G. MCGUIRE AND K. G. FALK 225 



nation by which the amylase is prevented from reacting with the 

 starch.^^ 



Since the existence of a sucrase was demonstrated in potato juice, 

 it was of interest to determine whether a carbohydrate upon which 

 this enzyme would act was present. As far as known, sucrase acts 

 only upon the carbohydrates, sucrose and raffinose. 



The sucrase solution^^ had been prepared from yeast, and the ex- 

 traneous matter removed by the method of Nelson and Born.^^ This 

 solution exerted no hydrolyzing action on soluble starch or maltose. 

 In order to test the action on potato juice without the interference 

 of the enzymes present in the juice, the latter was heated for 15 

 minutes in a boiHng water bath after the temperature of the juice 

 had reached 80°C. The final temperature was about 90°C. This 

 inactivated the enzymes. The juice was then filtered through paper. 

 It was assumed that the sucrose or raffinose, if present, would not be 

 destroyed and would remain in solution. That some change, pre- 

 sumably partial hydrolysis of some of the starchy materials present, 

 did take place, was shown by the increased reduction (20 to 50 per 

 cent) of the blanks. 



In carrying out the tests, the juices as prepared were brought to 

 "the requisite hydrogen ion concentrations and 2 cc. of a sucrase solu- 

 tion, made by diluting 1 cc. of the filtered stock solution to 500 cc, 

 were added. 0.5 and 1.0 per cent sucrose solutions similarly treated 

 were run simultaneously. Suitable blanks were also run in every 

 case. After incubation for 20 to 24 hours with toluene as a pre- 

 servative, the actions were determined by the reduction of Fehhng's 

 solution by 5 cc. of the solutions as described above. The results 

 are shown in Table V and are given in terms of mg. of CU2O obtained 

 .by the reduction by 5 cc. portions, corrected for all blanks. 



Each row represents a separate series of experiments. The differ- 

 ences in the sucrose results are due to deterioration of the sucrase 

 •solution which stood in a warm room for 3 months. The potato 

 juice results show satisfactory agreement in view of the differences in 



i^Wohl, A., and Glimm, E., Biochem. Z., 1910, xxvii, 349. 

 ^^ A solution of sucrase was supplied by Professor J. M. Nelson of Columbia 

 'University for the tests for the presence of sucrose or raflSnose. 



^^ Nelson, J. M., and Born, S., /. Am. Chem. Soc, 1914, xxxvi, 393. 



