2 



Dr. A. Compton. 



general lowering of the temperature range and corresponding fall of 

 optimum temperature, for the maltase of the preparation in question, when 



I 40 - 



o 



-i ' ' tuMt'iniTtimitt,! I 



< 10 20 30 40 50 60' 



^ TEMPERATURE > 



Fig. 1. 



0-6 cm.^M/100 H^SO* is added to a reaction mixture of total volume 5 em.^, 

 containing in solution 3 mgrm. of the enzyme preparation (enzyme con- 

 centration, 6 X 10~* mgrm. per cm.^). This addition of acid, as indicated on 

 the diagram, corresponds to a H"*" concentration of lO"^'**, the H"*" con- 

 centration for the natural reaction {i.e., without addition of acid) being 

 10~'"^. Under these circumstances, the maltase of the preparation is seen to 

 undergo a lowering of its optimum temperature from + 47° (natural reaction) 

 to + 35"5° (above mentioned acid reaction). 



In the experiments which follow, we have always operated in presence of 

 this constant addition of acid : 0'6 cm.^ H^SO* per 5 cm.^ of tlie reaction 

 mixture, for disabling effect ; while the quantities of enzyme present have 

 varied from 3 mgrm. to 7 mgrm. per 5 cm.^ total mixture, that is to say, 

 enzyme concentrations varying between 6 x 10~* and 14 x 10~* grm. per cm.-\ 

 The substrate concentration throughout was M/20, or 18 x 10"^ grm. of 

 hydrated maltose per cm.'^ of the reaction mixture. It was not practical to 

 study the course of events for superior enzyme concentrations, owing to 

 complete hydrolysis of the substrate being attained, in the conditions of the 

 experiments, and consequent want of definition in the matter of the optimum 

 temperature point. 



The practical details of the experiments carried out were as follows : 

 90 mgrm. of hydrated maltose, 6 cm.^ M/lOO H^SO*, and 3-4 cm.^ of pure 

 water — prepared from distilled water by redistillation under diminished 

 pressure — were introduced into four series of eight dry, clean, " resistance 

 glass " test-tubes, rendered clean by successive washing in acid, water, and 

 steam. The tubes were then plunged into water thermostats, regulated to 

 the 1/lOth of a degree, and, an equilibrium of temperature having been 



