ENZYMES. 61 



p = -^ =K (page B 32). It follows that the same equilibrium is attained irrespective 



JCz LS 



of whether we start with alcohol-f acid, or ester +H 2 0. The equilibrium is also 

 independent of the antecedents as well as the quantity of enzyme. 



On comparing the equilibrium constants (K) which are obtained with dif- 

 ferent quantities of ester or acid, it is shown that in the above equation VE 

 must be introduced instead of CE in order to obtain constant values for K. In 

 the saponification of the ester the reaction velocity is proportional to V(7#, 

 and not CE. According to DIETZ this is due to the fact that the system is a 

 heterogeneous one, and that only that part of the ester which is absorbed by 

 the solid phase (enzyme) takes part in the reaction. The velocity constant of 

 the ester formation is shown to be proportional to the quantity of enzyme. 



According to what was stated above (page 35), the equilibrium in a reversible 

 reaction must be independent of the nature of the catalyst. This was not the 

 case in DIETZ'S experiments. With picric acid as the catalyst a different equilib- 

 rium was obtained than with the pancreas enzyme. With the acid as catalyst 

 the equilibrium was moved toward the direction of the ester. While this action 

 is not understood it may perhaps be explained by the fact that the system in one 

 case was homogeneous and in the other case heterogeneous. 



Similar observations that the enzymotic end-condition can be different from 

 the stabile end-condition of the same system have previously been made by 

 TAMMANN, 1 but in these cases generally so-called false equilibrium existed, which 

 for example, by the addition of more enzyme changed, so that the cleavage pro- 

 ceeds further. These false equilibria are generally caused by the enzyme being 

 destroyed or put out of action in other ways. 



Among the enzymotic-ester syntheses we must also include) he or- 

 mation of carbohydrate phosphoric acid ester in fermenting sugar solu- 

 tions in the presence of soluble phosphates, as first observed by HARDEN 

 and YouNG. 2 These will be discussed in detail in Chapter III. 



It is seen that enzymotic syntheses are known. From this it fol- 

 lows that the questionable enzyme reactions are to be considered as 

 reversible. In certain cases another substance which cannot be split 

 by the enzyme is formed while in other cases the opposite direction of the 

 reaction can be detected by means of various constituents of the same 

 enzyme solution. 



Specificity of Enzyme Action. It has been known for a long time 

 that a great difference exists in regard to the action of enzymes in the 

 sense that different enzymes act only upon certain classes of bodies (pro- 

 teins, carbohydrates, fats). Then there also exist differences in the 

 manner in which different enzymes of the same group influence different 

 members of the same class (maltase, lactase, saccharase). Finally, it is 

 possible for one enzyme to attack one of two optical antipodes and the 

 other not at all, or only to a slight degree. That optical antipodes 

 are burned with unequal facility in the organism was shown by E. FISCHER, 

 and that of the numerous aldohexoses only three, d-glucose, d-mannose 



1 Zeitschr. f. physiol. Chem., 16, 271 (1892). 



2 Proc. Roy. Soc. B, 1908 p. 209. 



