546 SCIENCE PROGRESS 



their surface of the reacting substances, and that the reaction 

 velocity is thereby increased owing to more intimate contact, 

 it was argued that the activity of an enzyme should be 

 diminished by the addition to the reacting mixture of an 

 indifferent substance which might be preferentially absorbed. 

 Knowing that charcoal absorbs saponin more readily than 

 urea, some saponin was added to a mixture of urease and urea 

 on the assumption that the enzyme might absorb some of 

 the saponin to the exclusion of a certain amount of the urea. 

 It was found that the activity of the urease was in fact delayed 

 and also that bile salts and amyl alcohol had a similar effect. 

 While the observed facts fit in with the author's hypothesis, 

 it must be acknowledged that the surface forces controlling 

 enzyme action are as yet not sufficiently understood to justify 

 any very definite conclusion being drawn from these experi- 

 ments. 



Willstatter and Stoll, whose combined efforts have added 

 so much to our knowledge of chlorophyll, have now (Annalen, 

 191 8, 416, 21) undertaken a thorough investigation of enzymes 

 with a view to throwing some light on the three following 

 questions: (1) whether enzyme action is due to the co- 

 operation of a number of different substances or to a single 

 chemical individual ; (2) whether metals play an essential 

 role in enzyme activity; and (3) what particular groups are 

 associated with such activity. 1 he particular enzyme selected 

 for experiment was the peroxidase contained in horse-radish. 

 A somewhat elaborate process of extraction was adopted, of 

 which the following is an outline. Five kilos of finely sliced 

 horse-radish were first washed for some days in running water, 

 to remove soluble substances by dialysis through the cell 

 walls ; the material was then warmed for a few hours with a 

 o«4 per cent, solution of oxalic acid, whereby the enzyme was 

 precipitated, presumably absorbed on the coagulated protein ; 

 the residue was next crushed and washed on a filter with 

 1 5 litres of very dilute oxalic acid ; it was then ground up 

 with baryta water to liberate the enzyme and the expressed 

 liquid was treated with carbon dioxide to precipitate the 

 barium. The addition of alcohol precipitated slimy sub- 

 stances which were removed and the filtrate was then evapor- 

 ated to 50 cc. ; the addition of five times this bulk of alcohol 

 precipitated the crude enzyme ; the latter was purified by 



