The specification discloses modified Clostridial toxins comprising a Clostridial toxin substrate cleavage site located within the di-chain loop region; polynucleotide molecules encoding such modified Clostridial toxins comprising a Clostridial toxin substrate cleavage site located in the di-chain loop region; and method of producing modified Clostridial toxins comprising Clostridial toxin substrate cleavage site located within the di-chain loop region.
