The Proteases of Plants (VII). 
BY 
S. H. VINES, F.R.S. 
Sherardian Professor of Botany in the University of Oxford. 
I N a previous paper upon this subject (1 ; 1905) I gave an account of 
experiments with malt, which led me to the conclusion that it contains 
two proteases, the one a peptase, peptonizing fibrin; the other an ereptase, 
peptolyzing albumoses and peptones. I found further that the peptase was 
most active in an acid medium, whether of natural acidity, or when HC 1 had 
been added to the extent of o-i %: the addition of HC 1 to 0-3%, or of 
Na 2 C 0 3 to 1 %, arrested digestion. The ereptase digested Witte-peptone 
most actively in an acid medium, up to HC 1 0*2 %, and somewhat less 
rapidly in an alkaline medium containing up to 4 % Na 2 C 0 3 . The reaction- 
range of the peptase was thus determined to extend from 0-2 % HC1 to 
1 % Na 2 C 0 3 , whilst that of the ereptase was left undetermined, though the 
limit of alkalinity had been nearly reached at 4 % Na 2 C 0 3 . 
It occurred to me subsequently that since malt has such well-marked 
proteolytic activity, it was highly probable that the preparations of diastase 
which are used for medicinal purposes would possess them also. The 
following is an account of some experiments made in pursuance of this 
idea. 
Malt-Diastase. 
The first tentative experiment was made with an old specimen of 
diastase that had been in the laboratory for many years: the result was 
such as to justify further investigation. 
2 grms. were mixed with 100 c.c. distilled water: the liquid was neutral, and 
gave no tryptophane-reaction. 40 c.c. of it were put into each of two bottles: to the 
one was added 0-2 grm. fibrin, to the other 0-2 grm. of Witte-peptone, with some 
HCN as an antiseptic. After 24 hours’ digestion in the incubator at 40° C., the fibrin 
remained unaltered; and the contents of the other bottle gave a faint tryptophane- 
reaction. 24 hours later, the fibrin still remained unaltered, but the tryptophane- 
reaction had become marked. 
[Annals of Botany, Vol. XXIV. No. XCIII. January, 1910.] 
