1910.] 



Studies on Enzyme Action. 



359 



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- 

 addition of a drop of ammonia solution, the latter being used, as indicated by Lowry, to 

 establish e<iuilibriinn. The same polarinieter ttibe was used throughout the experiments.'' 



Time of 

 action. 



Initial rotation. 



Rotation after 

 addition of 

 aunnonia. 



Change in 

 rotation. 



Hours. 



C / 



0 / 



o / 



0 



-1 15 



-1 1.5 



0 0 



1 



-0 -16 



-1 11 



-0 25 



2 



-0 35 



-0 58 



-0 23 



3 



-0 34 



-0 57 



-0 23 



20 



-0 56 



-0 56 



0 0 



"With reference to these figures, it may be noted that a solution of 

 3 grammes of phaseolunatin in 20 c.c. of water will have an optical rotatory 

 power of — 4°'ll (approximately): in order to reduce this to the observed 

 — l°"2o, the solution must have been treated with almost three times its 

 volume of alumina cream, supposing the observations were made in 

 a 1-decimetre tube ; such an amount can scarcely be described as " small." 



Secondly, if we are to assume that the same proportion of alumina cream 

 was always used — and otherwise we do not understand the meaning of the 

 word " definite " — the changes in rotation given in the fourth column above 

 are far larger than can possibly have been produced by tlie muta-rotation of 

 glucose. The decomposition of the phaseolunatin contained in a 50-per-cent. 

 solution (the optical rotation of which in a 2-decimetre tube is identical with 

 the specific rotatory power of the glucoside) into hydrogen cyanide, acetone 

 and a-glucose would involve a change in the rotatory power of 104°, 27°'4: 

 being consequent on the destruction of the glucoside and 76°-6 on the libera- 

 tion of «-glucose. Assuming that the glucose set free does not change 

 spontaneously, any decrease in the Ifevo-rotatory power of a solution of 

 phaseolunatin which is undergoing hydrolysis will be one-fourth due 

 (27"4/104 exactly) to the disappearance of glucoside and three-fourths to 

 the liberation of a-glucose. The initial rotation is given as —1° 15' and 

 that after one hour as —0° 46', thus showing a fall in Irevo-rotation of 29'. 

 Of the latter, as indicated above, only three-fourths or approximately 21' can 

 be due to the production of a-glucose. The muta-rotation of glucose causes 

 a change in the specific rotatory power from 105° to 52""7, that is to say 

 roughly a decrease of 50 per cent. ; hence the fall of 21', due to the libera- 

 tion of a-glucose, will be reduced to lO' S on adding alkali, that is to say to 

 a change of 10' 5 (roughly), whereas that observed was 25'. The same argu- 

 ment can be applied to the other values gi\'en. 



