THE ACTIVITY OF INVERTASE IN VARIOUS ACID SOLUTIONS. 



The measurements of these activities were made in the manner 

 described in the preceding section, and the values are recorded in 

 Table 2. 



TABLE 2. Activity of purified invert asc in solutions of various acids. 



" Destruction of en/.ym occurs. 



In figure 1 the curves for the five strong acids hydrochloric, hydro- 

 bromic, nitric, sulphuric, and phosphoric fall so closely together 

 that one unbroken line is shown for them all. The enzym begins to 

 be destroyed by these mineral acids at a concentration of about 0.01 

 I'ormal and the measurements of the activity were not made above 

 this limit. The falling of the curve (fig. 1) with increasing acidity 

 shows a characteristic progression in the order, strong mineral acids, 

 oxalic, tartaric, citric, acetic, and boric, which is also the order of 

 the strengths of these acids. If the ionization of the acids is taken 

 into consideration and the activit}^ plotted against the actual hydro- 

 gen-ion concentration the various weaker acids all give curves agree- 

 ing closely with that for the strong mineral acids. The enzymotic 

 activity is thus primarily a function of the hydrogen-ion concentra- 

 tion. The theoretical interpretation of this characteristic relation 

 between the activity and the true acidity must be postponed until 

 further investigations have been made. 



[Cir. 55] 



