Amino groups in Clostridium perfringens epsilon prototoxin and epsilon toxin

Modification with succinic anhydride (SA) of Clostridium perfringens epsilon prototoxin or toxin resulted in a loss of activation by trypsin or lethal activity, respectively. The prototoxin was more sensitive to succinylation than the toxin. On the other hand, the succinylated prototoxin was activated and cleaved by chymotrypsin, but not by trypsin. The lethal activity of the toxin was also lost after treatment with 2,3-dimethylmaleic anhydride (DMA) or 2,4,6-trinitrobenzenesulfonic acid (TNBS). When the DMA-treated toxin treated with SA or TNBS was incubated under acidic condition, it regained lethal activity. Thus modification of amino groups (lysine residues) prevented activation of the prototoxin by trypsin, and abolished lethal activity of the toxin.