ACTION OF THE ENZYMES. 105 



also being dextrose. Maltose is formed as an intermediate 

 product, so that what was denned as the characteristic ac- 

 tivity of maltase appears here also. It is evident from this 

 that care must be exercised in deciding whether a ferment 

 present in animal or vegetable tissues and capable of pro- 

 ducing a sugar from starch is amylase or maltase, or whether 

 both are present. The recognition of the first is dependent 

 upon the identification of maltose as the end-product of the 

 reaction, that of the latter upon the recognition of dextrose. 

 The existence of maltase in the presence of amylase can be 

 proved by isolating a ferment which splits pure maltose into 

 dextrose. The recognition of amylase in the presence of 

 maltase is more difficult, and differences in resistance to 

 heat, chemical reagents, etc., must be utilized to bring about 

 their separation. 



Maltase seems to have been first discovered by BECHAMP 

 in the urine, and somewhat later by BROWN and HERON in the 

 pancreatic juice and in the small intestine. It is found also in 

 'the saliva. The commonest source of maltase to-day for the 

 study of its activities is corn, from which it can be obtained 

 in a very active state, by precipitation of a dilute acid- 

 alcohol extract of this cereal with strong alcohol. 1 The 

 ferment when obtained in this way is not pure. 



Qualitatively the maltase obtained from different sources 

 shows the same action upon maltose. Considerable differ- 

 ences exist, however, in the resistance of this enzyme to 

 external conditions when obtained from different animal 

 tissues or cereals. This has been taken to argue in favor 

 of the existence of different maltases. Since maltase has 

 not yet been obtained in a pure state, however, we can- 

 not be sure whether the differences found in the various 

 maltase preparations are due to specific differences in the 

 ferments themselves or to differences in the impurities with 

 which the preparations are contaminated. 



BEIJERINCK: Centralbl f. Bakteriologie, 1898, xxiii, 2te Abth. 



