AMYGDALIN, DHURRIN, ETC. 179 



This enzyme emulsin was originally supposed to be a 

 single substance but it has since been found to be composed 

 of two distinct enzymes known as amygdalase and prunase 

 respectively. The former is only able to hydrolyse the 

 amygdalin molecule into mandelonitrile glucoside (see p. 1 80) 

 and glucose according to the equation : 



C 20 H^NO n + H 2 = C 6 H 12 6 + C 14 H I7 N0 6 



Mandelonitrile 

 glucoside 



while the prunase effects the further hydrolysis of the man- 

 delonitrile glucoside : 



C 14 H 17 NO 6 + H 2 O = C 6 H 12 O 6 + HCN + C 6 H 5 CHO 



in the same way as it hydrolyses the natural glucoside prunasin 

 of Prunus padus (for formula see p. 169), in which plant it 

 occurs alone without amygdalase. 



The two stages of the hydrolyses may be demonstrated either 

 by carefully controlling the reaction of emulsin on amygdalin 

 and stopping the reaction at the right moment, before the 

 prunase is able to decompose the mandelonitrile glucoside, 

 or else by hydrolysis by means of acids.* 



An extract of yeast also only hydrolyses amygdalin as far 

 as mandelonitrile glucoside; this was thought to be due to 

 the action of maltase, but it has since been shown that this 

 extract also contains amygdalase as distinct from maltase. 



According to Giajaf amygdalin is broken up under the 

 action of the gastric juice of a snail (Helix pomatia) into 

 benzaldehyde, hydrocyanic acid and a disaccharide of unknown 

 constitution. 



Although the constitution of amygdalin cannot be said to 

 be established completely, it may be provisionally regarded as 

 an a/3-glucoside of benzaldehyde cyanhydrin of the formula : 



i i 



CH 2 OH CHOH CH(CHOH) 2 .CH.O.CH 2 CHOH CH.(CHOH) 2 CH.O.CH 



O - CN 



If crystals of amygdalin be dissolved in water and then 

 subjected to the action of maltase the hydrolysis will not 

 proceed further than is represented in the first of the two 



* Caldwell and Courtauld : " J. Chem. Soc.," 1907, 91, 666. 

 t Giaja : " Compt. rend.," 1910, 150, 793. 

 12* 



