1912.] 



Studies on Enzyme Action. 



3G1 



The introduction of prunasin, in place of amygdalin, as a test for prunase 

 therefore constitutes an important advance in technique.* If amygdalin be 

 used as a test material, assuming that it is hydrolysed only by the two 

 enzymes amygdalase and prunase, the determination of the amount of 

 hydrogen cyanide that is liberated serves as a means of estimating the 

 combined activity of these two enzmyes ; to ascertain if the former be present 

 without the latter, it is necessary to ascertain whether glucose be set free. 



But there is another possibility to be considered, since it has been shown 

 by Giajaf that amygdalin may be resolved into a diglucose, hydrogen cyanide 

 and benzaldehyde by means of the gastric juice of the snail. It is to be 

 supposed that this enzyme occurs in plants, as Bertrand succeeded in 

 converting vicianin into hydrogen cyanide, benzaldehyde and the arabino- 

 glucose, vicianose, by means of an enzyme present in the seeds of View, 

 anrjustifolia. 



In view of the results now brought forward, it may be desirable to point 

 out again* that the results obtained on using emulsin as a synthetic agent 

 cannot be regarded as due to a single enzyme. AVe are engaged in making 

 synthetic experiments with the simpler materials now at our disposal. 



The high values given under prunasin in Table I (p. 364) — which are 

 discussed in the next communication — are indicative inferentially of the 

 presence of prunase, on the assumption that (in the absence of linase) 

 prunase alone is able to hydrolyse prunasin. Until it has been shown that 

 such is the case, they must be subject to this reservation. 



Our desire is, we may say, to confine the term Prunase eventually to the 

 specific enzyme which is the true correlate of Prunasin. It may be well to 

 add that we apply the term /3-glucase to enzymes generally that are able 

 to resolve /3-glucosides and are controlled by glucose — in other words, 

 to enzymes which are adapted to the glucose section of the /3-glucosides. 



As the conclusions which we have formulated in earlier numbers of these 

 studies are to some extent called in question by Bayliss in jSTote E, in the 

 second edition of his monograph 'On the Nature of Enzyme Action,' we 

 may refer briefly to his criticisms. The results now brought forward should 

 remove some of his difficulties. Bayliss is inclined to question the doctrine 

 that enzymes are strictly specific agents. In our opinion — and we have 

 lived with them during so many years that we claim to have some feeling on 

 the subject — the evidence is overwhelming that they are, especially as there 



* Compare ' Proc. Physiol. Soc.,' 1910, xxxiii ; ' J. Physiol.,' vol. 40. 

 t ' Compt. Rend.,' 1910, vol. 150, p. 793. 

 \ Compare No. XII, p. 323. 



