Physiology. "The Influence of Neutral Salts on the Action of 



Urease''. By .1. Tkmminck Groll. (Commnnieated by Prof. 

 G. VAN Rijnbehk). 



(Communicated in the meeting of September 29, 1917). 



Ferments being colloids it is not impossible that the influence 

 that electrolytes exercise on the action of enzymes must be attributed 

 to modifications of the dispersity of the ferment. 



If this were really the case, then the chai'acter of one of the 

 two ions would have a domineering inflneiice over against that of 

 the other, as was likewise found by Hardy for the flaking of colloids : 

 it appeared namely that with colloids moving cathodically, which 

 are consequently charged positively, the anion of an electrolyte lias 

 the greater influence, whilst with colloids moving anodically the 

 influence of the kation was domineei'ing. 



A ferment will be either a positive colloid or a negative one, 

 and a ferment that has its action especially in alkaline surroundings, 

 will usually be negatively charged, whilst the ferments acting in 

 acid surroundings will be positive. We can consequently expect a 

 great influence either of the character of the anions or of that of 

 the kations, according to the ferment being eithei- positively or nega- 

 tively charged. Moreover with colloids the piienomenon presents 

 itself, that both the kations and the anions can be placed in a special 

 series according to their being able to cause a modification of dis- 

 persity either in a greater or in a- more restricted degree. 



With regard to the kations this series is not always entirely the 

 same, but in . the main there is no difference with various colloid- 

 phenomena. 



Some metals occasionally change place, or as Freundlich remarked : 

 "Die Reihe der Kationen ist wieder etwas verschrankl". 



Usually the series of the kations is : NH/, K-, Na', Ca-, Sr*-, 

 Ba •, Mg'. 



The series of the anions is CNS', J', Br', NO', CI', SO/'. 



In order to examine in how far the influence of salts on a fer- 

 ment-action corresponds with that on colloid-phenomena, it is advisable 

 to make use of an enzyme that decomposes a crystalline substrate 

 to crystalline products of decomposition, for if one takes a colloidal 



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