588 Prof. H. E. Armstrong and Mr. H. W. Gosney. [June 13, 



been formed that the acid served merely to liberate the enzyme from Ricinus 

 seed and was not directly effective as a co-enzyme in promoting the 

 hydrolysis of the ethereal salt. In other words, it appeared to be probable 

 that the zymogen in the seed was merely a salt which became active when 

 " neutralised " by an acid. 



Since 1906, at intervals, many attempts have been made by one of us to 

 arrive at an understanding of the peculiarities of Lipase but it has been 

 possible only recently to interpret the results in a simple and consistent 

 manner, so as to correlate the effects produced by this enzyme with those 

 observed in the case of other natural hydrolysts : in fact until the views 

 which are put forward in the previous communication had taken definite 

 shape and a clear conception had been formed of the manner- in which 

 enzymes generally effect hydrolysis, it was difficult, if not impossible, to 

 formulate an explanation of the manner in which an enzyme operates when 

 acting under such peculiar conditions and to appreciate the relative 

 significance of the various observations made with Lipase. 



Preparation of the Enzyme. — The most important advance made in recent 

 years in connexion with Lipase is the discovery by Yoshio Tanaka* that 

 an active enzyme may be prepared by digesting pressed castor oil seed with 

 a proper amount of acid, then washing to remove all soluble matter. 

 This material is most active in a neutral medium, less so in the presence 

 of acid, especially mineral acid. 



In a more recent communication, published in September 1912,f it is 

 stated that the optimum quantity of acid is 5 c.c. of if/10 sulphuric or 

 6-7 c.c. of N/10 acetic acid for each gramme of the pressed seed. The 

 method recommended is to digest 100 grin, of pressed or extracted castor 

 oil seed with 600-700 c.c. of the acetic or 500 c.c. of the sulphuric acid 

 at 30-35° and after about 30 minutes to wash the residue thoroughly with 

 water and then dry the pasty mass at a temperature not exceeding 40°. 

 If oil be digested at 30-35° with 3-4 per cent, of the dried Lipase powder 

 thus prepared and 6-10 times as much water as powder, about 90 per cent, 

 of the glyceride is hydrolysed within 7-10 hours. 



In our experience, the enzyme prepared with a very weak acid such as 

 acetic is distinctly superior to that obtained when a stronger acid is used : 

 the enzyme appears to be in some way altered by " fixation " of the acid 

 and the effect cannot be counteracted by neutralisation with alkali. 



We have usually prepared the enzyme by crushing the shelled castor oil 



* ' Journ. of the College of Engineering, Tokyo Imperial University,' 1910, vol. 5, 

 No. 2, p. 25. 



t Ibid., No. 4, p. 125. 



