1907.] 



Cyanogenesis in Plants. 



319 



Name of glucoside used. 



Amount of 



maltase 



preparation 



used. 



Time 

 of action. 



Amount of 



glucoside 



decomposed. 



A. a-Methyl glucoside, 0*2 gramme 

 Phaseolunatin, 0'3 gramme 



B. Phaseolunatin, 0"3 gramme 



„ 0*3 gramme 



a-Methyl glucoside, 0'2 gramme 



c.c. 

 20 

 20 



30 

 30 

 10 



hours. 

 25 

 25 



20 

 30 



20 



per cent. 

 59-0* 

 30 -5f 



22 *5t 

 30 -Of 

 26-0* 



* Determined by estimating the dextrose produced. 

 f M „ „ prussic acid produced. 



The action was found to proceed more readily, and could be more easily- 

 followed when, as suggested by Fischer,* dried yeast was substituted for the 

 extract. Thus, in one particular case, using yeast dried at 30° C, 85 per 

 cent, of the phaseolunatin was decomposed in 24 hours. 



These results indicate that phaseolunatin is an a-glucoside, since it is 

 decomposed by yeast -maltase. Attempts were therefore made to ascertain 

 by experiment whether a-dextrose is produced initially when the glucoside is 

 hydrolysed by an enzyme. 



Nature of the Dextrose Residue in Phaseolunatin. 



A preparation of the enzymes contained in the beans of Phaseolus lunatus 

 was made by extracting the beans with cold water, exposing the extract in 

 a vacuous desiccator over sticks of potassium hydroxide to remove the 

 hydrocyanic acid formed and then pouring the aqueous extract into excess of 

 alcohol. The precipitate so obtained was dried on a porous tile at the 

 atmospheric temperature. 



The characterisation of the sugar produced by the decomposition of 

 phaseolunatin was carried out as follows. To a solution of 3 grammes of the 

 glucoside in 20 c.c. of water, - 5 gramme of the enzyme preparation was 

 added and the mixture kept at 40° C. in a stoppered bottle. 



For each observation a few cubic centimetres of the liquid were withdrawn, 



mixed with a small definite quantity of alumina cream and immediately 



filtered through a closely felted pad of asbestos. The optical rotation of the 



clear filtrate was then determined before and after the addition of a drop of 



ammonia solution, the latter being used as indicated by Lowryf to establish 



equilibrium. The same polarimeter tube was used throughout the 



experiments. 



* ' Berichte,' 1894, vol. 27, p. 1479. 



t < Chem. Soc. Journ.,' 1899, vol. 75, p. 213. 



