366 



Prof. H. E. Armstrong and others. [Apr. 3, 



Vicianin in V. angustifolia* together with an enzyme (vicianase) by which it 

 is resolved into the arabino-glucose vicianose, benzaldehyde and hydrogen 

 cyanide. It may well be that the high values in the amygdalin column are 

 in some cases to be taken as indications of the presence of vicianase. 



It should be again pointed out, now that it is established that two enzymes 

 are concerned in the resolution of amygdalin, that failure in obtaining 

 hydrogen cyanide from amygdalin is proof only of the absence of amygdalase 

 (perhaps also of vicianase), not of that of an enzyme capable of liberating 

 hydrogen cyanide from a cyanophoric glucoside ; amygdalin, as before stated, is 

 not the proper test material to use in discovering enzymes of this latter class. 



The values recorded under Prunasin are high in a large proportion of cases, 

 showing that prunase (or a closely allied enzyme) is widely distributed. 



It is more difficult to interpret the results obtained with salicin in com- 

 parison with prunasin. Sigmundf has contended that the enzyme present in 

 Salix is not " emulsin " because it has no action on amygdalin ; such behaviour, 

 however, as pointed out above, is only proof of the absence of amygdalase. But 

 it will be noticed that whereas, in most cases, prunasin is more attacked than 

 Salicin, the reverse is true of Salix rubra and of an Epilobium angustifolium 

 of Swiss origin, the latter having proved to be five times as active towards 

 salicin as it was towards prunasin. It would seem probable, on the whole, 

 that prunase is less active towards salicin than towards prunasin ; also that a 

 distinct enzyme, salicase, exists, which is only capable of acting on salicin 

 perhaps and that the two enzymes occur together in some cases. 



The glucosides apparently may undergo hydrolysis in two ways, according 

 as they are attacked from the side of the glucose group or from that of the 

 radicle associated therewith. The importance of this conception has already 

 been demonstrated in the case of lactose (compare No. XII, 324). As prunase 

 is controlled by glucose, there is good reason to suppose that this enzyme 

 becomes attached to the glucose section of the molecule and that this is the 

 reason why it is able to determine the hydrolysis of so large a proportion 

 of the known /3-glucosides. The enzymes occurring together with many of 

 the glucosides may owe their specific character to the fact that they are 

 compatible not with the glucose group in the glucoside but with the radicle 

 which is associated with it. Salicase, from this point of view, is perhaps an 

 enzyme which acts on salicin through the agency of the saligeuin radicle. 

 On this account, it is interesting to note that Gaultheria procumbens has a 

 relatively slight action on salicin, though it contains a glucoside, gaultherin,. 

 which is closely related to salicin, thus : — 



* Bertrand, 'Compt. Bend.,' 1906, vol. 143, p. 832. 

 t ' Monatsch.,' 1909, vol. 30, p. 77. 



