Studies on Enzyme Action. 



361 



necessary to re-examine the action : ultimately, the retarding effect of 

 galactose was traced to the presence of an alkaline impurity.* 



In No. V, in which the action of emulsin on milk sugar is discussed, 

 attention is called to the evidence in favour of the view that emulsin is 

 capable of acting on /3-galactosides {i.e., milk sugar) as well as on /3-gluco- 

 sides ; also to Bourquelot and H^rissey's contention that probably lactase is 

 present in ordinary emulsin. Experiments to be described in a later com- 

 munication, made specially with the object of clearing up this question, leave 

 no doubt that the activity of emulsin as ordinarily prepared is due, as 

 Bourquelot and Herissey and also Pottevin have con tended, to the presence 

 of a distinct enzyme capable of affecting the /3-galactoside, on which emulsin 

 proper has no action. 



To state our opinion in brief, maltase is capable of hydrolysing a-glucosides 

 alone, whilst emulsin hydrolyses /5-glucosides. 



Correlation of Enzyme with Hydrolyte. — In view of these considerations, the 

 suggestions should be cancelled which were put forward in the third com- 

 munication-)* with reference to the extent to which configuration may be 

 modified without nullifying the action of an enzyme. 



Attention was directed in this communication to the evidence of a close 

 correlation in configuration between enzyme and hydrolyte afforded by the 

 controlling influence on the rate of change of a glucoside which the hexose 

 derived from it exerts ; welcome confirmation of this conclusion is afforded 

 by Ter Meulen's observations.:!: 



A further series of experiments has been made with specially purified 

 materials which enable us to confirm and extend the earlier observations ; 

 it is unnecessary to describe these in detail, as the method followed has 

 already been described. The results are summarised in the following table : — 



Enzyme. 



Hydrolyte. 



Inhibitants. 



Destitute of inhibiting power. 



Maltase 



Invertase 



Maltose 



Glucose, methyl-/3- 

 glucoside 



Glucose, fructose... 



Galactose, methyl- 

 a-galaotoside 



Galactose, fructose, mannose, sorbose, 

 arabinose, mannitol, dulcitol 



Galactose, mannose, mannitol, dulcitol 



Fructose, mannose, arabinose, xylose, 

 mannitol 



Cane sugar 



Milk sugar 





The evidence that enzyme and hydrolyte must be in complete correlation 

 appears to be little short of absolute in the case of the sucroclasts. 



* Cf. Caldwell, ' Eoy. Soc. Proc.,' 1906, vol. 78, p. 283. 



t Vol. 73, p. 525. 



% ' Eec. Trav. Chim.,' 1905, vol. 24, p. 444. 



