OXYGEN SUPPLY OF CERTAIN ANIMALS 305 



3. Production of oxygen by enzymatic action 



It is well known that plants, bj^ virtue of their chlorophyll 

 and the sunlight, can combine inorganic compounds, building 

 up complex organic compounds with the liberation of oxygen. 

 This is considered to be due to an enzymatic substance within 

 the plant. The oxygen, liberated in the atomic or active form, 

 will as such oxidize alcoholic tincture of guaiacum to a com- 

 pound having a blue color. It was therefore thought advisable 

 to look into the enzyme content of the chironomid larvae, the 

 object being to ascertain whether there might be enzymes in any 

 way connected with their oxygen supply. 



Most animal tissues contain an oxidizing enzyme which will 

 split off atomic oxygen from hydrogen peroxide or an organic 

 peroxide, and can be demonstrated by the oxidation of an 

 indicator, such as guaiacum or benzidine, to a colored compound. 

 On examination it was found that the chironomid larvae con- 

 tained a substance which would do this. The blood from a 

 chironomid larvae or an aqueous extract of their tissues would 

 immediately oxidize alcoholic tincture of guaiacum on the 

 addition of hydrogen peroxide or the organic peroxide found in 

 old turpentine. 



Whether or not this substance can be called an enzyme is 

 largely a matter of definition. If the definition of an enzyme 

 includes the statement that enzymes are destroyed by boiling, 

 then this substance cannot rightly be considered as such. It 

 was found that when the extract of a chironomid larva was 

 raised to the boiling point and even kept at that temperature 

 for some time, it still was capable of splitting off the oxygen from 

 a peroxide. In this respect it is different from true enzymes. 

 Iron seems to play an important role in the non-thermolabile 

 peroxidase of the chironomid larvae. Iron is of course found in 

 the haemoglobin of the chironomid blood, and was demon- 

 strated qualitatively by the writer in the ash of the tissues. 

 The exact role of iron in an enzyme is not known. Perrin ('05) 

 and Bayliss ('14) agree that an iron-containing peroxidase con- 

 sists of the union of an unstable collodial ferric hydroxide with 

 a stable colloid. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGT, VOL. 33, NO. 1 



