ix] GLUCOSIDE-SPLITTING ENZYMES 145 



CYANOPHOKIC GLUCOSIDES. 



The characteristic of these substances is that they yield prussic acid 

 as one of the products of hydrolysis. They are fairly widely distributed : 

 the following list (Greshoff, 15) includes most of the natural orders in 

 which such glucosides occur: Araceae, Asclepiadaceae, Berberidaceae, 

 Bignoniaceae, Caprifoliaceae, Celastraceae, Compositae, Convolvulaceae, 

 Cruciferae, Euphorbiaceae, Graminaceae, Leguminosae, Linaceae, 

 Myrtaceae, Oleaceae, Passifloraceae, Ranunculaceae, Rhamnaceae, 

 Rosaceae, Rubiaceae, Rutaceae, Saxifragaceae, Tiliaceae and Urticaceae. 



Amygdalin. This is one of the most important of the cyanophoric 

 glucosides. It occurs in the seeds of the bitter Almond (Prunus 

 Amygdalas) but it appears to be almost entirely absent from the sweet 

 or cultivated Almond. It also occurs in the seeds of the other species of 

 Prunus the Plum (P. domestica), the Peach (P. Persica), etc. of the 

 Apple (Pyrus Mains) and the Mountain Ash (P. Aucuparia). It occurs 

 sometimes in leaves, flowers and bark. 



By the action of an enzyme, originally termed emulsin, which occurs 

 in both the bitter and the sweet varieties of Almond, the glucoside is 

 broken up as follows in two stages: 



C2oH 27 NO n + H 2 = C 6 H 12 6 + C U H 17 NO 6 



mandelonitrile glucoside (prunasin) 



C 14 H 17 N0 6 + H 2 = C 6 H 12 6 + HCN + C 6 H 5 CHO 



benzaldehyde 



It should be noted that the sweet Almond contains emulsin although 

 it is almost entirely free from amygdalin. 



Recently (Armstrong, Armstrong and Horton, 8) emulsin has been 

 shown to consist of two enzymes, amygdalase and prunase : amygdalase 

 hydrolyzes amygdalin with formation of mandelonitrile glucoside and 

 glucose, whereas prunase hydrolyzes mandelonitrile glucoside (prunasin) 

 with formation of benzaldehyde, prussic acid and glucose. On the basis 

 of these reactions amygdalin is represented as: 



C 6 H 5 



CH 2 OH CHOH CH CHOH CHOH CH O ' CH 2 CHOH CH CHOH CHOH CH O CH 



CN 



Prunasin occurs naturally in the Bird Cherry (Cerasus Padiis), and 

 it is found that prunase may exist in a plant, e.g. Cherry Laurel 

 (P. Laurocerasus), which does not contain amygdalase. 



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