1309 



nc 1 



In the experimental verification of tlie fornnula ha + 



^ 0,434 ■ 1—y 



ay = nit there is, howex er, besides a lowering of the H-ion concen- 

 tration, another way .to cliange the relation between the coefKicients 



of log ■ and of y. 



• 1—y 



If only p^ can be kept constant, we ma}' raise ft, the concen- 

 tration of the urea, considerably. The realisation of this method 

 will be communicated further on in this paper. 



For the above mentioned reasons at high />// only the tirsl values 

 ot m have been used for tiie main present purpose : the determina- 

 tion of ))i at different H-ion concentration. 



For the purpose of comparing the values of in obtained, they 

 are all reduced to the same enzyme concentration, the unit of which 

 is again arbitrarily Chosen as resulting when 1 g. of Soja is extract- 

 ed in 100 c.c. of water + 7.28 g. of Na.HPO, 2 aq + 2,32 g. of 

 KHjPO^ and 50 c.c. of filtrate of this is mixed with 100 c.c. of 

 water -)- 9,6 g. of phosphate. 



m as a function of pu- 

 According to tiie mathematical formulation of the radiation theory, 



X 



—(L'=:ni dt, the constant ni is only dependent on the con- 



.1' -|- nc 



centration of urease present. 



When equal concentrations of urease are compai'ed or the effect 

 has been reduced to equal concentrations, i. e. when the enzyme 

 concentration is kept constant as well as the temperature, ni will 

 be proportional to the activity of the same urease concentration. 



From table J 2 it is clear, that the activity m changes with />/ƒ 

 in a peculiar manner. 



In figure 3 the mean values of rn, in arbitrary units, are plotted 

 against the values of pj/ as abscissae. The strikingly regular curve, 

 thus obtained, allows a further mathematical treatment to elucidate 

 the nature of urease. 



MiCHAKLis ^) had already shown, that enzyme activity, represented 

 as a function of />// gives in many cases a curve somewhat similar 

 to that of the undissociated part of an amphoteric electrolyte. The 

 vagueness and irregularity of the curves of Michaktjs and of those 

 of SöRKNSEN for invertase excluded, however, all further comparison 

 and analysis. 



ij Die VVasserstoffionen-Konzentration. Verlag von Juliu« S^RiNfiKR, 1014. 



85 

 Proceedings Royal Acad. Amsterdam. Vol. XXI. 



