196 IMMUNO-CATALYSIS 



counter of the substrates with the enzymes? That is, does the combina- 

 tion of the antibody with the enzyme block, without combining with, 

 the active areas of the enzyme preventing the contact between the sub- 

 strate and these areas? 



a. Studies on the Reactive Groups of Proteins. In recent years, 

 certain phases of the first question have been studied and continue to 

 be a hvely subject of interest. Let us briefly discuss the results of such 

 investigations. Investigators have pursued the line of reasoning that, if 

 the biological activity of a purified protein is first lost by the action of 

 group-specific reagents, and then, after reversal of the reaction, re- 

 gained, the group in question is assumed to play a positive role in the 

 biological activity of the said protein. Of the several types of 

 groups located in the side-groupings of the protein molecules SH, NH2 

 and phenolic groups have received most consideration as possible active 

 "centers" of enzymes, toxins, hormones, viruses, and antigens. The 

 subject has been variously reviewed during recent years (Herriott, 

 1947; Olcott and Fraenkel-Conrat, 1947; Anson, 1945; French and 

 Edsall, 1945; Landsteiner, 1945), and we can only briefly refer to 

 the pertinent phases of the subject. It should at the start be pointed 

 out that there is as yet no clear demonstration which of a given number 

 of specific groups are essentially related to the biological activity of a 

 protein. The data so far available would seem to indicate that a certain 

 number of a given group situated near or at a certain configurational 

 position, more than others, may play a positive role in regulating the 

 activity of a given species of proteins. 



b. Reaction of Formaldehyde with Proteins and Amino Acids. It is 

 a classical immunological fact that the action of formaldehyde converts 

 toxins into toxoids, products which are deprived of toxicity without loss 

 of antigenic potency and capacity to combine with antitoxins. French 

 and Edsall (1945) subjected a large number of studies on the reactions 

 of formaldehyde with amino acids and proteins to a comprehensive 

 treatment. It shows that formaldehyde frequently enters into an addi- 

 tion reaction with a compound containing an active hydrogen atom 

 with the formation of a mono-hydroxy-methyl compound, R-CH2OH, 

 which can enter into a condensation reaction forming a methylene 

 bridge, R-CH2-R'. Thus, numerous groups found in amino acids, 

 peptides and proteins are capable of undergoing addition and con- 

 densation reactions with formaldehyde. 



