426 



SCIENCE 



[N. S. Vol. XLVII. No. 1218 



ties and composition those which are gen- 

 erally taken to typify proteins. In the 

 pro'blem of isolating pure proteins, it has 

 been possible by careful treatment to ob- 

 tain bodies having the same properties at 

 different times. This is somewhat different 

 from obtaining a pure protein possessing 

 the same properties as when present in liv- 

 ing matter. The operations involved in 

 such isolations are always sufficient to 

 change the properties of the protein to 

 some extent. The problem of isolating a 

 pure lipase, for example, mu^t wait there- 

 fore for the solution of the problem of the 

 isolation of proteins possessing the proper- 

 ties which they exhibit in living matter, 

 using the term living to include also mat- 

 ter showing the actions of enzymes. 



If, therefore, there is little hope at pres- 

 ent of isolating a pure enzyme, consider- 

 ing also the colloidal nature of the mate- 

 rial with which it is necessary to work, 

 there is a possibility of attacking the prob- 

 lem in a somewhat different way. An 

 enzyme, as a rule, accelerates a more or less 

 specific reaction or group of reactions. 

 Considering the very complex nature of 

 the protean or other molecule which in- 

 cludes the enzyme, or with which the 

 enzyme may be associated, and the more or 

 less specific reaction which it accelerates, 

 it would appear as if some definite group- 

 ing in the complex enzyme molecule were 

 responsible for a given enzyme action. Al- 

 though this is an assumption tihere is con- 

 siderable ground for making it, consider- 

 ing the views held at present with regard 

 to the probable mechanism of the reaction 

 of ester hydrolysis, and the complex na- 

 ture of the protein enzyme molecule com- 

 pared with the comparatively simple ester, 

 acid, alcohol molecules involved in the 

 catalyzed reaction. At any rate, this is the 

 view upon which the work on the chem- 



ical nature of enzymes was based ; namely, 

 that part of the complex molecular group- 

 ing of the protein material is responsible for 

 a given action. The problem therefore re- 

 solves itself into a study of the chemical 

 nature of this grouping. 



The colloidal properties of the protein 

 and other molecules as a whole also influ- 

 ence the rates of reaction, especially with 

 insoluble fats in the case of lipase, for ex- 

 ample. Emulsifying agents also play a 

 part, but it appears from the experimental 

 evidence available that such agents do not 

 cause enzyme action in the absence of a 

 definite enzyme grouping, while, on the 

 other hand, enzjone action occurs even 

 without the emulsifying or other agent, 

 though perhaps not to as great extent as 

 in their presence. 



The main factor, therefore, may be 

 taken to be the chemical grouping, the 

 physical and other properties modifying to 

 a greater or less extent the typical action 

 of the active enzyme grouping though not 

 changing its nature. 



The point of view has been presented 

 from which the study of the chemical na- 

 ture of enzymes was developed. As stated 

 before, the experimental work was done for 

 the most part with lipase because of the bet- 

 ter known properties of the substrate and 

 its reaction products. The greater part of 

 the lipase work was carried out with prep- 

 arations from castor beans, although other 

 sources were also used. There has been a 

 general tendency in the study of enzyme 

 actions to attempt to attain conditions 

 under which the enzyme would show a 

 maximum action. This method of study- 

 ing the problem is likely to introduce a 

 number of new complicating factors, so that 

 it was considered that if the action was due 

 to some definite grouping, a study of the 

 factors which caused a loss of the action 



