Vines . — The Proteases of Plants. 
299 
Peptolysis. 
Inasmuch as the foregoing experiments on autolysis were gauged 
by the tryptophane-test, they were essentially experiments in peptolysis. 
Nevertheless, I thought it necessary to institute experiments as to the 
peptolytic action of yeast upon added albumoses and peptones, as con- 
tained in the substance known as Witte-peptone : the results, as might 
perhaps be expected, were similar to those of the autolysis-experiments. 
In the first place it was ascertained that a filtered watery extract 
of yeast was always peptolytically active, however short the period of 
extraction might be, even when the quantity of yeast used was small ; and 
further, that peptolysis was rapidly effected. The following experiment, 
in which the period of extraction was limited to the time necessary for 
filtration, illustrates both these points : — 
Experiment 1. 2 grms. of the dried yeast were extracted on a filter with 
100 cc. of distilled water containing 1 % toluol : within an hour 50 cc. of liquid were 
obtained, to which 0-5 grm. Witte-peptone was added, and were then placed in the 
incubator. The liquid gave no tryptophane-reaction. 
After digestion for one hour the liquid gave a marked tryptophane-reaction. 
Here, notwithstanding the short duration of both extraction and diges- 
tion, a dilute extract gave unmistakable evidence of peptolytic activity. 
The next experiment was made with the object of demonstrating 
the effect upon peptolysis of various strengths of acid and alkali. 
Experiment 2. 20 grms. of dried yeast were extracted with 400 cc. of toluol- 
water (1 %), and left to filter for several hours in a cold room. The filtered liquid, 
which gave a faint tryptophane-reaction, was distributed as follows : — 40 cc. were 
put into a bottle (No. 1) without further addition; in the remainder of the liquid 
10 grms. of Witte-peptone were dissolved, and 40 cc. of the solution were put into 
each of 8 bottles (Nos. 2-9): to No. 2, nothing more was added; to No. 3, added 
2 grms. of precipitated chalk; to No. 4, Na 2 C 0 3 to 1 % ; to No. 5, Na 2 C 0 3 to 2%; 
to No. 6, Na 2 C 0 3 to 3 % ; to No. 7, HC 1 to o-i %; to No. 8, HC 1 to 0*2 %; to 
No. 9, HC 1 to 0-5 %. 
After 4 hours in the incubator the tryptophane-reactions were : — No. 1, distinct; 
No. 2, marked; No. 3, strong; all three being acid: No. 4, distinct; No. 5, faint; 
No. 6, none ; all three being alkaline : No. 7, strong ; No. 8, marked ; No. 9, distinct. 
After 25 hours in the incubator the reactions were : — No. 1, distinct; Nos. 2 and 
3, strong; No. 4, marked; No. 5, distinct; No. 6, none; Nos. 7 and 8, strong; 
No. 9, marked. 
These results are in general agreement with those of the corresponding 
autolysis experiment (p. 295). 
It was further ascertained that here also the retarding or inhibiting 
effect of added acid or alkali was the more marked the more dilute the 
yeast-extract. 
