106 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



this class they tend to carry down with them other substances 

 which are present in solution, especially inorganic salts ; it is 

 therefore very difficult to obtain them free from ash. More- 

 over, in the course of the operations necessary to prepare them 

 in an approximately pure state, they tend to suffer a loss in 

 activity. So difficult indeed is it to obtain them as definite 

 chemical compounds that it has been seriously suggested 

 that enzyme action is really a property of matter, such, for 

 example, as radio-activity or static electrical potential. 



The following method will, however, serve to illustrate 

 the preparation of amylase in an approximately pure 

 condition. 



The precipitate, formed as already described by adding the 

 malt extract to alcohol, contains, besides the active enzyme, 

 a quantity of carbohydrate (dextrin and sugar) together with 

 albuminoid matter and salts. It is possible to eliminate the 

 carbohydrate and the albuminoid impurity to a large extent 

 by the action of yeast, if the latter has been previously 

 starved of nitrogen, by allowing it to remain for twenty-four 

 hours in a 10 per cent, solution of sugar. To prepare the 

 amylase in this way, 100 grams of crushed malt are macerated 

 with 300 c.c. of water at a temperature of 30 C. for eighteen 

 hours, stirring at half-hour intervals. The mass is filtered and 

 pressed and thoroughly washed with water, the washings being 

 mixed with the original extract. After filtering the solution 

 is made up to 300 c.c. with water, ten grams of beer yeast 

 added and left at a temperature of 28 C. for forty-eight hours. 

 The solution is then filtered and 700 c.c. of alcohol added to 

 the clear liquid ; the precipitated amylase is filtered through 

 a hardened filter paper, washed with small quantities of 

 absolute alcohol, and finally dried in a vacuum desiccator. 

 About three grams of a white powder are obtained which has 

 about 80 per cent, of the activity of the original extract. 



A product of diminished purity and activity can be obtained 

 if the treatment with yeast is omitted and the precipitate 



