MECHANISM OF ANTIBODY FORMATION 111 



According to Jacobson, the number of titratable groups per a-chymo- 

 trypsin molecule is greater by six to nine than that per chymotrypsino- 

 gen molecule, indicating a probable hydrolysis of four peptide bonds 

 during the conversion of chymotrypsinogen to a-chy mo trypsin. He 

 considers several possibilities to support or refute his assumption that 

 the above transformations involve the splitting of peptide bonds. 



He considered for chymotrypsinogen a protein structure as formu- 

 lated by Mirsky and Pauling (1936). According to these authors, the 

 native globular unconjugated proteins consist of an uninterrupted 

 polypeptide chain which is continuous throughout the molecule. The 

 polypeptide chain folds into an uniquely defined configuration. This 

 configuration is maintained by means of hydrogen-bonding betv^^een 

 the peptide nitrogen and oxygen atoms and also between the free amino 

 acid carboxyl groups of diamino and dicarboxylic amino acids. In the 

 case of chymotrypsinogen, the hydrolysis of peptide bonds, leading to 

 chymotrypsin with six to nine titratable groups more than the original 

 molecule, must occur near the ends of the peptide chain. The hydroly- 

 sis of certain terminal amide bonds by trypsin was taken into considera- 

 tion in view of the fact that trypsin is able to hydrolyze the amide 

 bond in benzoyl-glycyl-arginamide, benzoyl-arginamide, benzoyl-glycyl- 

 lysin-amide and benzoyl-lysin-amide (Bergmann, et al. 1939). Such 

 a hydrolysis of a protein should yield ammonia. The finding of 

 Butler (1941) that at the maximum activation by trypsin 1 NHs per 

 12 chymotrypsinogens is produced, and no increase in NHs took place 

 after 66 hours, was not considered of any significance by Jacobson. It 

 would, however, seem that the ease with which the amides are hydro- 

 lyzable might be in line not only wdth the catalytic conversion of 

 chymotrypsinogen into chymotrypsin by trypsin, but also, particularly, 

 with the spontaneous (wathout the presence of minute amounts of 

 trypsin) change of chymotrypsinogen into chymotrypsin as has been 

 observed. 



According to Jacobson, the splitting of a terminal amide bond from 

 chymotrypsinogen does not occur to any significant extent during the 

 tryptic hydrolysis leading to 7r-chymotrypsin. The splitting off of an 

 amino acid a-amide during the autolytic (or spontaneous) conversion 

 of TT-chymotrypsin leading to a-chymotrypsin is not impossible if such 

 bonds exist in chymotrypsinogen since a-chymotrypsin is reported to 

 possess such an activity (Bergmann and Fruton, 1938; Fruton and 



