6o 



F. F. NORD, M. BIER 



VOL. 12 (1953} 



comparison of the relative concentration of the two components and the tryptic activity 

 of the solution at different stages of selfdigestion could be evaluated. The data are 

 presented in Fig. 2 and Table IV. 



Fig. 2 



TABLE IV 



EFFECT OF SELFDIGESTION OF TRYPSIN ON ITS COMPOSITION 



Run 



Incubation time 



Residual 

 proteolytic 

 activity % 



Residual protein 

 concentration 



Ratio 



r Components I : II 



from area meas- , , ■ 



^ 0/ (ascending areas) 



ureinents 



* Digested in o.i M sodium acetate, 0.05 M MgCl^, pH 7-7.5 

 ** Digested in o.i M sodium acetate, 0.05 M CaCl^, pH 7-7.5 



Ultracentrifugation 



The ultracentrifugal behaviour of trypsin was investigated in several arbitrarily 

 differentiated pH-stability regions. At pH 2 .3 where the enzyme is most stable, sedimenta- 

 tion diagrams characteristic of a homogeneous protein were obtained as is exemplified 

 by the photographs in scries A of Fig. 3. The dependence of the sedimentation constant 

 on the concentration of the enzyme is presented in Table V. No significant concentration 

 dependence of the sedimentation constant below i % protein concentration was observed 

 and the average of the values obtained was s^f^,^ = 2.4 S. 



Freshly prepared solutions of trypsin in a borate buffer, pH 8, present similar 

 patterns as shown in scries B of Fig. 3. From the data in Table V it can be seen that the 

 sedimentation constants are not significantly higher at this pH, giving an average value 

 of S2o,a, ^ 2.5 S. Two runs performed on trypsinogen in the acid and alkaline buffer 

 present identical patterns and sedimentation constants as trypsin. 



References p. 66. 



