1912.] 



Studies on Enzyme Action. 



377 



by L. catharticum is of interest. It ma)' well happen that linase per se will 

 be found to be without action on prunasin — such a conclusion would be 

 justified, if a case could be found in which the values given under linamarin 

 and prunasin for L. catharticum were reversed. 



The problem is similar to that presented by "emulsin," which in the 

 course of these studies has been proved to contain at least two distinct 

 enzymes, amygdalase and prunase, both of which are concerned in the 

 resolution of amygdalin. Prunase having been found without linase in many 

 plants, the problem now before us is, if possible, to find linase without prunase. 



These arguments will at least serve to indicate the importance of the 

 inquiry on which we are engaged and the value of the method which has 

 been devised of studying plant enzymes comparatively. 



To consider the other materials hydrolysed, the amount of " amygdalase " 

 in the leaf material is evidently small but in the seed, in the case of 

 L. grandiflorum, the amount indicated is surprisingly large, particularly 

 when the low values given under prunasin are considered. 



But evidently much depends on the period of growth, as shown by the 

 following values (percentage activities) given by L. grandiflorum rvhrwm 

 (leaf material) in June and September, 1911 : — 





Linamarin. 





Amygdalin. 



June 



86 



74 



1 -7 





79 



80 



4-7 



It is noteworthy (Table I) that whilst the prunasin values obtained with 

 leaf materials are all very high relatively to the " amygdalin " values, in the 

 seed there is not the same disproportion between them, the amygdalin values 

 increasing apparently at the expense of the prunasin values. As amygdalin 

 is not present in the seed, it does not seem probable that the high amygdalin 

 values are due to the presence of amygdalase ; a more probable explanation 

 perhaps is that vicianase or an allied enzyme is present, especially in the seed. 



The salicin values appear to bear no direct relationship to the linamarin 

 values and are always below the prunasin values though often very near to 

 these latter. It is a question whether linase has any action on salicin. 

 Prunase apparently has the power of hydrolysing salicin and as the prunasin 

 values are never lower than the salicin values but often in excess of them, it 

 is not improbable that salicin is less readily hydrolysed by prunase than is 

 prunasin and that some other enzyme other than prunase, capable of 

 hydrolysing prunasin but not salicin, may be present at times together with 



