Studies on Enzyme Action. 351 



yeast (a bottom yeast) is capable of resolving the biose section of the 

 molecule alone, a true glucoside and glucose being formed : — 



C 6 H 5 CH(CN)O-C 12 H 21 O 10 + H 2 O ■*- C 6 H5CH(CN)0-C fl Hn05 + C 6 H ia 6 . 



In his earlier paper, Fischer speaks of the action as due to " invertin," but 

 afterwards attributed the hydrolysis to the enzyme present in yeast which 

 hydrolyses maltose. 



Fischer's investigation was carried out at a time when little was known of 

 the specific character of the enzymes. In the light of later work — especially 

 that of E. F. Armstrong — it was improbable that maltase was the agent, 

 emulsin (although highly active towards amygdalin) being without action on 

 maltose and methyl-a-glucoside, which are both easily resolved by maltase. 

 Our experiments were instituted to clear up this discrepancy: 



To prepare amygdonitrileglucoside, Fischer digested a mixture of amygdalin 

 with yeast-extract at 35°. On repeating the experiment in accordance with 

 his directions, using a dried English brewer's yeast, we were surprised to find 

 that the action took place far less rapidly than Fischer's description had led 

 us to suppose it would ; on testing the efficiency of the yeast-extract with 

 maltose it was found to be almost inactive : judging from the relative 

 stability of amygdalin and maltose in presence of acids, it was to be expected 

 that the maltose would have been more rapidly hydrolysed than the 

 amygdalin. 



On considering all the circumstances, it appeared that we had worked at 

 a higher temperature (35°) than that at which maltase exerts its maximum 

 activity according to E. F. Armstrong's observations. The question arose 

 whether the inactivity of the extract were not a consequence of overheating : 

 comparative experiments were made, therefore, in which extracts prepared at 

 different temperatures were digested, each at several temperatures, with 

 solutions containing equivalent quantities of amygdalin, maltose and 

 methyl-a-glucoside. These led to the discovery that the action on amygdalin 

 and also on methyl-a-glucoside persisted after heating the solutions to such 

 a temperature that the action on maltose was at an end — consequently, 

 that maltase was not the active agent. Similar experiments at higher 

 temperatures afforded evidence that the enzyme which hydrolysed amygdalin 

 could be destroyed without depriving the solution of its power of hydrolysing 

 cane-sugar. 



The proof was thus obtained of the existence of a specific enzyme capable 

 of effecting the separation of glucose from amygdalin. Whether or no this 

 enzyme also hydrolyses methyl-a-glucoside or whether besides maltase two 

 different enzymes are present in the extract, one of which attacks amygdalin, 



2 d 2 



