356 Prof. H. E. Armstrong and Mr. E. Horton. [Mar. 3, 



put into a separate 30-c.c. flask ; to each flask was then added 5 c.c. of an 

 M/2 solution of phaseohxnatin and 2*5 c.c. of water, thus giving six M/5 

 solutions of phaseolunatin containing respectively 4 c.c, 12 c.c, 20 c.c, 4 c.c, 

 12 c.c, and 20 c.c. of the original solution of phaseolunatase per 100 c.c. 

 These solutions were maintained at 25° during 24 hours and the amount 

 of hydrolysis effected was then determined by estimating the amount of 

 hydrogen cyanide liberated. The percentages of phaseolunatin decomposed 

 were as follows : — 



Volume (c.c.) of original enzyme 

 solution present per 100 c.c. 



Percentage of glucoside 

 hydrolysed. 



4 



9-0 



12 



28 -25 



20 



46-5 



4 



6 0 



12 



29 -0 



20 



40-7 



As an M/5 solution of phaseolunatin.containing 20 c.c of the same phaseo- 

 lunatase solution per 100 c.c. was hydrolysed to the extent of 45'25 per cent. 

 {i.e. 2'26 per cent, per 1 c.c. per 100 c.c.) in 24 hours at 25°, it is 

 evident that the enzyme was practically unaffected by contact with M/5 or 

 M/10 methyl-a-glucoside solution during 14 days either at 25° or at 37°. 



Action of Phaseolunatase on Maltose. — In a preliminary experiment the 

 reducing power of an M/5 solution of maltose, containing 10 c.c. of the 

 solution of the phaseolunatase per 100 c.c, was determined initially and after 

 24 hours at 25° 



2 c.c. of the liquid reduced initially 0'1568 gramme of copper. 

 . 2 c.c. „ finally 01509 



Since any hydrolysis of the maltose would increase the reducing power of 

 the solution, it must be concluded that none had taken place. 



An attempt was made to carry out a series of experiments siniflar to that 

 with methyl-a-glucoside. It was impossible, however, to filter off the reduced 

 cuprous oxide in any reasonable time, owing to the clogging of the filter 

 by the precipitated proteid ; so the experiments had to be abandoned. 



It appears to us that tlu; nii.stake Dunstan, Henry and Auld made was to 

 assume tliat they were dealing with yeast nialtase and to overlook the possible 

 ])re8ence in their yeast of an enzyme capable of hydrolysing y8-glucosides. 



Action of Yeast Extract on the Phaseolns Glucoside. — Tlie proof that the 

 I'haseolus enzyme is without action on iu(!thyl-a-glucosi(Ie and on maltose is 

 K\ifficient to show that it is luiither a-glucase nor inaltase ; it is nevertheless 



