming due to liberation of from H 2 C>2) is added 2 c.c. 

 of a mixture of equal parts m/10 pyrogallol and 3 per cent H 2 O 2 . 

 Light results. When this has disappeared (about 2 to 3 minutes) 

 2 more cubic centimeters of the pyrogallol-H 2 O 2 mixture are added and 

 a very faint light results. On adding a further 2 c.c. no light appears. 

 There is, however, in the final mixture plenty of pyrogallol +H 2 O 2 to 

 produce light, as may be shown by adding fresh potato-juice when 

 abundant light appears. The peroxidase has been completely used up. 

 A similar experiment with blood-extract gave a similar result. 



