318 Prof. Dunstan and Drs. Henry and Auld. [Feb. 27, 



unknown glucosidolytic enzyme by ascertaining whether it is active towards 

 the a-alkyl ethers of the hexoses or towards the stereo-isomeric /3-ethers. 

 E. F. Armstrong* has extended Fischer's work in this direction by showing 

 that when the a-alkyl ethers of the hexoses are decomposed hydrolytically 

 by enzymes of the maltase type the sugars immediately liberated are the 

 a-forms of the hexoses, and that, similarly, when the stereo-isomeric /3-ethers 

 are decomposed by enzymes, they furnish the /3-forms of the hexoses. 



In both cases the forms of the hexoses first liberated in the solution 

 change, gradually if left to themselves, or immediately if a trace of alkali be 

 added to the liquid, producing the equilibrium mixtures of the a- and /3-forms 

 of the hexoses, thus exhibiting the phenomenon of mutarotation which 

 Lowryj- first explained in this way. 



E. F. Armstrong! has extended these results to a number of the naturally 

 occurring sugars and also to several of the synthetic glucosides, and has 

 succeeded in showing that by the action of invertase on sucrose and rafflnose 

 the a-form of dextrose is produced and that emulsin decomposes /3-methyl 

 glucoside, liberating the /3-form of dextrose. 



Action of Yeast on Phaseolunatin. 



Since it had proved impossible to decompose phaseolunatin by emulsin, 

 which is an enzyme of the /3-class, it seemed advisable to ascertain if it could 

 be decomposed by yeast-maltase. The latter was prepared by mixing yeast, 

 previously dried at 30° C, with sand and grinding the mixture with a small 

 quantity of water in a mortar. The paste so obtained was set aside with 

 more water for 24 hours and maintained at a temperature of 35° C, 1 per 

 cent, of toluene being added as an antiseptic. 



The aqueous extract so obtained was filtered through a porous tube of 

 baked clay, and by this means a pale straw-coloured liquid was obtained free 

 from yeast cells. This liquid readily decomposed a-methyl glucoside and 

 phaseolunatin. The results of several of the experiments made are given in 

 the following table : — 



* 'Chem. Soc. Journ.,' 1903, vol. 83, p. 1305. 

 t < Chem. Soc. Journ., 5 1899, vol. 75, p. 213. 

 % Loc. cit. 



