178 IMMUNO-CATALYSIS 



sorbent properties, more and more of the enzyme is set free to act." 

 He stated further: "There is no doubt of the existence of substances 

 which have a markedly inhibiting action on certain enzymes, although 

 it leads to confusion if they are called 'anti-enzyme,' since there is no 

 evidence that they can be produced in response to the injection of 

 these enzymes into organisms." 



The question of non-specific adsorption of enzymes on various ad- 

 sorbents as a possible cause of the diminished enzyme activity and of 

 thereby accounting for the immune anti-enzyme inhibitory effect will 

 be discussed under the heading of non-specific adsorptions. We will 

 therefore discuss here the nature of the normal enzyme inhibitors 

 found in the living cell and compare their properties with those of 

 anti-enzyme antibodies. 



a. The Nature of the Trypsin Inhibitor Present in Sera in Re- 

 lation to Anti-Enzyme Antibody. The anti-tryptic action of certain 

 normal sera, referred to by Bayliss, appears to us to correspond to the 

 trypsin inhibitor of low molecular weight and of polypeptide nature 

 which has been studied by Schmitz (1938). As discussed previously 

 Schmitz isolated it from horse serum and characterized it as being 

 similar to that crystallized from pancreatic extract by Kunitz and 

 Northrop (1936). Both of these inhibitors are polypeptides of about 

 5000 molecular weight, which are not comparable at all with the anti- 

 trypsin immune globulin described by Ten Broeck (1934). Antitrypsin 

 antibody falls into the class of globulins having a molecular weight of 

 about 150,000 to 160,000. It is also to be noted that the antitrypsin 

 antibody is not present in the albumin fraction of the serum; in con- 

 trast, the trypsin inhibitor present in normal serum, as emphasized by 

 Bayliss and demonstrated by Schmitz, is solely in the albumin fraction 

 of serum. These facts make the further discussion of this subject un- 

 necessary. 



However, in this connection it is of interest to note an observation 

 by Maschmann (1937). He found that the proteolytic activity of the 

 toxin of CI. ferfringens was not inhibited at all by normal horse serum 

 which was shown to exercise an inhibitory effect on other bacterial 

 proteolytic enzymes. The proteolytic activity of the toxin, on the 

 other hand, was strongly inhibited by antitoxic horse serum. 



Smith and Lindsley (1939) studied the inhibition of the proteolytic 

 enzymes of bacteria by immune sera. They separated the constitu- 



