743 



solution the minimal solnbilitj would not be a matter of sur- 

 prise at all. Some of mj experimental results lend support to the 

 view that pepsin is indeed a compound. Firstly the movement of 

 the enzj'rae in the electric Held in acid solution appeared to be 

 anodal, that of the greater part of the protein cathodal. The se|mra- 

 tion, however, is by no means complete, nor can it be expected to 

 be SO; perhaps the protein moving towards (he cathode consists of 

 nothing else but decomposition products of pepsin. I have not been 

 able to ascertain this because of the incomplete separation and the 

 difficulty to procure larger quantities. 



Secondly I have noted the quantities of H- and Cl-ions that are 

 combined with the pepsin in the hydrochloric acid solution. !f the 

 pepsin, prepared after Pekelharing, is the enzyme itself, it will unlike 

 protein, not combine chiefly with H-ions, but with Cl-ions, as it is 

 always charged negatively. If, however, pepsin is a compound of 

 protein and the enzyme, the protein-constituent will most likely 

 combine chiefly with H-ions, whereas the enzyme-constituent will 

 unite with Cl-ions only. The enzyme itself may be expected to weigh 

 very little indeed, and to combine with only an inappreciable quantity 

 of Cl-ions. It would follow then that in this case, after all, oidy small 

 differences between the pepsin and the ordinary protein can be 

 expected, and that at most there would be comparatively oidy a 

 small majority of combined Cl-ions. This supposition was borne out 

 by determinations, performed with very small electrodes, as (he 

 ratios of the combined H-ions and the combined Cl-ions were in a 

 hydrochloric-acid concentration of 



0.029 n 'Vci for pepsin 3.00 and for albumoses 3.06 



of 0.0597 n „ „ „ 1.34 „ „ „ 1.42 



and of 0.116 n „ „ „ 1.01 „ „ „ 1.12 



In a still stronger hydrochloric acid, 0.235 n, tiie ratio was, it is 

 true, somewhat higher for pepsin than for albumoses, but with such 

 a strong acid the estimation is liable to so many errors, that the 

 results cannot be relied on. 



The mere fact that the pepsin combines chiefly with H-ions, refutes 

 the hypothesis that all the pepsin, as we prepared it, is the enzyme 

 itself, the latter being in\'ariably charged negatively. I, therefore, 

 maintain that my experiments confirm the supposition, that the pepsin, 

 as we prepared it after Pekelharing, is acompound (or an adsor[)tion 

 compound) of a highly complicated protein and the enzyme, the 

 latter being always charged negatively through combination with anions. 

 This combination of anions with the true enzyme betrays itself by 



' 48 " 



Proceedings Royal Acad. Amsterdam. Vol. XVllf. 



