THE INTRACELLULAR ENZYMES 75 



Resemblances of Enzymes and Toxins. As can be seen 

 from the above statements, the enzymes behave in many 

 respects like the toxins, both in their manner of acting upon 

 other substances and in the reaction they produce when intro- 

 duced 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. Korschun 1 has 

 even succeeded in obtaining an anti-antirennin. He also secured 

 rennin in an altered condition so that it did not coagulate milk, 

 but still did unite with antirennin a " fermentoid," according 

 to the Ehrlich nomenclature. This is a strong piece of evidence 

 of the similarity of enzymes and toxins. On the other hand, an 

 important difference between the enzymes and the toxins is that 

 toxins produce their effects according to the law of definite 

 proportions, which is quite different from the behavior of cata- 

 lyzing agents. Also some of the toxins have greater heat 

 resistance than most enzymes, whereas complement is more 

 easily destroyed than are the enzymes. 2 



THE INTRACELLULAR ENZYMES 



Until a very recent time our knowledge of enzymes in the ani- 

 mal 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 

 ^nter the blood or tissue in any other way. But with the more 

 recently disclosed intracellular enzymes, many of which are 

 present in every cell, the relation to pathology is very intimate. 

 These intracellular enzymes, as we now know them, and their 

 chief properties, are as follows : 



OXIDIZING ENZYMES 



Although oxidation of organic compounds is the chief source 

 of energy in the animal body, yet the way in which it is accom- 

 plished is very little understood. We only know that it is 

 brought about within the cells, 3 and that substances that out- 



1 Zeit. f. physiol. Chem., 1902 (36), 141 ; 1903 (37), 366. 



2 The supposed relationship of enzymes and toxins is questioned by Lieber- 

 mann, Deut. med. Woch., 1905 (31) r 1301. 



3 Lillie (Amer. Jour, of Physiol., 1902 (7) 412, has demonstrated that 

 oxidation occurs chiefly about or within the nucleus. 



