1911. | The Alcoholic Ferment of Yeast-juice. 463 
evolved, whereas in the presence of hexosephosphate 132°7 c¢.c. were 
obtained. The ratio of the totals produced in presence and in absence of 
phosphate is thus 132°7/1°5 = 88, a much greater value than had previously 
been observed.* | 
2. Acceleration of the Action of Hexosephosphatuse by Arsenate-——The direct 
replacement of phosphate by arsenate being excluded, the alternative explana- 
tion, that the arsenate accelerates the action of the hexosephosphatase, remains 
to be considered. This question can readily be investigated experimentally, 
and the result of such an examination is to show that the arsenate does in 
fact produce a very marked effect of this kind, and that it is to this accelera- 
tion that the enhanced rate of fermentation in the presence of arsenate 
is due. This has been proved separately for yeast-juice and zymin. 
In the three experiments carried out with yeast-juice, a comparison was 
made between the rates of fermentation in mixtures of yeast-juice with 
(a) hexosephosphate and arsenate; (0) water and arsenate; (c) hexose- 
phosphate alone. | 
In experiments such as these, done in the absence of added sugar, 
the rate of fermentation is controlled by the production of sugar (1) from 
the hexosephosphate ; and (2) from the glycogen and dextrins of the juice. 
Hence, by subtracting the rate of auto-fermentation in presence of arsenate (0) 
from the rate of fermentation of hexosephosphate also in presence of arsenate (@) 
a difference is obtained which represents the share of this enhanced rate 
which is due to the hydrolysis of the hexosephosphate. This is given by 
a—b, and a comparison of this with the rate of fermentation of hexose- 
phosphate in absence of arsenate shows whether the effect of the arsenate 
has been to increase the rate of hydrolysis of the hexosephosphate. (In order 
to obtain the true rate of evolution due solely to the hexosephosphate in 
absence of arsenate the rate of auto-fermentation of the juice should be 
subtracted from that observed in presence of hexosephosphate (c). As, how- 
ever, it 1s not certain what effect the presence of hexosephosphate may have 
upon the enzymic hydrolysis of glycogen, etc., this has not been done in the 
present instance. The effect of making this subtraction would be considerably 
to increase the cogency of the argument.) 
In order as far as possible to diminish the auto-fermentation, the yeast-juice 
employed in Experiments 19 and 20 was incubated for some time before the 
addition of the hexosephosphate and water, and the yeast employed for the 
preparation of the juice for Experiment 21 was treated for the removal of 
glycogen by the method described by Buchner and Mitscherlich, but still 
yielded a juice which gave a considerable amount of auto-fermentation. 
* “Roy. Soc. Proc.,’ B, 1908, vol. 80, p. 324. 
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