SYNTHETIC ACTION OF HYDROLYZING ENZYMES 223 



Similarly the Lactase in kephir yeast was found to synthesize, not 

 Lactose which it hydrolyzes, but Isolactose, which it does not hydrolyze. 



Since the publication of Croft Hill's fundamental observation a 

 great number of enzymatic syntheses have been accomplished. Among 

 carbohydrates, substances resembling Starch and Glycogen have been 

 synthesized through the action of Diastases, while Triacetyl Glucose 

 has been formed from acetic acid and glucose under the influence of 

 pancreas-extract. Among the fats Ethyl Butyrate has been synthesized 

 from ethyl alcohol and butyric acid, glyceryl butyrate, amyl butyrate, 

 methyl oleate, glyceryl triacetate and glyceryl trioleate have all been 

 synthesized from their components through the reversed action of 

 various Lipases. In the case of methyl oleate it has been shown that 

 the pancreas-lipase employed to bring about its synthesis definitely 

 does not affect the final equilibrium which is attained, for the proportion 

 of ester formed after a sufficient lapse of time is independent of the 

 quantity of enzyme employed, only the Speed with which the equilib- 

 rium is attained being affected. The following are illustrative data: 



SYNTHESIS OF METHYL OLEATE (POTTEVIN). 



Quantitative data of this description are very important because 

 the whole question whether the enzymes act as true catalyzers or, on 

 the contrary, enter into and affect the equilibria of the reactions which 

 they accelerate, turns upon the question whether the final proportion 

 of substrate to products is at all influenced by the presence of the 

 enzyme. The results of Pottevin indicate that there is no such influ- 

 ence in the case of pancreas-lipase synthesizing methyl oleate, because 

 if there were, then doubling the amount of enzyme should double the 

 displacement of equilibrium and since no measurable effect upon the 

 equilibrium results from doubling or even multiplying by ten the 

 quantity of enzyme employed, it follows that the single unit of enzyme 

 also did not affect the station of equilibrium. Similarly A. E. Taylor 

 has shown that the station of equilibrium in the hydrolysis of glyceryl 

 triacetate by lipase is exactly the same as that which is obtained when 

 sulphuric is used as the catalyzer. Such measurements are, however, 

 usually lacking in enzyme studies, frequently because of the technical 

 difficulty of measurements extending over the long periods required to 

 attain final equilibrium. 



In the case of Glyceryl Trioleate, which differs from the glyceride 

 studied by Taylor in being insoluble in water, H. C. Bradley has 

 attained results which point rather clearly toward a decided displace- 

 ment of equilibrium by the enzyme, for he finds it impossible to procure 



