608 VEGETABLE ENZYMES. XIX 



The change of soluble into insoluble sucrase upon the simple treat- 

 ments described illustrates the sensitive character of materials occur- 

 ring in living matter. In this case, the enzyme property is not 

 'destroyed but a different property (solubility), which can be traced 

 by following the enzyme action, is changed. 



Sucrase has been generally taken to be one of the most hardy of 

 the enzymes. It is not inactivated as rapidly as most other enzymes 

 or under conditions which cause these to lose their activity com- 

 pletely. On the other hand, amylase has been found to be highly 

 sensitive to outside influences and to be destroyed under compara- 

 tively simple conditions. 1^ It is possible that the simple treatments, 

 which changed the properties of the material carrying the sucrase 

 action without destroying that action, may destroy the amylase 

 action which would be expected to be present in the ripening banana. 

 Such an explanation would account for the failure to obtain a definite 

 and marked amylase action in banana pulp preparations or extracts. 



The question of the conversion of starch into simpler carbohydrates 

 may be considered further. For such an action in living, growing 

 matter, the presence of the enzyme amylase, on the basis of past 

 experience, is required. Experimental tests have not shown con- 

 clusively that this enzyme is present in the banana. Reasoning on 

 the basis of the active amylase preparations described by Sherman^^ 

 a minute quantity of such material would suffice to produce the 

 changes observed in the banana, but, on the other hand, it should be 

 possible to obtain experimental evidence of the presence of such an 

 enzyme. It is also possible that substances are present in the banana 

 which when brought into close contact, as by grinding, with the 

 enzyme material, inhibit the action. It is possible to imagine a 

 cellular structure of such nature that enzyme material and inactivat- 

 ing substance (possibly tannin) are separated in the fruit in the form 

 and shape in which it occurs in nature and that artificial treatment 

 involving destruction of the cell structure is accompanied or followed 

 by profound changes in the cellular contents. 



There is, however, another possible view-point. In ripening 

 "The most conspicuous change is the long-recognized conversion of 



^^ Sherman, H. C, and Schlesinger, M., /. Am. Chem. Soc, 1915, xxxvii, 1305. 



