524 



Dr. E. F. Armstrong. 



[Apr. 5, 



Time in 10 grammes maltose + 10 grammes 



hours. per 100 c.c. /3-methjl glucoside. 



2 10*2 7*7 



4 14-4 10-7 



6 21-0 17-0] 



One of the most remarkable conclusions to be derived from Fischer's 

 researches is that glucose and galactose are the only hexoses which 

 afford glucosidic derivatives attackable by sucroclastic enzymes : any 

 alteration in configuration other than that involved in the passage 

 from the one of these hexoses into the other or any shortening or 

 lengthening of the chain is sufficient to confer on the derivative 

 complete immunity from attack. Thus the methyl mannosides, the 

 methyl arabinosides and xylosides and the methyl glucoheptosides 

 cannot be hydrolysed by enzymes. Inasmuch as hydrolysis affects 

 only the OR radicle, this inhibition of hydrolysis by the very slightest 

 change in configuration must mean that the enzyme not only becomes 

 attached but that the attachment takes place along the entire chain of 

 the hexosides : in other words, enzyme and hydrolyte must be in 

 complete correlation. Probably this union is effected through the 

 agency of the hydroxyl groups and it may be of basic groups in the 

 enzyme — perhaps their union takes place not immediately but through 

 the intervention of water molecules. 



The only case in which there is evidence of partial or incomplete 

 attachment is that afforded by the inhibiting influence of a-methyl 

 glucoside on the hydrolysis of milk sugar by emulsin : in this case 

 it would seem that there is no interruption along the chain, the 

 correlation of hydrolyte and enzyme being incomplete only at the 

 terminal point. This argument is applicable not only to hydrolyte but 

 also to enzyme. Inasmuch as glucose inhibits the action of emulsin 

 and of maltase, it is to be supposed that the general configuration of 

 these enzymes is comparable with that of glucose : the departure must 

 be of such a character that the terminal element of the enzyme is 

 deflected in the one case in the direction which brings it into harmony 

 with the a- OR radicle whilst in the other it coincides in its space 

 orientation with the /3-OR radicle. It may be anticipated that /3-niethyl 

 glucoside will be found to inhibit the action of maltase on maltose. 



[Note added May 30, 1904. — This has since been found to be the case, 

 and as before mentioned whilst a-methyl galactoside hinders the action 

 of lactase, a-methyl glucoside is without influence on this enzyme.] 



Extent to ivhich Configuration may be modified. — Galactose differs from 

 glucose merely in having the radicles attached to the fourth carbon 

 atom in the reversed order : as galactose is fermented less readily than 

 glucose and galactosides are less easily hydrolysed by enzymes than 

 are the corresponding glucosides, the change in configuration, although 

 sufficient to hinder action, does not prevent it. 



