Specific peptides of casein pancreatic digestion enhance the production of tetanus toxin

Casein pancreatic digest is the basic bacterial growth medium used for diphtheria, botulinumand tetanus toxin vaccine production. It is known that the variation in the peptide content of thecasein digest directly affects final toxin yields. In this study, the identification and sequences ofeight peptides, four to eight amino acids in length, of casein pancreatic digestion, which seem tobe involved in the enhancement of tetanus toxin production, are described. They all contain one ortwo residues of proline/molecule and a predominance of hydrophobic amino acid residues. Themost active peptides show a general structure of Pro‐aromatic‐Pro, and this pattern resembled themotif displayed by bradykinin‐potentiating peptides found in snake venoms. By analogy with themechanism of bradykinin potentiation through inhibition of the proteolytic degradation ofbradykinin, it is suggested that the six peptides identified here could protect the tetanus toxin fromproteolysis, once secreted by the bacteria.