416 Dr. A. Compton. The Influence of the Hydrogen 



corresponding to the addition to the reaction mixture of 02 cm. 3 M/100 H 2 S0 4 

 per milligramme of enzyme. This is done in fig. 5. 



Fig. 5. 



hydrogen ion concentration of the medium in which the enzyme acts from 

 10~ 7-2 to 10 -3 it is possible to change the optimum temperature of the ferment 

 from +47° to + 35-5°, — i.e. through a range of 11'5°. This result alone shows 

 how important it is, when stating the optimum temperature of an enzyme, to 

 point out at the same time the H + concentration of the medium serving to 

 determine it. Thus, the optimum temperature of the maltase in question, in 

 an action of 16 hours' duration, may be expressed as [35 - 5°] io~ 3 - or [47°] io~'' 2 . 



Fig. 5 is further interesting from another aspect. The parallelism or 

 similarity of the two curves is very striking ; they are almost superposable. 

 Were they exactly so, and obviously that is only a question of sufficient 

 experimental patience, it would mean that the activity of the enzyme is the 

 same at corresponding temperatures over two equal although different ranges 

 of temperature, — the one curve being in that case simply a translation in the 

 plane of the paper of the other. It is proposed to term this, the phenomenon 

 of corresponding states. From a consideration of the locus lines of figs. 2 and 

 3, it is evident that for H + concentrations such that the maxima of the result- 

 ing optimum temperature curves are situated at the same level on these lines, 

 the enzyme should for the one and the other H + concentration be in " corre- 

 sponding states." 



The main conclusion of the present paper, in the insight which it affords 

 into the influence of the H + concentration of the medium on the physical 

 optimum of enzyme action, cannot perhaps be summarised to more advantage 

 at present than by placing it in its appropriate place in a differential table 

 briefly setting out our present knowledge of the relation of the physical and 

 the chemical optima of enzyme action to the experimental conditions involved 

 in determining them. 



20 30 4£ 



Temperature 



Fig. 5 shows at a glance that by the simple process of increasing the 



