K. G. FALK AND G. McGUIRE 605 



Conversion of Soluble into Insoluble Sucrase Preparation. 



The finding of soluble and insoluble sucrase preparations or mate- 

 rials showing sucrase actions led to further developments. The 

 optimum action for both was found to be at approximately the same pH 

 (nearly 4.0). This raises the question, which was developed at some 

 length in another connection/^ as to whether a definite enzyme action 

 was connected with a certain molecule or with a certain group which 

 may be present in different molecules. If the latter view is adopted 

 tentatively, the same active sucrase grouping would be present in 

 the one case in a soluble molecular species, and in the other case in an 

 insoluble molecular species. This point of view simplifies in some 

 ways the consideration of the experiments to be described in this 

 section. 



That sucrase-carrying substances of different solubilities are pres- 

 ent in banana pulp is shown by the fact that aqueous extraction yields 

 one such, normal sodium chloride solution extraction following the 

 aqueous extraction another, and the residue after repeated extraction 

 a third. To judge from the hydrogen ion concentration for optimum 

 action these sucrase actions are identical. 



The most active and satisfactory soluble preparation was obtained 

 by the salt extraction as described. The sodium chloride and the 

 soluble simple sugars, etc., were removed by dialyzing over night in 

 collodion bags against running tap water. The volume increased 

 as a rule about 60 to 80 per cent. If the dialyzed sucrase solution 

 was further dialyzed in a fresh collodion bag for 24 hours against 

 tap water, the volume did not increase but a gel separated. The 

 hydrogen ion concentration of the mixture did not change in the 

 course of dialysis on the 2nd day. The gel could be filtered out read- 

 ily by means of filter paper. The filtrate from the gel did not show 

 sucrase action but the gel showed very marked activity. The gel was 

 ground with alcohol twice and ether once and allowed to dry in the 

 air at room temperature. It did not dissolve in water, but formed a 

 gel with it. A suspension showed the following activity: 0.05 gm. of 

 material in 20 cc. of a 10 per cent sucrose solution in 4 hours at 35°C. 

 gave reducing substances producing 457 mg. of CU2O per 0.01 gm. of 



^^ Falk, K. G., The chemistry of enzyme actions, New York, 1921, 81. 



