343 
1910-11.] Small Degrees of Enzymatic Peptolysis. 
seeds or animal tissue there is always the possibility of subsidiary processes 
taking place which may give rise to change in the reaction. 
The synthetic production, by Emil Fischer and his school, of numerous 
di- and polypeptids made it possible to investigate peptolysis by studying 
the action of enzymes on such substances. The general employment of 
these ideal methods is, however, prevented by the difficulties attaching to 
the preparation of polypeptids. In order to overcome these a new method 
has been devised by Abderhalden ( Zeitschrift fur physiologisches Ghemie , 
vol. lxi.) which involves the use of a silk pepton — Pepton Roche. This, 
on hydrolysis, gives a large yield of ty rosin, which, being sparingly 
soluble, is precipitated, and may be filtered off, dried, and weighed, the 
weight indicating the degree of peptolysis and hence the enzymatic activity. 
Two difficulties arise here, however. The activity may be so slight that the 
amount of tyrosin thrown down is too small to determine accurately by 
weighing. Secondly, it is not always possible to use clear solutions, and 
even where such are used the possibility remains of insoluble substances 
other than tyrosin being produced. The formation of such substances has 
actually been observed in various instances during my experiments. 
Consequently, a method of estimating tyrosin by chemical means was 
sought. 
It was suggested to me at this point by Dr Westergaard that a 
colorimetric method might be applicable, and to this I turned my attention. 
A suitable colour reaction is described by Morner in the Zeitschrift fur 
physiologisches Ghemie , xxxvii. Morner s reagent, which consists of sulphuric 
acid and formol, gives with a small amount of tyrosin an intense green 
coloration easily determinable by tintometer. It now remained to prove, 
firstly, that the intensity of colour is in direct relation to the concentration 
of tyrosin, and, secondly, that the weight of tyrosin produced under 
standard conditions from the same quantities of enzyme and substrate is 
constant. In order to demonstrate the first of these relations, a series of 
estimations was carried out, using quantities of tyrosin varying from 
'004 gm. to '012 gm. The tyrosin used for this purpose was Merck’s 
preparation, which, although possibly not perfectly pure, is nevertheless 
sufficiently so for the purpose of showing the proportionality existing 
between the degree of colour and the quantity of tyrosin. The preparation 
gave on ignition a very small trace of reddish ash, the quantity obtained 
from T4 gm. tyrosin being too small to ascertain by weight. The solubility 
determined at 20° C. was slightly above that stated in the handbooks, being 
1 in 2090, while Beilstein gives it as 1 in 2454. The melting point is stated 
variously by different authors. Beilstein gives it as 235°, while Oppenheimer 
