1904.] Studies on Enzyme Action. 189 



(2) The action of emulsin on milk sugar is most retarded by glucose, 

 and only to a slight extent by galactose, whereas galactose alone 

 affects the action of lactase. This, again, would appear to afford proof 

 that the emulsin is directly active. 



(3) The curves for emulsin fall off very much more rapidly than 

 those for lactase, showing that the action of the products in removing 

 the enzyme is greater in the former case. 



It therefore appears that the differences apparent in the behaviour 

 of emulsin and lactase towards milk sugar are such as to render it 

 improbable that the action of the emulsin is due to the presence of a 

 small proportion of lactase ; it would seem, rather, that emulsin is 

 capable of acting on /3-galactosides as well as on /3-glucosides.* 



A different enzyme being required, as a rule, for each sugar, the 

 relative activities of enzymes cannot well be reported in terms of any 

 particular sugar taken as standard ; the only method open to us at 

 present is to determine the activity of a particular acid towards the 

 various sugars and to estimate, by direct comparison, the activity of 

 the enzyme in terms of this standard acid. But, unfortunately, acids 

 compare very unfavourably with enzymes as hydrolysts : so that, 

 in order to effect hydrolysis at any reasonable rate, it is necessary, 

 except in the case of cane sugar, to operate at elevated temperatures, 

 at which a direct comparison between acid and enzyme is impossible. 

 The experiments here described are to be regarded merely as a first 

 attempt in the direction indicated. 



Add Activity. The method adopted is substantially that previously 

 described. Solutions of the glucoside containing 3 grammes per 

 100 c.c. were hydrolysed by means of a half gramme molecular propor- 

 tion of hydrogen chloride at 74. The following tables give the 

 results obtained with the various hexosides. The values of the velocity 

 constant K, expressed in the last column, are calculated on the assump- 

 tion that the change is mono-molecular. 



* Pottevin's (' Ann. Inst. Pasteur,' 1903, vol. 17, p. 31) investigations seem to 

 show, however, that Aspergillus niger contains an enzyme which is capable of 

 hydrolysing /3-glucosides but not /3-galactosides or milk sugar. It remains an open 

 question whether this " emulsin" is identical with that obtained from almonds. 



