1910.] 



Studies 0)1, Enzyme Action. 



351 



was liberated on tlie fiirtlier addition of the mixture of enzymes prepaied from the beans 

 of Phaseolus lunatus or fi'om flax or cassava." 



Finding that abnoud cmulsin decomposed amygdalin and saliciu but not phaseolunatin, 

 whilst the "enzyme" associated with this last giueoside affected all three, they were led 

 to think that perhaps two enzymes were present in Phaseolus beans, etc. ; the 

 e.xperiments they then made led them to the conclusion that this was the case and that 

 the one enzyme was of the emulsin type, the other of the maltase type. In fact, as 

 before stated, they were led to think that phaseolunatin is an a-glucoside. 



The evidence on which this conclusion was based was twofold : in the first place, iu 

 coni])arative exj)eriments with methyl-n-glucoside and phaseoluiiatin, they found that 

 both compounds were hydrolysed iu contact with yeast extract and still more leadily 

 ■when the solution was digested with dried yeast. This led them to apply the method 

 developed by E. F. Armstrong, involving the determination of the forms iu which 

 dextrose is liberated on hydrolysing the glucosides by noticing the rotatory power of the 

 solution and then adding sufficient alkali to determine the rapid formation of an 

 ecjuilibrated mixture of the two isomeric forms of glucose. 



Finding that alkali caused an increase iu the htvorotatory power, they came to the 

 conclusion that glucose was liberated in the a-form. 



The conclusion finally arrived at svas that the extract prepared from Phaseolus beans 

 contains an a-enzyme which if not identical with yeast maltase is of the same type ; and 

 that it also contains a /3-enzyme identical with or similar to emulsin. These conclusions 

 were arrived at, it should be mentioned, in face of the known fact established by Henry 

 and Auld that yeast contains an emulsin-like enzyme.* 



The results arrived at by Dunstan and his co-workers are so remarkable, it 

 is so difficult to reconcile their views in all respects with existing opinion, 

 they cross our field of investigation in so many ways, that we have felt 

 compelled to include the Phaseolus giueoside and its attendant enzyme in our 

 programme of work. The results we have arrived at are such as to lead us 

 to conclusions very different from those we have referred to. 



In our opinion, the giueoside extracted from Phaseolus lunatus seeds is not 

 an a-glucoside and we are convinced also that the hydrolyst associated with it 

 is not of the a-type ; the evidence appears to us to be such as to justify the 

 conclusion that both the giueoside and tiie correlated enzyme belong to the 

 (8-series. 



Stress may be laid on the fact that in all the experiments described (except 

 some of those with methyl «-glucoside) the concentration of the giueoside in 

 the solutions studied was initially one-fifth molecular. We are strongly of 

 the opinion that concordance will not be apparent between the results of 

 different workers, even when using the same hydrolytes and the same enzymes, 

 until agreement be arrived at to carry out experiments under " molecularly " 

 comparable conditions. The concordance which probably exists between 

 apparently conflicting results published by different authors is, we think, often 

 hidden by the differences in the conditions under which observations are made. 



* 'Eoy. Soc. Proc.,' 1905, B,|vol. 76, p. 568. 



