1908. | Studies on Enzyme Action. 327 
Amount of enzyme. Velocity constant K. 
10 e.c. 0:0107 
20 0:0212 
40 0:0279 
60 0:0385 
While the evidence secured is sufficient, we consider, to prove the 
existence of a lactase in almonds distinct from emulsin proper (@-glucase), 
it in no way serves to distinguish the enzyme from that in Kephir grains, 
the action of which was considered in Nos. II and III. The proof on which 
we rely as a means of differentiating the two enzymes is that the one is 
controlled by glucose, the other by galactose. The effect of these hexoses 
on Kephir-lactase was considered in No. III. Results are now recorded in 
Table II which illustrate the behaviour of emulsin-lactase prepared in the 
manner described above; they afford complete confirmation of those obtained 
four years ago, which were then properly interpreted as proof of the 
non-identity of the two enzymes, although it was not then realised that 
emulsin proper (@-glucase) was incapable of hydrolysing milk-sugar. Such 
evidence, in our opinion, is a clear indication that the hydrolysis of milk- 
sugar 1s consequent on the attachment of the enzyme in the one case to 
the galactose section and in the other to the glucose section of the 
biose; we may point to this conclusion as a striking illustration of the 
diagnostic value of what may be termed the control method which has been 
developed in the course of these studies and as being also an interesting 
extension of our conception of the manner in which enzymes may affect 
hydrolysis. | 
The Amygdaloclastic Activity of Hmulsin—Although the individual 
substances which are formed when amyegdalin is hydrolysed—hydrogen 
cyanide, benzaldehyde and glucose—may be estimated more or less easily 
when apart, serious errors arise when the ordinary analytical methods are 
applied to their determination in admixture. 
_ Ripper’s method* of determining benzaldehyde gives low results, even with benzaldehyde 
alone, the values varying with the dilution. It is altogether vitiated by the presence of 
hydrogen cyanide. All attempts we have made to fix the cyanide as an insoluble or non- 
volatile cyanide have been unsuccessful, some always passing over during the removal of 
the benzaldehyde by distillation. 
The determination of benzaldehyde in the form of a difficultly soluble inydrazone is 
unsatisfactory, chiefly on account of the difficulty of securing its conversion completely 
into hydrazone and because of the readiness with which it is oxidised. 
Liebig’s method of estimating hydrogen cyanide cannot, as a rule, be applied directly 
to the solution in which hydrolysis has taken place, as the emulsin is liable to interfere 
with the determination of the end point, by rendering the solution turbid. The method 
* ‘Zeit. anal. Chem.,’ 1902, vol. 41, p. 61. 
iw) 
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VOL. LXXX.—B. 
