FORMATION AND ACTION OF A PEPTIDASE WHICH HYDROLYZES HISTIDINE PEPTIDES REQUIRED IN TETANUS TOXIN SYNTHESIS

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Abstract
When Clostridium tetani is grown on a toxigenic medium the cells contain an enzyme which hydrolyzes histidine peptides. This peptidase resembles mammalian carnosinase in its action spectrum and also in being activated by manganese or zinc and inhibited by cysteine. A positive correlation between the synthesis of toxin and the formation and action of the peptidase has been established. Histidine in peptide form is required for toxin formation. Peptides of histidine most suitable for toxigenesis are also those which are most readily attacked by the peptidase and it is possible to relate the toxigenic action of a given peptide to its affinity for the peptidase. In spite of numerous attempts, it has not been possible to induce peptidase formation in the absence of toxin production. The activities of the toxin and the peptidase are difficult to resolve but they appear to be carried on different proteins. When the cells in a mature culture lyse, both toxin and peptidase are released into the medium. Immunization with lysates or modified lysates gives rise to antipeptidase as well as antitoxin. The antipeptidase prevents the enzyme from hydrolyzing histidine peptides.