252 INACTIVATION OF TRYPSIN. II 



with a value for K of 0.1 as found above, and all done with the same 

 inhibiting solution to agree with the same value of P (or d) as well. 

 Several experiments were made which gave apparently regular results 

 for which, however, it was impossible to find any satisfactory value 

 for K and d. In every case of this kind it was found that the inhibit- 

 ing solution used contained either active trypsin or some substance 

 which could still be acted on by trypsin. In applying the formula, 

 it is assumed, of course, that the only trypsin present is that in the 

 trypsin solution added and that the substrate concentration is the 

 same in all tubes. These experiments seem to show that the formula 

 is not of such a general character as to fit any regular curve. As would 

 be expected, dififerent inhibiting solutions required different values 

 of P. The results shown in the figure were all calculated from the 

 same values of K' which were obtained from the first part of the 

 experiment in Curve A . All the other results were calculated before 

 the experiment was done, as were those described later in which the 

 conditions were varied in other respects. The figure shows that the 

 calculated and experimental results are identical. 



Column 6 in Table IV contains the values for Qd; i.e., the product 

 of the free trypsin into the total amount of inhibitor. It wiU be seen 

 that this value increases at first but becomes constant as d becomes 

 large with respect to Q. Q therefore becomes inversely proportional 

 to d. This may also be predicted from the mass action expression, 

 and, as Arrhenius^ pointed out, is the condition that leads to Schiitz's 

 rule. The steps in the derivation are as follows: 



Equation (1) may be written 



K{E-Q) 



as d increases the term (£ — Q) increases and approaches the constant 

 value E so that K (E — Q) approaches a constant value. If d is large 

 compared to E the term {E — Q) may be neglected in the denominator 

 and the equation written 



or Q, the amount of active trypsin is inversely proportional to the 

 amount of inhibitor, which is the experimental result referred to 



^ Arrhenius, S., Medd. Kong. Vetsakad. NobelinsL, 1908, i. 



