188 



Dr. E. F. Armstrong. 



[Aug. 26, 



[D 1850, 7050, 8010.] 



" Studies on Enzyme Action. V. Hydrolysis of Isomeric Gluco- 

 sides and Galactosides by Acids and Enzymes." By EDWARD 

 FRANKLAND ARMSTRONG, Ph.D., Salters' Company's Eesearch 

 Fellow, Chemical Department, City and Guilds of London 

 Institute, Central Technical College. Communicated by 

 Professor H. E. ARMSTRONG, F.E.S. Pteceived August 26, 

 1904. 



In view of the use constantly made, in contrasting the action of 

 sucroclastic enzymes, of the stereoisomeric a- and /3-methyl glucosides 

 and the corresponding galactosides as test materials, it was desirable 

 to gain some idea of the relative stability of these four compounds in 

 presence of acids and wherever possible towards enzymes, a know- 

 ledge of their behaviour being of importance, both as throwing light 

 on their intrinsic properties and for the purpose of correlating the 

 activities of the various compounds amenable to hydrolysis. 



As already pointed out,* in studying the hydrolysis of sugars under 

 the influence of enzymes, it is difficult to institute just comparisons, as 

 not only, as a rule, is a different enzyme required for each sugar, but 

 we have no means at present of determining the amount of enzyme 

 used ; and sooner or later, it will be necessary to accumulate data 

 correlating one or more analytical factors (nitrogen percentage, etc.) 

 with hydrolytic activity. The difficulty spoken of is enhanced by the 

 fact that, usually, several enzymes occur together so that no ordinary 

 analytical process can suffice for the determination of the amount of a 

 particular enzyme present in a solution. 



On the other hand, it will be of importance to determine whether 

 any one enzyme is capable of hydrolysing several different compounds 

 or whether each particular hydrolysis is ascribable to some one 

 particular enzyme. There is only one case at present known which 

 can be discussed with any degree of certainty. It has been urged by 

 some French workers, especially by Bourquelot and Herissey,t that the 

 action of emulsin on milk sugar, is due to the presence of small quantities 

 of lactase, together with the emulsin proper. The following facts, 

 brought forward in Nos. 2 and 3 of this series of papers, may, however, 

 be urged against this view. 



(1) The curve expressing the rate at which milk sugar changes 

 is not of the form to be expected if only a very small quantity of 

 enzyme (lactase) were present : in that case a linear expression should 

 apply during the early stages ; actually the curve is only of this form 

 when small quantities of emulsin are used. 



' Boy. Soc. Proc.,' 1904, vol. 73, p. 515. 

 t ' Compt. Bend.,' 1903, vol. 137, pp. 56, 59. 



