Physiology. — “On the Movement of Pepsin in a protein-containing 
or protein-free rel of Agar-agar”. By Prof. C. A. 
PEKELHARING. 
(Communicated at the meeting of November 26, 1921). 
In an earlier paper!) presented to this Academy I dwelt on a 
peculiar protein obtainable from the gastric mucous membrane, 
which could be procured in a purer condition from a dog’s gastric 
juice that is neither contaminated with swallowed matter nor with 
the constituents of the intestinal contents, so that the elementary 
analysis did not bring forth greater differences than are generally 
found with purified proteins. This peculiar protein evinced the 
properties of pepsin in such a marked degree and the digesting 
power was in different preparations so constant, that I felt justified 
in supposing that this protein could be the enzyme itself. Subsequent 
investigations have repeatedly confirmed this view. 
However, in discussing the nature of enzymes with our fellow 
member Brigertnck he raised an objection against this conception. 
According to his experience pepsin, or, chymosin (which enzymes I 
hold to be identical) diffuses in agar-agar about as quickly as al- 
bumoses. 
This was, indeed, a serious objection. The pepsin, as I prepare 
it, is split while being rapidly heated in an acid solution to the 
boiling point, so that albumoses which remain in solution, are liber- 
ated, while a considerable precipitate is being formed, from which, 
on heating with potassium hydrate, part of the sulphur is freed 
together with substances yielding a biuret-reaction. With acid a 
precipitate of a new protein can now be obtained from the alkaline 
fluid, which protein possesses comparatively energetic acid properties 
and is soluble in alcohol. This pepsin, then, is of a much higher 
composition than tbe simple proteins grouped under the name of 
albumoses. If my conception were correct, pepsin would surely not 
diffuse so easily as albumose in a gel of agar-agar. 
However, I put myself the question whether the movement of 
the enzyme is indeed to be ascribed entirely to diffusion. Might 
1) Proceedings of the Meeting of 25 Jan. 1902, p. 450, 
18 
Proceedings Royal Acad. Amsterdam. Vol. XXIV. 
