64 PLANT PHYSIOLOGY 



evident when purified preparations are used. For instance, 

 1 gm. of invertase can hydrolyze a whole ton of sucrose, a quan- 

 tity one miUion times its own weight. It must not be concluded, 

 however, that the quantity of enzyme is of no importance. On 

 the contrary, if the velocity of hydrolysis is taken into account, 

 the latter is found to be in direct proportion to the amount of 

 enzyme, provided that there is a sufficient amount of substrate. 

 Therefore, if rapid disintegration of a substance is desired, 

 large quantities of the enzyme must be applied. 



The question of the reversibility of enzymatic action is of 

 great importance and interest. According to the general laws 

 of physical chemistry, catalysts, accelerating the course of a 

 reaction, do not, as a rule, change the points of equilibrium 

 between the initial and the end products. But the reactions of 

 hydrolysis are, generally speaking, reversible, i.e., in the case 

 of a large number of products. 



Hydrolysis and the introduction of the elements of water 

 into the reaction products may be reversed in condensation and 

 the removal of water. Theoretically, at least, it should be 

 expected that the same enzymes will accelerate both the decompo- 

 sition and the synthesis of a complex reserve substance in the 

 organism. In the majority of enzymatic reactions, however, 

 this does not hold true. In a case in which it was possible to 

 obtain synthesis by the aid of an enzyme, the product was found 

 to be an isomer of the initial substance. From a concentrated 

 solution of glucose with the aid of maltase, Croft Hill (1898). 

 for instance, obtained not maltose, but isomaltose. Recently, 

 however, Bourquelot was successful in synthesizing with the aid- 

 of enzymes a large number of glucosides from the products of 

 their decomposition, and in such a way that the possibility of 

 enzymatic synthesis was irrefutably demonstrated. It can be 

 assumed with a great degree of probability, therefore, that 

 synthesis of polysaccharides, fats, and proteins, which are so 

 common in plant cells, proceed under the influence of the 

 same enzymes that cause their decomposition. The conditions 

 under which such enzymatic syntheses take place are not as 

 yet fully known. It seems to be certain, however, that the 

 continuous removal of water from the reaction is necessary. 

 Syntheses of this kind most probably take place in maturing 

 seeds, where the reserve substances are found. The hydrolytic 



