THE PRINCIPLES OF ENZYME ACTION 69 



and that they produce immune bodies when injected into exper- 

 imental animals, all suggests the probability of a relationship 

 between enzymes and toxins. This matter will be discussed more 

 fully in considering the chemistry of immunity against enzymes. 



General Properties of Enzymes. Other properties of 

 enzymes may be briefly mentioned. The speed of reaction they 

 produce increases with the amount of enzyme present, but not 

 in direct proportion (except with rennin). Very dilute acids 

 favor the action of nearly all ferments, and alkalies are unfa- 

 vorable for all but trypsin, ptyalin, and a few others. Weak 

 salt solutions also are more favorable than distilled water. 

 (These facts suggest strongly the possibility that ions play an 

 important role in the process.) Water and dilute glycerin dis- 

 solve enzymes, which form always colloidal solutions that are 

 very slightly dialyzable ; and they may be precipitated from 

 solution by alcohol, and redissolved again with but slight im- 

 pairment of strength. Filtration through porcelain filters is 

 not complete, from 10 to 25 per cent, of most enzymes being 

 lost in each filtration. * As before mentioned, many chemicals 

 poisonous to bacteria have little influence on most enzymes, but 

 nearly all substances when concentrated are injurious or destruc- 

 tive, and some enzymes are known that are more susceptible to 

 antiseptics than are the cells that contain them. Formaldehyde 

 is very destructive to enzymes, even when dilute. The effect of 

 proteid-coagulating antiseptics upon enzymes is, of course, 

 greatly modified by the amount of proteid substances mingled 

 with the enzymes ; and the effects of heat and other injurious 

 influences are greatly decreased by the presence of proteids and 

 other impurities. 



All enzymes are most active between 35 and 45 C., and it 

 is interesting to note that Robert 2 found this equally true for 

 enzymes derived from cold-blooded animals. Although enzymes 

 can stand temperatures of 100 C. or more when dry, in water 

 they are generally destroyed somewhat below 70 C. Low tem- 

 perature, even 190 C., 3 (liquid air), does not destroy them. 

 The loss of power through heating disappears gradually, and 

 there is no sharp line at which their action disappears. Sun- 

 light is harmful to enzymes in solution, but only in the presence 

 of oxygen 4 ; this effect is augmented by the presence of fluo- 

 rescent substances. Radium and arrays seem to have a dele- 



1 Literature, see Levy, Jour. Infectious Diseases, 1905 (2), 1. 



2 Pfliiger's Arch., 1903 (99), 116. 



3 Bickel, Dent. med. Woch., 1905 (31), 1383. 



4 lodlbauer and Tappeiner, Deut. Arch. klin. Med., 1905 (85), 386. 



