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Enzyme of Nepenthes (//). 
3. The discovery of true peptone among the products of 
digestion facilitates the classification of the enzyme. Green 1 
has found that the proteolytic ferment present in germinating 
seeds acts in an acid medium, producing a relatively large 
quantity of albumose together with peptone, leucin, and 
tyrosin ; that it is in fact a tryptic ferment, differing mainly 
from the trypsin of the pancreatic juice in requiring an acid 
medium for its digestive action. In all these respects (though 
I have not made out the production of tyrosin) the proteolytic 
enzyme of Nepenthes - pitcher closely resembles that of the 
germinating seed ; but it is much more rapid and energetic 
in its action, and apparently more stable in its nature. These 
two proteolytic enzymes are distinguished, by their activity 
in an acid medium, from those, such as papai'n 2 and the 
enzyme in the fruit of Cucumis utilissimus 3 , which are most 
active in a faintly alkaline medium. It is a remarkable fact 
that, whatever may be the reaction of the medium in which 
they can work, all these enzymes are essentially tryptic in 
their mode of action ; in fact it is not improbable that this 
may be a characteristic feature of all vegetable proteolytic 
enzymes whatsoever. 
1 Phil. Trans., 1887. 
2 See Martin, in Journ. of Physiol., V, 1884, and VI, 1885. 
3 See Green, in Annals of Botany, VI, 1892. 
