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



exercised by the enzymes which hydrolyse glucosides, for example, though 

 the fact that it acts preferentially on fats cannot be left out of account. It 

 would seem to be necessary to assume only that the enzyme is one in which 

 an attractive carboxylic centre is freely exposed. 



To judge from the properties of acids generally, it would seem that the 

 carboxylic group has a marked tendency to combine with itself — thus acetic 

 acid appears to exist under ordinary conditions as a polymerised form of the 

 fundamental molecule CH3.CO.OH ; and, judging from their slight solubility, 

 this is true also of a great many acids. The free carboxyl radicle, CO.OH, 

 probably has marked attractive power and far greater activity than is 

 apparent in acetic acid, for example. 



It is a question, therefore, whether the properties of lipase may not be 

 accounted for on the assumption that it is a colloid molecule possessed of a 

 carboxylic or even a phosphoric group so situated that it cannot be self- 

 neutralised but yet sufficiently near to a basic centre to be interfered with 

 by any acid which can combine with this latter. 



It may well be that the configuration of the enzyme is such as specially to 

 favour its association with glycerides of the higher fatty acids. But the associa- 

 tion of enzyme and hydrolyte is doubtless determined by an intervening water 

 film, i.e. the carboxylic centres in the two compounds are both to be thought of 

 as hydrolated and as brought into contact through the agency of the attached 

 water molecules. The number of molecules thus activated will depend on 

 the osmotic conditions which prevail in the mixture undergoing change. 



We are under the impression that the lipase powder contains an emulsi- 

 fying constituent and that its activity is perhaps in no small measure 

 dependent on this constituent. It is impossible to say at present whether 

 the intrinsic acidity of the powder prepared by means of a weak acid which 

 is not retained to any appreciable extent is that of the enzyme proper or of 

 a practically insoluble acid associated with it : we are inclined to think that 

 the intrinsic acidity of the powder is to be correlated with its emulsifying 

 power. As the decrease in the activity of the enzyme when it has a high 

 acid value is equally marked towards succinic ether, however, the inferiority 

 cannot well be attributed solely to loss of emulsifying power. 



Influence of the Products of Change. — Under ordinary conditions the 

 hydrolysis of fats by lipase powder is incomplete — partly perhaps because 

 the action is reversible but mainly, we think, on account of the retarding 

 influence of the products of change and the decay of the enzyme. 



With regard to the influence of the acid liberated from a fat on the course 

 of change, the conclusion arrived at recently by Tanaka will be obvious from 

 the following quotation : — 



