238 tNACTIVATION OF TRYPSIN. I 



ference is not much greater than the experimental error. The experi- 

 ment was repeated several times and it was found that in general the 

 reciprocal of the time required to cause a change of 10 points in the 

 bridge reading was directly proportional, within the experimental 

 error, to the amount of trypsin taken. This value has therefore been 

 used to express the amount of active trypsin present in the solution. 

 The unit of trypsin used in these experiments may be defined as that 

 quantity which when added to 25 cc. of gelatin solution having a pH 

 of 6.3 (adjusted + NaOH) and a specific conductivity of 2 X 10~* 

 (adjusted f KCl) will cause a change in the bridge reading of 10 

 points (500 — 490) in 1 hour at 33°C. (equivalent to an increase in the 

 conductivity of 0.0782 X 10"^ reciprocal ohms). 



Properties of the Trypsin Used. 



It has been stated by Vernon^^ and others that "trypsin" may be 

 separated more or less into a nimiber of enzymes some of which attack 

 gelatin more rapidly than other proteins and some of which act best 

 on peptones. If this is the case the experiments are evidently com- 

 plicated by another factor in addition to the many already present. 

 Many experiments were made but no evidence could be found to 

 show the presence of such enzymes in the sample of trypsin used in 

 these experiments. The trypsin was treated in a number of different 

 ways and the relative velocity with which it hydrolyzed gelatin or 

 peptone compared before and after the treatment. (The peptone 

 was prepared by the action of pepsin on gelatin sulfate solution. 

 The acid was then removed with barimn and the solution made 

 alkaline with NaOH.) A summary of these experiments is given in 

 Table II. It will be seen that there is no evidence for the existence 

 of any special "peptonase" or "gelatinase" in the sample of trypsin 

 used in these experiments. 



Efect of Dialysis on the Trypsin. 



It has already been stated that the trypsin was purified by dialysis. 

 The effect of this is shown in Table III. It will be seen that the 

 activity of the trypsin is more than doubled by the process and that 

 the solution obtained in this way contained only about 0.02 gm. per 

 cc. of total solids. 



