i LIVING MATTEE 31 



peculiar chemical action, do not form stable combinations with 

 the substances on which they act, or with the decomposition 

 products arising from their activity. An infinitesimal quantity of 

 enzyme is able to act upon a relatively enormous quantity of 

 fermentable substance. It has been found, e.g., that one part of 

 invertase is capable of splitting up 100,000 parts of saccharose, 

 and one part of chymosin or rennet of coagulating 400,000 parts 

 of caseinogen. 



A second property of enzymes is the specific character of their 

 action, inasmuch as any one enzyme acts only upon a definite 

 substance, or upon a restricted group of allied substances. Enzyme 

 action is always in strict relation with the configuration and con- 

 stitution of the atomic grouping of the relative molecules, to 

 which the enzyme is as rigorously adapted as the key to the wards 

 of a lock to repeat once more the picturesque expression of E. 

 Fischer. This specific action is, in fact, so conspicuous as to serve 

 as a method of distinguishing isomeric chemical compounds from 

 one another. 



Enzyme action is further influenced by various external 

 conditions, e.g. the reaction of the liquid : some ferments are 

 active only in an acid medium, others and far the greater number 

 in a neutral or faintly alkaline medium. 



Temperature has a marked influence on the course of enzyme 

 activity, which usually increases with the rise of temperature 

 to a certain point representing the optimum, after which a 

 further rise of temperature diminishes the enzyme action until 

 it disappears. 



The accumulation of cleavage products has a marked inhibitory 

 influence on the development of enzyme activity ; the inhibition 

 ceases so soon as these products are removed. 



How is it possible to explain the action of enzymes ? 



Certain inorganic substances exhibit properties highly similar 

 to those of the analytical enzymes we have been considering, since 

 they are capable of producing cleavage processes which do not 

 essentially differ from processes of fermentation. These sub- 

 stances, which have been known for some time to chemists, are 

 the so-called catalysers, and determine the process of catalysis 

 (Ostwald). A classical example of catalytic action is that repre- 

 sented by the decomposition of hydrogen peroxide (H 2 2 ) into 

 oxygen (0) and water (H 2 O) by platinum black. A trace of this 

 substance will decompose an enormous amount of hydrogen 

 peroxide without any loss of activity. 



Bredig (1899) has recently enlarged the class of catalysers by 

 showing that all metals in a colloidal state, to which he gives the 

 name of inorganic ferments, belong to it. Moreover, he has 

 brought out so many interesting coincidences between the action 

 of these catalysers and that of enzymes as to render the hypothesis 



