The Proteases of Plants, 
BY 
S. H. VINES, 
Sherardian Professor of Botany in the University of Oxford. 
INCE the publication in these pages (June, 1903) of my last paper 
O (1) on this subject, I have been continuing my investigations, and I have 
also come across several important papers by other observers, so that 
a considerable amount of further information has accumulated of which 
some account may now well be given. 
Before discussing the new facts, I propose to indicate very briefly 
the desirability of somewhat modifying the current method of describing 
the phenomena of proteid-digestion, and to suggest a terminology more 
in harmony with the present state of knowledge. Hitherto the proteases 
of both plants and animals have been classified as ‘ peptic * or as ‘ tryptic/ 
in accordance with their general resemblance to either the pepsin or the 
trypsin of the animal body ; and a digestion has been described as ‘ peptic ’ 
when it went no further than the conversion of the higher proteids into 
albumoses and peptones, and as ‘ tryptic ’ when the peptones formed were 
decomposed into non-proteid bodies such as leucin, tyrosin, &c. But with 
the discovery of erepsin by Cohnheim, this simple classification of the 
proteases has become inadequate, for erepsin is neither ‘ peptic * nor 
‘ tryptic.’ Of the two, it is more nearly allied with trypsin than with 
pepsin, inasmuch as it actively decomposes peptones : but it differs widely 
from trypsin in that it cannot peptonize the higher proteids, such as 
albumin and fibrin. It is, in fact, a representative of a new, third, class 
of proteases, which may be described as ‘ ereptic.’ 
Now as to the terms employed in describing the digestive process. 
The word ‘ proteolysis ’ is in common use, but not always in the same 
sense : it is sometimes applied to peptonization by pepsin : at other times, 
and more accurately, it is applied to the disruption of the proteid-molecule 
into non-proteid substances, and it is in this sense that I have used it in my 
more recent papers. But the most appropriate use of the word is its 
application to the sum-total of the processes involved in proteid-digestion, 
to all the changes determining the conversion of the higher proteids into 
such substances as leucin, tyrosin, &c. Accepting this connotation of 
[Annals of Botany, Vol. XVIII. No. LXX. April, 1904.] 
