1314 



TABLE 14. 



It is to be borne iji mind, that the equation 



VI — 3 = 



fCa kf, 



\0'"" 10~^'<'^ 



from whicli these constants had io be calfuiated, is an exponential 

 one. Slight variations in pj/ must therefore be expected to have a 

 large intlnence. 



However, as the deviations between the experimental curve and 

 that, repi'esenting the calculated values of in for, say ^i = 18, in 

 table 13, are within the limits of accuracy, set by the experimental 

 methods employed, it n\a.\ be concluded, that the equation for the 

 undissociated |)art of an amphoteric electrolyte i-epresents faiily well 

 the activity of urease as a function of /;//. 



An impoitant consequence of this is the possibility of obtaining 

 at least an approximate knowledge of the dissociation constants of 

 the enzyme urease. It is evident from table 14. that ^^ and Iv, appear 

 to be about 1.3 < 10 -« and 2.2 < IQ-^ or even higher. 



The dissociation constants of carbonic acid ^) and ammonia at 27° 

 are respectively 4.4 X 10-' and 1.9 X 10 5«). 



The approach of these constants to those of urease is in a line 

 with the author's view') that enzymes generally contain in some 

 active state the same molecule, which is liberated or acted upon 

 by them. 



Aimnonium-carbonate -\- carbonic acid as a bujfer-mixture. 



Ill the beginning of this study ii soon became clear to the writer, 

 that the commonly accepted statement as to the accelerating action 

 of CO, vvas not only not sufficiently borne out by experiment, but, 

 as a matter of fact, might be total I v erroneous. 



1) MiCHAELis und RoNA, Biochem. Zeitschr. 1914, 67, 18"2 



') LuNDEN, Affinitatsmessungen an schw'achen Saiiien und Baseu. 



') BARENDRECHT, Biochem, J. 1913, 7, 549. 



