54 ENZYMES 



upon which they act, that they are susceptible to heat, and that they 

 produce immune bodies when injected into experimental animals, all 

 suggest the probability of a relationshij) between enzymes and toxins. 

 This matter will be discussed more fully in considering the chemistry 

 of immunity against enzjanes. 



General Properties of Enzymes. — Other properties of enzymes may be briefly 

 mentioned. The speed of reaction they produce increases with the amount of 

 enzymes present. Very dihite acids favor the action of nearly all ferments, and 

 alkalies are unfavorable 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 glycerol dissolve 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 sUght impairment of strength. Filtra- 

 tion through porcelain filters is not complete, from 10 to 25 per cent, of most en- 

 zymes being lost in each filtration and enzymes are subject to great absorption by 

 surfaces, e. g., charcoal, kaolin.^ As before mentioned, many chemicals poison- 

 ous to bacteria have little influence on most enzymes, but nearly all substances 

 when concentrated are injurious or destructive, and some enzymes are kno^^Ti 

 that are more susceptible to antiseptics than are the cells that contain them. 

 Formaldehyde is very destructive to most enzj^mes, even when dilute. The 

 effect of protein-coagulating antiseptics upon enzymes is, of course, greatly modified 

 by the amount of protein substances mingled with the enzymes ; and the effects of 

 heat and other injurious influences are greatly decreased by the presence of 

 proteins and other impurities. 



All enzymes are most active between 35° and 45° C, and it is interesting to 

 note that tvobert 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 tempera- 

 ture, even — 190° C. (liquid air), does not destroy them. The loss of power 

 through heating occurs gradiially, and there is no sharp line at which their action 

 disappears. Sunlight is harmful to enzymes in solution, but only in the presence 

 of oxygen; this effect is augmented by the presence of fluorescent substances. 

 Nascent oxygen is destructive to enzymes. '-' Radium and .x-rays seem to have a 

 deleterious effect upon most enzymes, and retard their rate of action ; but apparently, 

 autolytic enzymes (Neuberg"-) and tyrosinase (Willcock-'O are not injured by 

 these agencies. -^ Ultra violet rays are also injurious to enzymes,-^ and they 

 can be destroyed by violent shaking (Shaklee and Meltzer.-*^). Labile as enzymes 

 are, their persistence when dry is remarkable; Kobert found active trypsin in the 

 bodies of spiders that had been in the Nuremberg Museum for 150 years, and Seiirt'-^ 

 found that the muscle tissue of mummies contained active glvcolytic ferment. 



All enzymes as ordinarily prepared have the property of decomposing hydro- 

 gen peroxide, a property possessed by substances of varied nature; this effect is 

 prevented by CNH, which does not prevent other enzyme manifestations, indi- 

 cating that this property is due to an associated enzyme, catalase. 



The retardation of enzyme action by accumulation of the products of their 



'9 See Hedin, Ergebnisse d. Physiol., 1910 (9). 433. 



20 However, Hosaka (Mitt. med. Gesell. Tokio, 1017 (31), 1) states that frog 

 pancreatic diastase is most active between 5° and 37°, whereas for guinea pig 

 pancreatic diastase the optimum temperature is 27°-55°. Activity begins to be 

 inhibited at 45° and 65° respectively. 



•^1 See Burge, Amer. Jour. Pliysiol., 1914 (34), 140. 



" Berl. klin. Woch., 1904 (41), 1081. 



" Jour, of Physiol., 1906 (34), 207. 



24 Gudzent (Zeit. Strahlenther., 1914 (4), 666) denies that radium acts on 

 enzymes. 



" Agulhon, Ann. Inst. Pasteur, 1912 (26), 38; Burge etal, Amer. Jour. Phvsiol., 

 1916 (40), 42C.. 



2« Amer. .lour. Physiol., 1909 (25), 81. 



" Berl. kliii. Woch., 1904 (41), 497. 



