HYDROGEN ION CONCENTRATION AND PROTEOLYSIS. 171 



2. The greatest activity was manifested in the medium of which the 

 original Ph was 5.42. In the same medium the rate of proteolysis increased 

 most remarkably after its Ph was changed to 6.99 or higher. 



3. The least proteolytic activity was observed in flask 9, at the end of 

 two hundred and forty hours. 



4. The formol titrating nitrogen increased slowly, especially in flasks 

 5 and 9, up to one hundred and forty-four hours, and then a rapid increase 

 took place. This slow increase at the beginning may be due to the inhibi- 

 tory reaction of the hydrogen ion concentrations upon the enzjnnes. After 

 there had been a sufficient amount of protective substance produced the 

 enzj''me assumed greater activity'. 



5. It is probable that the enzyme which brought about the proteolysis 

 in the investigation is tryptic-like in its nature, according to the present 

 conception of the enzymatic classification. The greatest proteolysis took 

 place toward the optimum hydrogen ion concentration, which is Ph = 8.076 

 in this case. It has been shown that the optimum hydrogen ion concen- 

 tration for trypsin varies according to the temperature, the materials 

 used and other factors of environment. For instance, Pahtzsch and 

 Walbima * obtained the following results from their experiment, in which 

 they employed 0.4 per cent, trypsin solution and 6 per cent, gelatin 

 solution. 



These results indicate that as the temperature increases the optimum 

 point changes toward the neutral point. 



Again, Oppenheimer^ quoted from Mesernitzky's^ work on B. pro- 

 digiosus, and stated that the optimum hydrogen ion concentration 

 for the proteolytic action of the organism is sfightly less than that of 

 trypsin (10'^). 



These references seem to confirm the author's deduction. 



' Biochem. Zeitschr., Bd. 47, Heft 1, S. 34. 



' Oppenheimer, C. Die Fermente u. Ihre Wirkungen, 4 Auflage, Bd. II, S. 617. 



3 Mesernitzky, P. Biochem. Zeitschr., 29, 104, 1910. 



