ENZYME STUDIES OF LOWER FUNGI 43 



nishes the food material for the mold. If these various manifes- 

 tations of enzymotic activity are to be regarded as due to individual 

 specific enzymes, it must be assumed that each enzyme performs 

 some specific function in the nutrition of the fungus. But it is 

 difficult to understand why a long category of enzymes should be 

 produced in the absence of their specific substrata. The argu- 

 ment that these enzymes were developed during past generations 

 when their presence may have been requisite and that they now 

 represent inherited characters that were acquired under special 

 conditions in the previous history of the species is scarcely valid, 

 in view of the extreme improbability of certain of these substrata 

 ever having served as nutrient material. At any rate it is incon- 

 ceivable that a substance like hippuric acid could have been pre- 

 sented as food material through a sufficient number of generations 

 for the mold to adapt itself permanently by the secretion of an 

 enzyme for that purpose, since experiments in which attempts 

 have been made to develop enzymes that are known to be wanting 

 have so far resulted in failure. 2 Again it may be argued that the 

 function of these enzymes is to assist in building up or synthe- 

 sizing the various complex cell components, since enzyme action 

 is known to be reversible. This is undoubtedly true to some 

 extent, but the presence of an enzyme like raffinase is still unac- 

 counted for. 



From the data obtained by the study of fungus enzymes there 

 is much to argue against our present conceptions of the specificity 

 of enzymes. Very few, if any, really " specific" enzymes are 

 known, and the assumption that the hydrolysis of different sub- 

 strata by one and the same preparation is due to the presence of 

 several enzymes has little experimental evidence in its support. 

 The "side chain theory" by which the various manifestations 

 are explained as due to specific groups or atom complexes con- 

 tained in some gigantic enzyme molecule is just as difficult of 

 application to the case in hand. It seems more than likely that 

 some time in the future we shall have to readjust our conception 

 of the specificity of enzymes. 



2 The enzyme "tannase," recently studied by Knudsen. is apparently an ex- 

 ception, since its presence is determined by the presence of tannin in the 

 culture medium. 



