604 VEGETABLE ENZYMES. XIX 



Insoluble Sucrase Preparation from Ripe Bananas. 



It was found that the water (or salt solution) insoluble residue 

 from the ripe banana pulp possessed considerable sucrose-hydrolyz- 

 ing action. ^2 



2,760 gm. of pulp were ground with 700 cc. of N sodium chloride 

 solution, 16 liters of water added, thoroughly stirred, allowed to 

 stand over night at room temperature, and filtered through paper. 

 The moist residue was treated with 10 liters of water similarly, and 

 the residue (drained more thoroughly than the first residue) treated 

 again with 6 liters of water and then with 8 liters. The filtrate from 

 the last gave no sucrase action. The residue was dried by grinding 

 twice with alcohol and then with ether. 0.75 gm. of this residue 

 tested in 20 cc. of a 10 per cent sucrose solution gave reducing sub- 

 stances in 4 hours at 35°C. producing 355 mg. of CU2O per 0.10 gm. 

 of residue. 



The possibility that the cell walls of the banana pulp were not 

 broken and that the sucrase was retained within the cells was tested 

 a number of times by using different methods of grinding and extract- 

 ing. Vigorous grinding in a mortar with sand as well as long con- 

 tinued grinding in a ball mill, also followed in some cases by grinding 

 in a mortar, gave, after thorough extraction, active insoluble residues. 

 In place of filtering through paper, the residue was also obtained by 

 centrifuging or by filtering through asbestos, and showed similar 

 actions. It was obtained as a grayish brown powder by grinding 

 twice with 95 per cent alcohol, separating by centrifuging, and finally 

 washing with ether and drying on filter paper at room temperature. 

 This residue gave a nitrogen content of nearly 1 per cent. 



A series of determinations with the centrifuged moist residue at 

 different hydrogen ion concentrations gave an optimum action 

 between pH 4.0 and 4.5 with a rapid falling off beyond 6.0. In view 

 of the character of the material, a more careful determination was not 

 made. The results showed an optimum similar to that of the soluble 

 sucrase preparation which was the main question involved. 



^2 Euler and Svanberg (Euler, H., and Svanberg, O., Z. physiol. Chem., cvii, 

 269) recently studied the sucrase actions of the residue from autolyzed and 

 extracted yeast. 



