58 



The writer has also noted cases of the regeneration of the peroxi- 

 dase after its apparent destruction by heat, especially in the 

 case of the oxidase of the sweet-potato. Hasselbring and Als- 

 berg^^ have recently found that only in the presence of coagulable 

 protein are the oxidases easily destroyed by heat. 



With the exception of catalase there is probably no enzyme 

 more common among plants and animals than peroxidase. 

 There is hardly a plant or any part of its organs that does not 

 blue tincture of guaiacum in the presence of hydrogen peroxide, 

 thus proving the presence of peroxidases. The oxidases also 

 play an important part in many industrial processes. The curing 

 of tobacco, the production of the bouquet of wines, and the 

 formation of commercial indigo from Indigofera anil in India, all 

 seem to be somewhat dependent upon the oxidases. Green tea 

 is produced when the freshly picked leaves are immediately 

 spread on hot plates which, of course, destroys the oxidases, 

 while the slow curing with consequent activity of the oxidases 

 yields the black tea of commerce. The aroma of the vanilla- 

 bean and the fragrance of the English meadow-sweet {Ulmaria 

 Ulmaria) have also been attributed to oxidase action. Leptomin 

 is really a peroxidase but Raciborski,^^ finding the indirect oxidase 

 localized in the leptome (phloem) of plants, considered it a 

 new enzyme, and one distinct from the direct ox dase. With 

 guaiacum and hydrogen peroxide the strongest bluing is localized 

 in the phloem through which the sieve-tubes pass, the latter 

 acting as carriers of the food materials of the plant. This so- 

 called leptomin is present in largest amount in the phloem of the 

 latex plants. These illustrations will serve to show the distri- 

 bution and importance of the oxidases in plants. 



Catalase 



It has long been known that finely divided metals, blood, 

 plant juices and fluids from the animal body cause the rapid 

 decomposition of hydrogen peroxide. But this fact did not 



22 Hasselbring and Alsberg. Studies upon Oxidases [an abstract]. Science 

 II. 31: 637. 1910. 



23 Raciborski. Ein Inhalts-korper des Leptoms. Ber. Botan. Gesell. 16: 52. 



