62 ENZYMES 



immunization with trypsin is simply an increase in nonspecific resist- 

 ance, such as follows injection of peptone and man}' other poisonous 

 substances. Wago*^ was able to demonstrate precipitins and com- 

 plement fixing antibodies in antitryptic sera that were not strongly 

 antienzymatic, and Young^° was unable to produce antitryptic 

 sera by immunizing with trypsin-, in spite of the presence of active 

 precipitins for the injected trypsin solutions. There is, indeed, a 

 growing suspicion that much of the evidence of specific antibodj^ 

 formation for enzymes must be revised. 



Resemblances of Enzymes and Toxins. — As can be seen from the al)ove state- 

 ments, the enzymes behave in many respects lilce the toxins, both in tlieir manner 

 of acting upon other substances and in the reaction they produce when introduced 

 into the bodies of animals. As Oppenheimer says, "the bonds between enzymes 

 and toxins are drawing closer and closer." According to some experiments, the 

 enzymes behave much as if they possessed a haptophore and a toxophore group, 

 the former of which combines with the substance that is to be acted upon; and 

 immunity appears to be produced by the development of receptors that combine 

 the haptophore groups, these receptors constituting the antiferments. There is 

 abundant evidence of a toxin-like structure in enzymes, from the numerous ob- 

 servations on the formation of "zymoids" which can neutralize anti-enzymes 

 or combine with the substrate, although no longer active as enzymes. The 

 oxidizing enzymes especially, with their complex relationship of substrate, com- 

 bining body (peroxides) and enzyme, present striking analogies to immune reac- 

 tions (Moore^')? and the proteolytic substances of the blood resemble the lysins 

 in certain respects (Dick).'^ Enzymes and toxins also resemble one another in 

 being readily absorbed by membranes, precipitates, and highly developed sur- 

 faces in general.^' Finally, there is much reason to believe that the hemolytic 

 toxin of cobra venom is a lipase, which acts by splitting lecithin into hemolytic 

 substances (Coca).^^ 



THE INTRACELLULAR ENZYMES « 



Until a recent time our knowledge of enzymes in the animal body 

 was limited to those present in the digestive secretions. With few 

 exceptions these are without influence in pathological processes, since 

 they seem to be but little absorbed, and rarely enter the blood or 

 tissues in any other way. But with the more recently disclosed intra- 

 cellular enzymes, many of which are present in every cell,^^ the rela- 

 tion to pathology is very intimate. These intracellular enzymes, as 

 we now know them, and their chief properties, are as follows: 



s" Biochem. Jour., 1918 (12), 499. 



9' Biochem. Jour., 1909 (4), 165. 



»2 Jour. Infectious Diseases, 1911 (9), 282. 



9' See Porter, C,)uart. Jour. Exp. Physiol., 1910 (3), 375. 



9' Jour. Infect. Dis., 1915 fl7), 351. 



^'' Sv.G Vernon, Ergebnissc d. Pliysiol., 1910 (9), 138; also liis monograph, 

 "Intracellular Enzvmes," London, 1908. 



9« Hcrlitzka (Arch. ital. biol., 1907 (48), 119) and others have shown that 

 the diiferent enzymes appear one by one in the development of tiie ovum. Their 

 activity is modified considerably by infections (Siel)er, Hiochem. Zeit., 1911 (32), 

 108) aiid other diseases ((irossinanh, ibid., 1912 (11), ISl). 



