1910.] 



Studies on Enzyme Action. 



357 



conceivable that yeast lias an action on the glucoside in virtue of the presence 

 of amygdalasc, the enzyme characterised by Caldwell and Courtauld, although 

 this is in no way prol)able in view of the fact that the Phaseolus enzyme has 

 but little action on amygdaliii. The existence of this enzyme was not yet 

 recognised at the time when Dunstan, Henry and Auld were led to conclude 

 that the Phaseolus glucoside is an a-derivative.* 



Although the experiments we have made with heated and unheated extracts- 

 from various yeasts have given very irregular results, it appears to us that they 

 afford conclusive evidence that phaseolunatase is not amygdalase. As often as 

 not, little or no action was noticeable, whilst in some cases 5 or 6 per cent, 

 at most of the Phaseolus glucoside was hydrolysed within 24 hours at 25° : 

 any action observed in such cases we are inclined, therefore, to attribute to 

 the presence of a minute proportion of "emulsin." . 



In preparing Fischer's glucoside from amygdalin by means of yeast, some 

 hydrogen cyanide is always liberated, the yield of the glucoside being by no 

 means satisfactory. 



On one occasion an exceptionally strong extract prepared by digesting 

 20 grammes of a particular fresh yeast with 100 c.c. of water was found to 



* Auld has made the assumption that amygdalase is an a-enzyme and has described 

 experiments which he assumes afford proof that the glucose liberated when amygdalin is 

 resolved into Fischer's glucoside and glucose is the a-form and that liberated from 

 Fischers glucoside the /3-form. In our opinion, his argument is rendered invalid by 

 the fact that both amygdalin and Fischer's glucoside are " racemised " somewhat rapidly 

 by alkali ; E. F. Armstrong's method, therefore, cannot well be applied to these materials. 



The following observations are quoted as showing the extent to which change takes 

 place. A solution of mandelonitrile-glucoside contained in a 2-decimetre jacketed 

 polarimeter tube kept at 25° having been mixed with a drop of 3N ammonia, observations 

 of the optical rotation were taken at minute intervals. 



Before the addition of alkali the rotation was — 1-77 



1 min. after the addition of alkali the rotation was — 1"85 



2 mins. „ „ „ „ -1-93 



2 » !> j> )) )> ~ 2'03 



^ )» 11 11 11 2*12 



^ 11 11 11 11 11 — 2'21 



6 11 V 11 II 11 ~ 2'27 



' 11 II 11 11 i> — 2'35 



^ 11 11 11 11 11 ~ 2 42 



9 11 11 11 i» 1) ~ 2'47 



l*-* 11 11 11 11 11 ~ 2'53 



30 — 3'23 



Three comparative experiments were also made by taking equivalent solutions of 

 amygdalin, mandelonitrile-glucoside and ordinary (a) glucose ; after observing the 

 optical rotatory power, each was mixed with the same proportion of alkali (one drop of 

 3N ammonia) and the change of rotation determined when all three solutions were kept 



2 F 2 



