380 



Prof. H. E. Armstrong and Dr. E. Ormerod. [June 14, 



(a) 



Time 90 hours 

 3 weeks 



3-2 

 2-8 



Time 



90 hours 

 3 weeks 



5-6 

 2-6 

 1-7 



According to Mcloux, glycerol retards the hydrolysis. Our experiments 

 indicate that up to 25 per cent, glycerol has little, if any, influence ; in 

 larger proportion, it certainly retards hydrolysis. All observers agree that 

 alcohol hinders the change : our experiments show that its influence is 

 approximately proportional to the amount which is present. 



The ethereal salts which are hydrolysed under the influence of lipase are 

 all compounds of the type 



Since E' and X' may be varied within wide limits, it cannot well be 

 supposed that the selective action of the enzyme is exercised with reference 

 either to E' or X' : consequently the controlling influence must be 

 attributed to the carboxyl radicle (CO.O) ; the enzyme must be so con- 

 stituted that it can " fit itself to this group." 



The problem to be solved is — why should ethereal salts derived from the- 

 lower terms of the acetic series be so much less readily hydrolysed than the 

 higher ? The differences in stability do not account for the differences in 

 behaviour of homologous salts ; in fact, ordinary hydrolytic agents appear to> 

 act more readily on the lower terms. Nor can the difference be attributed 

 to the destruction of the enzyme by the acid which is liberated from the 

 salt, as this destructive effect can be avoided by diluting the solutions to 

 the necessary extent. 



Our experiments have led us to form the provisional hypothesis that the 

 hydrolysis of the ethereal salt by lipase involves the direct association of the 

 enzyme with the carboxyl centre and that such association may be prevented 

 by the " hydration " of this centre : consequently, that those salts which are 

 the more attractive of water will be the less readily hydrolysed. The facts 

 generally seem to be in accordance with this view, inasmuch as the solu- 

 bility in water of ethereal salts diminishes as the series is ascended ; salts 

 such as ethylic formate and acetate undoubtedly tend to form hydrates 

 (hydrols) in solution, such as 



E'.CO.OX'. 



CH 3 .CO.OEt + OH 2 = CH3.C(OEt)< 



OH 

 OH 



The following comparative results are of interest from this point of view : — 



