3 H 
Vines.— -The Proteases of Plants. 
The observed facts are, on the whole, favourable to the latter conclusion. 
To begin with, the results of the peptolysis-experiment No. 2, suggest that 
the rapid peptolysis and the slow peptonization should be interpreted 
as being due to the presence of two proteases, the one readily soluble 
in water, the other less soluble. Again, the superior peptonizing activity 
of NaCl extracts compared with watery extracts (see p. 310), suggests that 
the protease concerned is more readily soluble in 2 °/ o NaCl solution than 
in distilled water. The importance of NaCl as a solvent is demonstrated 
in Expt. 9 (p. 310). 
The inference drawn from these observations on solubility is supported 
by the observations upon the effect of added acid and alkali on peptolysis 
and peptonization respectively. Taking the limits of peptonization as 
HC 1 on °/ o and Na 2 C 0 3 1 °/ o (p.311), those of peptolysis are less restricted, 
extending beyond these limits in both directions. 
The Nature of the Proteases. 
The generally accepted opinion with regard to the two Fungi in 
question is that they contain a single protease. In the case of yeast, 
Hahn and Geret, Bokorny, and others, regard this protease as a trypsin : 
and Hjort has made the same suggestion in the case of the Basidiomycetous 
Fungi investigated by him. My observations, as already explained, lead 
me to the conclusion that two proteases exist in these plants, the one 
peptolytic, the other peptonizing. It remains now to consider what the 
nature of these proteases may be. 
At a meeting of the Linnean Society of London, on November 20, 
1902 (Proceedings, 1902-3, p. 42), I announced the discovery in many 
plants and different parts of plants of a peptolytic enzyme analogous to the 
recently discovered entero-erepsin of the animal body : a more complete 
account of my researches was soon afterwards (January, 1903) published in 
this periodical (13), the mushroom having been one of the plants investigated. 
The further observations, of which an account has now been given, 
confirm me in the conclusion that the mushroom contains an erepsin, 
that is, a peptolytic enzyme which is unable to peptonize the higher 
proteids such as fibrin and albumin ; and they justify the extension of 
the conclusion to yeast. 
This vegetable erepsin is not, however, identical in properties with 
either the entero-erepsin discovered by Cohnheim or the pancreato-erepsin 
discovered by Vernon (see p. 290). The action of both these animal 
erepsins is limited to neutral or feebly alkaline liquids, whilst I have found 
that vegetable erepsin can act through a fairly wide range of acid and 
alkaline reaction, its greatest activity being manifested when the reaction 
of the liquid is at or near natural acidity. Hence vegetable erepsin affords 
a new type of ereptic action. 
